BRAIN II RUNOFF
The cerebral cortex neurons are organized into layers. Lamination is a feature of all cortical regions, although different cortical regions characteristically contain different numbers of layers. Approximately 95% of the cerebral cortex contains at least six cell layers; this cortex is commonly called neocortex because it dominates the cerebral cortex of phylogenetically higher vertebrates such as mammals. The remaining 5% of cortex, which is termed allocortex, is morphologically distinct. Allocortex is involved in olfaction and aspects of learning and memory.
Provide a summary of connections in the cortical layers.
The Cerebral Cortex Has an Input-Output Organization
The Cytoarchitectonic Map of the Cerebral Cortex is the Basis for a Map of cortical function
The cerebral cortex neurons are organized into layers. Lamination is a feature of all cortical regions, although different cortical regions characteristically contain different numbers of layers. Approximately 95% of the cerebral cortex contains at least six cell layers; this cortex is commonly called neocortex because it dominates the cerebral cortex of phylogenetically higher vertebrates such as mammals. The remaining 5% of cortex, which is termed allocortex, is morphologically distinct. Allocortex is involved in olfaction and aspects of learning and memory.
Provide a summary of connections in the cortical layers.
The Cerebral Cortex Has an Input-Output Organization
The Cytoarchitectonic Map of the Cerebral Cortex is the Basis for a Map of cortical function
Brain Runoff
The brain and spinal cord are covered with the meninges, the dura mater, pia mater and arachnoid villus which enclose an envelope of cerebrospinal fluid with provides mechanical support and hydraulic protection and a matrix for distribution of the blood supply. The dura mater guards against desiccation (moisture removal) and reduces mechanical trauma. The meninges are important supporting elements of the central nervous system and include the dura mater, arachnoid villus and pia mater.
The outermost fibrous membrane, the dura mater, consists of two layers of connective tissue that are fused, except in certain regions where they separate to form the intracranial venous sinuses. The dura mater is folded into the cranial cavity in two areas to form distinct fibrous barriers: the falx cerebri, located between the two cerebral hemispheres and the tentorium cerebelli which demarcates the superior limit of the posterior fossa.
The third ventricle shows how comparatively small the diencephalon is.
The brain and spinal cord are covered with the meninges, the dura mater, pia mater and arachnoid villus which enclose an envelope of cerebrospinal fluid with provides mechanical support and hydraulic protection and a matrix for distribution of the blood supply. The dura mater guards against desiccation (moisture removal) and reduces mechanical trauma. The meninges are important supporting elements of the central nervous system and include the dura mater, arachnoid villus and pia mater.
The outermost fibrous membrane, the dura mater, consists of two layers of connective tissue that are fused, except in certain regions where they separate to form the intracranial venous sinuses. The dura mater is folded into the cranial cavity in two areas to form distinct fibrous barriers: the falx cerebri, located between the two cerebral hemispheres and the tentorium cerebelli which demarcates the superior limit of the posterior fossa.
The third ventricle shows how comparatively small the diencephalon is.
THE BRAIN RUNOFF
and the spinal cord is in the spinal column. Cranial and peripheral nerves must pass through these surrounding structures to reach more peripheral structures
The nervous system is generally divided into four major regions; supratentorial, posterior fossa, spinal and peripheral.
The major portions of the central nervous system located below the foramen magnum of the skull is the spinal cord and it is contained within the vertebral column. The spinal levels traverse from the skull to the sacrum but the spinal cord itself does not extend that entire length. A series of spinal nerves arise from the spinal cord and exit through the intervertebral foramina. All neuromuscular structures located outside the skull and vertebral column, including the peripheral nerves, their branches, and the structures (including muscle) that are innervated by these nerves are peripheral. The skull, meninges, blood vessels and ventricular system are supporting structures present at multiple levels.
The Cerebral Hemispheres have a complex three dimensional configuration and are the most highly developed part of the nervous system. The cerebral cortex is separated into four lobes of distinct function and are named after the cranial bones that are superior to them; frontal parietal, occipital and temporal. The poles define the extremities of the brain.
Still more rostral is the prefrontal cortex and frontal lobes which have no direct sensory or motor function but provide long-term goal directed planning.
although most of the lobe is devoted to the planning and production of body and eye movements, speech, cognition, and emotions.
Association cortical areas are involved in the complex processing of sensory and other information for higher brain functions, including emotions, organizing behavior, thoughts, and memories.
Areas closer to the frontal pole comprise the prefrontal association cortex, which is important in cognition and emotions.
, such as the direction and speed of reaching
The cingulate gyrus and most of the orbital gyri are important for emotional functions.
The basal (bottom layer) forebrain, which is on the ventral surface of the frontal lobe, contains a special population of neurons that use acetylcholine to regulate cortical excitability.
Although the olfactory bulb is located on the ventral surface of the frontal lobe, its connections are predominantly with the temporal lobe.
These functions are carried out by the primary somatic sensory cortex, which is located in the post-central gyrus.
Primary sensory areas are the initial cortical processing stages for sensory information.
Rostral to the occipital lobe is the parietal cortex which extends all the way to the central sulcus (a deep fold in the cortex) rostrally and to the ventral surface of the cortex inferiorly.
***Rostral to the central sulcus is the pre-central motor cortex. Here reside neuronal cell bodies whose axons project into the spinal cord as the corticospinal tract (tract is a bundle or fascicle of axons and an axon is the long-distance projection process of a neuron). Corticospinal thus refers to a tract whose origin is cortical and whose termination is in the spinal cord. The corticospinal axons make synaptic terminations on spinal motoneurons that in turn are presynaptic to skeletal muscle. Hence, information about muscle contraction and relaxation crosses two synapses, one in the spinal cord, the other at the junction of the motoneuron to muscle synapse.***
***The remaining portion of the parietal lobe on the lateral brain surface consists of the superior and inferior parietal lobules, which are separated by the intraparietal sulcus. The superior parietal lobule contains higher-order somatic sensory areas, for further processing of somatic sensory information and other sensory areas. Together these areas are essential for a complete self-image of the body, and they mediate behavioral interactions with the world around us. A lesion in this portion of the parietal lobe in the right hemisphere, the side of the brain that is specialized for spatial awareness, can produce bizarre neurological signs that include neglecting a portion of the body on the side opposite the lesion. For example, a patient may not dress one side of her body or comb half of her hair. The inferior parietal lobule is involved in integrating diverse sensory information for perception and language, mathematical thought and visuospatial cognition. Interestingly, the inferior parietal lobule was greatly enlarged in Albert Einstein's brain. It is intriguing to speculate that Einstein's intellectual gifts reflect this structural difference.***
, the term primary means that damage here causes a massive functional loss, blindness
The functions of the occipital lobe are primarily visual.
For example, on the ventral brain surface is a portion of the occipto-temporal gyrus in the occiptal lobe (also termed the fusiform gyrus) that is important for recognizing faces. Patients with a lesion of this area con confuse faces with inanimate objects.
Tortex is one inch thick, convoluted to adapt increased surface area within a confined space within the skull and is comprised of components of neural circuitry. Elevated convolutions are called gyri and grooves are called sulci or fissures (particularly deep sulci). The cerebral hemispheres themselves are separated by the Sagittal Fissure.
and the spinal cord is in the spinal column. Cranial and peripheral nerves must pass through these surrounding structures to reach more peripheral structures
The nervous system is generally divided into four major regions; supratentorial, posterior fossa, spinal and peripheral.
The major portions of the central nervous system located below the foramen magnum of the skull is the spinal cord and it is contained within the vertebral column. The spinal levels traverse from the skull to the sacrum but the spinal cord itself does not extend that entire length. A series of spinal nerves arise from the spinal cord and exit through the intervertebral foramina. All neuromuscular structures located outside the skull and vertebral column, including the peripheral nerves, their branches, and the structures (including muscle) that are innervated by these nerves are peripheral. The skull, meninges, blood vessels and ventricular system are supporting structures present at multiple levels.
The Cerebral Hemispheres have a complex three dimensional configuration and are the most highly developed part of the nervous system. The cerebral cortex is separated into four lobes of distinct function and are named after the cranial bones that are superior to them; frontal parietal, occipital and temporal. The poles define the extremities of the brain.
Still more rostral is the prefrontal cortex and frontal lobes which have no direct sensory or motor function but provide long-term goal directed planning.
although most of the lobe is devoted to the planning and production of body and eye movements, speech, cognition, and emotions.
Association cortical areas are involved in the complex processing of sensory and other information for higher brain functions, including emotions, organizing behavior, thoughts, and memories.
Areas closer to the frontal pole comprise the prefrontal association cortex, which is important in cognition and emotions.
, such as the direction and speed of reaching
The cingulate gyrus and most of the orbital gyri are important for emotional functions.
The basal (bottom layer) forebrain, which is on the ventral surface of the frontal lobe, contains a special population of neurons that use acetylcholine to regulate cortical excitability.
Although the olfactory bulb is located on the ventral surface of the frontal lobe, its connections are predominantly with the temporal lobe.
These functions are carried out by the primary somatic sensory cortex, which is located in the post-central gyrus.
Primary sensory areas are the initial cortical processing stages for sensory information.
Rostral to the occipital lobe is the parietal cortex which extends all the way to the central sulcus (a deep fold in the cortex) rostrally and to the ventral surface of the cortex inferiorly.
***Rostral to the central sulcus is the pre-central motor cortex. Here reside neuronal cell bodies whose axons project into the spinal cord as the corticospinal tract (tract is a bundle or fascicle of axons and an axon is the long-distance projection process of a neuron). Corticospinal thus refers to a tract whose origin is cortical and whose termination is in the spinal cord. The corticospinal axons make synaptic terminations on spinal motoneurons that in turn are presynaptic to skeletal muscle. Hence, information about muscle contraction and relaxation crosses two synapses, one in the spinal cord, the other at the junction of the motoneuron to muscle synapse.***
***The remaining portion of the parietal lobe on the lateral brain surface consists of the superior and inferior parietal lobules, which are separated by the intraparietal sulcus. The superior parietal lobule contains higher-order somatic sensory areas, for further processing of somatic sensory information and other sensory areas. Together these areas are essential for a complete self-image of the body, and they mediate behavioral interactions with the world around us. A lesion in this portion of the parietal lobe in the right hemisphere, the side of the brain that is specialized for spatial awareness, can produce bizarre neurological signs that include neglecting a portion of the body on the side opposite the lesion. For example, a patient may not dress one side of her body or comb half of her hair. The inferior parietal lobule is involved in integrating diverse sensory information for perception and language, mathematical thought and visuospatial cognition. Interestingly, the inferior parietal lobule was greatly enlarged in Albert Einstein's brain. It is intriguing to speculate that Einstein's intellectual gifts reflect this structural difference.***
, the term primary means that damage here causes a massive functional loss, blindness
The functions of the occipital lobe are primarily visual.
For example, on the ventral brain surface is a portion of the occipto-temporal gyrus in the occiptal lobe (also termed the fusiform gyrus) that is important for recognizing faces. Patients with a lesion of this area con confuse faces with inanimate objects.
Tortex is one inch thick, convoluted to adapt increased surface area within a confined space within the skull and is comprised of components of neural circuitry. Elevated convolutions are called gyri and grooves are called sulci or fissures (particularly deep sulci). The cerebral hemispheres themselves are separated by the Sagittal Fissure.
Spinal Cord Blood Supply Runoff
The spinal and radicular arteries supply blood to the spinal cord
The spinal cord is supplied with blood by a network of communicating arteries from two main sources, the anterior and posterior spinal arteries which are in turn branches of the vertebral arteries, which are in turn branches of segmental vessels, such as the cervical, intercostal, and lumbar arteries. Neither anterior nor posterior spinal arteries typically form a single continuous vessel along the entire length of the dorsal or ventral spinal cord but each forms a network of communicating, channels oriented along the rostrocaudal axis of the spinal cord. The radicular arteries feed into this network along the entire length of the spinal cord.
The spinal cord is richly supplied with blood by a network of arteries and
It receives the basilar plexus at the base of the skull.
carotid means super - internal carotid supplies 75% of blood supply to the brain
opthalmic artery goes to the eyeball
anterior cerebral - supplies the cerebral hemispheres - surrounds the outer rim
middle cerebral - supplies the cerebral hemispheres - - supplies the internal area
broca's area - motor speech - is middle cerebral
angiography
ascending artery , first branch that comes off is common carotid, one beyond the subclavian is the vertebral artery that has an unusual pathway as it goes up the neck to the brain, at the base of the brain we have foramen magnum, 7 cervical vertebrae and the vertebral arteries goe of the transverse processes of the cervical vertebrae through the foramen magnum.
the subclavian artery comes around and comes to the axilla and changes name to axillary artery and in arm is the brachial artery where the blood pressure is taken, a centimeter below the elbow branches into radius and ulnar artery and the hand have the palmar arch and the digitals in the fingers, we take our pulse distal radial
decending aorta descends and goes thoracic aorta, within have espophegeal, intercostals arteries and bronchial arteries go to the lungs and abdominal aorta many vessels coming off, some are paired, some are not paired, renal arteries, gonadal arteries, ovarian arteries, testicular arteries, vascular surgeon
The spinal and radicular arteries supply blood to the spinal cord
The spinal cord is supplied with blood by a network of communicating arteries from two main sources, the anterior and posterior spinal arteries which are in turn branches of the vertebral arteries, which are in turn branches of segmental vessels, such as the cervical, intercostal, and lumbar arteries. Neither anterior nor posterior spinal arteries typically form a single continuous vessel along the entire length of the dorsal or ventral spinal cord but each forms a network of communicating, channels oriented along the rostrocaudal axis of the spinal cord. The radicular arteries feed into this network along the entire length of the spinal cord.
The spinal cord is richly supplied with blood by a network of arteries and
It receives the basilar plexus at the base of the skull.
carotid means super - internal carotid supplies 75% of blood supply to the brain
opthalmic artery goes to the eyeball
anterior cerebral - supplies the cerebral hemispheres - surrounds the outer rim
middle cerebral - supplies the cerebral hemispheres - - supplies the internal area
broca's area - motor speech - is middle cerebral
angiography
ascending artery , first branch that comes off is common carotid, one beyond the subclavian is the vertebral artery that has an unusual pathway as it goes up the neck to the brain, at the base of the brain we have foramen magnum, 7 cervical vertebrae and the vertebral arteries goe of the transverse processes of the cervical vertebrae through the foramen magnum.
the subclavian artery comes around and comes to the axilla and changes name to axillary artery and in arm is the brachial artery where the blood pressure is taken, a centimeter below the elbow branches into radius and ulnar artery and the hand have the palmar arch and the digitals in the fingers, we take our pulse distal radial
decending aorta descends and goes thoracic aorta, within have espophegeal, intercostals arteries and bronchial arteries go to the lungs and abdominal aorta many vessels coming off, some are paired, some are not paired, renal arteries, gonadal arteries, ovarian arteries, testicular arteries, vascular surgeon
Blood Vascular Runoff
The anterior and posterior arterial systems connect at several locations which is clinically important because increased flow in one system can compensate for decreased flow in the other.
One site of interconnection is on the ventral brain surface, where the communicating arteries are located. Together the proximal portions of the cerebral arteries and the communicating arteries form the circle of Willis. This is an example of a network of interconnected arteries, or an anastomosis.
Brain vasculature is closely related to the ventricular system and cerebrospinal fluid because most cerebrospinal fluid is produced by active secretion of ions from blood plasma by the choroid plexus. To maintain a constant brain volume, cerebrospinal fluid is returned to the blood through valves between the subarachnoid space and the dural sinuses.
The vertebral arteries join at the junction of the medulla and pons (or pontomedullary junction) to form the basilar artery, which lies unpaired along the midline.
The anterior and posterior circulations are not independent but are connected by networks of arteries on the ventral surface of the diencephalon and midbrain and on the cortical surface. Whereas the cerebral hemispheres receive blood from both the anterior and posterior circulations, the brain stem receives blood only from the posterior circulation.
Cerebral and spinal arteries drain into veins. Although spinal veins are part of the general systemic circulation and return blood directly to the hear, most cerebral veins drain first into the dural sinuses, a set of large venous collection channels in the dura mater.
Blood enters the skull via two arterial systems. The brain is supplied posteriorly by the vertebro-basilar system and anteriorly by the carotid arteries.
A series of anastomotic channels lying at the base of the brain, known as the circle of Willis, permits communication between these two systems.
Each organ in the body must have blood vessels to provide a relatively constant supply of oxygen and other nutrients and to remove metabolic waste. Vascular structures are found at all levels of the nervous system and include the arteries, arterioles, capillaries, veins, and dural sinuses. These supply supratentorial, posterior fossa, spinal, and peripheral structures.
The petrous segment of the internal carotid artery enters the cranium via foramen lacerum. After entering the cranium, each internal carotid artery forms an S-shaped curve, the carotid siphon, and lies within the cavernous sinus. As the artery leaves the cavernous sinus, it pierces the cranial dura and arachnoid to enter the subarachnoid space at the base of the brain.
The indominate artery divides into the right common carotid and the right subclavian arteries. The left common carotid artery arises directly from the apex of the aortic arch. The right and left common carotid arteries ascend in the neck lateral to the trachea. slightly below the angle of the jaw, the common carotid artery bifurcates into the internal and external carotid arteries. The internal carotid artery on each side enters the skull, without branching, through the carotid canal located in the petrous portion of the temporal bone.
The origin of the left common carotid artery is different from that on the right, as there is no left brachiocephalic artery. The left common carotid artery arises directly from the aorta, sightly to the left of the midline. The left subclavian artery also arises directly from the aorta immediately lateral to the left common carotid artery.
The right and left common carotid artery bifurcates into the internal and external carotid arteries. The internal carotid artery enters the skull on each side without branching, through the carotid canal located in the petrous portion of the temporal bone. All of the arteries that supply the supratentorial and posterior fossa structures arise form the aortic arch.
The internal carotid artery enters the skull on each side without branching, through the carotid canal located in the petrous portion of the temporal bone. The external carotid arteries supply the facial region and anterior neck.
The right subclavian artery is one of the branches of the brachiocephalic artery. The brachiocephalic artery arises directly from the arch of the aorta. The left subclavian artery arises from the aortic arch just lateral to the origin of the left common carotid artery.
The vertebral arteries arise as the first branches of the right and left subclavian arteries. Each artery ascends through foramina in the transverse processes of the upper six cervical vertebrae and enters the subarachnoid space at the level of the upper cervical spinal cord. The vertebral arteries enter the cranial cavity through the foramen magnum. The two vertebral arteries are often of unequal caliber, one being dominant.
As the vertebral artery enters the posterior fossa of the cranial cavity via the foramen magnum, it lies on the ventral lateral aspect of the medulla.
By way of the posterior communicating arteries from the first part of the posterior cerebral vessels, the vertebral-basilar system has access to the carotid system.
The vertebral arteries enter the cranium and ascend on the ventrolateral surface of the medulla oblongata. At the lower border of the pons, they unite to form the basilar artery. Major branches form the basilar artery includes: anterior inferior cerebellar artery, superior cerebellar artery, and multiple median and paramedian perforators. At the level of the midbrain, the basilar artery divides into the right and left posterior cerebral arteries.
Blood leaves the head by way of veins that course over the cerebral hemispheres to converge into large channels, the venous sinuses, contained within the layers of the dura mater.
The major venous channels merge in the occipital region and form the transverse and sigmoid sinuses, which exit through the skull via the jugular foramen as the internal jugular veins.
The anterior and posterior arterial systems connect at several locations which is clinically important because increased flow in one system can compensate for decreased flow in the other.
One site of interconnection is on the ventral brain surface, where the communicating arteries are located. Together the proximal portions of the cerebral arteries and the communicating arteries form the circle of Willis. This is an example of a network of interconnected arteries, or an anastomosis.
Brain vasculature is closely related to the ventricular system and cerebrospinal fluid because most cerebrospinal fluid is produced by active secretion of ions from blood plasma by the choroid plexus. To maintain a constant brain volume, cerebrospinal fluid is returned to the blood through valves between the subarachnoid space and the dural sinuses.
The vertebral arteries join at the junction of the medulla and pons (or pontomedullary junction) to form the basilar artery, which lies unpaired along the midline.
The anterior and posterior circulations are not independent but are connected by networks of arteries on the ventral surface of the diencephalon and midbrain and on the cortical surface. Whereas the cerebral hemispheres receive blood from both the anterior and posterior circulations, the brain stem receives blood only from the posterior circulation.
Cerebral and spinal arteries drain into veins. Although spinal veins are part of the general systemic circulation and return blood directly to the hear, most cerebral veins drain first into the dural sinuses, a set of large venous collection channels in the dura mater.
Blood enters the skull via two arterial systems. The brain is supplied posteriorly by the vertebro-basilar system and anteriorly by the carotid arteries.
A series of anastomotic channels lying at the base of the brain, known as the circle of Willis, permits communication between these two systems.
Each organ in the body must have blood vessels to provide a relatively constant supply of oxygen and other nutrients and to remove metabolic waste. Vascular structures are found at all levels of the nervous system and include the arteries, arterioles, capillaries, veins, and dural sinuses. These supply supratentorial, posterior fossa, spinal, and peripheral structures.
The petrous segment of the internal carotid artery enters the cranium via foramen lacerum. After entering the cranium, each internal carotid artery forms an S-shaped curve, the carotid siphon, and lies within the cavernous sinus. As the artery leaves the cavernous sinus, it pierces the cranial dura and arachnoid to enter the subarachnoid space at the base of the brain.
The indominate artery divides into the right common carotid and the right subclavian arteries. The left common carotid artery arises directly from the apex of the aortic arch. The right and left common carotid arteries ascend in the neck lateral to the trachea. slightly below the angle of the jaw, the common carotid artery bifurcates into the internal and external carotid arteries. The internal carotid artery on each side enters the skull, without branching, through the carotid canal located in the petrous portion of the temporal bone.
The origin of the left common carotid artery is different from that on the right, as there is no left brachiocephalic artery. The left common carotid artery arises directly from the aorta, sightly to the left of the midline. The left subclavian artery also arises directly from the aorta immediately lateral to the left common carotid artery.
The right and left common carotid artery bifurcates into the internal and external carotid arteries. The internal carotid artery enters the skull on each side without branching, through the carotid canal located in the petrous portion of the temporal bone. All of the arteries that supply the supratentorial and posterior fossa structures arise form the aortic arch.
The internal carotid artery enters the skull on each side without branching, through the carotid canal located in the petrous portion of the temporal bone. The external carotid arteries supply the facial region and anterior neck.
The right subclavian artery is one of the branches of the brachiocephalic artery. The brachiocephalic artery arises directly from the arch of the aorta. The left subclavian artery arises from the aortic arch just lateral to the origin of the left common carotid artery.
The vertebral arteries arise as the first branches of the right and left subclavian arteries. Each artery ascends through foramina in the transverse processes of the upper six cervical vertebrae and enters the subarachnoid space at the level of the upper cervical spinal cord. The vertebral arteries enter the cranial cavity through the foramen magnum. The two vertebral arteries are often of unequal caliber, one being dominant.
As the vertebral artery enters the posterior fossa of the cranial cavity via the foramen magnum, it lies on the ventral lateral aspect of the medulla.
By way of the posterior communicating arteries from the first part of the posterior cerebral vessels, the vertebral-basilar system has access to the carotid system.
The vertebral arteries enter the cranium and ascend on the ventrolateral surface of the medulla oblongata. At the lower border of the pons, they unite to form the basilar artery. Major branches form the basilar artery includes: anterior inferior cerebellar artery, superior cerebellar artery, and multiple median and paramedian perforators. At the level of the midbrain, the basilar artery divides into the right and left posterior cerebral arteries.
Blood leaves the head by way of veins that course over the cerebral hemispheres to converge into large channels, the venous sinuses, contained within the layers of the dura mater.
The major venous channels merge in the occipital region and form the transverse and sigmoid sinuses, which exit through the skull via the jugular foramen as the internal jugular veins.
Receptor Runoff
The cranial nerves for the face, head and neck are a separate system which transmit directly to the brain for interpretation and response. The
Stimuli from the external environment are constantly impinging on our body surface. These stimuli are sensed by specialized ending s of sensory neurons called receptors and are then transmitted by these neurons to the spinal cord, or, in the case of cranial nerves, to the brain for interpretation and response. Various kinds of stimuli are sensed by receptors of the skin, ranging from touch (tactile sensation) and temperature to pressure and pain. Some of these receptor types have been shown to be specialized for one or more specific kinds of stimuli. Neurologists discriminate between two types of somatic sensation; epicritic and protophathic
Receptors
Receptors are essentially transducers (a device that converts variations in a physical quantity, such as pressure or brightness into an electrical signal or vice versa); that is, they receive the energy of the stimulus in one form and transform that energy into another form. In the case of the majority of receptors in the skin, mechanical energy presses on, displaces, or deforms the receptor (mechanoreceptor), which converts the energy into an electrochemical event, resulting in a nerve impulse. Receptor: There are many kinds of receptors. The most common classification of receptors (proposed by Sherrington in 1906) organizes receptors according to their position of the body. "Exteroceptors" receive stimuli on the surface of the body: "proprioceptors" receive stimuli from muscles, tendons, and joints. and "interoceptors" receive stimuli from internal surfaces, such as walls of viscera and blood vessels. Exteroceptors are further classified by the kinds of stimuli to which they respond and the structure of the receptor.
The cranial nerves for the face, head and neck are a separate system which transmit directly to the brain for interpretation and response. The
Stimuli from the external environment are constantly impinging on our body surface. These stimuli are sensed by specialized ending s of sensory neurons called receptors and are then transmitted by these neurons to the spinal cord, or, in the case of cranial nerves, to the brain for interpretation and response. Various kinds of stimuli are sensed by receptors of the skin, ranging from touch (tactile sensation) and temperature to pressure and pain. Some of these receptor types have been shown to be specialized for one or more specific kinds of stimuli. Neurologists discriminate between two types of somatic sensation; epicritic and protophathic
Receptors
Receptors are essentially transducers (a device that converts variations in a physical quantity, such as pressure or brightness into an electrical signal or vice versa); that is, they receive the energy of the stimulus in one form and transform that energy into another form. In the case of the majority of receptors in the skin, mechanical energy presses on, displaces, or deforms the receptor (mechanoreceptor), which converts the energy into an electrochemical event, resulting in a nerve impulse. Receptor: There are many kinds of receptors. The most common classification of receptors (proposed by Sherrington in 1906) organizes receptors according to their position of the body. "Exteroceptors" receive stimuli on the surface of the body: "proprioceptors" receive stimuli from muscles, tendons, and joints. and "interoceptors" receive stimuli from internal surfaces, such as walls of viscera and blood vessels. Exteroceptors are further classified by the kinds of stimuli to which they respond and the structure of the receptor.
Auditory Runoff
physical dimension: wavelength
psychological dimension: pitch, which is a function of experience, culture and musical training
timber is a complex interaction of fundamental and overtone series that modulate one another harmonically to produce unique combinations of overtones
Behavior of sound waves in air is complex and involves pitch, timbral and echoic cues
rarefaction and condensation waves use sound emitted by an object to estimate departure and approach
doppler shifting is the physical correlate of these departing and approaching wavefronts
Structure of Sound Waves
Introduction to the Physics of Sound
neural transmission emerged in evolution as the range of frequencies represented in the cochlea expanded beyond the physical limits imposed by substrate-borne stimuli
Audiotory system in phylogeny
The ear has evolved several times and is adapted specifically for terrestrial and marine environments
A biological examination: bat echolocation embodies many of the principles common to mammals and certain unique properties
- PHYSICS OF SOUND
- sound waves
- the dB (decibel) is a logarithmic scale measurement of sound pressure level
- approximate scale values
- a whisper is about 30 dB
- loud conversation about 50 dB
- a jet taking off about 120 dB
- a howitzer (artillery) firing about 150 dB
- THE EAR GENERAL
- The Ear; outer ear, middle ear, inner ear (cochlea) where the first processing of sound occurs and where the sensory receptors are located.
- Sound conduction to the cochlea; the outer ear captures and funnels sound into the external auditory meatus, the middle ear functions as an impedance transformer that facilitates transmission of airborne sound into vibrations of the fluid in the cochlea.
- middle ear filled with air and acts as a cushion behind the tympanic membrane.
- proper function depends on air pressure in middle ear cavity being equal to the ambient pressure, the opening and closing of the eustachian tube
- incus, malleus and stapes are the smallest bones in the body that transduce sound
- the stapes performs like a piston line in and out motion that sets the fluid in the cochlea into motion
physical dimension: wavelength
psychological dimension: pitch, which is a function of experience, culture and musical training
timber is a complex interaction of fundamental and overtone series that modulate one another harmonically to produce unique combinations of overtones
Behavior of sound waves in air is complex and involves pitch, timbral and echoic cues
rarefaction and condensation waves use sound emitted by an object to estimate departure and approach
doppler shifting is the physical correlate of these departing and approaching wavefronts
Structure of Sound Waves
- physical dimension: amplitude
- psychological dimension: loudness, a subjective estimate influenced by ambient noise, expectations and experience
- the dB (decibel), a logarithmic scale, is a measure of sound pressure level
- approximate scaling values
- a whisper is about 30 dB
- loud conversation about 50 dB
- a jet taking off about 120 dB
- a howitzer (artilery) firing about 150 dB
Introduction to the Physics of Sound
neural transmission emerged in evolution as the range of frequencies represented in the cochlea expanded beyond the physical limits imposed by substrate-borne stimuli
Audiotory system in phylogeny
The ear has evolved several times and is adapted specifically for terrestrial and marine environments
- bone conduction and mechanico-hydraulic transduction are an early form of substrate-driven hearing that is useful at low frequencies
- neural transmission emerged in evolution as the range of frequencies represented in the cochlea expanded beyond the physical limits imposed by substrate-borne stimuli
A biological examination: bat echolocation embodies many of the principles common to mammals and certain unique properties
- basilar membrane specializations include mechanical adaptations and expansions representing the doppler shifted constant frequency portion of the spectrum
- central representations are massively hypertrophied, especially those devoted to the acoustic "fovea"
Brain Anatomy & Physiology
The Cerebral Cortex; Surface Topography of Cranial Nerves!
The Brain II
BRAIN III RUNOFF
Winer
Cerebral Cortex
Main Features of cortical organization
a. pyramidal cells are the main source of long-distance projections and of cortical output
1. they usually have a large cell body, a myelinated axon, and use glutamate, aspartate, or acetylcholine as a transmitter; about 75% of cortical neurons fit this description
b. stellate cells and other types of non-pyramidal cells (such as bipolar or basket cells) are the main source of local and intralaminar projections
1. they usually have a small cell body, an unmyelinated axon, and use GABA as a neurotransmitter
c. the spatial and temporal control of the excitability of cortical neurons is precise: the pyramidal cell as a model
1. the axon initial segment receives presynaptic inhibitory input from GABAergic chandelier cells
2. large axosomatic inhibitory terminals from GABAergic basket cells end near the spike-generating zone
3. the cell body is enveloped by a fine web of serotonergic endings of subcortical origin
4. the distal dendrites receive a misture of excitatory synaptic inputs on shafts and spines from the thalamus
5. the presence of Ca2+ signal amplificaiton regions at distal dendritic bifurcations may boost decremental spike informatio transfer; the most remote dendrites are richest in such bifurcations, and may be important in signal processing even if isolated electrically
Anatomy of the cerebral cortex: Specific connections have particular laminar targes
a. synaptic input is spatially segreagated onto postsynaptic cells; the laminar basis for connectional specificity
1. varieties of input to the dendrite arbors of a pyramidal cell
a. input from local circuits onto apical dendrites in layer I
b. non-specific thalamic input to dendritic segments in layer VI
c. specific thalamic input to dendritic segments in layer IV
Connections of the cerebral cortex
a. intrinsic connections within a lyer provide for local feedback and feedforward loops
1. local collaterals of pyramidal cell axons within layer V provide for intrinsic excitatory interactions
b. interlaminar connections between different layers
1. projections from layer VI cells to layer IV cells in visual cortex; a possible structural basis for end-stopped receptive fields
c. short ipsilateral corticocortical connections within an area may provide further local processing
1. focal corticocortical prjectoins connect area 17 whith itself: blob-to blob or interblob to interblob pathways
d. medium-lentgh corticocortical projectons link different areas within a modality
1. such connections link A1 with A2, S1 with S2 and area 17 with area 18
e. long corticocortical projections allow for interacions between different modalities
1. convergence of visual, auditory, and somatic sensory information in the superior temporal sulcus permits large-scale transfer of information across modalities and the comparison of results with expectations
f. commissural projections may interconnect homo- or heterotypic cortical regions
1. some cortcial areas (for example area A1) have rich commissural connections, others have not while still others have intermediate patterns
Summary of connections in the cortical layers
Martin 42
Cerebral Cortex Neurons Are Organized Into Layers
The dorsal column-medial lemniscal system projects to the cerebral cortex which is also the origin of the corticospinal tract. Its neurons are organized into layers. Lamination is a feature of all cortical regions, although different cortical regions characteristically contain different numbers of layers. Approximtely 95% of the cerebral cortex contains at least six cell layers; this cortex is commonly called neocortex because it dominates the cerebral cortex of phylogenetically higher vertebrates such as mammals. The remaining 5% of cortex, which is termed allocortex, is morphologically distinct. Allocortex is involved in olfaction and aspects of learning and memory.
Each region of neocortex that subserves a different function has its own microscopic anatomy: the thickness of the six principal cell layers varies, as does the density of neurons in each layer. Areas that subserve sensation have a thick layer IV. This is the layer in which axons from most thalamic sensory neurons synapse. In contrast, the primary motor cortex has a thin layer IV and a thick layer V. Layer V contains the neurons that project to the spinal cord, via the corticospinal tract. Association areas of the cerebral cortex, such as prefrontal and parietal-temporal-occiital association cortex, have a morphology that is intermediate between those of sensory cortex and motor cortex.
The Cerebral Cortex Has an Input-Output Organization
The cerebral neocortex, of which the somatic sensory cortical areas are part, has six principal cell layers. Thalamic neurons that project to the cortex send their axons primarily to layer IV. This is the input layer of cortex. There they synapse on dendrites of layer IV neurons, as well as neurons whose cell bodies are located in other layers, but they have dendrites in layer IV. Neurons in layer IV distribute this These incoming information to neurons in other layers. Layers II, III, V, and VI are the output layers of cortex. Pyramidal neurons in these layers project to other cortical areas as well as to subcortical structures. layer I does not contain many neurons in the mature brain, only dendrites of neurons located in deeper layers and elsewhere.
The cortex contains three kinds of efferent projections from the output layers, mediated by three separate classes of pyramidal neurons: corticocortical association, callosal, and descending projections. The efferent projection neurons with different targets are located in different cortical layers;
Corticocortical association neurons, located predominantly in layers II and III, project to cortical areas on the same side.
Callosal neurons are also located in layers II and III. they project their axons to the contralateral cortex via the corpus callosum
Descending projection neurons are separate classes of projection neurons whose axons descend to 1 the straiatum (the caudate nucleus and putamen) 2 the thalamus, 3 the brain stem or 4 the spinal cord. Descending projection neurons that terminate in the striatum brain stem, and spinal cord are found in layer V whereas thos projecting to the thalamus are located in layer VI
The Cytoarchitectonic Map of the Cerebral Cortex is the Basis for a Map of cortical function
Based primarily on differences in the thickness of cortical layers and on the sizes and shapes of neurons, the German anatomist Korbinian Brodmann identified over 50 divisions (now termed Brodmann's areas;) These divisions are based only on the neuronal architecture, or cytoarchitectrue, of he cortex, such as the size and shapes of neurons in the different laminae and their packing densities. It is remarkable that research on the functions of the cerebral cortex has shown that different functional areas of the cortex have a different cytoarchitecture. In humans, by noting the particular behavioral changes that follow discrete cortical lesions and using functional imaging approaches, such as positron emission tomography and functional MRI, we have gained some insight into the functions of most of the cytoarchitectonic divisions identified by Brodmann.
Winer
Cerebral Cortex
Main Features of cortical organization
a. pyramidal cells are the main source of long-distance projections and of cortical output
1. they usually have a large cell body, a myelinated axon, and use glutamate, aspartate, or acetylcholine as a transmitter; about 75% of cortical neurons fit this description
b. stellate cells and other types of non-pyramidal cells (such as bipolar or basket cells) are the main source of local and intralaminar projections
1. they usually have a small cell body, an unmyelinated axon, and use GABA as a neurotransmitter
c. the spatial and temporal control of the excitability of cortical neurons is precise: the pyramidal cell as a model
1. the axon initial segment receives presynaptic inhibitory input from GABAergic chandelier cells
2. large axosomatic inhibitory terminals from GABAergic basket cells end near the spike-generating zone
3. the cell body is enveloped by a fine web of serotonergic endings of subcortical origin
4. the distal dendrites receive a misture of excitatory synaptic inputs on shafts and spines from the thalamus
5. the presence of Ca2+ signal amplificaiton regions at distal dendritic bifurcations may boost decremental spike informatio transfer; the most remote dendrites are richest in such bifurcations, and may be important in signal processing even if isolated electrically
Anatomy of the cerebral cortex: Specific connections have particular laminar targes
a. synaptic input is spatially segreagated onto postsynaptic cells; the laminar basis for connectional specificity
1. varieties of input to the dendrite arbors of a pyramidal cell
a. input from local circuits onto apical dendrites in layer I
b. non-specific thalamic input to dendritic segments in layer VI
c. specific thalamic input to dendritic segments in layer IV
Connections of the cerebral cortex
a. intrinsic connections within a layer provide for local feedback and feedforward loops
1. local collaterals of pyramidal cell axons within layer V provide for intrinsic excitatory interactions
b. interlaminar connections between different layers
1. projections from layer VI cells to layer IV cells in visual cortex; a possible structural basis for end-stopped receptive fields
c. short ipsilateral corticocortical connections within an area may provide further local processing
1. focal corticocortical prjectoins connect area 17 whith itself: blob-to blob or interblob to interblob pathways
d. medium-lentgh corticocortical projectons link different areas within a modality
1. such connections link A1 with A2, S1 with S2 and area 17 with area 18
e. long corticocortical projections allow for interacions between different modalities
1. convergence of visual, auditory, and somatic sensory information in the superior temporal sulcus permits large-scale transfer of information across modalities and the comparison of results with expectations
f. commissural projections may interconnect homo- or heterotypic cortical regions
1. some cortcial areas (for example area A1) have rich commissural connections, others have not while still others have intermediate patterns
Summary of connections in the cortical layers
Martin 42
Cerebral Cortex Neurons Are Organized Into Layers
The dorsal column-medial lemniscal system projects to the cerebral cortex which is also the origin of the corticospinal tract. Its neurons are organized into layers. Lamination is a feature of all cortical regions, although different cortical regions characteristically contain different numbers of layers. Approximtely 95% of the cerebral cortex contains at least six cell layers; this cortex is commonly called neocortex because it dominates the cerebral cortex of phylogenetically higher vertebrates such as mammals. The remaining 5% of cortex, which is termed allocortex, is morphologically distinct. Allocortex is involved in olfaction and aspects of learning and memory.
Each region of neocortex that subserves a different function has its own microscopic anatomy: the thickness of the six principal cell layers varies, as does the density of neurons in each layer. Areas that subserve sensation have a thick layer IV. This is the layer in which axons from most thalamic sensory neurons synapse. In contrast, the primary motor cortex has a thin layer IV and a thick layer V. Layer V contains the neurons that project to the spinal cord, via the corticospinal tract. Association areas of the cerebral cortex, such as prefrontal and parietal-temporal-occiital association cortex, have a morphology that is intermediate between those of sensory cortex and motor cortex.
Winer
Cerebral Cortex
Main Features of cortical organization
a. pyramidal cells are the main source of long-distance projections and of cortical output
1. they usually have a large cell body, a myelinated axon, and use glutamate, aspartate, or acetylcholine as a transmitter; about 75% of cortical neurons fit this description
b. stellate cells and other types of non-pyramidal cells (such as bipolar or basket cells) are the main source of local and intralaminar projections
1. they usually have a small cell body, an unmyelinated axon, and use GABA as a neurotransmitter
c. the spatial and temporal control of the excitability of cortical neurons is precise: the pyramidal cell as a model
1. the axon initial segment receives presynaptic inhibitory input from GABAergic chandelier cells
2. large axosomatic inhibitory terminals from GABAergic basket cells end near the spike-generating zone
3. the cell body is enveloped by a fine web of serotonergic endings of subcortical origin
4. the distal dendrites receive a misture of excitatory synaptic inputs on shafts and spines from the thalamus
5. the presence of Ca2+ signal amplificaiton regions at distal dendritic bifurcations may boost decremental spike informatio transfer; the most remote dendrites are richest in such bifurcations, and may be important in signal processing even if isolated electrically
Anatomy of the cerebral cortex: Specific connections have particular laminar targes
a. synaptic input is spatially segreagated onto postsynaptic cells; the laminar basis for connectional specificity
1. varieties of input to the dendrite arbors of a pyramidal cell
a. input from local circuits onto apical dendrites in layer I
b. non-specific thalamic input to dendritic segments in layer VI
c. specific thalamic input to dendritic segments in layer IV
Connections of the cerebral cortex
a. intrinsic connections within a lyer provide for local feedback and feedforward loops
1. local collaterals of pyramidal cell axons within layer V provide for intrinsic excitatory interactions
b. interlaminar connections between different layers
1. projections from layer VI cells to layer IV cells in visual cortex; a possible structural basis for end-stopped receptive fields
c. short ipsilateral corticocortical connections within an area may provide further local processing
1. focal corticocortical prjectoins connect area 17 whith itself: blob-to blob or interblob to interblob pathways
d. medium-lentgh corticocortical projectons link different areas within a modality
1. such connections link A1 with A2, S1 with S2 and area 17 with area 18
e. long corticocortical projections allow for interacions between different modalities
1. convergence of visual, auditory, and somatic sensory information in the superior temporal sulcus permits large-scale transfer of information across modalities and the comparison of results with expectations
f. commissural projections may interconnect homo- or heterotypic cortical regions
1. some cortcial areas (for example area A1) have rich commissural connections, others have not while still others have intermediate patterns
Summary of connections in the cortical layers
Martin 42
Cerebral Cortex Neurons Are Organized Into Layers
The dorsal column-medial lemniscal system projects to the cerebral cortex which is also the origin of the corticospinal tract. Its neurons are organized into layers. Lamination is a feature of all cortical regions, although different cortical regions characteristically contain different numbers of layers. Approximtely 95% of the cerebral cortex contains at least six cell layers; this cortex is commonly called neocortex because it dominates the cerebral cortex of phylogenetically higher vertebrates such as mammals. The remaining 5% of cortex, which is termed allocortex, is morphologically distinct. Allocortex is involved in olfaction and aspects of learning and memory.
Each region of neocortex that subserves a different function has its own microscopic anatomy: the thickness of the six principal cell layers varies, as does the density of neurons in each layer. Areas that subserve sensation have a thick layer IV. This is the layer in which axons from most thalamic sensory neurons synapse. In contrast, the primary motor cortex has a thin layer IV and a thick layer V. Layer V contains the neurons that project to the spinal cord, via the corticospinal tract. Association areas of the cerebral cortex, such as prefrontal and parietal-temporal-occiital association cortex, have a morphology that is intermediate between those of sensory cortex and motor cortex.
The Cerebral Cortex Has an Input-Output Organization
The cerebral neocortex, of which the somatic sensory cortical areas are part, has six principal cell layers. Thalamic neurons that project to the cortex send their axons primarily to layer IV. This is the input layer of cortex. There they synapse on dendrites of layer IV neurons, as well as neurons whose cell bodies are located in other layers, but they have dendrites in layer IV. Neurons in layer IV distribute this These incoming information to neurons in other layers. Layers II, III, V, and VI are the output layers of cortex. Pyramidal neurons in these layers project to other cortical areas as well as to subcortical structures. layer I does not contain many neurons in the mature brain, only dendrites of neurons located in deeper layers and elsewhere.
The cortex contains three kinds of efferent projections from the output layers, mediated by three separate classes of pyramidal neurons: corticocortical association, callosal, and descending projections. The efferent projection neurons with different targets are located in different cortical layers;
Corticocortical association neurons, located predominantly in layers II and III, project to cortical areas on the same side.
Callosal neurons are also located in layers II and III. they project their axons to the contralateral cortex via the corpus callosum
Descending projection neurons are separate classes of projection neurons whose axons descend to 1 the straiatum (the caudate nucleus and putamen) 2 the thalamus, 3 the brain stem or 4 the spinal cord. Descending projection neurons that terminate in the striatum brain stem, and spinal cord are found in layer V whereas thos projecting to the thalamus are located in layer VI
The Cytoarchitectonic Map of the Cerebral Cortex is the Basis for a Map of cortical function
Based primarily on differences in the thickness of cortical layers and on the sizes and shapes of neurons, the German anatomist Korbinian Brodmann identified over 50 divisions (now termed Brodmann's areas;) These divisions are based only on the neuronal architecture, or cytoarchitectrue, of he cortex, such as the size and shapes of neurons in the different laminae and their packing densities. It is remarkable that research on the functions of the cerebral cortex has shown that different functional areas of the cortex have a different cytoarchitecture. In humans, by noting the particular behavioral changes that follow discrete cortical lesions and using functional imaging approaches, such as positron emission tomography and functional MRI, we have gained some insight into the functions of most of the cytoarchitectonic divisions identified by Brodmann.
Winer
Cerebral Cortex
Main Features of cortical organization
a. pyramidal cells are the main source of long-distance projections and of cortical output
1. they usually have a large cell body, a myelinated axon, and use glutamate, aspartate, or acetylcholine as a transmitter; about 75% of cortical neurons fit this description
b. stellate cells and other types of non-pyramidal cells (such as bipolar or basket cells) are the main source of local and intralaminar projections
1. they usually have a small cell body, an unmyelinated axon, and use GABA as a neurotransmitter
c. the spatial and temporal control of the excitability of cortical neurons is precise: the pyramidal cell as a model
1. the axon initial segment receives presynaptic inhibitory input from GABAergic chandelier cells
2. large axosomatic inhibitory terminals from GABAergic basket cells end near the spike-generating zone
3. the cell body is enveloped by a fine web of serotonergic endings of subcortical origin
4. the distal dendrites receive a misture of excitatory synaptic inputs on shafts and spines from the thalamus
5. the presence of Ca2+ signal amplificaiton regions at distal dendritic bifurcations may boost decremental spike informatio transfer; the most remote dendrites are richest in such bifurcations, and may be important in signal processing even if isolated electrically
Anatomy of the cerebral cortex: Specific connections have particular laminar targes
a. synaptic input is spatially segreagated onto postsynaptic cells; the laminar basis for connectional specificity
1. varieties of input to the dendrite arbors of a pyramidal cell
a. input from local circuits onto apical dendrites in layer I
b. non-specific thalamic input to dendritic segments in layer VI
c. specific thalamic input to dendritic segments in layer IV
Connections of the cerebral cortex
a. intrinsic connections within a layer provide for local feedback and feedforward loops
1. local collaterals of pyramidal cell axons within layer V provide for intrinsic excitatory interactions
b. interlaminar connections between different layers
1. projections from layer VI cells to layer IV cells in visual cortex; a possible structural basis for end-stopped receptive fields
c. short ipsilateral corticocortical connections within an area may provide further local processing
1. focal corticocortical prjectoins connect area 17 whith itself: blob-to blob or interblob to interblob pathways
d. medium-lentgh corticocortical projectons link different areas within a modality
1. such connections link A1 with A2, S1 with S2 and area 17 with area 18
e. long corticocortical projections allow for interacions between different modalities
1. convergence of visual, auditory, and somatic sensory information in the superior temporal sulcus permits large-scale transfer of information across modalities and the comparison of results with expectations
f. commissural projections may interconnect homo- or heterotypic cortical regions
1. some cortcial areas (for example area A1) have rich commissural connections, others have not while still others have intermediate patterns
Summary of connections in the cortical layers
Martin 42
Cerebral Cortex Neurons Are Organized Into Layers
The dorsal column-medial lemniscal system projects to the cerebral cortex which is also the origin of the corticospinal tract. Its neurons are organized into layers. Lamination is a feature of all cortical regions, although different cortical regions characteristically contain different numbers of layers. Approximtely 95% of the cerebral cortex contains at least six cell layers; this cortex is commonly called neocortex because it dominates the cerebral cortex of phylogenetically higher vertebrates such as mammals. The remaining 5% of cortex, which is termed allocortex, is morphologically distinct. Allocortex is involved in olfaction and aspects of learning and memory.
Each region of neocortex that subserves a different function has its own microscopic anatomy: the thickness of the six principal cell layers varies, as does the density of neurons in each layer. Areas that subserve sensation have a thick layer IV. This is the layer in which axons from most thalamic sensory neurons synapse. In contrast, the primary motor cortex has a thin layer IV and a thick layer V. Layer V contains the neurons that project to the spinal cord, via the corticospinal tract. Association areas of the cerebral cortex, such as prefrontal and parietal-temporal-occiital association cortex, have a morphology that is intermediate between those of sensory cortex and motor cortex.
BRAIN RUNOFF
*LH*
Meninges - Dura Mater, Blood Brain Barrier, shape
tentorium cerebelli - between cerebellum and inferior surface of cerebrum,
falx cerebelli - fold in dura forming a vertical partition between cerebellar hemispheres
falx cerebri - folds within the medial longitudinal fissure (MLF) separating the cerebral hemispheres
Pia Mater - Soft Mother; innermost layer of meninges, envelops brain tissue, carries blood vessels into the brain, sheaths cranial nerves passing through the outer meningeal layer
arachnoid villus - middle layer of meninges, spider-web like; follows contours of dura and does not tuck into crevices of brain
Cerebrum - Two Hemipsheres
Diencephalon; Thalamus, Hypothalamus
Cortex; 1/8" outer surface of cerebral hemispheres, grey matter composed of 75% of the nerve cell bodies in the nervous system
Sulcus - Grooves
Gyrus - outer part
Major cortical divisions - central sulcus, lateral sulcus, parieto occiptial sulcus
Fissures - Medial Longitudinal Fissure (MLF) - sylvian fissure
MLF - divides 2 cerebral hemispheres along the midline, corpus callosum is deep within the MLF has white nerve fibers that connects the 2 cerebral hemispheres together
Central Sulcus - Divides Frontal & Parietal Lobes; precentral gyrus is the motor cortex and Post central gyrus is the sensory cortex
Sylvian Fissure - separates frontal and parietal lobes from the temporal lobe
Parieto occipital fissure - not well defined on the lateral aspect of cerebral hemispheres, separates the parietal and occipital lobes
Lobes: Frontal, Parietal, Temporal, Occipital; Lateral View, Superior View
Frontal Lobe; reasoning, planning, speech (Broca's area), emotions, problems solving *Kandel tennis player making judgements*
Parietal Lobe; perception of sensory stimuli, post central gyrus, orientation, recognition
Temporal Lobe; perception and recognition of auditory stimuli, heschl's gyrus, memory, speech (Wernicke's Area)
Occipital Lobe; Visual Processing, Striate Cortex
The Homunculus - Cortical Distribution Motor and Sensory Cortex; functional distribution
Speech - Most people are hemispheric dominant for language (speech, writing and reading). 90% of people are left hemispheric dominant. non-dominant hemisphere specializes in non-verbal functions and controls emotion and interactive thinking
Broca's Area - initiation of speech, motor speech, located just above sylvian fissure and two convolutions anterior to the rolandic fissure. a lesion in this area results in motor aphasia; one knows what he intends to say but is unable to talk, verbalization is garbled
Wernicke's area: speech comprehension, located in the caudal aspect of the superior temporal gyrus, lesion results in receptive aphasia, one can hear words but cannot understand what is being said.
White Matter - Myelinated axons that connect areas between the cerebral hemispheres, nerve fibers carrying signals between nerve cells and other parts of the brain and body
tract - group of neuron fibers having a common origin and destination, name of tract indicates origin and termination of fibers, example; the corticospinal tract begins in the cortex and ends on ventral horn of spinal cord
collection of nerve fibers containing more than one tract; fasciculus, peduncle, lemniscus, funiculus
Commisures - collections of nerve fibers connecting similar areas on both sides of the head; anterior commissure, corpus callosum
Medial Brain Surface; cingulate gyrus, corpus callosum, thalamus, hypothalamus, pons cerebellum, medulla
Thalamus, relays sensory signals from the PNS to CNS, relays motor signals from CNS to PNS, 2 egg-shaped masses that lie alon the wall of the third ventricle
Hypothalamus controls - Behavior, coordinates growth and reproduction, body temperature, heart rate, sleep and wakefullness, arterial blood pressure, body weight, drinking and eating, visceral function, salivation and sweating, coordination of autonomic function, subconscious control of skeletal muscle
Cross section of the brain - corpus callosum, caudate nucleus, lateral ventricle, thalamus, 3rd ventricle, internal capsule, putamen, globus pallidus
Basal Ganglia - grey matter deep within white matter of cerebral hemispheres, relay motor impulses to the cerebrum, bridge between sensory and motor systems
Basal Ganglia structures; caudate nucleus, putamen, globus pallidus
Basal Ganglia function; balance, muscle tone, posture, locomotion
Internal Capsule; myelinated axon tracts lateral to the thalamus and medial to the basal ganglia, conducts impulses to and from the cortex
brainstem - midbrain, pons and medulla oblongata
*LH*
Meninges - Dura Mater, Blood Brain Barrier, shape
tentorium cerebelli - between cerebellum and inferior surface of cerebrum,
falx cerebelli - fold in dura forming a vertical partition between cerebellar hemispheres
falx cerebri - folds within the medial longitudinal fissure (MLF) separating the cerebral hemispheres
Pia Mater - Soft Mother; innermost layer of meninges, envelops brain tissue, carries blood vessels into the brain, sheaths cranial nerves passing through the outer meningeal layer
arachnoid villus - middle layer of meninges, spider-web like; follows contours of dura and does not tuck into crevices of brain
Cerebrum - Two Hemipsheres
Diencephalon; Thalamus, Hypothalamus
Cortex; 1/8" outer surface of cerebral hemispheres, grey matter composed of 75% of the nerve cell bodies in the nervous system
Sulcus - Grooves
Gyrus - outer part
Major cortical divisions - central sulcus, lateral sulcus, parieto occiptial sulcus
Fissures - Medial Longitudinal Fissure (MLF) - sylvian fissure
MLF - divides 2 cerebral hemispheres along the midline, corpus callosum is deep within the MLF has white nerve fibers that connects the 2 cerebral hemispheres together
Central Sulcus - Divides Frontal & Parietal Lobes; precentral gyrus is the motor cortex and Post central gyrus is the sensory cortex
Sylvian Fissure - separates frontal and parietal lobes from the temporal lobe
Parieto occipital fissure - not well defined on the lateral aspect of cerebral hemispheres, separates the parietal and occipital lobes
Lobes: Frontal, Parietal, Temporal, Occipital; Lateral View, Superior View
Frontal Lobe; reasoning, planning, speech (Broca's area), emotions, problems solving *Kandel tennis player making judgements*
Parietal Lobe; perception of sensory stimuli, post central gyrus, orientation, recognition
Temporal Lobe; perception and recognition of auditory stimuli, heschl's gyrus, memory, speech (Wernicke's Area)
Occipital Lobe; Visual Processing, Striate Cortex
The Homunculus - Cortical Distribution Motor and Sensory Cortex; functional distribution
Speech - Most people are hemispheric dominant for language (speech, writing and reading). 90% of people are left hemispheric dominant. non-dominant hemisphere specializes in non-verbal functions and controls emotion and interactive thinking
Broca's Area - initiation of speech, motor speech, located just above sylvian fissure and two convolutions anterior to the rolandic fissure. a lesion in this area results in motor aphasia; one knows what he intends to say but is unable to talk, verbalization is garbled
Wernicke's area: speech comprehension, located in the caudal aspect of the superior temporal gyrus, lesion results in receptive aphasia, one can hear words but cannot understand what is being said.
White Matter - Myelinated axons that connect areas between the cerebral hemispheres, nerve fibers carrying signals between nerve cells and other parts of the brain and body
tract - group of neuron fibers having a common origin and destination, name of tract indicates origin and termination of fibers, example; the corticospinal tract begins in the cortex and ends on ventral horn of spinal cord
collection of nerve fibers containing more than one tract; fasciculus, peduncle, lemniscus, funiculus
Commisures - collections of nerve fibers connecting similar areas on both sides of the head; anterior commissure, corpus callosum
Medial Brain Surface; cingulate gyrus, corpus callosum, thalamus, hypothalamus, pons cerebellum, medulla
Thalamus, relays sensory signals from the PNS to CNS, relays motor signals from CNS to PNS, 2 egg-shaped masses that lie alon the wall of the third ventricle
Hypothalamus controls - Behavior, coordinates growth and reproduction, body temperature, heart rate, sleep and wakefullness, arterial blood pressure, body weight, drinking and eating, visceral function, salivation and sweating, coordination of autonomic function, subconscious control of skeletal muscle
Cross section of the brain - corpus callosum, caudate nucleus, lateral ventricle, thalamus, 3rd ventricle, internal capsule, putamen, globus pallidus
Basal Ganglia - grey matter deep within white matter of cerebral hemispheres, relay motor impulses to the cerebrum, bridge between sensory and motor systems
Basal Ganglia structures; caudate nucleus, putamen, globus pallidus
Basal Ganglia function; balance, muscle tone, posture, locomotion
Internal Capsule; myelinated axon tracts lateral to the thalamus and medial to the basal ganglia, conducts impulses to and from the cortex
brainstem - midbrain, pons and medulla oblongata
THE BRAIN RUNOFF
Structures involved in linguistic processing
Broca's motor speech area (45) lies just inferior to the premotor cortex, adjoining the primary motor cortex. Wernicke's receptive speech area (22) adjoins the primary auditory cortex, arcuate fasciculus axons interconnecting Broca's and Wernicke's area provide for ipsilateral corticocortical communication.
Syndromes:
Wernicke's aphasia, damage to parietotemporal association cortex, cardinal systems are disturbances in understanding and naming.
Broca's aphasia, damage to motor association cortex of caudolateral part of frontal lobes; cardinal symptoms include poverty of speech with normal understanding. Word blindness; alexia, the complete loss of reading ability. Apraxias, disorders in comprehension of motor commands associated with learned movement.
The Cerebral Cortex is the "highest" part of the brain. It is responsible for perception, organizing complex and fine motor activities, planning and decision making and learning and memory.
The Cerebral Cortex is highly interconnected neural tissue. Synchronization of neural activity is characteristic of normal brain function, which underlies EEG waves.
The cerebral cortex contains many different areas which have been distinguished on the bases of their cell types, number and configuration of layers, afferent, efferent and corticocortical connections; physiological organization and function. Here is a very brief tutorial that may be useful in thinking about cortex.
Main features of cortical organization; pyramidal cells are the main source of long-distance projections and of cortical output. The spatial and temporal control of the excitability of cortical neurons is precise. Specific connections have specific laminar targets. Connections of the cerebral cortex, intrinsic connections within a layer provide for local feedback and feed-forward loops.
Gross Cortical Anatomy 324-327; figs 17-3,4,5
Cellular Cortical Anatomy 327-333; figs 17-5,6,7,8,9,10,12
Structures involved in linguistic processing
Broca's motor speech area (45) lies just inferior to the premotor cortex, adjoining the primary motor cortex. Wernicke's receptive speech area (22) adjoins the primary auditory cortex, arcuate fasciculus axons interconnecting Broca's and Wernicke's area provide for ipsilateral corticocortical communication.
Syndromes:
Wernicke's aphasia, damage to parietotemporal association cortex, cardinal systems are disturbances in understanding and naming.
Broca's aphasia, damage to motor association cortex of caudolateral part of frontal lobes; cardinal symptoms include poverty of speech with normal understanding. Word blindness; alexia, the complete loss of reading ability. Apraxias, disorders in comprehension of motor commands associated with learned movement.
The Cerebral Cortex is the "highest" part of the brain. It is responsible for perception, organizing complex and fine motor activities, planning and decision making and learning and memory.
The Cerebral Cortex is highly interconnected neural tissue. Synchronization of neural activity is characteristic of normal brain function, which underlies EEG waves.
The cerebral cortex contains many different areas which have been distinguished on the bases of their cell types, number and configuration of layers, afferent, efferent and corticocortical connections; physiological organization and function. Here is a very brief tutorial that may be useful in thinking about cortex.
Main features of cortical organization; pyramidal cells are the main source of long-distance projections and of cortical output. The spatial and temporal control of the excitability of cortical neurons is precise. Specific connections have specific laminar targets. Connections of the cerebral cortex, intrinsic connections within a layer provide for local feedback and feed-forward loops.
Gross Cortical Anatomy 324-327; figs 17-3,4,5
- 4 lobes named by bones; Frontal, Temporal, Parietal, Occipital
- gyri (circles) and sulci (furrows, ditches)
- grey matter (56% of cortical volume) & white matter (44% of cortical volume)
- primary motor areas, primary sensory areas and association areas
Cellular Cortical Anatomy 327-333; figs 17-5,6,7,8,9,10,12
- 6 layers of cortex
- molecular layer (dendrites)
- external granule cell layer
- external pyramidal cell layer
- internal granule cell layer - connections from the thalamus
- internal pyramidal cell layer
- polymorphic layer
- Two major cell types
- projection neurons; II, V, VI, glutamate
- Interneurons; all layers, GABA
- subcortical nuclei; 331-333 fig 17-2
Physiology of Spinothalamic Neurons
Nerve Physiology RUNOFF
There are strategies for the relief of intractable pain; reducing ganglion cell output with subdural anesthetic injections. Anterolateral cordotomy to interrupt spinothalamic lemniscal axons ascending toward the brain stem. Medullary tractomy to sever trigeminothalamic lemniscal fibers in cases of trigeminal neuralgia. Direct electrical stimulation of spinothalamic areas in the dorsal horn with implanted electrodes. Comparison of the dorsal column and spinothalamic systems. These pathways carry different types of neural information.
Knowing the location and function of the structural components of the nervous system permits localization of the site of a lesion.
Although myelin is relatively inert metabolically, it has a significant turnover and responds to various dis-ease states. For instance, myelin may be lost (demyelination) in certain immunologic disorders.
There are strategies for the relief of intractable pain; reducing ganglion cell output with subdural anesthetic injections. Anterolateral cordotomy to interrupt spinothalamic lemniscal axons ascending toward the brain stem. Medullary tractomy to sever trigeminothalamic lemniscal fibers in cases of trigeminal neuralgia. Direct electrical stimulation of spinothalamic areas in the dorsal horn with implanted electrodes. Comparison of the dorsal column and spinothalamic systems. These pathways carry different types of neural information.
Knowing the location and function of the structural components of the nervous system permits localization of the site of a lesion.
Although myelin is relatively inert metabolically, it has a significant turnover and responds to various dis-ease states. For instance, myelin may be lost (demyelination) in certain immunologic disorders.
Receptor/Receptive Field Runoff
Physiology of the Dorsal Column System
Receptive fields: definition
1. center-surround organization reflects neural integration
2. role of inhibition in the construction and modulation of receptive fields
3. input from peripheral nerves defines the dermatome; the dermatome is made up of many receptive fields
4. dermatomal organization is analagous to the cortical and spinal representation of muscle
5. parallels in receptive field organization in the visual and auditory systems
Parallel processing of touch, pressure, vibration, and joint sensibility
1. the somatic sensory cortex contains representation of the body surface
a. superimposed on these maps is a second layer of organization, in which alternating cortical columns contain neurons tuned preferentially to slowly or rapidly adapting mechanoreceptor populations; this means that a specific cortical column (and a particular neuron) specifies
1. modality
2. body surface position
3. speed of adaptation
Multiple maps of the body surface in the dorsal column nuclei, sensory thalamus and somatic sensory cortex are the physiological manifestation of parallel pathways
Why are there so many sensory and motor maps in the brain?
1. the maps are not redundant or functionally duplicative
2. the maps are co-participants in serial processing, such as the projection of S1 to S2
Summary
Somatic Sensory Pathways
There are two major somatic sensory pathways; the dorsal column-medial lemniscal system, which mediates touch and limb position sense, and the anterolateral system which mediates pain, temperature, and itch senses and crude touch. These systems differe in four major ways
1 modality sensitivity of input from dorsal root ganglion neurons
2 location of first relay site
3 level of decussation and
4 functional and anatomical homogeneity of the pathway.
Dorsal root ganglion neruons are pseudounipolar neurons. They receive somatic sensory information and transmit it from the periphery to the spinal cord. This distal terminal of dorsal root ganglion neurons is the sensory receptor.
Neurons sensitive to noxious and thermal stimuli or histamine have bare nerve endings and small-diameter axons.Those sensitive to mechanical stimuli have encapsulated ending s and large-diameter axons. Four major mechanorecepotors innervate glabrous skin and subcutaneous tissue. Meissner's corpuscles, pacinian corpuscles, Merkel's receptors, and Ruffini's corpuscles. The muscle spindle is the key receptor for muscle sretch and the Golgi tendon organ, for force
Inputs from thalamus arrive at layer IV of the cortex. Efferent projections from the somatic sensory cortical areas arise from specific cortical layers. Corticocortical association connections (with other cortical areas on the same side of the cerebral cortex) are made by neurons in layers II and III. Callosal connections (with the other side of the cerebral cortex are also made by neurons in layers II and III.) Descending projections to the striatum, brain stem, and spinal cord originate from neurons located in layer V, whereas the projection to the thalamus originates from neurons located in layer VI.
Physiology of the Dorsal Column System
Receptive fields: definition
1. center-surround organization reflects neural integration
2. role of inhibition in the construction and modulation of receptive fields
3. input from peripheral nerves defines the dermatome; the dermatome is made up of many receptive fields
4. dermatomal organization is analagous to the cortical and spinal representation of muscle
5. parallels in receptive field organization in the visual and auditory systems
Parallel processing of touch, pressure, vibration, and joint sensibility
1. the somatic sensory cortex contains representation of the body surface
a. superimposed on these maps is a second layer of organization, in which alternating cortical columns contain neurons tuned preferentially to slowly or rapidly adapting mechanoreceptor populations; this means that a specific cortical column (and a particular neuron) specifies
1. modality
2. body surface position
3. speed of adaptation
Multiple maps of the body surface in the dorsal column nuclei, sensory thalamus and somatic sensory cortex are the physiological manifestation of parallel pathways
Why are there so many sensory and motor maps in the brain?
1. the maps are not redundant or functionally duplicative
2. the maps are co-participants in serial processing, such as the projection of S1 to S2
Summary
Somatic Sensory Pathways
There are two major somatic sensory pathways; the dorsal column-medial lemniscal system, which mediates touch and limb position sense, and the anterolateral system which mediates pain, temperature, and itch senses and crude touch. These systems differe in four major ways
1 modality sensitivity of input from dorsal root ganglion neurons
2 location of first relay site
3 level of decussation and
4 functional and anatomical homogeneity of the pathway.
Dorsal root ganglion neruons are pseudounipolar neurons. They receive somatic sensory information and transmit it from the periphery to the spinal cord. This distal terminal of dorsal root ganglion neurons is the sensory receptor.
Neurons sensitive to noxious and thermal stimuli or histamine have bare nerve endings and small-diameter axons.Those sensitive to mechanical stimuli have encapsulated ending s and large-diameter axons. Four major mechanorecepotors innervate glabrous skin and subcutaneous tissue. Meissner's corpuscles, pacinian corpuscles, Merkel's receptors, and Ruffini's corpuscles. The muscle spindle is the key receptor for muscle sretch and the Golgi tendon organ, for force
Inputs from thalamus arrive at layer IV of the cortex. Efferent projections from the somatic sensory cortical areas arise from specific cortical layers. Corticocortical association connections (with other cortical areas on the same side of the cerebral cortex) are made by neurons in layers II and III. Callosal connections (with the other side of the cerebral cortex are also made by neurons in layers II and III.) Descending projections to the striatum, brain stem, and spinal cord originate from neurons located in layer V, whereas the projection to the thalamus originates from neurons located in layer VI.
Anterolateral runoff II
Each receptor is selectively activated by a distinct type and degree of stimulus (spatial and qualitative) and able to compute a barrage of daily characteristically complex somatic stimuli. Populations of nerve endings are the principal receptors. Free/Bare nerve endings are the principal receptors that initiate the spectrum of pain sensation, detecting a squeeze, pinch or puncture of the skin. Spectral classes of thermal receptors relay a spectrum of temperature (cold, cool, warm, and hot) sensation. Their impulses are conducted via fibers to the primary neurons of the spiral root/dorsal root ganglion. from both thin myelinated and unmyelinated fibers, bare, free nerve endings
Dorsal root ganglion activation (primary/first neurons) enters impulses to the spinal cord. dorsal root ganglion cell - the receptors for each modality have distinct morphological and molecular specializations that allow them to sense specific types of stimuli.Inputs to Lissauer tract in superficial part of the dorsal horn and yes it has somatotopic organization, at the ventrolateral quadrant of the spinal cord contralateral to the side of entry from decussation. Ascends one level after entering lissauers fasciculus before entering the posterior horn to synapse with secondary neuronsand then Decussates immediately at the level of the spinal cord first synapse.
There are numerous pools of secondary neurons (interneurons) in the posterior horn, just as there are numerous areas of terminations in the thalamus. For example, secondary neurons associated with the lateral spinaothalamic tract are found primarily in laminae I, IV, V and VII of the spinal cord and project to the ventral posterior lateral nucleus of the thalamus; neurons in the intermediate zone project to the intalaminar nuclei of the thalamus. axons cross through the ventral white commissure and then ascend contralaterally from the side of input. Tract has somatotopic organization in the spinal cord. sacral dermatomes represented dorsolaterally and the cervical dermatomes ventromedially. spinothalamic tract ascends in the lateral portion of the brain stem.
In the medulla it is dorsal to the lateral aspect of the inferior olivary nucleus and in the pons and mid brain, it is lateral to the medial lemniscus. At the mesodiencephalic junction, the spinothalmic tract and medial leminscus join. spinothalamic tract maintains a somatotopic organization throughout it's course. axons synapse on third-order/tertiary neurons in several thalamic nuclei particularly the ventral posteriolateral nuclues that in turn projects to primary somatosensory corex in the post-central gyrus. immediately in the grey matter and ascends to second synapse at the ventral lateral posterior nucleus of thalamus.
As the spinothalamic tract ascends, it migrates from a lateral position (lower medulla) to a posterolateral position (upper medulla). In the midbrain of the , the tract lies adjacent to the medial lemniscus. The axons of the secondary neurons terminate in one of a number of centers in the thalamus, including the ventral posterior lateral nucleus, the posterior region adjacent to the medial geniculate body and the intralaminar nuclei. Pain impulses ascending through the reticular formation reach the PO and intralaminar nuclei of the thalamus.
Third synapse in non-specific or interlaminar thalamic nuclei, (indirect targets are the central gray, reticular formation and hypothalamic centers. Interlaminar thalamic nuclei can activate large expanses of sensory and motor cortex. The central gray participates in the descending control of nociception The reticular formation helps to direct attention and vigilance. The hypothalamus is a source of preganglionic parasympathetic synaptic drive for the autonomic nervous system. Fourth synapse the cerebral cortex where the representation of nociception is surprisingly diffuse.) arriving at cortex where all information is combined into a unified somatic precept. Axons of tertiary neurons project through the internal capsule and corona radiate to the postcentral gyrus of the cerebral cortex, with the exception of axons from the thalamic PO region, which project to the secondary sensory cortex within the lateral fissure.
mediate nociceptive and thermal sensation and deliver them to the brain through nerve fibers that ascend to the spinal cord.
Each receptor is selectively activated by a distinct type and degree of stimulus (spatial and qualitative) and able to compute a barrage of daily characteristically complex somatic stimuli. Populations of nerve endings are the principal receptors. Free/Bare nerve endings are the principal receptors that initiate the spectrum of pain sensation, detecting a squeeze, pinch or puncture of the skin. Spectral classes of thermal receptors relay a spectrum of temperature (cold, cool, warm, and hot) sensation. Their impulses are conducted via fibers to the primary neurons of the spiral root/dorsal root ganglion. from both thin myelinated and unmyelinated fibers, bare, free nerve endings
Dorsal root ganglion activation (primary/first neurons) enters impulses to the spinal cord. dorsal root ganglion cell - the receptors for each modality have distinct morphological and molecular specializations that allow them to sense specific types of stimuli.Inputs to Lissauer tract in superficial part of the dorsal horn and yes it has somatotopic organization, at the ventrolateral quadrant of the spinal cord contralateral to the side of entry from decussation. Ascends one level after entering lissauers fasciculus before entering the posterior horn to synapse with secondary neuronsand then Decussates immediately at the level of the spinal cord first synapse.
There are numerous pools of secondary neurons (interneurons) in the posterior horn, just as there are numerous areas of terminations in the thalamus. For example, secondary neurons associated with the lateral spinaothalamic tract are found primarily in laminae I, IV, V and VII of the spinal cord and project to the ventral posterior lateral nucleus of the thalamus; neurons in the intermediate zone project to the intalaminar nuclei of the thalamus. axons cross through the ventral white commissure and then ascend contralaterally from the side of input. Tract has somatotopic organization in the spinal cord. sacral dermatomes represented dorsolaterally and the cervical dermatomes ventromedially. spinothalamic tract ascends in the lateral portion of the brain stem.
In the medulla it is dorsal to the lateral aspect of the inferior olivary nucleus and in the pons and mid brain, it is lateral to the medial lemniscus. At the mesodiencephalic junction, the spinothalmic tract and medial leminscus join. spinothalamic tract maintains a somatotopic organization throughout it's course. axons synapse on third-order/tertiary neurons in several thalamic nuclei particularly the ventral posteriolateral nuclues that in turn projects to primary somatosensory corex in the post-central gyrus. immediately in the grey matter and ascends to second synapse at the ventral lateral posterior nucleus of thalamus.
As the spinothalamic tract ascends, it migrates from a lateral position (lower medulla) to a posterolateral position (upper medulla). In the midbrain of the , the tract lies adjacent to the medial lemniscus. The axons of the secondary neurons terminate in one of a number of centers in the thalamus, including the ventral posterior lateral nucleus, the posterior region adjacent to the medial geniculate body and the intralaminar nuclei. Pain impulses ascending through the reticular formation reach the PO and intralaminar nuclei of the thalamus.
Third synapse in non-specific or interlaminar thalamic nuclei, (indirect targets are the central gray, reticular formation and hypothalamic centers. Interlaminar thalamic nuclei can activate large expanses of sensory and motor cortex. The central gray participates in the descending control of nociception The reticular formation helps to direct attention and vigilance. The hypothalamus is a source of preganglionic parasympathetic synaptic drive for the autonomic nervous system. Fourth synapse the cerebral cortex where the representation of nociception is surprisingly diffuse.) arriving at cortex where all information is combined into a unified somatic precept. Axons of tertiary neurons project through the internal capsule and corona radiate to the postcentral gyrus of the cerebral cortex, with the exception of axons from the thalamic PO region, which project to the secondary sensory cortex within the lateral fissure.
mediate nociceptive and thermal sensation and deliver them to the brain through nerve fibers that ascend to the spinal cord.
Anterolateral Spinothalamic System Runoff
--------
DIAMOND
*The different components of the spinothalamic tract include 1a direct pathway, the neospinothalamic pathway, which mediates the discriminative aspect of pain and temperature and is important for localization and 2 several indirect pathways for the affective-arousal components of pain; they form part of the core, or inner tube, of the neuraxis.
whose pathways are associated for pain and temperature; thermal, visceral and simple tactile info
, contrasted with epicritic which is fine sensation,
The sense of temperature is mediated by the bare endings of thinly myelinated or unmyelinated nerves sensitive to specific ranges of thermal energy. Separate classes of thermal receptors sense temperatures that are perceived as cold, cool, warm, and hot, as they differe in their peak sensitivities and temperature ranges. Painful sensations are mediated by free nerve endings, called nociceptors, that sense destructive mechanical stimuli that squeeze, pinch, or puncture the skin; extremely hot or cold temperatures that might burn or freeze the skin; or chemical substances released from cells as a result of tissue damage.
The lateral spinothalamic tract carries sensations of pain and temperature from receptors throughout the body (except the face) to the brain. Both of these sensations are modified (as are others) by our emotional state and altered by our cultural surroundings, a fact exemplified by the soldier who, though suffering a traumatic wound, feels no pain and the yogi who reposing in quiet mediations lies on the points of a thousand nails. Different organs exhibit varying degrees of pain: A passing stone in the bile duct or ureter can bring excruciating pain, whereas an intravenous injection with a needle brings little discomfort.
It should be noted that the distinction between the lateral and anterior spinothalamic tracts is now thought to have little anatomical significance. Although the pathways are separated here we alert you to the fact that this separation is no longer so clearly defined.
thalamus; three major thalamic regions receive input from these pathways for various aspects of somatic sensation; the ventral posterior nucleus (has a lateral division), the ventromedial posterior nucleus and the medial dorsal nucleus.
The anterolateral tract consists of three ascending pathways; the spinothalamic, spinoreticular and spinomesencephalic. The spinothalamic tract conveys information about painful and thermal stimuli directly to the ventral posterior lateral nucleus of the thalamus. Axons in the spinoreticular tract synapse on neurons in the reticular formation of the medulla and pons, which then relay information to the intralaminar and posterior nuclei of the thalamus and to other structures in the diencephalon, such as the hypothalamus.
Free nerve endings are now thought to be the principal receptors for both pain and temperature. The related impulses are conducted to the cell bodies of the primary neurons in the spinal ganglion along thin, myelinated and unmyelinated peripheral processes. The short central processes of the primary neurons enter Lissauer's fasciculus and ascend at least one segment before entering the posterior horn to synapse with the secondary neurons. Some fibers ascend ipsilaterally within Lissauer's fasciculus and reach the thalamus.
*The direct tract consists of second-order axons from both nociceptive-specific and wide dynamic range neurons. The axons cross through the ventral white commissure and ascend strictly contralaterally in the anterolateral quadrant of the spinal cord. The tract has a somatotopic organization in the spinal cord, with the sacral dermatomes represented dorsolaterally and the cervical dermatomes ventromedially. The spinothalamic tract ascends in the lateral portion of the brainstem. in the medulla, it is dorsal to the lateral aspect of the inferior olivary nucleus, and in the pons and midbrain, it is lateral to the medial lemniscus. At the mesodiencephalic unction, the spinothalamic tract and medial lemniscus join. Throughout its course, the spinothalamic tract maintains a somatotopic organization. The spinothalamic tract axons synapse on third-order neurons in several thalamic nuclei, particularly the ventral posterolateral nucleus that, in turn, projects to the primary sensory cortex in the post-central gyrus.
Pain and temperature sense are conveyed by thinly myelinated and unmyelinated nerves that terminate in the most superficial layers of the spinal or trigeminal dorsal horn. These modalities are conveyed directly, and through multisynaptic networks, to the thalamus through the contralateral anterolateral pathway.
The dorsal column-medial lemniscal and anterolateral systems each receive input from different functional classes of dorsal root ganglion neurons, the primary somatic sensory receptor neuron. This is why the two systems have such different functions. The anterolateral system's first relay is in the dorsal horn of the spinal cord. Anterolateral system decussates in the spinal cord.
The anterolateral system ascends along its ventrolateral margin. (For the spinothalamic and spinomesencephalic tracts) the medulla and pons simply serve as a conduit through which axons pass to reach more rostral locations. (For the spinoreticular tract the axons terminate in the reticular formation of the pons and medulla.)
The four modalities are conveyed in separate ascending pathways to the thalamus and cerebral cortex. Touch and proprioception are transmitted by large diameter axons with fast conduction velocities to the dorsal horn of the spinal cord and then to the brain stem and thalamus through the dorsal-column medial lemniscal system.
The axons of the secondary neurons cross the midline in the anterior white commissure and ascend as the lateral spinothalamic tract in the anterior part of the lateral funiculus. Fibers relating to the lower body are located in the lateral part of the tract (peripheral fibers) while those relating to the upper body are added successively to the medial part of the tract (medial fibers) This laminated axon pattern is important to the surgeon in the even that spinothalamic fibers in the cord need to be selectively severed to control severe pain in one part of the body. As these medial and lateral fiber bundles ascend, many give off branches, particularly to the reticular formation of the brain stem and the periaqueductal gray of the midbrain. It is possible that sharp, well-localized pain is conducted via the slower ascending fibers in the reticular formation. The collaterals from the spinothalamic tract to the reticular formation and periaqueductal gray are in a position to activate the pain inhibitory system and thus start an intrinsic pain-suppression mechanism.
The somatic sensory stimuli that we encounter in every day life are complex, cover large areas of skin, and have many characteristics. Each type of receptor is selectively activated by distinct spatial and qualitative properties of a stimulus. Different types of information about an object are transmitted by populations of different types of sensory neurons, and conveyed in parallel pathways to the primary somatosensory cortex, where all the information is combined into a unified somatic precept.
--------
DIAMOND
*The different components of the spinothalamic tract include 1a direct pathway, the neospinothalamic pathway, which mediates the discriminative aspect of pain and temperature and is important for localization and 2 several indirect pathways for the affective-arousal components of pain; they form part of the core, or inner tube, of the neuraxis.
whose pathways are associated for pain and temperature; thermal, visceral and simple tactile info
, contrasted with epicritic which is fine sensation,
The sense of temperature is mediated by the bare endings of thinly myelinated or unmyelinated nerves sensitive to specific ranges of thermal energy. Separate classes of thermal receptors sense temperatures that are perceived as cold, cool, warm, and hot, as they differe in their peak sensitivities and temperature ranges. Painful sensations are mediated by free nerve endings, called nociceptors, that sense destructive mechanical stimuli that squeeze, pinch, or puncture the skin; extremely hot or cold temperatures that might burn or freeze the skin; or chemical substances released from cells as a result of tissue damage.
The lateral spinothalamic tract carries sensations of pain and temperature from receptors throughout the body (except the face) to the brain. Both of these sensations are modified (as are others) by our emotional state and altered by our cultural surroundings, a fact exemplified by the soldier who, though suffering a traumatic wound, feels no pain and the yogi who reposing in quiet mediations lies on the points of a thousand nails. Different organs exhibit varying degrees of pain: A passing stone in the bile duct or ureter can bring excruciating pain, whereas an intravenous injection with a needle brings little discomfort.
It should be noted that the distinction between the lateral and anterior spinothalamic tracts is now thought to have little anatomical significance. Although the pathways are separated here we alert you to the fact that this separation is no longer so clearly defined.
thalamus; three major thalamic regions receive input from these pathways for various aspects of somatic sensation; the ventral posterior nucleus (has a lateral division), the ventromedial posterior nucleus and the medial dorsal nucleus.
The anterolateral tract consists of three ascending pathways; the spinothalamic, spinoreticular and spinomesencephalic. The spinothalamic tract conveys information about painful and thermal stimuli directly to the ventral posterior lateral nucleus of the thalamus. Axons in the spinoreticular tract synapse on neurons in the reticular formation of the medulla and pons, which then relay information to the intralaminar and posterior nuclei of the thalamus and to other structures in the diencephalon, such as the hypothalamus.
Free nerve endings are now thought to be the principal receptors for both pain and temperature. The related impulses are conducted to the cell bodies of the primary neurons in the spinal ganglion along thin, myelinated and unmyelinated peripheral processes. The short central processes of the primary neurons enter Lissauer's fasciculus and ascend at least one segment before entering the posterior horn to synapse with the secondary neurons. Some fibers ascend ipsilaterally within Lissauer's fasciculus and reach the thalamus.
*The direct tract consists of second-order axons from both nociceptive-specific and wide dynamic range neurons. The axons cross through the ventral white commissure and ascend strictly contralaterally in the anterolateral quadrant of the spinal cord. The tract has a somatotopic organization in the spinal cord, with the sacral dermatomes represented dorsolaterally and the cervical dermatomes ventromedially. The spinothalamic tract ascends in the lateral portion of the brainstem. in the medulla, it is dorsal to the lateral aspect of the inferior olivary nucleus, and in the pons and midbrain, it is lateral to the medial lemniscus. At the mesodiencephalic unction, the spinothalamic tract and medial lemniscus join. Throughout its course, the spinothalamic tract maintains a somatotopic organization. The spinothalamic tract axons synapse on third-order neurons in several thalamic nuclei, particularly the ventral posterolateral nucleus that, in turn, projects to the primary sensory cortex in the post-central gyrus.
Pain and temperature sense are conveyed by thinly myelinated and unmyelinated nerves that terminate in the most superficial layers of the spinal or trigeminal dorsal horn. These modalities are conveyed directly, and through multisynaptic networks, to the thalamus through the contralateral anterolateral pathway.
The dorsal column-medial lemniscal and anterolateral systems each receive input from different functional classes of dorsal root ganglion neurons, the primary somatic sensory receptor neuron. This is why the two systems have such different functions. The anterolateral system's first relay is in the dorsal horn of the spinal cord. Anterolateral system decussates in the spinal cord.
The anterolateral system ascends along its ventrolateral margin. (For the spinothalamic and spinomesencephalic tracts) the medulla and pons simply serve as a conduit through which axons pass to reach more rostral locations. (For the spinoreticular tract the axons terminate in the reticular formation of the pons and medulla.)
The four modalities are conveyed in separate ascending pathways to the thalamus and cerebral cortex. Touch and proprioception are transmitted by large diameter axons with fast conduction velocities to the dorsal horn of the spinal cord and then to the brain stem and thalamus through the dorsal-column medial lemniscal system.
The axons of the secondary neurons cross the midline in the anterior white commissure and ascend as the lateral spinothalamic tract in the anterior part of the lateral funiculus. Fibers relating to the lower body are located in the lateral part of the tract (peripheral fibers) while those relating to the upper body are added successively to the medial part of the tract (medial fibers) This laminated axon pattern is important to the surgeon in the even that spinothalamic fibers in the cord need to be selectively severed to control severe pain in one part of the body. As these medial and lateral fiber bundles ascend, many give off branches, particularly to the reticular formation of the brain stem and the periaqueductal gray of the midbrain. It is possible that sharp, well-localized pain is conducted via the slower ascending fibers in the reticular formation. The collaterals from the spinothalamic tract to the reticular formation and periaqueductal gray are in a position to activate the pain inhibitory system and thus start an intrinsic pain-suppression mechanism.
The somatic sensory stimuli that we encounter in every day life are complex, cover large areas of skin, and have many characteristics. Each type of receptor is selectively activated by distinct spatial and qualitative properties of a stimulus. Different types of information about an object are transmitted by populations of different types of sensory neurons, and conveyed in parallel pathways to the primary somatosensory cortex, where all the information is combined into a unified somatic precept.
Anterolateral System Runoff
THALAMUS
Martin 125
Three Separate Nuclei in the Thalamus Process Somatic Sensory Information
The thalamus is a nodal (point in a network at which lines or pathways intersect or branch) point for the transmission of sensory information to the cerebral cortex. Indeed, with the exception of olfaction, information from all sensory systems is processed in the thalamus and then relayed to the cerebral cortex. The dorsal column-medial lemniscal and anterolateral systems are no exceptions. Three major thalamic regions receive input from these pathways for various aspects of somatic sensation: then ventral posterior nucleus, the ventromedial posterior nucleus, and the medial dorsal nucleus.
The ventral posterior nucleus has a lateral division, the ventral posterior lateral nucleus which receives input from both the medial lemniscus and the spinothalamic tract and projects to the primary somatic sensory cortex.
Martin 109
The dorsal column-medial lemniscal and anterolateral systems each receive input from different functional classes of dorsal root ganglion neurons, the primary somatic sensory receptor neuron. This is why the two systems have such different functions.
The first major relay in the dorsal column-medial lemniscal system is in the dorsal column nuclei, in the medulla. Here, the first-order neurons in the pathway, the primary sensory neurons, synapse on second-order neurons in the central nervous system.
In contrast, the anterolateral system's first relay is in the dorsal horn of the spinal cord.
The two ascending somatic sensory pathways decussate at different levels of the neuraxis
Virtually all sensory and motor pathways have a neuron whose axon decussates, or crosses the midline, somewhere along it course, although the reason for this decussation is unknown. Knowing the level of decussation is clinically important for determining where an injury to the nervous system has occurred. The dorsal column-medial lemniscal system decussates in the medulla, whereas the anterorlateral system crosses in the spinal cord. Curiously, for both systems, the axon of the second neuron in the circuit decussates!
AL - Anterolateral System is an ascending pathway
Spinothalamic system for pain and temperature, the protopathic alerting system. Inputs to the tract of Lissauer in the superficial part of the dorsal horn, it has somatotopic organization. The first synapse, the dorsal horn review of ascending intraspinal course of the anterolateral tract; pain control by anterolateral tractomy, compare spinal course of anterolateral and dorsal columns. Second synapse in the posterior thalamus. Third synapse in non-specific or interlaminar thalamic nuclei; indirect targets are the central gray, reticular formation and hypothalamic centers. Interlaminar thalamic nuclei can activate large expanses of sensory and motor cortex. The central gray participates in the descending control of nociception The reticular formation helps to direct attention and vigilance. The hypothalamus is a source of preganglionic parasympathetic synaptic drive for the autonomic nervous system. Fourth synapse the cerebral cortex where the representation of nociception is surprisingly diffuse.
Spinothalamic Tract
The sensations of pain and temperature are transmitted primarily via the spinothalamic tract, which ascends in the ventrolateral quadrant of the spinal cord contralateral to the side of entry of the primary afferents. The spinothalamic tract is complex and functionally heterogeneous. It mediates the discriminative and arousal-emotional components of pain sensation as well as thermal, visceral, and simple tactile information.
The different components of the spinothalamic tract include 1a direct pathway, the neospinothalamic pathway, which mediates the discriminative aspect of pain and temperature and is important for localization and 2 several indirect pathways for the affective-arousal components of pain; they form part of the core, or inner tube, of the neuraxis.
The direct tract consists of second-order axons from both nociceptive-specific and wide dynamic range neurons. The axons cross through the ventral white commissure and ascend strictly contralaterally in the anterolateral quadrant of the spinal cord. The tract has a somatotopic organization in the spinal cord, with the sacral dermatomes represented dorsolaterally and the cervical dermatomes ventromedially. The spinothalamic tract ascends in the lateral portion of the brainstem. in the medulla, it is dorsal to the lateral aspect of the inferior olivary nucleus, and in the pons and midbrain, it is lateral to the medial lemniscus. At the mesodiencephalic unction, the spinothalamic tract and medial lemniscus join. Throughout its course, the spinothalamic tract maintains a somatotopic organization. The spinothalamic tract axons synapse on third-order neurons in several thalamic nuclei, particularly the ventral posterolateral nucleus that, in turn, projects to the primary sensory cortex in the post-central gyrus.
CEREBELLUM
The spinocerebellar tracts transmit information about the activity of the effector muscles or motor neuron pools to the cerebellum, where it is integrated and processed. The cerebellum is capable of modifying the action of different muscle groups so that movements are performed smoothly and accurately. Because the information carried by these pathways does not reach consciousness directly, it is referred to as unconscious proprioception. The two spinal cord pathways that convey unconscious proprioceptive information to the cerebellum are the dorsal and ventral spinocerebellar tracts. They have some features in common, but they also have important anatomical and functional differences. Both tracts 1 originate from neurons in the intermediate gray matter; 2 contain large-diameter rapidly conducting secondary axons (among the fastest conducting pathways in the nervous system); 3 transmit information from the lower extremities; and 4 provide input predominantly to the ipsilateral cerebellum.
Martin 120
Dorsal column axons synapse on neurons in the dorsal column nuclei, the first major relay in the ascending pathwway for touch and limb position senses. Thses and other somatic sensory relay nuclei enhance contrast and spatial resolution so that when adjacent portions of the skin are touched, the person can discern the difference.
Axons of the gracile fascicle synapse inthe gracile nucleus, which is located close to the midline, whereas those from the cuneate fascicle synapse inthe cuneate nucleus. Figure 5-12 illustrates a parasagittal section close to the midline, through the gracile nucleus plane of section is indicated in figure 5-11. From the dorsal column nuclei, the axons of the second order neurons sweep ventrally through the medulla, where they are called the internal arcuate fibers, and decussate. Immediately after crossing the midline, the fibers ascend to the thalamus in the medial lemniscus. Axons from the gracile nucleus decussate ventral to axons from the cuneate nucleus and ascend in the ventral part of the medial lemniscus, compared with axons from the cuneate nucleus. Because of this pattern, the somatotopic organization of the medial lemniscus in the medulla resembles a person standing upright. In the pons the medial lemniscus is located more dorsally than in the medulla and is oriented from medial to lateral.
In contrast to the dorsal column-medial medulla, the anterolateral system ascends along its ventrolateral margin. For the spinothalamic and spinomesencephalic tracts the medulla and pons simply serve as a conduit through whihc axons pass to reach more rostral locations. For the spinoreticular tract the axons terminate in the reticular formation of the pons and medulla.
THALAMUS
Martin 125
Three Separate Nuclei in the Thalamus Process Somatic Sensory Information
The thalamus is a nodal (point in a network at which lines or pathways intersect or branch) point for the transmission of sensory information to the cerebral cortex. Indeed, with the exception of olfaction, information from all sensory systems is processed in the thalamus and then relayed to the cerebral cortex. The dorsal column-medial lemniscal and anterolateral systems are no exceptions. Three major thalamic regions receive input from these pathways for various aspects of somatic sensation: then ventral posterior nucleus, the ventromedial posterior nucleus, and the medial dorsal nucleus.
The ventral posterior nucleus has a lateral division, the ventral posterior lateral nucleus which receives input from both the medial lemniscus and the spinothalamic tract and projects to the primary somatic sensory cortex.
Martin 109
The dorsal column-medial lemniscal and anterolateral systems each receive input from different functional classes of dorsal root ganglion neurons, the primary somatic sensory receptor neuron. This is why the two systems have such different functions.
The first major relay in the dorsal column-medial lemniscal system is in the dorsal column nuclei, in the medulla. Here, the first-order neurons in the pathway, the primary sensory neurons, synapse on second-order neurons in the central nervous system.
In contrast, the anterolateral system's first relay is in the dorsal horn of the spinal cord.
The two ascending somatic sensory pathways decussate at different levels of the neuraxis
Virtually all sensory and motor pathways have a neuron whose axon decussates, or crosses the midline, somewhere along it course, although the reason for this decussation is unknown. Knowing the level of decussation is clinically important for determining where an injury to the nervous system has occurred. The dorsal column-medial lemniscal system decussates in the medulla, whereas the anterorlateral system crosses in the spinal cord. Curiously, for both systems, the axon of the second neuron in the circuit decussates!
AL - Anterolateral System is an ascending pathway
- dorsal root ganglion activation enters impulses to the spinal cord,
- type of information relayed is pain and temperature
- crosses the mid-line, decussates immediately at the level of the spinal cord
- synapses immediately in the grey matter and ascends to the ventral lateral posterior nucleus before arriving at the cortex
Spinothalamic system for pain and temperature, the protopathic alerting system. Inputs to the tract of Lissauer in the superficial part of the dorsal horn, it has somatotopic organization. The first synapse, the dorsal horn review of ascending intraspinal course of the anterolateral tract; pain control by anterolateral tractomy, compare spinal course of anterolateral and dorsal columns. Second synapse in the posterior thalamus. Third synapse in non-specific or interlaminar thalamic nuclei; indirect targets are the central gray, reticular formation and hypothalamic centers. Interlaminar thalamic nuclei can activate large expanses of sensory and motor cortex. The central gray participates in the descending control of nociception The reticular formation helps to direct attention and vigilance. The hypothalamus is a source of preganglionic parasympathetic synaptic drive for the autonomic nervous system. Fourth synapse the cerebral cortex where the representation of nociception is surprisingly diffuse.
Spinothalamic Tract
The sensations of pain and temperature are transmitted primarily via the spinothalamic tract, which ascends in the ventrolateral quadrant of the spinal cord contralateral to the side of entry of the primary afferents. The spinothalamic tract is complex and functionally heterogeneous. It mediates the discriminative and arousal-emotional components of pain sensation as well as thermal, visceral, and simple tactile information.
The different components of the spinothalamic tract include 1a direct pathway, the neospinothalamic pathway, which mediates the discriminative aspect of pain and temperature and is important for localization and 2 several indirect pathways for the affective-arousal components of pain; they form part of the core, or inner tube, of the neuraxis.
The direct tract consists of second-order axons from both nociceptive-specific and wide dynamic range neurons. The axons cross through the ventral white commissure and ascend strictly contralaterally in the anterolateral quadrant of the spinal cord. The tract has a somatotopic organization in the spinal cord, with the sacral dermatomes represented dorsolaterally and the cervical dermatomes ventromedially. The spinothalamic tract ascends in the lateral portion of the brainstem. in the medulla, it is dorsal to the lateral aspect of the inferior olivary nucleus, and in the pons and midbrain, it is lateral to the medial lemniscus. At the mesodiencephalic unction, the spinothalamic tract and medial lemniscus join. Throughout its course, the spinothalamic tract maintains a somatotopic organization. The spinothalamic tract axons synapse on third-order neurons in several thalamic nuclei, particularly the ventral posterolateral nucleus that, in turn, projects to the primary sensory cortex in the post-central gyrus.
CEREBELLUM
The spinocerebellar tracts transmit information about the activity of the effector muscles or motor neuron pools to the cerebellum, where it is integrated and processed. The cerebellum is capable of modifying the action of different muscle groups so that movements are performed smoothly and accurately. Because the information carried by these pathways does not reach consciousness directly, it is referred to as unconscious proprioception. The two spinal cord pathways that convey unconscious proprioceptive information to the cerebellum are the dorsal and ventral spinocerebellar tracts. They have some features in common, but they also have important anatomical and functional differences. Both tracts 1 originate from neurons in the intermediate gray matter; 2 contain large-diameter rapidly conducting secondary axons (among the fastest conducting pathways in the nervous system); 3 transmit information from the lower extremities; and 4 provide input predominantly to the ipsilateral cerebellum.
Martin 120
Dorsal column axons synapse on neurons in the dorsal column nuclei, the first major relay in the ascending pathwway for touch and limb position senses. Thses and other somatic sensory relay nuclei enhance contrast and spatial resolution so that when adjacent portions of the skin are touched, the person can discern the difference.
Axons of the gracile fascicle synapse inthe gracile nucleus, which is located close to the midline, whereas those from the cuneate fascicle synapse inthe cuneate nucleus. Figure 5-12 illustrates a parasagittal section close to the midline, through the gracile nucleus plane of section is indicated in figure 5-11. From the dorsal column nuclei, the axons of the second order neurons sweep ventrally through the medulla, where they are called the internal arcuate fibers, and decussate. Immediately after crossing the midline, the fibers ascend to the thalamus in the medial lemniscus. Axons from the gracile nucleus decussate ventral to axons from the cuneate nucleus and ascend in the ventral part of the medial lemniscus, compared with axons from the cuneate nucleus. Because of this pattern, the somatotopic organization of the medial lemniscus in the medulla resembles a person standing upright. In the pons the medial lemniscus is located more dorsally than in the medulla and is oriented from medial to lateral.
In contrast to the dorsal column-medial medulla, the anterolateral system ascends along its ventrolateral margin. For the spinothalamic and spinomesencephalic tracts the medulla and pons simply serve as a conduit through whihc axons pass to reach more rostral locations. For the spinoreticular tract the axons terminate in the reticular formation of the pons and medulla.
DCML - Dorsal Column Medial Lemniscus is an ascending pathway
- dorsal root ganglion activation enters impulses to the spinal cord, ascends and synapses in the medulla
- type of information relayed is touch, vibration, pressure
- ascends to medulla to the pyramidal decussation
- synapses in the medulla and ventral lateral posterior nucleus before arriving at the cortex
Ascending pathways
DCML - Dorsal Column Medial Lemniscal System
DCML - Dorsal Column Medial Lemniscal System
- Mediates tactile sense, limb proprioception 22-14
- DC's are central branches of dorsal root ganglion cells, ascending to the medulla
- some (up to 50%) are axons of secondary dorsal horn cells
- at upper spinal levels the DC consists of 2 bundles (fascicles)
- gracile - medial; from spinal cord, lumbar, lower trunk; to gracile n
- cuneate - lateral; from upper trunk, cervical; to cuneate n
Diamond DCML Runoff
Ascending Pathways: Posterior/Dorsal Columns
This plate is concerned with the posterior columns (fasiculi gracilis and cuneatus of the posterior funiculus) and the medial lemnisci, which convey impulses concerned with well-localized (epicritic; relating to or denoting those sensory nerve fibers of the skin that are capable of fine discrimination of touch or temperature stimuli.) touch and with the sense of movement and position (kinesthesis). Important in moment-to-moment (temporal; relating to time) and point-to-point (spatial) discrimination, the posterior columns make it possible for you to put a key in a door lock withouth light or visualize the position of any part of your body without looking. Lesions (pathologic wounds from destructive tumors, hemorrhage, scar tissue, swelling, infections, direct trauma, etc.) of this system abolish or diminish tactile sensations and movement of position sense.
The cell bodies of the primary neurons in the posterior column pathway are in the spinal ganglion. The peripheral processes of these neurons begin at receptors in joint capsules (joint capsule receptor) and muscles as well as skin (tactile an pressure receptors, not shown).
The central processes of these neurons enter the cord and pass directly into the posterior funiculus without synapsing. Fibers coming in from the lumbosacral region enter the lowest (most caudal) part of the posterior columns and therefore occupy their most medial portions, close to the posterior median septum. Fibers entering progressively higher up the cord occupy more lateral positions within the columns. These lateral fibers (from the thoracic and cervical regions of the cord) are separated from the more medial lumbosacral axons by the posterior intermediate septum; the more medial group becomes known as the fasciculus gracilis and the more lateral group as the fasciculus cuneatus. The fibers of the two fasiculi ascend to the medulla oblongata of the brain stem, where they synapse with the cell bodies of the secondary neurons in their respective nuclei, gracilis and cuneatus.
From the nuclei cuneatus and gracilis in the mid medulla, the axons of the secondary neurons sweep down and across the contralateral side as the internal arcuate fibers and ascend in the brain stem as the medial lemniscus. The relationships of the medial lemniscus will be illustrated in Unit Five. The axons of the secondary neurons terminate in the ventral posterior lateral nucleus of the thalamus, where they synapse with the tertiary (third-order) neurons. The axons of these neurons pass rostrally through a great boomerang-shaped band of fibers, the internal capsule, and on through certain radiations of the subcortical white matter, the corona radiata. In this manner they reach the neurons of the postcentraly gyrus, where many body sensations are processed.
Fibers bringing sensations from the lower part of the body project to the superior aspect of the cortex,; fibers from the thoracic and cervical regions end in the more inferior aspect of the cortex. This arrangement contributes to an inverted representation of the contralateral body half on the cortex known as the homunculus ("little man")
Insert picture of the homunculus!
Ascending Pathways: Posterior/Dorsal Columns
This plate is concerned with the posterior columns (fasiculi gracilis and cuneatus of the posterior funiculus) and the medial lemnisci, which convey impulses concerned with well-localized (epicritic; relating to or denoting those sensory nerve fibers of the skin that are capable of fine discrimination of touch or temperature stimuli.) touch and with the sense of movement and position (kinesthesis). Important in moment-to-moment (temporal; relating to time) and point-to-point (spatial) discrimination, the posterior columns make it possible for you to put a key in a door lock withouth light or visualize the position of any part of your body without looking. Lesions (pathologic wounds from destructive tumors, hemorrhage, scar tissue, swelling, infections, direct trauma, etc.) of this system abolish or diminish tactile sensations and movement of position sense.
The cell bodies of the primary neurons in the posterior column pathway are in the spinal ganglion. The peripheral processes of these neurons begin at receptors in joint capsules (joint capsule receptor) and muscles as well as skin (tactile an pressure receptors, not shown).
The central processes of these neurons enter the cord and pass directly into the posterior funiculus without synapsing. Fibers coming in from the lumbosacral region enter the lowest (most caudal) part of the posterior columns and therefore occupy their most medial portions, close to the posterior median septum. Fibers entering progressively higher up the cord occupy more lateral positions within the columns. These lateral fibers (from the thoracic and cervical regions of the cord) are separated from the more medial lumbosacral axons by the posterior intermediate septum; the more medial group becomes known as the fasciculus gracilis and the more lateral group as the fasciculus cuneatus. The fibers of the two fasiculi ascend to the medulla oblongata of the brain stem, where they synapse with the cell bodies of the secondary neurons in their respective nuclei, gracilis and cuneatus.
From the nuclei cuneatus and gracilis in the mid medulla, the axons of the secondary neurons sweep down and across the contralateral side as the internal arcuate fibers and ascend in the brain stem as the medial lemniscus. The relationships of the medial lemniscus will be illustrated in Unit Five. The axons of the secondary neurons terminate in the ventral posterior lateral nucleus of the thalamus, where they synapse with the tertiary (third-order) neurons. The axons of these neurons pass rostrally through a great boomerang-shaped band of fibers, the internal capsule, and on through certain radiations of the subcortical white matter, the corona radiata. In this manner they reach the neurons of the postcentraly gyrus, where many body sensations are processed.
Fibers bringing sensations from the lower part of the body project to the superior aspect of the cortex,; fibers from the thoracic and cervical regions end in the more inferior aspect of the cortex. This arrangement contributes to an inverted representation of the contralateral body half on the cortex known as the homunculus ("little man")
Insert picture of the homunculus!
DCML RUNOFF
WINER
Definition of the dorsal column system
a. a neural pathway for conscious appreciation of fine touch, pressure, and muscle proprioception
b. receptors
1. pacinian corpuscles are rapidly-adapting mechanoreceptors sensitive to high-frequency mechanical stimuli
2. neuromuscular spindles (1a) are less rapidly-adapting stretch receptors embedded in muscle which send data on muscle length
toward the brain and spinal cord
3. importance of slowly and rapidly adapting receptors for neural signaling
a. slowly adapting; tonic output, duration-sensitive, static sensors
b. rapidly adapting: phasic output, onset-offset responsive, dynamic sensory
4. why damaging a dorsal root has such severe functional consequences
c. dermatomes retain their somatotopic organization in the dorsal columns
d. first synapse: gracile nucleus (hindlimb representation) or cuneate nucleus (forelimb representation) or trigeminal nucleus (facial sensory representation)
e. formation of internal arcuate fibers, their decussation, and the origin of the medial lemniscus
1. are there maps of the body surface in the dorsal column nuclei?
2. maps do not simply recapitulate the body surface, but integrate input and expand or compress representations via convergence of receptive fields
a. elementary structure of center-surround receptive field organization
f. second synapse: the projection of thalamic neurons to the somatic sensory cortex in the post-central gyrus
1. transformations and distortions of the body map in cortex reduce some representations and expand others
g. third synapse: the projection of thalamic neurons to the somatic sensory cortex in the post-central gyrus
1. transformations and distortions of the body map in cortex reduce some representations and expand others
h. fourth synapse: corticocortical projections from the post-central somatic sensory cortex to the pre-central motor cortex
i. corticofugal projections: descending systems for the selective control of lower sensory or motoneurons
1. the ventral posterior thalamus and other thalamic nuclei (corticothalamic) for selective attention to modality specfic processing
2. the dorsal column nuclei (gracile and cuneate nuclei)(corticobulbar): for feedback about limb position preparatory to new movement sequences?
3. reticular formation (corticoreticular): for attentional adjustments integrating expectation with sensory feedback
4. spinal cord (corticospinal): for rapid, voluntary adjustments of skeletal muscle
5. what are the functions of cortifofugal projections?
a. feedback for error control
b. preparatory for the next series of postural and locomotor events
c. anticipation of and planning for future events
d. focusing attention on a particular modality or set of muscles
Dorsal - Posterior
Column - Vertical Organization
Medial - Midline Organization
Lemniscus is a bundly of sensory fibers in the brain stem; means ribbon named because the lemniscus spirals or turns as it ascends
The SEP is mediated exclusively by the dorsal column medial lemniscus pathway
Medial lemniscus terminates in specific relay nuclei of the diencephalon
large ascending bundle of heavily myelinated axons that decussate in the brainstem, specifically in the medulla oblongata.
The medical lemniscus is formed by the crossings of the internal arcuate fibers, which are composed of axons of the nucleus gracilis and nucleus cuneatus. The axons of the nucleus gracilis and nucleus cuneatus in the medial lemniscus have cell bodies that lie contralaterally.
The medial lemniscus is part of the of the dorsal column medial lemniscal pathway which ascends from the skin to the thalamus, is important for somatosensation from the skin and joints, therefore, lesion of the medial lemnisci causes an impairment of vibratory and touch-pressure sense.
After neurons carrying proprioceptive or fine touch information synapse at the gracile and cuneate nuclei, axons from secondary neurons decussate at the level of the medulla and travel up the brainstem as the medial lemniscus on the contralateral (opposite) side. It is part of the posterior column-medial lemniscus pathway, which transmits touch, vibration sense, as well as the pathway for proprioception.
The medial lemniscus carries axons from most of the body and synapses in the ventral posterolateral nucleus of the thalamus, at the level of the mammillary bodies. Sensory axons transmitting information from the head and neck via the trigeminal nerve synapse at the ventral posteromedial nucleus of the thalamus.
Location through the brainstem
The direct dorsal column pathway is the most important component of the lemniscal system and consists of large myelinated, primary dorsal root axons that ascend ipsilaterally to reach the dorsal column nuclei in the medulla. This pathway is critical for spatiotemporal tactile discrimination and fine motor control the two major anatomical divisions of the dorsal columns are the fasciculus gracilis, which is medial and carries information from the lower extremities and the lower trunk (spinal segment T-7 and lower), and the fasciculus cuneatus, which is lateral and carries input from the upper extremities and the upper trunk (T-6 and higher).
Cutaneous and proprioceptive inputs terminate in the nucleus cuneatus of the medulla. Muscle receptor afferents traveling in the fasciculus cuneatus leave this tract in the medulla and terminate in the external, or accessory, cuneate nucleus (analogous to Clarke's nucleus). Therefore, the dorsal columns are functionally heterogeneous and carry mostly cutaneous and some proprioceptive inputs to the dorsal column nuclei and proprioceptive input to cerebellar relay nuclei. Lesions in the dorsal columns at any spinal cord level interfere with input from rapidly adapting cutaneous mechanoreceptors, but lesions above the thoracic cord largely spare input from muscle receptors in the lower trunk and lower extremities.
The second-order neurons of the direct dorsal column pathway are located in the dorsal column nuclei of the lower medulla. They are the nucleus gracilis, which receives cutaneous inputs from the lower extremity via the fasciculus gracilis, and the nucleus cuneatus, which receives cutaneous and some proprioceptive inputs from the upper extremities via the fasiculus cuneatus. The dorsal column nuclei are not simple relay stations but are sites of modulation of sensory transmission critical for sensory discrimnation. second-order axons from the dorsal column nuclei cross to the opposite side in the lower medulla as the internal arcuate fibers (the decussation of the medial lemniscus) and form the medial lemniscus which ascends to the thalamus. The medail lemniscus terminates in the ventral posteriolateral nucleus and other subdivisions of the ventral posterior complex of the thalamus.
AM
The Somatosensory System
SSEP mainly used on the spine; fixation after trauma, operations where the spinal cord could be at risk, resection of tumors, during operations where there is a risk of ischemia as a result of compromised blood supply to the part of the brain that is involved in the generation of SSEP.
Sensory Receptors - natural input to the somatosensory system is mecahnical stimulation of receptors in the skin, muscles and joints; meissner, merkel, ruffini and pacinian corpuscles
Ascending Somatosensory pathways
sensory receptors to the body is conveyed by the fibers of the sensory parts of peripheral nerves to the spinal cord where they enter as the dorsal roots. cell bodies. sensory receptors of the head are innervated by cranial nerves. Ther nerve fibers that reeive input from the body enter the dorsal horn of the spinal cord and ascend in the dorsal column of the spinal cord on the ipsilateal side to terminate in cells in the dorsal column nuclei
nerve fibers that innerate temperature and pain receptors also travel in peripheral nerves and enter the dorsal horn of the spinal cord but these fibers terminate in cells in the spinal cord at segmental level
dorsal column system
upper portion cuneate nucleus lower body in gracilis nucleus; gracilis medial, cuneate lateral, the difference bet
dorsal column nuclei
organization of somatosensory cortex
upper limb ssep, lower limb ssep, erb's point
somatosensory evoked potential response showing p9, p11, p14, n18, n20
Conscious pathways via the dorsal column system and assorted relay nuclei proved parallel input for the epicritic analysis of muscle length, tension and limb position. Output of somatic sensory and somatic motor cortex to the striatum enables conscious influences to reach centers involved in subconscious motor planning.
The dorsal column-medial lemnisal system, the principal pathway for touch, and the corticospinal tract, the key pathway for voluntary movement, each have a longitudinal organization, spanning virtually the entire neuraxis. These two pathways are good examples of how particular patters of connetions between structures at different levels of the neruaxis produce a circuit with a limited number of functions. The dorsal column-medial lemniscal system is termed an ascending pathway because it brings informtion from the sensory receptors in the periphery to lower levels of the central nervous system, such as the brain stem, and then to higher levels, such as the thalamus and cerebral cortex. In contrast, the corticospinal tract, a descending pathway, carries information from the cerebral cortex to a lower level of the central nervous system, the spinal cord.
The general organization of the ascending somatic sensory pathways of the dorsal column-medial lemniscal system
Axons in the dorsal colunns synapse primarily on neurons in the dorsal column nuceli, which transmit information to the ventral posterior lateral nucleus of the thalamus and then to the primary somatic sensory cortex in the postcentral gyrus.
MARTIN page 8
The Spinal Cord Displays the simplest organization of all seven major divisions
The spinal cord participates in processing sensory information from the limbs, trunk, and many internal organs; in controlling body movements directly; and in regulating many visceral functions. It also provides a conduit for the transmission of both sensory information in the tracts that ascend to the brain and motor information in the descending tracts. The spinal cord is the only part of the central nervous system that has an external segmental organization, reminiscent of its embryonic and phylogenetic origins. The spinal cord has a modular organization, in which every segment has a similar basic structure.
Each spinal cord segment contains a pair of nerve roots (and associated rootlets) called the dorsal and ventral roots. (the terms dorsal and ventral describe the spatial relations of structures). Dorsal roots contain only sensory axons, which transmit sensory information into the spinal cord. By contrast, ventral roots contain motor axons, which transmit motor commands to muscle and other body organs. Dorsal and ventral roots exemplify the separation of function in the nervous system,. These sensory and motor axons, which are part of the peripheral nervous system, become intermingled in the spinal nerves en route to their peripheral targets.
The dorsal column-medial lemnisal system, the principal pathway for touch, and the corticospinal tract, the key pathway for voluntary movement, each have a longitudinal organization, spanning virtually the entire neuraxis. These two pathways are good examples of how particular patters of connetions between structures at different levels of the neruaxis produce a circuit with a limited number of functions. The dorsal column-medial lemniscal system is termed an ascending pathway because it brings informtion from the sensory receptors in the periphery to lower levels of the central nervous system, such as the brain stem, and then to higher levels, such as the thalamus and cerebral cortex. In contrast, the corticospinal tract, a descending pathway, carries information from the cerebral cortex to a lower level of the central nervous system, the spinal cord.
The first neurons in the circuit are the dorsal root ganglion neurons, which translate stimulus energy into neural signals and transmit this information directly to the spinal cord and brain stem. This component of the system is a fast transmission line that is visible on the dorsal surface of the spinal cord as the dorsal column.
The first synapse is made in the dorsal column nucleus, a relay nucleus in the medulla. A relay nucleus processes incoming signals and transmits this information to the next component of the circuit. The cell bodies of the second neurons in the pathway are located in the dorsal column nucleus. The axons of these second-order neurons cross the midline, or decussate. Because of this decussation, sensory information from the right side of the body is processed by the left side of the brain. Most sensory (and motor) pathways decussate at some point along their course. Surprisingly, we do not know why neural systems decussate.
After crossing the midline the axons ascend in the brain stem tract, the medial lemniscus, to synapse in a relay nucleus in the thalamus. From here, third-order neurons send their axons through the white matter underlying the cortex, in the internal capsule. These axons synapse on neurons in the primary somatic sensory cortex, which is located in the postcentral gyrus of the parietal lobe. Each sensory system has a primary cortical area and several higher-order areas. the primary area receives input directly from the thalamus and processes basic sensory information. The higher-order areas receive input predominantly from the primary and other cortical areas and participate in the elaboration of sensory processing leading to perception.
The Dorsal Column-Medial Lemniscal and Anterolateral Systems Synapse in Different Brain Stem, Diencephalic and Cortical Regions
Regional Anatomy of the Spinal Somatic Sensory Pathways
Regional approach to the spinal somatic sensory systems. progressing in order from periphery to cerebral cortex, the chapter examines the key components of the dorsal column-medial lemniscal system and the anterolateral system. Knowledge of the regional anatomy is important for understanding how injury to a discrete portion of the central nervous sytem affects different functional systems indiscriminately.
WINER
Definition of the dorsal column system
a. a neural pathway for conscious appreciation of fine touch, pressure, and muscle proprioception
b. receptors
1. pacinian corpuscles are rapidly-adapting mechanoreceptors sensitive to high-frequency mechanical stimuli
2. neuromuscular spindles (1a) are less rapidly-adapting stretch receptors embedded in muscle which send data on muscle length
toward the brain and spinal cord
3. importance of slowly and rapidly adapting receptors for neural signaling
a. slowly adapting; tonic output, duration-sensitive, static sensors
b. rapidly adapting: phasic output, onset-offset responsive, dynamic sensory
4. why damaging a dorsal root has such severe functional consequences
c. dermatomes retain their somatotopic organization in the dorsal columns
d. first synapse: gracile nucleus (hindlimb representation) or cuneate nucleus (forelimb representation) or trigeminal nucleus (facial sensory representation)
e. formation of internal arcuate fibers, their decussation, and the origin of the medial lemniscus
1. are there maps of the body surface in the dorsal column nuclei?
2. maps do not simply recapitulate the body surface, but integrate input and expand or compress representations via convergence of receptive fields
a. elementary structure of center-surround receptive field organization
f. second synapse: the projection of thalamic neurons to the somatic sensory cortex in the post-central gyrus
1. transformations and distortions of the body map in cortex reduce some representations and expand others
g. third synapse: the projection of thalamic neurons to the somatic sensory cortex in the post-central gyrus
1. transformations and distortions of the body map in cortex reduce some representations and expand others
h. fourth synapse: corticocortical projections from the post-central somatic sensory cortex to the pre-central motor cortex
i. corticofugal projections: descending systems for the selective control of lower sensory or motoneurons
1. the ventral posterior thalamus and other thalamic nuclei (corticothalamic) for selective attention to modality specfic processing
2. the dorsal column nuclei (gracile and cuneate nuclei)(corticobulbar): for feedback about limb position preparatory to new movement sequences?
3. reticular formation (corticoreticular): for attentional adjustments integrating expectation with sensory feedback
4. spinal cord (corticospinal): for rapid, voluntary adjustments of skeletal muscle
5. what are the functions of cortifofugal projections?
a. feedback for error control
b. preparatory for the next series of postural and locomotor events
c. anticipation of and planning for future events
d. focusing attention on a particular modality or set of muscles
Dorsal - Posterior
Column - Vertical Organization
Medial - Midline Organization
Lemniscus is a bundly of sensory fibers in the brain stem; means ribbon named because the lemniscus spirals or turns as it ascends
The SEP is mediated exclusively by the dorsal column medial lemniscus pathway
Medial lemniscus terminates in specific relay nuclei of the diencephalon
large ascending bundle of heavily myelinated axons that decussate in the brainstem, specifically in the medulla oblongata.
The medical lemniscus is formed by the crossings of the internal arcuate fibers, which are composed of axons of the nucleus gracilis and nucleus cuneatus. The axons of the nucleus gracilis and nucleus cuneatus in the medial lemniscus have cell bodies that lie contralaterally.
The medial lemniscus is part of the of the dorsal column medial lemniscal pathway which ascends from the skin to the thalamus, is important for somatosensation from the skin and joints, therefore, lesion of the medial lemnisci causes an impairment of vibratory and touch-pressure sense.
After neurons carrying proprioceptive or fine touch information synapse at the gracile and cuneate nuclei, axons from secondary neurons decussate at the level of the medulla and travel up the brainstem as the medial lemniscus on the contralateral (opposite) side. It is part of the posterior column-medial lemniscus pathway, which transmits touch, vibration sense, as well as the pathway for proprioception.
The medial lemniscus carries axons from most of the body and synapses in the ventral posterolateral nucleus of the thalamus, at the level of the mammillary bodies. Sensory axons transmitting information from the head and neck via the trigeminal nerve synapse at the ventral posteromedial nucleus of the thalamus.
Location through the brainstem
- The cuneate and gracile nuclei reside at the closed (lower) medulla, so the lemniscus is not formed at this level. Fibres from these nuclei will pass to the contralateral side of the brainstem, as the internal arcuate fibres.
- At the open medulla (further up the brainstem), the medial lemniscus contains axons from the trigeminal nerve (which supplies the head region), as well as the arms and legs. It sits very close to the midline, at the same orientation of the midline, with head fibres more dorsal (closer to the back), towards the fourth ventricle.
- By mid-pons, the medial lemniscus has rotated. Fibres from the head are medial, fibres from the leg are lateral.
- The orientation in the midbrain is similar to that in the pons.
The direct dorsal column pathway is the most important component of the lemniscal system and consists of large myelinated, primary dorsal root axons that ascend ipsilaterally to reach the dorsal column nuclei in the medulla. This pathway is critical for spatiotemporal tactile discrimination and fine motor control the two major anatomical divisions of the dorsal columns are the fasciculus gracilis, which is medial and carries information from the lower extremities and the lower trunk (spinal segment T-7 and lower), and the fasciculus cuneatus, which is lateral and carries input from the upper extremities and the upper trunk (T-6 and higher).
Cutaneous and proprioceptive inputs terminate in the nucleus cuneatus of the medulla. Muscle receptor afferents traveling in the fasciculus cuneatus leave this tract in the medulla and terminate in the external, or accessory, cuneate nucleus (analogous to Clarke's nucleus). Therefore, the dorsal columns are functionally heterogeneous and carry mostly cutaneous and some proprioceptive inputs to the dorsal column nuclei and proprioceptive input to cerebellar relay nuclei. Lesions in the dorsal columns at any spinal cord level interfere with input from rapidly adapting cutaneous mechanoreceptors, but lesions above the thoracic cord largely spare input from muscle receptors in the lower trunk and lower extremities.
The second-order neurons of the direct dorsal column pathway are located in the dorsal column nuclei of the lower medulla. They are the nucleus gracilis, which receives cutaneous inputs from the lower extremity via the fasciculus gracilis, and the nucleus cuneatus, which receives cutaneous and some proprioceptive inputs from the upper extremities via the fasiculus cuneatus. The dorsal column nuclei are not simple relay stations but are sites of modulation of sensory transmission critical for sensory discrimnation. second-order axons from the dorsal column nuclei cross to the opposite side in the lower medulla as the internal arcuate fibers (the decussation of the medial lemniscus) and form the medial lemniscus which ascends to the thalamus. The medail lemniscus terminates in the ventral posteriolateral nucleus and other subdivisions of the ventral posterior complex of the thalamus.
AM
The Somatosensory System
SSEP mainly used on the spine; fixation after trauma, operations where the spinal cord could be at risk, resection of tumors, during operations where there is a risk of ischemia as a result of compromised blood supply to the part of the brain that is involved in the generation of SSEP.
Sensory Receptors - natural input to the somatosensory system is mecahnical stimulation of receptors in the skin, muscles and joints; meissner, merkel, ruffini and pacinian corpuscles
Ascending Somatosensory pathways
sensory receptors to the body is conveyed by the fibers of the sensory parts of peripheral nerves to the spinal cord where they enter as the dorsal roots. cell bodies. sensory receptors of the head are innervated by cranial nerves. Ther nerve fibers that reeive input from the body enter the dorsal horn of the spinal cord and ascend in the dorsal column of the spinal cord on the ipsilateal side to terminate in cells in the dorsal column nuclei
nerve fibers that innerate temperature and pain receptors also travel in peripheral nerves and enter the dorsal horn of the spinal cord but these fibers terminate in cells in the spinal cord at segmental level
dorsal column system
upper portion cuneate nucleus lower body in gracilis nucleus; gracilis medial, cuneate lateral, the difference bet
dorsal column nuclei
organization of somatosensory cortex
upper limb ssep, lower limb ssep, erb's point
somatosensory evoked potential response showing p9, p11, p14, n18, n20
Conscious pathways via the dorsal column system and assorted relay nuclei proved parallel input for the epicritic analysis of muscle length, tension and limb position. Output of somatic sensory and somatic motor cortex to the striatum enables conscious influences to reach centers involved in subconscious motor planning.
The dorsal column-medial lemnisal system, the principal pathway for touch, and the corticospinal tract, the key pathway for voluntary movement, each have a longitudinal organization, spanning virtually the entire neuraxis. These two pathways are good examples of how particular patters of connetions between structures at different levels of the neruaxis produce a circuit with a limited number of functions. The dorsal column-medial lemniscal system is termed an ascending pathway because it brings informtion from the sensory receptors in the periphery to lower levels of the central nervous system, such as the brain stem, and then to higher levels, such as the thalamus and cerebral cortex. In contrast, the corticospinal tract, a descending pathway, carries information from the cerebral cortex to a lower level of the central nervous system, the spinal cord.
The general organization of the ascending somatic sensory pathways of the dorsal column-medial lemniscal system
Axons in the dorsal colunns synapse primarily on neurons in the dorsal column nuceli, which transmit information to the ventral posterior lateral nucleus of the thalamus and then to the primary somatic sensory cortex in the postcentral gyrus.
MARTIN page 8
The Spinal Cord Displays the simplest organization of all seven major divisions
The spinal cord participates in processing sensory information from the limbs, trunk, and many internal organs; in controlling body movements directly; and in regulating many visceral functions. It also provides a conduit for the transmission of both sensory information in the tracts that ascend to the brain and motor information in the descending tracts. The spinal cord is the only part of the central nervous system that has an external segmental organization, reminiscent of its embryonic and phylogenetic origins. The spinal cord has a modular organization, in which every segment has a similar basic structure.
Each spinal cord segment contains a pair of nerve roots (and associated rootlets) called the dorsal and ventral roots. (the terms dorsal and ventral describe the spatial relations of structures). Dorsal roots contain only sensory axons, which transmit sensory information into the spinal cord. By contrast, ventral roots contain motor axons, which transmit motor commands to muscle and other body organs. Dorsal and ventral roots exemplify the separation of function in the nervous system,. These sensory and motor axons, which are part of the peripheral nervous system, become intermingled in the spinal nerves en route to their peripheral targets.
The dorsal column-medial lemnisal system, the principal pathway for touch, and the corticospinal tract, the key pathway for voluntary movement, each have a longitudinal organization, spanning virtually the entire neuraxis. These two pathways are good examples of how particular patters of connetions between structures at different levels of the neruaxis produce a circuit with a limited number of functions. The dorsal column-medial lemniscal system is termed an ascending pathway because it brings informtion from the sensory receptors in the periphery to lower levels of the central nervous system, such as the brain stem, and then to higher levels, such as the thalamus and cerebral cortex. In contrast, the corticospinal tract, a descending pathway, carries information from the cerebral cortex to a lower level of the central nervous system, the spinal cord.
The first neurons in the circuit are the dorsal root ganglion neurons, which translate stimulus energy into neural signals and transmit this information directly to the spinal cord and brain stem. This component of the system is a fast transmission line that is visible on the dorsal surface of the spinal cord as the dorsal column.
The first synapse is made in the dorsal column nucleus, a relay nucleus in the medulla. A relay nucleus processes incoming signals and transmits this information to the next component of the circuit. The cell bodies of the second neurons in the pathway are located in the dorsal column nucleus. The axons of these second-order neurons cross the midline, or decussate. Because of this decussation, sensory information from the right side of the body is processed by the left side of the brain. Most sensory (and motor) pathways decussate at some point along their course. Surprisingly, we do not know why neural systems decussate.
After crossing the midline the axons ascend in the brain stem tract, the medial lemniscus, to synapse in a relay nucleus in the thalamus. From here, third-order neurons send their axons through the white matter underlying the cortex, in the internal capsule. These axons synapse on neurons in the primary somatic sensory cortex, which is located in the postcentral gyrus of the parietal lobe. Each sensory system has a primary cortical area and several higher-order areas. the primary area receives input directly from the thalamus and processes basic sensory information. The higher-order areas receive input predominantly from the primary and other cortical areas and participate in the elaboration of sensory processing leading to perception.
The Dorsal Column-Medial Lemniscal and Anterolateral Systems Synapse in Different Brain Stem, Diencephalic and Cortical Regions
Regional Anatomy of the Spinal Somatic Sensory Pathways
Regional approach to the spinal somatic sensory systems. progressing in order from periphery to cerebral cortex, the chapter examines the key components of the dorsal column-medial lemniscal system and the anterolateral system. Knowledge of the regional anatomy is important for understanding how injury to a discrete portion of the central nervous sytem affects different functional systems indiscriminately.
Winer
Dorsal Column System
Definition of the dorsal column system
a. a neural pathway for conscious appreciation of fine touch, pressure, and muscle proprioception
b. receptors
1. pacinian corpuscles are rapidly-adapting mechanoreceptors sensitive to high-frequency mechanical stimuli
2. neuromuscular spindles (1a) are less rapidly-adapting stretch receptors embedded in muscle which send data on muscle length
toward the brain and spinal cord
3. importance of slowly and rapidly adapting receptors for neural signaling
a. slowly adapting; tonic output, duration-sensitive, static sensors
b. rapidly adapting: phasic output, onset-offset responsive, dynamic sensory
4. why damaging a dorsal root has such severe functional consequences
c. dermatomes retain their somatotopic organization in the dorsal columns
d. first synapse: gracile nucleus (hindlimb representation) or cuneate nucleus (forelimb representation) or trigeminal nucleus (facial sensory representation)
e. formation of internal arcuate fibers, their decussation, and the origin of the medial lemniscus
1. are there maps of the body surface in the dorsal column nuclei?
2. maps do not simply recapitulate the body surface, but integrate input and expand or compress representations via convergence of receptive fields
a. elementary structure of center-surround receptive field organization
f. second synapse: the projection of thalamic neurons to the somatic sensory cortex in the post-central gyrus
1. transformations and distortions of the body map in cortex reduce some representations and expand others
g. third synapse: the projection of thalamic neurons to the somatic sensory cortex in the post-central gyrus
1. transformations and distortions of the body map in cortex reduce some representations and expand others
h. fourth synapse: corticocortical projections from the post-central somatic sensory cortex to the pre-central motor cortex
i. corticofugal projections: descending systems for the selective control of lower sensory or motoneurons
1. the ventral posterior thalamus and other thalamic nuclei (corticothalamic) for selective attention to modality specfic processing
2. the dorsal column nuclei (gracile and cuneate nuclei)(corticobulbar): for feedback about limb position preparatory to new movement sequences?
3. reticular formation (corticoreticular): for attentional adjustments integrating expectation with sensory feedback
4. spinal cord (corticospinal): for rapid, voluntary adjustments of skeletal muscle
5. what are the functions of cortifofugal projections?
a. feedback for error control
b. preparatory for the next series of postural and locomotor events
c. anticipation of and planning for future events
d. focusing attention on a particular modality or set of muscles
Dorsal Column System
Definition of the dorsal column system
a. a neural pathway for conscious appreciation of fine touch, pressure, and muscle proprioception
b. receptors
1. pacinian corpuscles are rapidly-adapting mechanoreceptors sensitive to high-frequency mechanical stimuli
2. neuromuscular spindles (1a) are less rapidly-adapting stretch receptors embedded in muscle which send data on muscle length
toward the brain and spinal cord
3. importance of slowly and rapidly adapting receptors for neural signaling
a. slowly adapting; tonic output, duration-sensitive, static sensors
b. rapidly adapting: phasic output, onset-offset responsive, dynamic sensory
4. why damaging a dorsal root has such severe functional consequences
c. dermatomes retain their somatotopic organization in the dorsal columns
d. first synapse: gracile nucleus (hindlimb representation) or cuneate nucleus (forelimb representation) or trigeminal nucleus (facial sensory representation)
e. formation of internal arcuate fibers, their decussation, and the origin of the medial lemniscus
1. are there maps of the body surface in the dorsal column nuclei?
2. maps do not simply recapitulate the body surface, but integrate input and expand or compress representations via convergence of receptive fields
a. elementary structure of center-surround receptive field organization
f. second synapse: the projection of thalamic neurons to the somatic sensory cortex in the post-central gyrus
1. transformations and distortions of the body map in cortex reduce some representations and expand others
g. third synapse: the projection of thalamic neurons to the somatic sensory cortex in the post-central gyrus
1. transformations and distortions of the body map in cortex reduce some representations and expand others
h. fourth synapse: corticocortical projections from the post-central somatic sensory cortex to the pre-central motor cortex
i. corticofugal projections: descending systems for the selective control of lower sensory or motoneurons
1. the ventral posterior thalamus and other thalamic nuclei (corticothalamic) for selective attention to modality specfic processing
2. the dorsal column nuclei (gracile and cuneate nuclei)(corticobulbar): for feedback about limb position preparatory to new movement sequences?
3. reticular formation (corticoreticular): for attentional adjustments integrating expectation with sensory feedback
4. spinal cord (corticospinal): for rapid, voluntary adjustments of skeletal muscle
5. what are the functions of cortifofugal projections?
a. feedback for error control
b. preparatory for the next series of postural and locomotor events
c. anticipation of and planning for future events
d. focusing attention on a particular modality or set of muscles
Spinal Cord Runoff
The renshaw cell is a key player in the intrinsic modulation of motoneurons. By recurrent inhibition onto a motoneuron, runaway excitation is checked. Renshaw cell-mediated inhibition of 1a inhibitory interneurons results in a disinhibition of neighboring motoneurons. Renshaw cells are under descending control of the cerebral cortex and propriospinal influences as well; these are properties shared with all other spinal neurons. *Reciprocal facilitation of ipsilateral synergist motoneurons; the adaptive significance of reciprocal inhibition and facilitation.
Intraspinal and supraspinal modulation of reflexes, propriospinal connections.
Cross sections; gray and white matter 18-1
Also from cortex and brain stem to spinal grey.
The ventral columns are responsible for pain and thermal sensation.
Motor control of axial muscles and posture.
Spinal Grey Anatomy 33-13, 34-1
Nerve Root Ganglion; sensory cell bodies
The renshaw cell is a key player in the intrinsic modulation of motoneurons. By recurrent inhibition onto a motoneuron, runaway excitation is checked. Renshaw cell-mediated inhibition of 1a inhibitory interneurons results in a disinhibition of neighboring motoneurons. Renshaw cells are under descending control of the cerebral cortex and propriospinal influences as well; these are properties shared with all other spinal neurons. *Reciprocal facilitation of ipsilateral synergist motoneurons; the adaptive significance of reciprocal inhibition and facilitation.
Intraspinal and supraspinal modulation of reflexes, propriospinal connections.
Cross sections; gray and white matter 18-1
Also from cortex and brain stem to spinal grey.
The ventral columns are responsible for pain and thermal sensation.
Motor control of axial muscles and posture.
Spinal Grey Anatomy 33-13, 34-1
Nerve Root Ganglion; sensory cell bodies
Muscles Runoff
muscles of the jaw; temporalis originates on squamous portion of temporal bone and insertion on coronoid process of mandible; contracts it closes the jaw; can exert significant amount of pressure, very powerful muscles. masseter means chewer, originates on the zygomatic arch and insert on ramus of jaw to close it
Myology is the study of
skeletal muscle; longest muscle cell is sartorius muscle cell - 35 cm
smallest bones are in the internal ear, smallest muscles are in the internal ear- 10 um
muscles of the jaw; temporalis originates on squamous portion of temporal bone and insertion on coronoid process of mandible; contracts it closes the jaw; can exert significant amount of pressure, very powerful muscles. masseter means chewer, originates on the zygomatic arch and insert on ramus of jaw to close it
Myology is the study of
skeletal muscle; longest muscle cell is sartorius muscle cell - 35 cm
smallest bones are in the internal ear, smallest muscles are in the internal ear- 10 um
Skeletal System Runoff
*LH*
What is different about each level?
Vertebral Column
24 individual vertebrae arranged in cervical thoracic and lumbar regions; sacral and coccygeal vertebrae are fused
*LH*
What is different about each level?
Vertebral Column
24 individual vertebrae arranged in cervical thoracic and lumbar regions; sacral and coccygeal vertebrae are fused
- 7 cervical; neck and head
- 12 thoracic; thorax, trunk, head and neck, articulates with the twelve ribs
- 5 lumbar; support the upper body, torso and lower back
- 5 sacral
- 4-5 coccygeal
3 dimensional organization runoff
Example: The surgical repair of a herniated intervertebral disc requires that the surgeon have knowledge of the normal trajectory before clinical intervention and the accurate interpretation of MRI images entails a knowledge of the normal position and appearance of the cerebral cortex before definitive diagnosis is possible.
Example: The surgical repair of a herniated intervertebral disc requires that the surgeon have knowledge of the normal trajectory before clinical intervention and the accurate interpretation of MRI images entails a knowledge of the normal position and appearance of the cerebral cortex before definitive diagnosis is possible.
RUNOFF ANESTHESIA II
KEY POINTS FROM NATURE; https://www.nature.com/articles/nrn1496%E2%80%8B
The methods to provide anesthesia are local; major anesthesia by the surgeon, iv sedation and analgesia allowing for awake testing and clinical correlation (local loss of bodily sensation with or without loss of consciousness
types); dissociative anesthesia; iv dissociative; regional (nerve block) (
regional - epidural, nerve or plexus block, spinal); supplemental sedation and anesthesia; blocks monitoring in regions; and general; (general - patient is unconscious and intubated)(amnesia, analgesia & relaxation) which are the strongest implications for monitoring.
insensitivity to pain, especially as artificially induced by the administration of gases or the injection of drugs before surgical operations.
In addition, in sub anesthetic doses it can produce a powerful psychedelic-like altered state of consciousness. Its various psychoactive properties were documented in 1800 by the British chemist Humphrey Davy, marking the first detailed study of the effects of a defined chemical substance on the human mind.
Sedation/Amnesia
increases SSEP/cortical amplitudes have used in pediatric cases
MAC; basic language of Inhaled Agents
KEY POINTS FROM NATURE; https://www.nature.com/articles/nrn1496%E2%80%8B
- General anaesthetics are defined by their capacity to produce a state in which surgery can be tolerated without the need for further drugs. They are widely used in both clinical medicine and neuroscience research, but we are only just beginning to understand the molecular mechanisms that underlie their actions.
- The goals of the anaesthetic state are immobility, unconsciousness and amnesia. It is widely accepted that general anaesthetics cause immobility by depressing spinal neurons, and amnesia and hypnosis by acting on neurons in the brain. However, there is evidence that their spinal actions also influence sedative and hypnotic effects, and conversely, that descending signals from the brain to the spinal cord modify their immobilizing effects.
- There is a long list of molecular targets, the activity of which is mediated by at least one general anaesthetic, including numerous types of ligand-gated ion channel. In recent years, the GABAA (γ-aminobutyric acid type A) receptor system has attracted considerable attention as a target for general anaesthetics.
- The great heterogeneity of GABAA receptors has long precluded the attribution of physiological and pharmacological functions to specific subtypes. However, using knock-in point mutations in mice, it has been possible to identify specific GABAA-receptor subtypes that are involved in the actions of the intravenous anaesthetics etomidate and propofol.
- By integrating results from pharmacological, molecular genetic, functional imaging and electrophysiological studies, we should be able to gain further insights into the mechanisms of anaesthetic action. These insights might also provide avenues for the design of new general anaesthetics with an improved side-effect profile.
The methods to provide anesthesia are local; major anesthesia by the surgeon, iv sedation and analgesia allowing for awake testing and clinical correlation (local loss of bodily sensation with or without loss of consciousness
types); dissociative anesthesia; iv dissociative; regional (nerve block) (
regional - epidural, nerve or plexus block, spinal); supplemental sedation and anesthesia; blocks monitoring in regions; and general; (general - patient is unconscious and intubated)(amnesia, analgesia & relaxation) which are the strongest implications for monitoring.
insensitivity to pain, especially as artificially induced by the administration of gases or the injection of drugs before surgical operations.
In addition, in sub anesthetic doses it can produce a powerful psychedelic-like altered state of consciousness. Its various psychoactive properties were documented in 1800 by the British chemist Humphrey Davy, marking the first detailed study of the effects of a defined chemical substance on the human mind.
- muscle relaxants or NMBs
- used for muscle relaxation to prevent movement
- binds to acetylcholine receptors on the motor end plates blocking acetylcholine activation
- depolarizers - depolarize the motor end plate when binding to acetylcholine receptors, muscle fasciculation may be noticed in response to depolarization; succinylcholine - short acting (3-10) minutes
- great for intubation so can get baselines as quick as possible
- non-depolarizers - bind the acetylcholine receptors without causing depolarization
- intermediate acting (30-60 minutes); vecuronium, rocuronium
- long acting; pancuronium
- Used for induction and maintenance
- Milk of Amnesia
- Hypnotic
- Mechanism; GABA agonist; inhibitory agonist
- side effects; vasodilation and hypotension, respiratory suppression
- patients will often have pain in the arm that propofol is injected into
Sedation/Amnesia
- Propofol; others are disappearing from practice
- rapid kinetics, very titratable
- possible problem with egg allergy
- fatal lactic acidosis, prolonged use, especially children
- propofol is the most common TIVA sedative
- consider reducing propofol by adding ketamine; consider analgesia/sedation with ketamine
-
increases SSEP/cortical amplitudes have used in pediatric cases
- Ketamine
- provides amnesia and analgesia
- inexpensive as infusion in TIVA
- problem of hallucinations
- increase ICP with intracranial pathology
- my inc seizures
MAC; basic language of Inhaled Agents
- Monitored Anesthesia Care; a form of anesthesia care when the anesthesiologist monitors the vital signs and provides supplemental analgesia and/or sedation
- Minimum Alveolar Concentration; the inspired concentration of an inhalational anesthetic where 50% of subjects move in a response to a painful stimulus (spinal reflex) (Halothane 0.8%; Enflurane 1.7%; Isoflurane 1.15%; Sevoflurane 1.7%; Desflurane 6%; Nitrous Oxide 120%)
- The blocking movement of MAC is thought to be due to blocking of reflex activity at the spinal cord and is independent of anesthesia effects at the Brain and Brainstem
Anesthesia Runoff
Drugs and the Brain; Repeated perturbation of the brain's chemistry may bring about changes in the circuitry of the brain that may underlie lasting changes in behavior. Changes in the brain's circuitry presumably reflect the strengthening and weakening of synapses through mechanisms such as changes in the number of receptors, changes in the amount of neurotransmitter released, and changes in intracellular biochemical pathways that are activated by membrane receptors. Growth of new dendrites to form new synapses or deterioration of existing synapses may also be involved.
It is likely that extended use of any psychoactive drug will bring about homeostatic changes in brain physiology that will result in symptoms of withdrawal if use of the drug is stopped.
The mind is a collection of mental states, including thoughts, feelings and perceptions, experienced by the organism. The current working hypothesis in neuroscience is that the mind is associated with the brain, and that neural processes taking place in the brain somehow generate the qualities of mind. Consciousness is an aspect of mind that involve s awareness of these mental states.
KEY POINTS FROM NATURE; https://www.nature.com/articles/nrn1496%E2%80%8B
Papaver somniferum, native to the Middle East and north Africa, now grown throughout the world.
In 1803, morphine became the first physiologically active compound to be isolated and identified from a plant.
Acting at opioid receptors in the digestive system, opioids slow intestinal motility and thus are valuable treatments for diarrhea.
Anesthesiologist Focus
Anesthesia is the loss of bodily sensation with or without the loss of consciousness.
Biochemical reactions; see presti for more information
Theory of anesthesia
Changes in monitoring/Mechanisms of Anesthesia
Stage 1 -Analgesia or Induction - patient experiences slight dizziness, a sense of unreality and a lessening sensitivity to touch and pain. The patients sense of hearing is increased and responses to noises are intensified. Induction - initiation of anesthesia via intravenous and possibly inhalation anesthetics. because the drugs enter the bloodstream, usually cause unconsciousness in less than 1 minute. gasses also act quickly but they must be inhaled for a short time before they cause unconsciousness
cardiovascular, pulmonary and renal emergence
Drugs and the Brain; Repeated perturbation of the brain's chemistry may bring about changes in the circuitry of the brain that may underlie lasting changes in behavior. Changes in the brain's circuitry presumably reflect the strengthening and weakening of synapses through mechanisms such as changes in the number of receptors, changes in the amount of neurotransmitter released, and changes in intracellular biochemical pathways that are activated by membrane receptors. Growth of new dendrites to form new synapses or deterioration of existing synapses may also be involved.
It is likely that extended use of any psychoactive drug will bring about homeostatic changes in brain physiology that will result in symptoms of withdrawal if use of the drug is stopped.
The mind is a collection of mental states, including thoughts, feelings and perceptions, experienced by the organism. The current working hypothesis in neuroscience is that the mind is associated with the brain, and that neural processes taking place in the brain somehow generate the qualities of mind. Consciousness is an aspect of mind that involve s awareness of these mental states.
KEY POINTS FROM NATURE; https://www.nature.com/articles/nrn1496%E2%80%8B
- General anaesthetics are defined by their capacity to produce a state in which surgery can be tolerated without the need for further drugs. They are widely used in both clinical medicine and neuroscience research, but we are only just beginning to understand the molecular mechanisms that underlie their actions.
- The goals of the anaesthetic state are immobility, unconsciousness and amnesia. It is widely accepted that general anaesthetics cause immobility by depressing spinal neurons, and amnesia and hypnosis by acting on neurons in the brain. However, there is evidence that their spinal actions also influence sedative and hypnotic effects, and conversely, that descending signals from the brain to the spinal cord modify their immobilizing effects.
- There is a long list of molecular targets, the activity of which is mediated by at least one general anaesthetic, including numerous types of ligand-gated ion channel. In recent years, the GABAA (γ-aminobutyric acid type A) receptor system has attracted considerable attention as a target for general anaesthetics.
- The great heterogeneity of GABAA receptors has long precluded the attribution of physiological and pharmacological functions to specific subtypes. However, using knock-in point mutations in mice, it has been possible to identify specific GABAA-receptor subtypes that are involved in the actions of the intravenous anaesthetics etomidate and propofol.
- By integrating results from pharmacological, molecular genetic, functional imaging and electrophysiological studies, we should be able to gain further insights into the mechanisms of anaesthetic action. These insights might also provide avenues for the design of new general anaesthetics with an improved side-effect profile.
Papaver somniferum, native to the Middle East and north Africa, now grown throughout the world.
In 1803, morphine became the first physiologically active compound to be isolated and identified from a plant.
Acting at opioid receptors in the digestive system, opioids slow intestinal motility and thus are valuable treatments for diarrhea.
Anesthesiologist Focus
- Patient Safety
- Amnesia & Awareness
- Medical management
- Physiologic Homeostasis
- Special Procedures
- Monitor: Blood Pressure, Pulse, Reflex Movement, EEG, Stimulated EMG
- Keep the patient paralyzed so they don't move/Keep the patient un-paralyzed and keeping them from moving
- Planning for when the patient wakes up/Keeping the patient asleep so they don't have awareness
- Keeping the blood pressure down to reduce blood loss/Keeping the blood pressure high to reduce chance of blindness and neurological injury; ability to monitor motor evoked potential
Anesthesia is the loss of bodily sensation with or without the loss of consciousness.
Biochemical reactions; see presti for more information
Theory of anesthesia
- Brainstem Depression
- Block sensory inputs at the thalamus
- Block cortical information processing
Changes in monitoring/Mechanisms of Anesthesia
- Synaptic Inhibition
- Thalamic Blocking; Keeping Asleep
- Spinal Cord Blocking; Keeping from moving
- Blocking of the neuromuscular junction
- Physiological effects; blood pressure
Stage 1 -Analgesia or Induction - patient experiences slight dizziness, a sense of unreality and a lessening sensitivity to touch and pain. The patients sense of hearing is increased and responses to noises are intensified. Induction - initiation of anesthesia via intravenous and possibly inhalation anesthetics. because the drugs enter the bloodstream, usually cause unconsciousness in less than 1 minute. gasses also act quickly but they must be inhaled for a short time before they cause unconsciousness
- Stage 3 - Surgical Anesthesia - the skeletal muscles relax and the patients breathing becomes regular. eye movements slow, then stop and surgery can begin. Stage 3 can be divided into 4 planes
- blink and swallowing reflexes present, regular respiration with good chest motion. This stage would be considered "light"
- loss of blink reflexes, pupils become fixed in one position (usually central) and respiration is still regular with good use of the chest muscles and diaphragm
- patient starts to lose the ability to use the chest muscles and abdominal muscles for respiratory efforts, so breathing become shallow and assisted ventilation is best "deep anesthesia"
- patient does not use the chest muscles and abdominal muscles at all, which means that all respiratory effort may cease
cardiovascular, pulmonary and renal emergence
Peripheral Nerves
Spinal Cord II Runoff
Talk about the segmental nature of the spinal cord, cervical and lumbar enlargements and the relationship of size to innervation and dynamic effect on muscles. The butterfly pattern, the dorsal versus ventral, white matter versus gray. cuneate versus gracilis, intermediolateral cell column, the different tracts, etcetera.
The slice through the spinal cord shown in Figure 2-3A is stained for myelinated axons.
Motor cell bodies (anterior horn cells) are located in the ventral gray matter of the spinal cord and project their axons to skeletal muscle.
The dorsal column medial lemniscal tract are composed of primary afferent axons which convey somatic sensory information to brain stem lateral columns and from the brainstem lateral columns to and higher centers. Between the gray matter on the two sides of the spinal cord is the central canal, a component of the ventricular system. Portions of the central canal become closed in the adult.
Gray & White Matter/Information Transfer/Ascending & Descending/Afferent & Efferent/Circuitry/Dynamic Function
Organization of dorsal root ganglia and the segmental organization of the spinal cord
A cross section of the spinal cord illustrates the butterfly shape and there is the cervical and lumbar enlargement and a build up from sacral to cervical. pattern of innervation to the areas of enlargements illustrate the dynamic function of ***Butterfly shaped pattern, Lissauer's
The dorsal horn serves as a highway for entering ganglion cell fibers but receives no touch-related synaptic endings. Intercalated spinal interneuron and reciprocal inhibition ensure precise and protective motor control.
Adequate stimulus is the strength of a sensory cue required to elicit a motor output.
Spinal interneurons: a model system for the study of control of motoneuron discharge.
The dermatomes provide a segmental map of the body surface that is conserved in the brain. Innervation density is proportional to sensitivity or fineness of movement.
Lissauer's tract is the entry zone into the dorsal spinal cord.***
Talk about the segmental nature of the spinal cord, cervical and lumbar enlargements and the relationship of size to innervation and dynamic effect on muscles. The butterfly pattern, the dorsal versus ventral, white matter versus gray. cuneate versus gracilis, intermediolateral cell column, the different tracts, etcetera.
The slice through the spinal cord shown in Figure 2-3A is stained for myelinated axons.
Motor cell bodies (anterior horn cells) are located in the ventral gray matter of the spinal cord and project their axons to skeletal muscle.
The dorsal column medial lemniscal tract are composed of primary afferent axons which convey somatic sensory information to brain stem lateral columns and from the brainstem lateral columns to and higher centers. Between the gray matter on the two sides of the spinal cord is the central canal, a component of the ventricular system. Portions of the central canal become closed in the adult.
Gray & White Matter/Information Transfer/Ascending & Descending/Afferent & Efferent/Circuitry/Dynamic Function
Organization of dorsal root ganglia and the segmental organization of the spinal cord
A cross section of the spinal cord illustrates the butterfly shape and there is the cervical and lumbar enlargement and a build up from sacral to cervical. pattern of innervation to the areas of enlargements illustrate the dynamic function of ***Butterfly shaped pattern, Lissauer's
The dorsal horn serves as a highway for entering ganglion cell fibers but receives no touch-related synaptic endings. Intercalated spinal interneuron and reciprocal inhibition ensure precise and protective motor control.
Adequate stimulus is the strength of a sensory cue required to elicit a motor output.
Spinal interneurons: a model system for the study of control of motoneuron discharge.
The dermatomes provide a segmental map of the body surface that is conserved in the brain. Innervation density is proportional to sensitivity or fineness of movement.
Lissauer's tract is the entry zone into the dorsal spinal cord.***
Winer Spinal Cord
Spinal Cord Runoff
Spinal cord vs brain stem Similarities
only structure that his modular..., reminiscent of its embryonic and phylogenetic origins
(the terms dorsal and ventral describe the spatial relations of structures)
There are differences and similarities between brain stem and spinal structures. The cranial nerves are functinally homologous to spinal nerves but more complex and functionally defined. The reticular formation is similar to the intermediate zone of spinal gray. They differ as the long ascending and descending tracts do not run on the outside and the cerebellum and it's pathways are incorporated.
The spinal cord is a thin cylindrical structure consisting of bundles of nerve fibers and associated tissue that is enclosed in the vertebral column and connects nearly all parts of the body to the brain, with which it forms the central nervous system.
consists of bundles of nerve fibers and associated tissue that is enclosed and descends caudally through the vertebral column. It is approximately 45 cm long and with a diameter of approximately 8mm (pencil thick).
It begins superiorly/rostrally at the foramen magnum of the skull and ends at the level of the first or second lumbar vertebra as the conus medullaris. It is approximately the diameter of a pencil.
The spinal cord is protected by the individual vertebrae and collectively in the vertebral column and surrounded by fluid called cerebral spinal fluid.
The Conus Medullaris is termination of spinal cord, in most adults at L1/L2. The Cauda Equina (horses tail) is below the level of the spinal cord and conus medullaris and consists of the spinal nerves that extend downwards into the canal prior to exiting into the foramen of the vertebrae
The spinal cord is surrounded by meninges (dura mater) similar to those that surround the brain. The adult spinal cord begins at the caudal margin of the medulla at the level of and exiting through the foramen magnum and terminates opposite the caudal margin of approximately the first lumbar vertebra.
Spinal Segments
1 C1
2 C2
3 C3
4 C4
5 C5
6 C6
7 C7
8 C8
9 T1
10 T2
11 T3
12 T4
13 T5
14 T6
15 T7
16 T8
17 T9
18 T10
19 T11
20 T12
21 L1
22 L2
23 L3
24 L4
25 L5
26 S1
27 S2
28 S3
29 S4
30 S5
31 CO1
Martin 32
Lower Extremity Nerves
Peripheral Nerve
Internal structure different at different levels 18-2;
The spinal cord has a modular organization, in which every segment has a similar basic structure.
Spinal cord vs brain stem Similarities
- cranial nerves are functional homologous to spinal nerves 44-1, 44-2 but more complex and functionally defined
- dorsal afferents, ventral afferents 44-6, 44-7
- reticular formation like intermediate zone of spinal grey 44-10
- long ascending and descending tracts don't run on the outside 18-4, 22-14
- cerebellum and it's pathways are incorporated 41-1
only structure that his modular..., reminiscent of its embryonic and phylogenetic origins
(the terms dorsal and ventral describe the spatial relations of structures)
There are differences and similarities between brain stem and spinal structures. The cranial nerves are functinally homologous to spinal nerves but more complex and functionally defined. The reticular formation is similar to the intermediate zone of spinal gray. They differ as the long ascending and descending tracts do not run on the outside and the cerebellum and it's pathways are incorporated.
The spinal cord is a thin cylindrical structure consisting of bundles of nerve fibers and associated tissue that is enclosed in the vertebral column and connects nearly all parts of the body to the brain, with which it forms the central nervous system.
consists of bundles of nerve fibers and associated tissue that is enclosed and descends caudally through the vertebral column. It is approximately 45 cm long and with a diameter of approximately 8mm (pencil thick).
It begins superiorly/rostrally at the foramen magnum of the skull and ends at the level of the first or second lumbar vertebra as the conus medullaris. It is approximately the diameter of a pencil.
The spinal cord is protected by the individual vertebrae and collectively in the vertebral column and surrounded by fluid called cerebral spinal fluid.
The Conus Medullaris is termination of spinal cord, in most adults at L1/L2. The Cauda Equina (horses tail) is below the level of the spinal cord and conus medullaris and consists of the spinal nerves that extend downwards into the canal prior to exiting into the foramen of the vertebrae
The spinal cord is surrounded by meninges (dura mater) similar to those that surround the brain. The adult spinal cord begins at the caudal margin of the medulla at the level of and exiting through the foramen magnum and terminates opposite the caudal margin of approximately the first lumbar vertebra.
Spinal Segments
- 8 Cervical
- 12 Thoracic
- 5 Lumbar
- 5 Sacral
1 C1
2 C2
3 C3
4 C4
5 C5
6 C6
7 C7
8 C8
9 T1
10 T2
11 T3
12 T4
13 T5
14 T6
15 T7
16 T8
17 T9
18 T10
19 T11
20 T12
21 L1
22 L2
23 L3
24 L4
25 L5
26 S1
27 S2
28 S3
29 S4
30 S5
31 CO1
Martin 32
Lower Extremity Nerves
Peripheral Nerve
Internal structure different at different levels 18-2;
The spinal cord has a modular organization, in which every segment has a similar basic structure.
Spinal Cord Runoff
I would like to introduce you to the regional and segmental levels of the spinal cord.
The dura mater surrounding the brain continues downward and completely envelopes the spinal cord. The outer or periosteal layer of dura is closely adherent to the walls of the vertebral (spinal) canal, serving as its periosteum. the inner or meningeal layer of dura forms a closed tube around the cord and continues caudally as far as the second sacral vertebra, at which level it encloses the filum terminale (9-12). extensions of the dura pass laterally like sleeves along the spinal roots to become continuous with the epineural sheaths of the spinal nerves. The limited space between the inner and outer dural layers is called the epidural space. It contains aggreagates of adipose tissue and the internal vertebral venous plexus. This space is often used as a site for the administration of anesthetic agents in the lumbar or sacral regions, especially in obstetcs.
the spinal cord is closely covered by a thin layer of arachnoid and an inner layer of pia mater. The subarachnoid space contains most of the vessels to the cord. it is this same space that becomes the dural sac caudal to the termination of the spinal cord. Between dural sleeves, along the length of the spinal cord, the pia mater thickens and extends laterally across the subarachnoid space to the meningeal layer of dura mater. These denticulate ligaments suspend the cord within the canal - somewhat like the vertical support cables supporting the roadway of a suspension bridge - and separate the anterior and posterior roots.
Spinal roots; sacral, lumbar, thoracic, cervical, denticular ligaments (mechanical isolation), spinal dura, plexusus (brachial: C1-T1). Sympathetic chain ganglia promotes visceral output for digestion and urine production and parasympathetic ganglia are essential for voluntary control of micturition, ejaculation and milk ejection. The dermatomes provide a segmental map of the body surface that is conserved in the brain. Innervation density is proportional to sensitivity or fineness of movement.
Two subdivisions of the peripheral nervous system are the Autonomic and Somatosensory. Sensory input plays an important part role in motor control as it allows input from the periphery which allows the brain to make conscious control of limbs and movement and *somatic propioception or kinesthesia
A brain stem stroke would affect spinal nerves but not necessarily cranial nerves which would allow for eye blinking but not necessarily control of lower limbs
Runoff Spinal Cord
Spinal Roots
sacral
lumbar
thoracic
cervical
denticular ligaments provide mechanical isolation so that the spinal cord is not subject to physical stress
spinal dura
plexuses (for example, brachial: - C1-T1)
a. clinical importance of the plexuses
b. sympatehtic (thoracicolumbar) chain ganglia: promotes visceral output for digestion and urine production
c. parasympathetic (craniosacral) ganglia: essential for voluntary control of micturition, ejaculation and milk ejection
The Dermatomes provide a segmental map of the body surface that is conserved in the brain
Innervation density is proportional to sensitivity or fineness of movement
filum terminale (plate 9-2)
I would like to introduce you to the regional and segmental levels of the spinal cord.
The dura mater surrounding the brain continues downward and completely envelopes the spinal cord. The outer or periosteal layer of dura is closely adherent to the walls of the vertebral (spinal) canal, serving as its periosteum. the inner or meningeal layer of dura forms a closed tube around the cord and continues caudally as far as the second sacral vertebra, at which level it encloses the filum terminale (9-12). extensions of the dura pass laterally like sleeves along the spinal roots to become continuous with the epineural sheaths of the spinal nerves. The limited space between the inner and outer dural layers is called the epidural space. It contains aggreagates of adipose tissue and the internal vertebral venous plexus. This space is often used as a site for the administration of anesthetic agents in the lumbar or sacral regions, especially in obstetcs.
the spinal cord is closely covered by a thin layer of arachnoid and an inner layer of pia mater. The subarachnoid space contains most of the vessels to the cord. it is this same space that becomes the dural sac caudal to the termination of the spinal cord. Between dural sleeves, along the length of the spinal cord, the pia mater thickens and extends laterally across the subarachnoid space to the meningeal layer of dura mater. These denticulate ligaments suspend the cord within the canal - somewhat like the vertical support cables supporting the roadway of a suspension bridge - and separate the anterior and posterior roots.
Spinal roots; sacral, lumbar, thoracic, cervical, denticular ligaments (mechanical isolation), spinal dura, plexusus (brachial: C1-T1). Sympathetic chain ganglia promotes visceral output for digestion and urine production and parasympathetic ganglia are essential for voluntary control of micturition, ejaculation and milk ejection. The dermatomes provide a segmental map of the body surface that is conserved in the brain. Innervation density is proportional to sensitivity or fineness of movement.
Two subdivisions of the peripheral nervous system are the Autonomic and Somatosensory. Sensory input plays an important part role in motor control as it allows input from the periphery which allows the brain to make conscious control of limbs and movement and *somatic propioception or kinesthesia
A brain stem stroke would affect spinal nerves but not necessarily cranial nerves which would allow for eye blinking but not necessarily control of lower limbs
Runoff Spinal Cord
Spinal Roots
sacral
lumbar
thoracic
cervical
denticular ligaments provide mechanical isolation so that the spinal cord is not subject to physical stress
spinal dura
plexuses (for example, brachial: - C1-T1)
a. clinical importance of the plexuses
b. sympatehtic (thoracicolumbar) chain ganglia: promotes visceral output for digestion and urine production
c. parasympathetic (craniosacral) ganglia: essential for voluntary control of micturition, ejaculation and milk ejection
The Dermatomes provide a segmental map of the body surface that is conserved in the brain
Innervation density is proportional to sensitivity or fineness of movement
filum terminale (plate 9-2)
Cranial Nerve Runoff
In Neuroanatomy, the study of sensation and motor control of cranial structures has traditionally been separate from that of the limbs and trunk. This is because cranial nerves innervate the head, and spinal nerves innervate the limbs and trunk.
The trigeminal system, which mediates somatic sensation from the face and head is analogous to the dorsal column-medial lemniscal and anterolateral systems of the spinal cord. The brain stem neural system that processes sensory information from the body's internal organs. This system is closely aligned with the trigeminal system.
The reticular formation defines a multisensory system for arousal and vigilance. It is present throughout the neuraxis; spinal, medulla, pontine, mesencephalic, diencephalic and intralaminar thalamic nuclei projects to the cortex. Receptive fields are polymodal, broad tuning and pain, temperature and vestibular responses dominate. The neurons of the reticular formation extend dendrites into nearby cranial nerve nuclei.
Cranial nerves are each associated with a specific region of the embryonic brain. Thus cranial nerve I arises from the telencephalon, cranial nerve II from the diencephalon, and so on.
In Neuroanatomy, the study of sensation and motor control of cranial structures has traditionally been separate from that of the limbs and trunk. This is because cranial nerves innervate the head, and spinal nerves innervate the limbs and trunk.
The trigeminal system, which mediates somatic sensation from the face and head is analogous to the dorsal column-medial lemniscal and anterolateral systems of the spinal cord. The brain stem neural system that processes sensory information from the body's internal organs. This system is closely aligned with the trigeminal system.
The reticular formation defines a multisensory system for arousal and vigilance. It is present throughout the neuraxis; spinal, medulla, pontine, mesencephalic, diencephalic and intralaminar thalamic nuclei projects to the cortex. Receptive fields are polymodal, broad tuning and pain, temperature and vestibular responses dominate. The neurons of the reticular formation extend dendrites into nearby cranial nerve nuclei.
Cranial nerves are each associated with a specific region of the embryonic brain. Thus cranial nerve I arises from the telencephalon, cranial nerve II from the diencephalon, and so on.
Nuwer Anatomy
The Organization/Construction of the Brain/Nervous System
Topography of Cranial Nerves
Cranial Nerve RUNOFF
Brainstem runoff: Arousal is controlled by the locus coerulus...
Martin 135
Cranial Nerves and the Trigeminal and Viscerosensory Systems
Martin 259
Cranial Nerve Motor Nuclei and Brain Stem Motor Functions
Organization and Functional Anatomy of Cranial Nerve Motor Nuclei
There are Three Columns of Cranial Nerve Motor Nuclei
The Cranial Motor Nuclei are Controlled by the Cerebral Cortex and Diencephalon
Neurons in the Somatic Skeletal Motor Columns Innervate the Tongue and Extraocular Muscles
Regional Anatomy of Cranial Motor Nuclei Martin Page 269
The Trigeminal Motor Nucleus is Medial to the Main Trigeminal Sensory Nucleus
The Fibers of the Facial Nerve Have a Complex Trajectory Through The Pons
The Glossopharyngeal Nerve Enters and Exits from the Rostral Medulla
A Level Through the Midmedulla Reveals the Locations of Six Cranial Nerve Nuclei
The Spinal Acccessory Nucleus Is Located at the Junction of the Spinal Cord and the Medulla
Summary
Somatic Skeletal Motor Nuclei
Branchiomeric Motor Nuclei
Autonomic Nuclei
Brainstem runoff: Arousal is controlled by the locus coerulus...
Martin 135
Cranial Nerves and the Trigeminal and Viscerosensory Systems
Martin 259
Cranial Nerve Motor Nuclei and Brain Stem Motor Functions
Organization and Functional Anatomy of Cranial Nerve Motor Nuclei
There are Three Columns of Cranial Nerve Motor Nuclei
The Cranial Motor Nuclei are Controlled by the Cerebral Cortex and Diencephalon
Neurons in the Somatic Skeletal Motor Columns Innervate the Tongue and Extraocular Muscles
Regional Anatomy of Cranial Motor Nuclei Martin Page 269
The Trigeminal Motor Nucleus is Medial to the Main Trigeminal Sensory Nucleus
The Fibers of the Facial Nerve Have a Complex Trajectory Through The Pons
The Glossopharyngeal Nerve Enters and Exits from the Rostral Medulla
A Level Through the Midmedulla Reveals the Locations of Six Cranial Nerve Nuclei
The Spinal Acccessory Nucleus Is Located at the Junction of the Spinal Cord and the Medulla
Summary
Somatic Skeletal Motor Nuclei
Branchiomeric Motor Nuclei
Autonomic Nuclei
Brainstem Pathways
Brain Stem Runoff
Descending Brain Stem Pathways 33-14, 33-15
Medial Pathways
Physiological Mechanisms
arousal controlled by the brainstem - locus coeruleus in pons release norepinephrine; vigilance posterior hypo serotonin
slow wave sleep; anterior hypothalamus and basal forebrain lesions cause insomnia leading to coma and death
2 systems of shut down
Descending Brain Stem Pathways 33-14, 33-15
Medial Pathways
- vestibulospinal (medial and lateral) from vestibular nuclei; balance and reflex data from vestibular labyrinth
- reticulospinal; medial from large neurons in pons; facilitates extensors; postural support; gait initiation; lateral inhibits spinal and cranial motor neurons (eg REM sleep) -- from reticular formation of pons and medulla
- connect to interneurons and motor neurons; maintenance of posture; integrate cortical and vestibular info; premotor and motor cortex to reticular formation = cortico-reticulospinal pathway
- suppresses spinal reflexes
- tectospinal - descending ipsilateral ventral columns; terminate on interneurons, long proprioception, some medial motor neurons; superior colliculus (midbrain), projects contralaterally to the cervical cortico-tectospinal pathway -- head and eye -- gaze
- lateral pathway; rubrospinal -- from magnocellular red nucleus in the midbrain; along lateral white to dorsolateral mn, lateral interneurons, fine control, reaching and manipulating, in humans the red nucleus is small
Physiological Mechanisms
arousal controlled by the brainstem - locus coeruleus in pons release norepinephrine; vigilance posterior hypo serotonin
slow wave sleep; anterior hypothalamus and basal forebrain lesions cause insomnia leading to coma and death
2 systems of shut down
- serotonergic and noradrenergic neurons become silent
- acetlycholinergic neurons in pons become active
RUNOFF BRAIN STEM
Continued as The Pontine Nuclei and The Dorsal Surface of the Midbrain on page 37
The next several sections address brain stem anatomy by examining transverse sections through five key levels: 1 the spinal cord-medullary junction, 2 the caudal medulla, 3 the middle medulla 4 the caudal pons and 5 the rostral midbrain. Knowledge on the surface features of the brain stem helps in recognizing the level of a particular section
Martin 8
The Brain Stem and Cerebellum Regulate Body Functions and Movements
Parts of the pons and midbrain play a key role in the control of eye movement.
The brainstem generally has three functions.
The brainstem consists of the portion of the brain that remains after removal of the cerebral and cerebellar hemispheres and includes the midbrain, pons and
For example, portions of the medulla participate in essential blood pressure and respiratory regulatory mechanisms.
The rostral spinal cord merges with the brain stem, as can be seen in Figure 2-5 which illustrates the dorsal and ventral surfaces of these structures.
Martin 35
Surface Features of the Brain Stem Mark Key Internal Structures
The medullary section in Figure 2-7 is from a person who sustained a corticospinal system injury. Axons in the pyramid on one side have degenerated. Because of the absence of staining of that pyramid, the ventral border of the medial lemniscus is apparent.
Some neurons of the modulatory systems described above are located in the reticular formation.
Continued as The Pontine Nuclei and The Dorsal Surface of the Midbrain on page 37
The next several sections address brain stem anatomy by examining transverse sections through five key levels: 1 the spinal cord-medullary junction, 2 the caudal medulla, 3 the middle medulla 4 the caudal pons and 5 the rostral midbrain. Knowledge on the surface features of the brain stem helps in recognizing the level of a particular section
Martin 8
The Brain Stem and Cerebellum Regulate Body Functions and Movements
Parts of the pons and midbrain play a key role in the control of eye movement.
The brainstem generally has three functions.
The brainstem consists of the portion of the brain that remains after removal of the cerebral and cerebellar hemispheres and includes the midbrain, pons and
For example, portions of the medulla participate in essential blood pressure and respiratory regulatory mechanisms.
The rostral spinal cord merges with the brain stem, as can be seen in Figure 2-5 which illustrates the dorsal and ventral surfaces of these structures.
Martin 35
Surface Features of the Brain Stem Mark Key Internal Structures
The medullary section in Figure 2-7 is from a person who sustained a corticospinal system injury. Axons in the pyramid on one side have degenerated. Because of the absence of staining of that pyramid, the ventral border of the medial lemniscus is apparent.
Some neurons of the modulatory systems described above are located in the reticular formation.
Brain Vascular RUNOFF
The origin, course and distribution of the internal carotid arteries are illustrated in a schematic anterior view.
At the root of the internal carotid artery, a swelling or thickening in the arterial wall, called the carotid sinus, incorporates pressure receptors connected to the sinus nerve.
In this plate, three views of the brain illustrate the inter-related distribution of branches of these three arteries.
This plate offers a semi-schematic view of the deep forebrain vessels branching from the three major cortical arteries.
The origin, course and distribution of the internal carotid arteries are illustrated in a schematic anterior view.
At the root of the internal carotid artery, a swelling or thickening in the arterial wall, called the carotid sinus, incorporates pressure receptors connected to the sinus nerve.
In this plate, three views of the brain illustrate the inter-related distribution of branches of these three arteries.
This plate offers a semi-schematic view of the deep forebrain vessels branching from the three major cortical arteries.
Runoff Blood Vascular
Extremely critical; circle of willis, pathway extending from the heart to the brain; cerebral arteries, jugular, vs vertebral arteries and the percentage of blood they bring. sensitivity of positioning
*LH*
Blood supply
Brain requirements - 20% of blood pumped by the heart, 20% of bodies oxygen, blood flow cessation; 5-10 seconds results in temporary neuronal changes, 5-10 minutes can result in permanent neuronal changes or death
Circulation in the brain - the circle of willis; internal carotid artery, basilar artery, vertebral arteries, anterior cerebral artery, middle cerebral artery, posterior cerebral artery, anterior communicating artery, posterior communicating artery
Middle cerebral watershed area
anterior cerebral watershed area
posterior cerebral watershed area
Extremely critical; circle of willis, pathway extending from the heart to the brain; cerebral arteries, jugular, vs vertebral arteries and the percentage of blood they bring. sensitivity of positioning
*LH*
Blood supply
Brain requirements - 20% of blood pumped by the heart, 20% of bodies oxygen, blood flow cessation; 5-10 seconds results in temporary neuronal changes, 5-10 minutes can result in permanent neuronal changes or death
Circulation in the brain - the circle of willis; internal carotid artery, basilar artery, vertebral arteries, anterior cerebral artery, middle cerebral artery, posterior cerebral artery, anterior communicating artery, posterior communicating artery
Middle cerebral watershed area
anterior cerebral watershed area
posterior cerebral watershed area
Diamond
Blood Supply to the Brain: Internal Carotid Arteries
Blood Supply to the Brain: Internal Carotid Arteries
RUNOFF PHYSIOLOGY OF NEURONS
Knowing the location and function of the structural components of the nervous system permits localization of the site of a lesion.
The temporal (timing) profile of the major types of disease assists in identifying the cause of the disorder
The one temporal profile that has not yet been considered is that of the transient or rapidly reversible abnormality. many diseases that produce signs or symptoms of brief duration may not produce destructive changes in cells and may occur without demonstrable histologic.
Many diseases that produce signs or symptoms of brief duration may not produce destructive changes in cells and may occur without demonstrable histologic abnormality of the involved structures. To understand transient manifestations of disease, it is necessary to understand the mechanism by which the cells of the nervous system process information and to understand their physiology. transient alterations in the physiology of the cells cause transient symptoms and signs.
Knowing the location and function of the structural components of the nervous system permits localization of the site of a lesion.
The temporal (timing) profile of the major types of disease assists in identifying the cause of the disorder
The one temporal profile that has not yet been considered is that of the transient or rapidly reversible abnormality. many diseases that produce signs or symptoms of brief duration may not produce destructive changes in cells and may occur without demonstrable histologic.
Many diseases that produce signs or symptoms of brief duration may not produce destructive changes in cells and may occur without demonstrable histologic abnormality of the involved structures. To understand transient manifestations of disease, it is necessary to understand the mechanism by which the cells of the nervous system process information and to understand their physiology. transient alterations in the physiology of the cells cause transient symptoms and signs.
Runoff Motor Cortex
There is a hierarchy of motor systems:
There is a hierarchy of motor systems:
- Spinal cord, motor systems of the brain stem and motor areas of the cortex; SC < BS < Cerebral Cortex
- Spinal Cord - mediates reflexes, contains pattern generators, can "learn", motor neurons = the final common path
- The Brain Stem - regulates spinal networks, integration of visual and vestibular information, nuclei control head and eye movements
- Cerebral Cortex - motor cortex, premotor cortex, supplementary motor area; direct connection to spinal cord through corticospinal tract and indirect connections through the brain stem
- parallel organization; e.g. cortex controls the brain stem and spinal cord
- Cerebellum, basal ganglia are independent, subcortical motor areas
- inputs from motor association areas, S1, brain stem
- homunculi and plasticity thereof
- output through corticospinal tracts
- M1 encodes force and direction
- force from Evarts experiments
- force from Fetz experiments
- broad directional tuning of individual units; good directionality from population 18-5,6,7,8
- spinoreticular --pain, temperature; anterolateral tract
- spinomesencephalic - spinotectal -- crude touch
- inputs from motor association areas, S1, brain stem
- homunculi and plasticity thereof
- output through corticospinal tracts
- M1 encodes force and direction
- force from Evarts experiments
- force from Fetz experiments
- broad directional tuning of individual units; good directionality from population 18-5,6,7,8
- spinoreticular --pain, temperature; anterolateral tract
- spinomesencephalic - spinotectal -- crude touch
Runoff Motor Cortex
Ventral roots; efferent fibers traveling in both peripheral and cranial nerves; and muscle, the major effector organ of the motor system. Also included in the motor system are the cerebellum and basal ganglia.
The Primary motor cortex receives inputs from motor associations, S1 and the brainstem. The Motor Homunculuis is topically arranged and outputs through the corticospinal tracts. M1 encodes force and direction. Spinoreticular pathway, pain and temperature in the anterolateral tract. Spinomesencephalic and spinotectal crude touch.
recruitment of motor neurons affected by force, not displacement. more neuronal activity if one pushed a heavy box 10 feet versus a cotton ball 10 feet.
Primary Motor Cortex is M1.
Ventral roots; efferent fibers traveling in both peripheral and cranial nerves; and muscle, the major effector organ of the motor system. Also included in the motor system are the cerebellum and basal ganglia.
The Primary motor cortex receives inputs from motor associations, S1 and the brainstem. The Motor Homunculuis is topically arranged and outputs through the corticospinal tracts. M1 encodes force and direction. Spinoreticular pathway, pain and temperature in the anterolateral tract. Spinomesencephalic and spinotectal crude touch.
recruitment of motor neurons affected by force, not displacement. more neuronal activity if one pushed a heavy box 10 feet versus a cotton ball 10 feet.
Primary Motor Cortex is M1.
SENSORY SYSTEM
Primary Somatosensory Cortex 20-1, 3,4,5,6,7
Primary Somatosensory Cortex is S1. There is S1, S1 and S3
Primary Somatosensory Cortex 20-1, 3,4,5,6,7
- inputs from the periphery through the thalamus
- 3 cytoarch. areas
- homunculus, plasticity of the homunculus figs 18-5,6
- outpus to other areas of cortex, to cerebellum, to brain stem and spinal cord
Primary Somatosensory Cortex is S1. There is S1, S1 and S3
Primary Motor Cortex 38-1,4,6,7,8,10,12,13,17
- inputs from motor association areas, S1, brain stem
- homunculi and plasticity thereof
- output through corticospinal tracts
- M1 encodes force and direction
- force from Evarts experiments
- force from Fetz experiments
- broad directional tuning of individual units; good directionality from population 18-5,6,7,8
- spinoreticular --pain, temperature; anterolateral tract
- spinomesencephalic - spinotectal -- crude touch
Neural/Motor Control of Muscle
Neuromuscular Motor Control
BRAIN II MENINGES RUNOFF
The major structures of the central nervous system - the brain, brain stem and the spinal cord are surrounded by three fibrous connective tissue linings called meninges.
The major structures of the central nervous system - the brain, brain stem and the spinal cord are surrounded by three fibrous connective tissue linings called meninges.
Neuromuscular Junction Runoff
Neuromuscular junction
Neuromuscular junction
- overview
- presynaptic differentiation
- postsynaptic differentiation
- agrin
- neurregulin
- activity
- modal systems
- timeline of events
- chapter 55 in Kandel
- end of axon (terminal, synaptic bouton) has specialization for action potential
- vesicle fusion
- calcium coming in for fusion of vesicles
- pre and post synaptic elements must come together
- recognize post syanptic targe; there is a recognition process
- growth cone responsible for making navigational choice to get into the right place
- vesicles and quanta
- advantage of neuromuscular junction synapse is that it's huge
- alpha bungrotoxin has high affinity for acetylcholine receptors
- invagination of membrane has folds that allow for many connections
- motor neurons innervate muscle, muscle is made up of fibers
- each muscle fiber gets input from one motor neuron
- basal lamina - larger of extracellular matrix that lies over the muscle
- underneath is important for synaps
- motor neuron, muscle fiber, schwann cells
Molecular Components of the Neuromuscular Junction
- emphasized proteins
- identify proteins in whatever stage and then knock them out
- immunocytochemistry - put fluorescent tags and watch what happens
- growth cone approaches myotube (muscle fiber)
- have vesicles in them
- spits out acetylcholine even before reaches tube
- basal lamina appears
- multiple axons innervate; polyinnervation
- synapse elimination so there is only one
- growth cones are functional, can release vesicles
- Moo Ming Poo saw synaptic currentsin presynaptic cell releasing acetylcholine
- as soon as touches muscle there is a rapid enhancement of releasing neurotransmitter
- spontaneous fusion events leads to rapid increase in size and frequency
- complicated events of calcium influx to release vescicles ? to happen immediately which results in to behave as normal axon
- Rapid presynaptic maturation
Nervous system anatomy consists of Peripheral and Central Components
Peripheral
Central
Peripheral
- ganglia and peripheral nerves
- Somatic; sensory neurons of dorsal root and cranial ganglia innervating skin, muscles and joints
- Autonomic; motor systems of the viscera, smooth muscles, exocrine glands. 3 spatially segregated subdivisions
- sympathetic system -- response to stress
- parasympathetic system -- homeostasis, conserve resources
- enteric system -- the gut
Central
- Coordinates include rostral to caudal & ventral to dorsal
- 6 main regions
- spinal cord
- medulla
- pons and cerebellum
- midbrain
- diencephalon
- cerebral hemispheres
Runoff Cerebral Cortex
Martin 11
The Cerebral Hemispheres have the most complex three dimensional configuration of all central nervous system divisions
The cerebral hemispheres are the most highly developed portions of the human central nervous system. Each hemisphere is a distinct half, and each has four major components: cerebral cortex, hippocampal formation, amygdala, and basal ganglia. Togehter, these structures mediate the most sophisticated of human behaviors, and they do so through complex anatomical connections.
The four lobes of the cerebral cortex each have distinct functions
The cerebral cortex, which is located on the surface of the brain, is highly convoluted. Convolutions are an evolutionary adaptation to fit a greater surface area within the confined space of the cranial cavity. In fact, only one quarter to one third of the cerebral cortex is exposed on the surface. The elevated convolutions on the cortical surface, called gyri, are separated by grooves called sulci or fissures (which are particularly deep sulci). The cerebral hemispheres are separated from each other by the sagittal fissure.
The four lobes of the cerebral cortex are named after the cranial bones that overlie them: frontal, parietal, occipital, and temporal. The functiions of the different lobes are remarkably distinct, as are the functions of individual gyri within each lobe.
Martin 11
The Cerebral Hemispheres have the most complex three dimensional configuration of all central nervous system divisions
The cerebral hemispheres are the most highly developed portions of the human central nervous system. Each hemisphere is a distinct half, and each has four major components: cerebral cortex, hippocampal formation, amygdala, and basal ganglia. Togehter, these structures mediate the most sophisticated of human behaviors, and they do so through complex anatomical connections.
The four lobes of the cerebral cortex each have distinct functions
The cerebral cortex, which is located on the surface of the brain, is highly convoluted. Convolutions are an evolutionary adaptation to fit a greater surface area within the confined space of the cranial cavity. In fact, only one quarter to one third of the cerebral cortex is exposed on the surface. The elevated convolutions on the cortical surface, called gyri, are separated by grooves called sulci or fissures (which are particularly deep sulci). The cerebral hemispheres are separated from each other by the sagittal fissure.
The four lobes of the cerebral cortex are named after the cranial bones that overlie them: frontal, parietal, occipital, and temporal. The functiions of the different lobes are remarkably distinct, as are the functions of individual gyri within each lobe.
Nervous System Development
- The entire nervous system arises from the ectoderm
- 3 main layers in the gastrula
- endoderm; gut, lungs and liver
- mesoderm; connective tissue, muscle, vascular system
- ectoderm; central and peripheral nervous systems, epidermis of the skin
- neural plate folds into the neural tube (neurulation); caudal part becomes the spinal cord, rostral part becomes the brain
- proliferation of cells forms 3 vesicles:
- forebrain; telencephalon; cerebral cortex, basal ganglia, hippocampus, amygdale, olfactory bulb and diencephalon
- midbrain; mesencephalon; midbrain
- hindbrain; metencephalon; pons and cerebellum
- myelencephalon; medulla
10 to the 9 neurons in the adult, 10 to the 12 synapses in the adult, much more in children, lose inappropriate synapses as age
enhanced environment promotes synaptic growth and strengthening
neuromuscular junction refinement muscle undergoes refinement post natally; retracted axons form multi innervated muscle
neutrototoxin - from the pufferfish is a potent neurotoxin that blocks voltage gated sodium channels; TTX blocks nerve conduction at the axon pre and post synaptic activity
enhanced environment promotes synaptic growth and strengthening
neuromuscular junction refinement muscle undergoes refinement post natally; retracted axons form multi innervated muscle
neutrototoxin - from the pufferfish is a potent neurotoxin that blocks voltage gated sodium channels; TTX blocks nerve conduction at the axon pre and post synaptic activity
Sleep and dreaming
prion protein - those w/ insomnia don't have which causes it to fold the wrong way. a misfolded aggregate only need one allele; dominant train
sleep is different from a coma because of reversability, monitored by electrical recordings
Stages of sleep; EMG, EEG NREM sleep have activity, EOG REM Sleep
Sensations
Wake - vivid, externally generated
NREM - dull or absent
REM - vivid internally generated, not induced by external stimuli; dreaming; EMG is low, completely relaxed low muscle tone EEG has some coding
Stage 1 - wakefullness ; solwer freq waves emerge EEG; EMG some activity due to skeletal muscle
Stage 2 sleep si=pindles brain inhibiting gen activity; high ampl, slow delta waves, slow wave activity increase and dominates the EEG record
Stages REM - Rapid eye movement; body temperature and metabolic rate rises
neurons in PONS - LGN and occipital cortex fire more ntensely than during wakefulness, PO waves prominantly find during REM sleep
REM sleep - no muscle tone but brain is very negative
never go from awakeness to REM sleep, as time progresses spend a lot more time in REM sleep
Fourth Ventricle; spinocerebellum
dentate - motor planning lateral corticospinal tract; distal limb coordination;
vermis and flocculonodular balance and vestibuloocular reflexes; medial longitudinal fasciculus
prion protein - those w/ insomnia don't have which causes it to fold the wrong way. a misfolded aggregate only need one allele; dominant train
sleep is different from a coma because of reversability, monitored by electrical recordings
Stages of sleep; EMG, EEG NREM sleep have activity, EOG REM Sleep
Sensations
Wake - vivid, externally generated
NREM - dull or absent
REM - vivid internally generated, not induced by external stimuli; dreaming; EMG is low, completely relaxed low muscle tone EEG has some coding
Stage 1 - wakefullness ; solwer freq waves emerge EEG; EMG some activity due to skeletal muscle
Stage 2 sleep si=pindles brain inhibiting gen activity; high ampl, slow delta waves, slow wave activity increase and dominates the EEG record
Stages REM - Rapid eye movement; body temperature and metabolic rate rises
neurons in PONS - LGN and occipital cortex fire more ntensely than during wakefulness, PO waves prominantly find during REM sleep
REM sleep - no muscle tone but brain is very negative
never go from awakeness to REM sleep, as time progresses spend a lot more time in REM sleep
Fourth Ventricle; spinocerebellum
dentate - motor planning lateral corticospinal tract; distal limb coordination;
vermis and flocculonodular balance and vestibuloocular reflexes; medial longitudinal fasciculus
RUNOFF
and has been postulated to play a role in binding together neural assemblies responding to stimuli to create a packet of tissue responsive to and capable of recognizing complex stimuli. However, circuits interconnected by excitatory synapses are inherently unstable and over-stimulation or over synchronization can lead to uncontrolled or paroxysmal excitation, disrupting normal information processing functions. Normally, inhibitory circuits hold excitatory circuits in check but if inhibition is compromised, focal seizures can result. When this occurs, sensory perception is interrupted (if it happens in sensory cortex), physical seizures result (if it happens in motor cortex) or lapses of judgement, awareness or consciousness result (if it happens in association cortex).
Dorsal and Ventral Pre-Motor Cortex
Neural Plasticity - Neighboring areas will reduce in compensation with areas that grow
and has been postulated to play a role in binding together neural assemblies responding to stimuli to create a packet of tissue responsive to and capable of recognizing complex stimuli. However, circuits interconnected by excitatory synapses are inherently unstable and over-stimulation or over synchronization can lead to uncontrolled or paroxysmal excitation, disrupting normal information processing functions. Normally, inhibitory circuits hold excitatory circuits in check but if inhibition is compromised, focal seizures can result. When this occurs, sensory perception is interrupted (if it happens in sensory cortex), physical seizures result (if it happens in motor cortex) or lapses of judgement, awareness or consciousness result (if it happens in association cortex).
Dorsal and Ventral Pre-Motor Cortex
Neural Plasticity - Neighboring areas will reduce in compensation with areas that grow
Cerebral Cortex Runoff
supra chiasmatic nucleus
ocular dominance columns
cortical plasticity and ocular dominance
auditory, olfaction, visual system; labeled line as combinational code
hebbian plasticity; ca-3 ca1 synapse; NMDA receptor
inferior olivary nucleus
climbing and mossy fiber synapse
LTD and climbing fiber
Long term depression and LT potentiation
coincidence firing causes something to change
autonomic nervous system ANS; sympathetic vs parasympathetic
decussation of DCML vs Anterolateral System
supra chiasmatic nucleus
ocular dominance columns
cortical plasticity and ocular dominance
auditory, olfaction, visual system; labeled line as combinational code
hebbian plasticity; ca-3 ca1 synapse; NMDA receptor
inferior olivary nucleus
climbing and mossy fiber synapse
LTD and climbing fiber
Long term depression and LT potentiation
coincidence firing causes something to change
autonomic nervous system ANS; sympathetic vs parasympathetic
decussation of DCML vs Anterolateral System
Many drug treatments for epilepsy focus on re-invigorating synaptic inhibition, particularly at synapses using the transmitter GABA. GABA receptors have a secondary binding site for a class of drugs called benzodiazepines, such as diazepam. Diazepam binding itself does not open the receptor channel but it enhances the frequency of opening in the presence of GABA thus strengthening inhibitory function. Barbiturates also bind at a secondary site to GABA receptors and their effect is to prolong receptor channel openings activated by GABA barbiturates also block excitatory glutamate receptors. A third class of anti-convulsion drug, exemplified by phenoytin reduces sodium accumulation in nerve terminals reducing the magnitude of PTP and hence reducing synaptic strength following repetitive activy. All these drugs are used clinically in the treatment of epilepsy.
This is just what happens in epilepsy, a neurological disorder usually due to compromised inhibition that results in localized seizures or specific loss sensation due to sudden, temporary, paroxysmal but focal cortical neuronal discharges. In generalized epilepsy, these focal seizures spread to larger brain areas, resulting in loss of consciousness or collapse and large scale muscle seizures. Seizures begin with recurrent focal bursts of action potentials occurring in synchrony among principal neurons in a cortical region, called iterictal spikes because they occur before the onset of overt seizures. Each such spike is triggered by a depolarizing shift occurring in individual cells, due to an envelope of EPSPs not counterbalanced by the usual inhibition. Riding on the EPSPs are action potentials in each cell. Synchronized spiking in cells appears extracellularly as a large synchronous negative field potential, due to synchronous action potential firing. The underlying wave of EPSPs also appears extracellularly as a negative field potential in regions near cell dendrites where most synapses are located, which act as sinks of synaptic current. This current flows out of cell bodies, which act as extracellular sources and near them the depolarizing shift will appear as a positive field potential. Full-blown seizures are accompanied by longer and larger bouts of activity called ictal discharges.
Summary of the Connections of the Cortical Layers
Afferent Input
non-specific thalamic
corticocortical
commissural
corticocortical
commissural
non-specific thalamic
non-specific thalamic
corticocortical
commissural
corticocortical
commissural
non-specific thalamic
Efferent Target
interlaminal
corticocortical
commissural
corticocortical
midbrain, brain stem, sc
thalamus
interlaminal
corticocortical
commissural
corticocortical
midbrain, brain stem, sc
thalamus
Main Neuron Type
non-pyramidal
pyramidal
pyramidal
non-pyramidal
pyramidal
pyramidal
non-pyramidal
pyramidal
pyramidal
non-pyramidal
pyramidal
pyramidal
Main Functions
intrinsic processing
intrinsic processing
interhemispheric pj
initial thalamocort
broad corticofugal
corticofugal thal.
intrinsic processing
intrinsic processing
interhemispheric pj
initial thalamocort
broad corticofugal
corticofugal thal.
Runoff - Cortex
The term cortex means "bark-like" as in the bark on a tree.
The term cortex means "bark-like" as in the bark on a tree.
Runoff
The peripheral nervous system is myelinated by Schwann cells and in the central nervous system oligodendrogliocytes provide myelin sheaths (Amyotrophic Lateral Sclerosis provides an insight into the critical importance of myelin).
The peripheral nervous system is myelinated by Schwann cells and in the central nervous system oligodendrogliocytes provide myelin sheaths (Amyotrophic Lateral Sclerosis provides an insight into the critical importance of myelin).
Runnoff
Afferent sensory neurons are ganglion cells which convey sensory information to the brain and spinal cord.
There are projection neurons that interconnect remote regions of the brain with one another, interneuron cells that contribute to local processing within a nucleus, motor neurons that transmit brain commands to the skeletal muscle and autonomic neurons that sample the interior milieu and make sensory-motor adjustments that are effected by smooth muscle.
Afferent sensory neurons are ganglion cells which convey sensory information to the brain and spinal cord.
There are projection neurons that interconnect remote regions of the brain with one another, interneuron cells that contribute to local processing within a nucleus, motor neurons that transmit brain commands to the skeletal muscle and autonomic neurons that sample the interior milieu and make sensory-motor adjustments that are effected by smooth muscle.
SYNAPSE RUNOFF
The basic structure of a synapse, the types of synapses and the fine detail of the synaptic elements and their functions.
synapses
presynaptic neuron
post-synaptic neuron
presyntaptic terminal
synaptic cleft
receptive membrane
initial segment
neurotransmitter
The basic structure of a synapse, the types of synapses and the fine detail of the synaptic elements and their functions.
synapses
presynaptic neuron
post-synaptic neuron
presyntaptic terminal
synaptic cleft
receptive membrane
initial segment
neurotransmitter
THE NEURON RUNOFF
General descriptive terms:
Afferent - centripetal transfer (toward the CNS) as of information, nerve impulses, etc
Efferent - centrifugal transfer, away from the CNS
Distal - farther from the center of the body
Proximal - closer to the center of the body
Anterior and Posterior - terms sometimes used by human anatomists (because of the human's erect position) for ventral and dorsal, respectively. Thus, sometimes the afferent dorsal root of a spinal nerve may be called the posterior root. Similarly, the ventral horn of the gray matter of the spinal cord is frequently called the anterior horn
Orthodromic - conduction in the "usual" direction (i.e. centrifugal flow of nerve impulses in a motor nerve fiber)
Antidromic - conduction in the "unusual" direction (i.e. centripetal flow of nerve impulses in a motor nerve fiber)
An axon which conducts impulses from the cell body. Axon - neuroanatomic usage; a neuronal process carrying impulses away from the cell body. neurophysiologcal usage; a neuronal process specialized for long-range, self-propagating information transfer toward or away from the cell body or both. Axons do not contain Nissl substance. An axon terminal or synaptic bouton that is the end-point of axon transmission and a synapse, a junction to another nerve cell, that consists of a minute gap across which impulses pass by diffusion of a neurotransmitter. Axon Hillock - small area at the base of the axon that would be considered part of the cell body except that observations with the light microscope show no Nissl substance in this area.
Axon Hillock - small area at the base of the axon that would be considered part of the cell body except that observations with the light microscope show no Nissl substance in this area; axons do not contain nissl substance.
Nissl substance is dark-staining "particles" seen in the light microscope when basic dyes are used to stain nervous tissue. Nissl substance is not found in neuroglial cells - thus its presence differentiates neurons from neuroglia. Nissl substance is found in the cell body and dendrites but not in the axons of nerve cells. Since the advent of the electron microscope., it has been shown that Nissl substance actually consists of parallel rows of interconnecting tubules of rough endoplasmic reticulum
Sensory Ending - that part of a sensory neuron specialized to receive information from the cell's environment (rather than from another nerve cell). Sensory endings respond to either the external or the internal environment of the body.
The microscopic anatomy of the neuron.
General descriptive terms:
Afferent - centripetal transfer (toward the CNS) as of information, nerve impulses, etc
Efferent - centrifugal transfer, away from the CNS
Distal - farther from the center of the body
Proximal - closer to the center of the body
Anterior and Posterior - terms sometimes used by human anatomists (because of the human's erect position) for ventral and dorsal, respectively. Thus, sometimes the afferent dorsal root of a spinal nerve may be called the posterior root. Similarly, the ventral horn of the gray matter of the spinal cord is frequently called the anterior horn
Orthodromic - conduction in the "usual" direction (i.e. centrifugal flow of nerve impulses in a motor nerve fiber)
Antidromic - conduction in the "unusual" direction (i.e. centripetal flow of nerve impulses in a motor nerve fiber)
An axon which conducts impulses from the cell body. Axon - neuroanatomic usage; a neuronal process carrying impulses away from the cell body. neurophysiologcal usage; a neuronal process specialized for long-range, self-propagating information transfer toward or away from the cell body or both. Axons do not contain Nissl substance. An axon terminal or synaptic bouton that is the end-point of axon transmission and a synapse, a junction to another nerve cell, that consists of a minute gap across which impulses pass by diffusion of a neurotransmitter. Axon Hillock - small area at the base of the axon that would be considered part of the cell body except that observations with the light microscope show no Nissl substance in this area.
Axon Hillock - small area at the base of the axon that would be considered part of the cell body except that observations with the light microscope show no Nissl substance in this area; axons do not contain nissl substance.
Nissl substance is dark-staining "particles" seen in the light microscope when basic dyes are used to stain nervous tissue. Nissl substance is not found in neuroglial cells - thus its presence differentiates neurons from neuroglia. Nissl substance is found in the cell body and dendrites but not in the axons of nerve cells. Since the advent of the electron microscope., it has been shown that Nissl substance actually consists of parallel rows of interconnecting tubules of rough endoplasmic reticulum
Sensory Ending - that part of a sensory neuron specialized to receive information from the cell's environment (rather than from another nerve cell). Sensory endings respond to either the external or the internal environment of the body.
The microscopic anatomy of the neuron.
THE NEURON
Neuronal organization is principally the patterns of connections between nerve cells which defines neural circuits and neural systems as servomechanisms feedback plays an essential role in learning and motor behavior.
The neuronal membrane system regulates production of the nuclear membrane, endoplasmic reticulum, Golgi apparatus, plasma membrane and other aspects of cellular metabolism. Microtubules and neurofilaments are the fibrous structural elements of the cytoskeleton that maintain neuronal shape and participate in the transport of materials along the axon - transport that is bidirectional; anterograde, retrograde, both types, subtypes, and dendritic transport (more slowly).
The neuron (nerve cell) is the basic information processing unit of the nervous system.
The structural aspects of neurons; within the soma, protein synthesis and integration of signals for growth, degeneration and regeneration of neuronal processes an axon, transmitter release and connectivity for neuronal communication, target finding, growth and remodeling (axons can also receive input from other axons), dendrites receptive membrane of neurons for the target of much synaptic input.
The genesis of membrane potentials in all parts of a neuron
The basic mechanisms of long-range transmission
How sensory endings work
Output - input interaction at the synapse between nerve and skeletal muscle cells
The synapses of CNS and some of the complex interactions that can take place during short-range transmission when many synapses are present within a confined membrane area
Bringing together all these components in a description of the motor and sensory control of muscle function - the systems required to provide accurate control of movement and posture.
A background understanding of the control systems discussed. Thus you can see that this book is organized along the lines of the functional classification just described.
Anatomy/Cytology of Neural Tissue
Neurons, Interneurons and Neuroglia
Physiological classification of parts of a neuron
Basic Concepts of Neuronal Function
The Neuron, Particular and Generalized
Classification of Neurons
Repair/Regeneration
Types/Classifications of Neurons
Neuronal organization is principally the patterns of connections between nerve cells which defines neural circuits and neural systems as servomechanisms feedback plays an essential role in learning and motor behavior.
The neuronal membrane system regulates production of the nuclear membrane, endoplasmic reticulum, Golgi apparatus, plasma membrane and other aspects of cellular metabolism. Microtubules and neurofilaments are the fibrous structural elements of the cytoskeleton that maintain neuronal shape and participate in the transport of materials along the axon - transport that is bidirectional; anterograde, retrograde, both types, subtypes, and dendritic transport (more slowly).
The neuron (nerve cell) is the basic information processing unit of the nervous system.
The structural aspects of neurons; within the soma, protein synthesis and integration of signals for growth, degeneration and regeneration of neuronal processes an axon, transmitter release and connectivity for neuronal communication, target finding, growth and remodeling (axons can also receive input from other axons), dendrites receptive membrane of neurons for the target of much synaptic input.
The genesis of membrane potentials in all parts of a neuron
The basic mechanisms of long-range transmission
How sensory endings work
Output - input interaction at the synapse between nerve and skeletal muscle cells
The synapses of CNS and some of the complex interactions that can take place during short-range transmission when many synapses are present within a confined membrane area
Bringing together all these components in a description of the motor and sensory control of muscle function - the systems required to provide accurate control of movement and posture.
A background understanding of the control systems discussed. Thus you can see that this book is organized along the lines of the functional classification just described.
Anatomy/Cytology of Neural Tissue
Neurons, Interneurons and Neuroglia
Physiological classification of parts of a neuron
Basic Concepts of Neuronal Function
The Neuron, Particular and Generalized
Classification of Neurons
Repair/Regeneration
Types/Classifications of Neurons
Body
Upper Extremity
Trapezius
Deltoid
Biceps
Triceps
Flexor Carpi Ulnaris
Extensor Carpi Radialis
Thenar
Hypothenar
Intercostals
Abdominals
Median Nerve
Radial Nerve
Ulnar Nerve
Upper Extremity
Trapezius
Deltoid
Biceps
Triceps
Flexor Carpi Ulnaris
Extensor Carpi Radialis
Thenar
Hypothenar
Intercostals
Abdominals
Median Nerve
Radial Nerve
Ulnar Nerve
Body
Lower Extremity
Iliopsoas
Rectus Femoris
Vastus Lateralis
Tibialis Anterior
Vastus Medialis
Adductor Longus
Biceps Femoris
Gastrocnemius
Foot Flexors
Foot Extensors
Posterior Tibial Nerve
Lower Extremity
Iliopsoas
Rectus Femoris
Vastus Lateralis
Tibialis Anterior
Vastus Medialis
Adductor Longus
Biceps Femoris
Gastrocnemius
Foot Flexors
Foot Extensors
Posterior Tibial Nerve
musculus is latin; little mouse
General Functions
1 movement of skeleton - control of openings examples, mouth, anus
2 stabilize our joints - maintain posture
3 produce heat; exercise
4 facial expression; get ideas of what people are thinking; sad, happy, fearful, etcetera
5 protection; closing eyes, close mouth, bring arms up in front of face
Nomenclature
1 shape, deltoid; upside down
2 # of heads; biceps, 2 heads, triceps, 3 heads, quadriceps, 4 heads
3 length, brevis - short, longus, long; extensor carpus radialis longus (lateal because of radialis); biceps brachii - arm
biceps femoris; thigh, intercostals; between the ribs, temporalis; on the temporal bone; can figure these out by names
4 prime mover - main muscle carrying out function, antagonist , protagonist
5 flexors, extensors, adductors, abductors, supinators (palm up), pronators (palm down), prone vs. supine
muscles attaching upper extremities to the trunk
2 posterior
1 anterior - trapezius, has a trapezoid shape;
trapezius means trapezoid - action is adducting the scapula
lattisimus dorsi - just means broad, is inferior and posterior, lower back, lumbar and thoracic vertebra; originates from thoracolumbar fascie; a layer of strong connective tisue, fascia comes up from ilium; thoracolumbar fascia, attaches to the crest of the ilium and lower thoracic spines, attaches to the lattisiumus dorsi and blends with the muscle and inserts on the anterior intertuburcular groove of the humerus.; it medial rotates the humerus
anterior superior - pectoralis major; chest, giving you a foundation which to build; have the sternum, and clavicle, adducts humerus, medial rotate the humerus,
rotator cuff
arm and forearm -
arm muscles are designed for strength
forearm for dexterity
olecranon process of ulna - has nerve exposed there; extends the forearm
posterior side of ulna has olecranon which stabilizes the joint
brachioradialis - comes from humerus to radius, lateral forearm, shape of the lateral forearm, anterior portion have flexors of wrist and fingers, posterior have extensors
thenar eminence - base of thumb, one big muscle
abdominal muscles - rectus (straight) abdominus - protect and support abdominal and pelvic viscera; have spleen and pancreas, need to support and protect, all anterior, they contract to flex the spine/vertebral column;
in between the xiphoid (zi-phoid) and pubic bones, umbiicus, have a cross section through a and b, have two bellies of muscle, have other muscles, the external oblique, internal oblique and transversus rectus, in the middle they connect with the aperneurosis. developed a thin midline that doesn't have any muscle but a layer of connective tissue, linea alba, no blood vessels, just a white line, if you cut through the linea alba you won't have any bleeding.
external oblique, supports and protects abdominal and pelvic viscera
flexes the vertebral column
aids in vomiting
aids in defacating
aids in childbirth
muscles of the pelvic floor -
1 levator ani - originates on the pubic bone and ischium, inserts on the coccyx posterior and median raphe; in women have three openings, urethra, vagina, anus; levator ani is medial and lateral support, median raphe is posterior to the anus, strengthen the anus
2 superficial transversus -
lower extremity
muscles of the hip - 19 muscles here
function in general, flex, extend, adduct, abduct
fascia lata, thin, strong encacement of connective tissue fascia around thigh muscles; fascia lata, there is an iliotibial band
gluteal muscles, pelvis, gluteus maxiumus, ilieum to femur, medius, minimus
thigh muscles - crosses from anterior iliac spine to medial proximal tibia - sartorius - tailors muscle, flexes the hip, flexes the knee joint
big thigh muscles are the quads; - quadriceps
anterior thigh, encased in fascia lata
1 rectus femoris - comes from the ilium - insert quadriceps tendon surrounding the patella and patellar ligament inserts on tibial tuberosity
2 vastus lateralis - comes from proximal femur
3 vastus intermedius - comes from proximal femur
4 vastus medialis - comes from proximal femur
femoral triangle - femoral nerve, femoral artery at surface, need to be careful when placing electrodes for iliopsoas
posterior thigh - hamstrings - bicpes femoris, semimembranosis, semitendinosus, give the shape to the posterior thigh
medial thigh
anterior leg - tibialis anterior - lateral head of tibia to first metatarsal and first tarsal bone
posterior thigh - gastrocnemius - gives the shape to the posterior leg; very large; part of a human condition/characteristic, originates at the medial and lateral epicondyles of the femur
General Functions
1 movement of skeleton - control of openings examples, mouth, anus
2 stabilize our joints - maintain posture
3 produce heat; exercise
4 facial expression; get ideas of what people are thinking; sad, happy, fearful, etcetera
5 protection; closing eyes, close mouth, bring arms up in front of face
Nomenclature
1 shape, deltoid; upside down
2 # of heads; biceps, 2 heads, triceps, 3 heads, quadriceps, 4 heads
3 length, brevis - short, longus, long; extensor carpus radialis longus (lateal because of radialis); biceps brachii - arm
biceps femoris; thigh, intercostals; between the ribs, temporalis; on the temporal bone; can figure these out by names
4 prime mover - main muscle carrying out function, antagonist , protagonist
5 flexors, extensors, adductors, abductors, supinators (palm up), pronators (palm down), prone vs. supine
muscles attaching upper extremities to the trunk
2 posterior
1 anterior - trapezius, has a trapezoid shape;
trapezius means trapezoid - action is adducting the scapula
lattisimus dorsi - just means broad, is inferior and posterior, lower back, lumbar and thoracic vertebra; originates from thoracolumbar fascie; a layer of strong connective tisue, fascia comes up from ilium; thoracolumbar fascia, attaches to the crest of the ilium and lower thoracic spines, attaches to the lattisiumus dorsi and blends with the muscle and inserts on the anterior intertuburcular groove of the humerus.; it medial rotates the humerus
anterior superior - pectoralis major; chest, giving you a foundation which to build; have the sternum, and clavicle, adducts humerus, medial rotate the humerus,
rotator cuff
arm and forearm -
arm muscles are designed for strength
forearm for dexterity
olecranon process of ulna - has nerve exposed there; extends the forearm
posterior side of ulna has olecranon which stabilizes the joint
brachioradialis - comes from humerus to radius, lateral forearm, shape of the lateral forearm, anterior portion have flexors of wrist and fingers, posterior have extensors
thenar eminence - base of thumb, one big muscle
abdominal muscles - rectus (straight) abdominus - protect and support abdominal and pelvic viscera; have spleen and pancreas, need to support and protect, all anterior, they contract to flex the spine/vertebral column;
in between the xiphoid (zi-phoid) and pubic bones, umbiicus, have a cross section through a and b, have two bellies of muscle, have other muscles, the external oblique, internal oblique and transversus rectus, in the middle they connect with the aperneurosis. developed a thin midline that doesn't have any muscle but a layer of connective tissue, linea alba, no blood vessels, just a white line, if you cut through the linea alba you won't have any bleeding.
external oblique, supports and protects abdominal and pelvic viscera
flexes the vertebral column
aids in vomiting
aids in defacating
aids in childbirth
muscles of the pelvic floor -
1 levator ani - originates on the pubic bone and ischium, inserts on the coccyx posterior and median raphe; in women have three openings, urethra, vagina, anus; levator ani is medial and lateral support, median raphe is posterior to the anus, strengthen the anus
2 superficial transversus -
lower extremity
muscles of the hip - 19 muscles here
function in general, flex, extend, adduct, abduct
fascia lata, thin, strong encacement of connective tissue fascia around thigh muscles; fascia lata, there is an iliotibial band
gluteal muscles, pelvis, gluteus maxiumus, ilieum to femur, medius, minimus
thigh muscles - crosses from anterior iliac spine to medial proximal tibia - sartorius - tailors muscle, flexes the hip, flexes the knee joint
big thigh muscles are the quads; - quadriceps
anterior thigh, encased in fascia lata
1 rectus femoris - comes from the ilium - insert quadriceps tendon surrounding the patella and patellar ligament inserts on tibial tuberosity
2 vastus lateralis - comes from proximal femur
3 vastus intermedius - comes from proximal femur
4 vastus medialis - comes from proximal femur
femoral triangle - femoral nerve, femoral artery at surface, need to be careful when placing electrodes for iliopsoas
posterior thigh - hamstrings - bicpes femoris, semimembranosis, semitendinosus, give the shape to the posterior thigh
medial thigh
anterior leg - tibialis anterior - lateral head of tibia to first metatarsal and first tarsal bone
posterior thigh - gastrocnemius - gives the shape to the posterior leg; very large; part of a human condition/characteristic, originates at the medial and lateral epicondyles of the femur
Body
Upper Extremity
Head and Neck
Shoulder Girdle/Brachial Plexus
Arms
Humerus
Radius/Ulna
Bones of the Hand
Lower Extremity
Pelvis
Femur
Fibula
Tibia
Bones of the Foot
Upper Extremity
Head and Neck
Shoulder Girdle/Brachial Plexus
Arms
Humerus
Radius/Ulna
Bones of the Hand
Lower Extremity
Pelvis
Femur
Fibula
Tibia
Bones of the Foot
Vertebrae
Cervical
C1-C7
C8th Nerve
C1, C2 atlas/axis
Thoracic
T1-12
T1-6 Clavicles, Ribs & Abdominal
Lumbar
L1-5
Sacral
S1-5
Cervical
C1-C7
C8th Nerve
C1, C2 atlas/axis
Thoracic
T1-12
T1-6 Clavicles, Ribs & Abdominal
Lumbar
L1-5
Sacral
S1-5
Sternum - Manubrium, Body, Xiphoid Process (Sword-like) can break
jugular notch at the superior aspect of the manubrium, you can feel it if you palpate it
sternal angle where the manubrium meets the body, most frequently fractured area
Attached to it are the intercostal cartilages
12 ribs
7 true 1 - 7; called true ribs because their costal cartilage attaches directly to the sternum
5 false ribs that do not attach to the sternum
3 attach to superior costal cartilage
2 don't attach, floating ribs
1st costal cartilage at manubrian
2nd at sternal angle
3rd - 7th attach to sternum
8th attaches to the 7th
9th attaches to the 8th
10th to the 9th
and then floating ribs
all have attachments posteriorly to thoracic vertebrae which gives us our rib cage or thoracic cage more accurately
the appendicular skeleton; start with the pectoral girdle which consists of two bones, the clavicle anteriorly and scapula posteriorly
the clavicle articulates with the sternum at the manubrium (two curvatures on clavicle, medial covex, laterally concave)
*always have your body as a foundation
we have the sternoclavicular joint, laterally we have the achromial clavicular joint, these are basics, the only articulation is here, the rest is held up by muscle
scapula is posterior, it is thin, lies over 2nd to 7th ribs posteriorly, triangularly shaped
from posterior, have spine of the scapula expanding into an acromial process, it divides the scapula into two segments, suprispinous fossa and infraspinal fossa *we will have muscles here.
the glanoid cavity, the head of the humerus articulates with the scapula at the glanoid cavity
anterior view, small process called the coracoid process which receives the short head of the biceps originates here
upper extremity; we have the arm, the humerus which has a head, a greater tubercle, and then the shaft coming down which has the deltoid tuberosity and two necks, anatomical neck and the surgical neck, fracture most commonly occurs at the surgical neck.
At the distal end, have the medial epicondyle of the humerus and the lateral epicondyle, you can feel them, big bones
radius laterally, ulna medially, the head of the radius allows for rotation. the radial tuberosity just below it and the biceps will insert here, distal part of the ulna has two characteristics, olecranon process, bend elbow and feel the pointy part. semi-lunar notch, distal we have the styloid process.
Wrist bones- the carpal bones, 8 of them, two rows of four bones each
knuckles, and phalanges, fingers with three each, in thumb, two
Pelvic girdle; pelvis means basin; three bones, ilium, ishium and pubic bone, these three all come together in one part called the acetabulum (vinegar cup)
Ilium, anterior iliac spine, ischial tuberosities, you are sitting on your ishial tuberosity
inferior conchae - lateral nasal cavity, respiration, two inferior conchae
one vomer - medial nasal cavity, common term is the septum, sometimes people have deviated septums that go sideways
lower extremity - tibia is the weight bearing bone, medial bone of our leg, very capable, triangular shaped, if you feel you can feel the apex of the triangle with no muscle covering on it, you are feeling the periosteum beneath the skin which is filled with nerve fibers right beneath the surface. articulation at the proximal end is with the femur and fibula. distal articulation with the ankle bone, which is called the talus and fibula. there is a protrusion on the medial aspect which is the medial malleolus which means hammer
fibula is the thin and long bone laterally, proximal articulation is with the tibia and distally articulates with the talus, it is not weight bearing, has muscle attachments only, there is also a lateral malleolus, ankle is a leg bone
tarsal bones - there are 7 of them, the 2 largest are the calcaneus or heel bone, what attaches to the heel bone, the achilles tendon, also articulates with the talus
metatarsals - sole 5 of them, 1st is the largest, weight bearing, 5th metatarsal is frequently fractured
we have the phalanges, big toe has 2, the rest have the 3. big difference in the finger articulation and toe articulation.
fractures - severe bleeding which forms a blood clot, the periosteum which is surrounded in connective tissue cells which forms fibroblasts will form osteoblasts which are bone forming cells, they are going to be forming fragments of bone within the clot this is called a callus
joint movement: flexion - decreasing an angle
extension - increasing the angle;
adduction - bring the limb toward the midline; deltoid is an adductor
abduction - away from the midline;
circumduction is circular motion
; the sternum and ribs protect the heart and the lungs, liver and digestive system.
Thoracic cavity - Sternum, the costal cartilages, the ribs and posteriorly the bodies of thoracic vertebrae in the vertebral column
jugular notch at the superior aspect of the manubrium, you can feel it if you palpate it
sternal angle where the manubrium meets the body, most frequently fractured area
Attached to it are the intercostal cartilages
12 ribs
7 true 1 - 7; called true ribs because their costal cartilage attaches directly to the sternum
5 false ribs that do not attach to the sternum
3 attach to superior costal cartilage
2 don't attach, floating ribs
1st costal cartilage at manubrian
2nd at sternal angle
3rd - 7th attach to sternum
8th attaches to the 7th
9th attaches to the 8th
10th to the 9th
and then floating ribs
all have attachments posteriorly to thoracic vertebrae which gives us our rib cage or thoracic cage more accurately
the appendicular skeleton; start with the pectoral girdle which consists of two bones, the clavicle anteriorly and scapula posteriorly
the clavicle articulates with the sternum at the manubrium (two curvatures on clavicle, medial covex, laterally concave)
*always have your body as a foundation
we have the sternoclavicular joint, laterally we have the achromial clavicular joint, these are basics, the only articulation is here, the rest is held up by muscle
scapula is posterior, it is thin, lies over 2nd to 7th ribs posteriorly, triangularly shaped
from posterior, have spine of the scapula expanding into an acromial process, it divides the scapula into two segments, suprispinous fossa and infraspinal fossa *we will have muscles here.
the glanoid cavity, the head of the humerus articulates with the scapula at the glanoid cavity
anterior view, small process called the coracoid process which receives the short head of the biceps originates here
upper extremity; we have the arm, the humerus which has a head, a greater tubercle, and then the shaft coming down which has the deltoid tuberosity and two necks, anatomical neck and the surgical neck, fracture most commonly occurs at the surgical neck.
At the distal end, have the medial epicondyle of the humerus and the lateral epicondyle, you can feel them, big bones
radius laterally, ulna medially, the head of the radius allows for rotation. the radial tuberosity just below it and the biceps will insert here, distal part of the ulna has two characteristics, olecranon process, bend elbow and feel the pointy part. semi-lunar notch, distal we have the styloid process.
Wrist bones- the carpal bones, 8 of them, two rows of four bones each
knuckles, and phalanges, fingers with three each, in thumb, two
Pelvic girdle; pelvis means basin; three bones, ilium, ishium and pubic bone, these three all come together in one part called the acetabulum (vinegar cup)
Ilium, anterior iliac spine, ischial tuberosities, you are sitting on your ishial tuberosity
inferior conchae - lateral nasal cavity, respiration, two inferior conchae
one vomer - medial nasal cavity, common term is the septum, sometimes people have deviated septums that go sideways
lower extremity - tibia is the weight bearing bone, medial bone of our leg, very capable, triangular shaped, if you feel you can feel the apex of the triangle with no muscle covering on it, you are feeling the periosteum beneath the skin which is filled with nerve fibers right beneath the surface. articulation at the proximal end is with the femur and fibula. distal articulation with the ankle bone, which is called the talus and fibula. there is a protrusion on the medial aspect which is the medial malleolus which means hammer
fibula is the thin and long bone laterally, proximal articulation is with the tibia and distally articulates with the talus, it is not weight bearing, has muscle attachments only, there is also a lateral malleolus, ankle is a leg bone
tarsal bones - there are 7 of them, the 2 largest are the calcaneus or heel bone, what attaches to the heel bone, the achilles tendon, also articulates with the talus
metatarsals - sole 5 of them, 1st is the largest, weight bearing, 5th metatarsal is frequently fractured
we have the phalanges, big toe has 2, the rest have the 3. big difference in the finger articulation and toe articulation.
fractures - severe bleeding which forms a blood clot, the periosteum which is surrounded in connective tissue cells which forms fibroblasts will form osteoblasts which are bone forming cells, they are going to be forming fragments of bone within the clot this is called a callus
joint movement: flexion - decreasing an angle
extension - increasing the angle;
adduction - bring the limb toward the midline; deltoid is an adductor
abduction - away from the midline;
circumduction is circular motion
; the sternum and ribs protect the heart and the lungs, liver and digestive system.
Thoracic cavity - Sternum, the costal cartilages, the ribs and posteriorly the bodies of thoracic vertebrae in the vertebral column
What can happen?
Break, Fracture, etcetera
Break, Fracture, etcetera
for example, if you have a tumor in or on your spinal cord, a surgeon will perform a laminectomy which allows access to the spinal cord so the surgeon can lift off the spinous processes. Which portion of the cord is more prone to tumors? The thoracic area is the most common site for tumor formation. So it's important to know your spinal cord
scoliosis; characteristically more frequent in females than males, typically appears during puberty. Can get adjusted so you get the full support of the vertebral column.
Nasal bones at the inferior medial orbit
Zygomatic bones which form the middle aspect of the cheek bone; zygomatic process of the maxilla, whole cheek bone is made up of three bones, zygomatic process of maxilla, zygomatic bone and the zygomatic process of the temporal bone.
2 palatine bones form the posterior portion of your roof of the mouth or hard palate; anterior have the maxillary bone/maxillary, posteriorly have the palatine bones
Inferior conchae; lateral nasal cavity
1 Vomer on the medial nasal cavity; common term is the septum
The only moveable joint of the skull is the mandible
Condyloid process forms the tempromandibular joint
Coronoid process has a muscle coming down to close the mouth
Ramus (branch) angle
Hyoid is u shaped, in the neck, inferior to the mandible and superior to your larynx (adams apple), no bony attachments, only muscles and ligaments
The skull is formed by the union of a number of bones and can be grossly subdivided into
1 the facial bones and orbits
2 the sinus cavities within the bones that form the anterior aspect of the skull and
3 the cranial bones. T
turkish saddle, bones of the skull, frontal, temporal, parietal, occipital, cribiform plate, orbits, maxilla, mandible.
Zygomatic bones which form the middle aspect of the cheek bone; zygomatic process of the maxilla, whole cheek bone is made up of three bones, zygomatic process of maxilla, zygomatic bone and the zygomatic process of the temporal bone.
2 palatine bones form the posterior portion of your roof of the mouth or hard palate; anterior have the maxillary bone/maxillary, posteriorly have the palatine bones
Inferior conchae; lateral nasal cavity
1 Vomer on the medial nasal cavity; common term is the septum
The only moveable joint of the skull is the mandible
Condyloid process forms the tempromandibular joint
Coronoid process has a muscle coming down to close the mouth
Ramus (branch) angle
Hyoid is u shaped, in the neck, inferior to the mandible and superior to your larynx (adams apple), no bony attachments, only muscles and ligaments
The skull is formed by the union of a number of bones and can be grossly subdivided into
1 the facial bones and orbits
2 the sinus cavities within the bones that form the anterior aspect of the skull and
3 the cranial bones. T
turkish saddle, bones of the skull, frontal, temporal, parietal, occipital, cribiform plate, orbits, maxilla, mandible.
Skull
Frontal
Temporal
Parietal
Olfactory
Occipital
Ocular
Maxillofacial
Frontal
Temporal
Parietal
Olfactory
Occipital
Ocular
Maxillofacial
The skull has two major components: The calvarium 8 bones and the facial bones 15 bones
Calvarium (Calvaria means skull)
Let's look at the floor of the skull
Calvarium (Calvaria means skull)
- Frontal - forms the forehead and inside the skull anterior fossa of the base of the skull. if you drill in will find the sinus,
- Parietal - means wall, so makes up the sides, two parietals
- Temporal - has four parts 1 squamous, thin, flat part, squamous portion of the temporal bone, very thin 2 mastoid (breast) portion of the temporal bone 3 Zygomatic Process; posterior portion of your cheek bone 4 Petrous portion of temporal bone houses inner ear. Mandible articulates with the temporal bone at the tempromandibuluar joint. Maxilla is the upper jaw which is the keystone of the facial bones, all facial bones touch the maxilla but one, the mandible. anterior roof of the mouth is the maxilla.
- Occiptial - major portion of the occipital bone has the foramen magnum, where the spinal cord attaches to the brain, also has the ability to articulate with the first cervical (neck) vertebrae (C1/Atlas holds up the skull)
Let's look at the floor of the skull
- Sphenoid - The Keystone of the floor because it holds all bones together. inside, the floor of the skull, lies mediolaterally, the sphenoid is posterior to the frontal bone, anterior to the petrous portion of the temporal bone and occipital bone. There is a sphenoid sinus that forms the lateral wall of the orbit/eye socket. Forms the sella turcica or turkish saddle, which has 4 processes called clinoid processes which surrounds the pituitary gland from anterior to posterior. Put one finger at the bridge of your nose and the superior part of your ear, where your fingers intersect is your pituitary gland.
- Ethmoid - means sieve, the cribiform plate of the ethmoid, filled with little holes so smell impulses can reach the brain, convey to the olfactory nerves which enter the skull via the cribiform plate, many little nerve fibers
The principles of neuronal organization are the pattern of connections between nerve cells that define neural circuits. Neural systems serve as servomechanisms, a powered mechanism producing motion or forces at a higher level of energy than the input level, e.g. in the brakes and steering of large motor vehicles, especially where feedback is employed to make the control automatic): feedback plays an essential role in learning and motor behavior.
Obviously, faster transmission was needed over the course of evolution as animals became larger and as the brain enlarged.
Dorsal and ventral roots of the spinal cord merge as they leave the spine, forming the peripheral nerves. The dorsal and ventral roots each conducts information in only one direction and their peripheral nerves, with their many branches in which information is transmitted in both directions because the peripheral nerves contain processes of both sensory and motor neurons.
Within each of the seven central nervous system divisions resides a component of the ventricular system, a labyrinth of fluid filled cavities that serve various supportive functions
We are here to enhance the triad relationship between surgeons, anesthesiologists and the surgical neurophysiologist to utilize intraoperative neuromonitoring to their advantage and give the patient the best possible outcome. Insight into the purposes of tests and executed techniques can elicit confidence in the surgical approach and predict a surgical outcome with a proper balance of anesthesia on board. The patient gains piece of mind that mere irritation of nervous structures at risk can be observed and reversed before any serious violation of structural integrity occurs. A myriad of techniques are available to the surgeons disposal to promote a clearer definition of the state of the patient's nervous system, before, during and predicting an outcome after surgery.
For the Surgeon and Anesthesiologist
Technologists are key members of the IOM team. They need to have sufficient experience in neurophysiologic testing, techniques, basic sciences, and relevant clinical sciences before being left in an operating room for IOM. Usually, this includes several years of experience conducting EEG and EPs in regular inpatients and outpatients. That provides a basis in experience for knowing what signals look like, what various changes and abnormalities occur among patients, and how to deal with technical problems. Even with such experience outside the operating room, any technologist should be proctored and subject to progressively lessened supervision when introduced to IOM. The technologists's supervision and privileging should be specific to individual types of procedures. for example, a technologist who knows how to monitor EEG during a CEA does not necessarily know how to monitor somatosensory EPs in the same case. it depends instead on the individuals own skills, knowledge abilities, training and experience. The fellow should have extensive clinical experience with common clinical uses of IOM.
For the Technologist
We are here to enhance the skills and abilities of the technologists who may lack the medical knowledge or clinical perspective to efficiently troubleshoot and confidently advise the surgeon. Arming the technologist with more knowledge enhances communication with the online supervisor to be able to make better decisions together and helps to contribute to a more positive clinical outcome. We are also here for the neurosurgeon, orthopedic surgeon, ENT surgeon and any other professional that believes that intraoperative neurophysiology can help them with better outcomes for the patient. With this course, I hope to improve the outcome of cases across the world with better education, we are here to give you a clinical perspective, gain the respect of the neurosurgeon, and build your skills.
Using specialized knowledge of the nervous system, a triad relationship between the surgeon, anesthesiologist and intraoperative neurophysiologist can foster a correct balance of anesthesia that can otherwise mask the response of nervous tissue.
Martin 21
An introduction to neuroanatomical terms
The terminology of neuroanatomy is specialized for dexribing the brain's complex three-dimensional organizaiton. The central nervous system is organized along the rostrocaudal and dorsoventral axes of the body. These axes are most easliy understood in animals with a central nervous system that is simpler than that of humans. In the rate, for example, the rostrocaudal axis runs approximately in a straight line form the nose to the tail. This axis is the longitudinal axis of the nervous system and is often termed the neuraxis because the central nervous system has a predominant longitudinal organization. the dorsoventral axis, which is perpendicular to the rostrocaudal axis, runs from the back of the abdomen. The terms posterior and anterior are synonymous with dorsal and ventral, respectively.
We define three principal planes relative to the longitudinal axis of the nervous system in which anatomical sections are made. Horizontal sections are cut parallel to the longitudinal axis, from one side to the other. Transverse sections are cut perpendicular to the longitudinal axis, between the dorsal and ventral surfaces. Transverse sections through the cerebral hemisphere are roughly parallel to the coronal suture and as a consequence, are also termed coronal sections. sagittal sections are cut parallel both to the longitudinal axis of the central nervous system and to the midline, between the dorsal and ventral surfaces. A midsagittal section divides the central nervous systm into tw symmetrical halves, whereas a parasagittal section is cut off the midline. radiological images are also obtained in these places
An introduction to neuroanatomical terms
The terminology of neuroanatomy is specialized for dexribing the brain's complex three-dimensional organizaiton. The central nervous system is organized along the rostrocaudal and dorsoventral axes of the body. These axes are most easliy understood in animals with a central nervous system that is simpler than that of humans. In the rate, for example, the rostrocaudal axis runs approximately in a straight line form the nose to the tail. This axis is the longitudinal axis of the nervous system and is often termed the neuraxis because the central nervous system has a predominant longitudinal organization. the dorsoventral axis, which is perpendicular to the rostrocaudal axis, runs from the back of the abdomen. The terms posterior and anterior are synonymous with dorsal and ventral, respectively.
We define three principal planes relative to the longitudinal axis of the nervous system in which anatomical sections are made. Horizontal sections are cut parallel to the longitudinal axis, from one side to the other. Transverse sections are cut perpendicular to the longitudinal axis, between the dorsal and ventral surfaces. Transverse sections through the cerebral hemisphere are roughly parallel to the coronal suture and as a consequence, are also termed coronal sections. sagittal sections are cut parallel both to the longitudinal axis of the central nervous system and to the midline, between the dorsal and ventral surfaces. A midsagittal section divides the central nervous systm into tw symmetrical halves, whereas a parasagittal section is cut off the midline. radiological images are also obtained in these places
Exploration of the structure of the central nervous system has for more than a century been based on the detailed study of slices or sections cut through the brain substance in one or another group of specified orientations. Thus our understanding of internal structure or the relationship of structures is dependent on a knowledge of the planes of sections illustrated here.
The median plane divides a structure along its longitudinal axis into left and right halves. Median or midline sections of the hemispheres are used frequently to study structure immediately adjacent to the midline.
The sagittal plane runs along the longitudinal axis parallel to the median plane. sagittal sections of the hemispheres, brain stem or cerebellum are often employed to study internal structures.
The coronal or transverse plane divides a structure perpendicular to the long axis. Coronal sections (slices) of the hemispheres are frequently used to study internal structure. The term cross section is also applied to transverse sections of the spinal cord and brain stem.
The horizontal plane is perpendicular to both the coronal and sagittal planes and is parallel with the earth's horizon. Horizontal sections of the hemispheres are often employed to study internal structure.
The median plane divides a structure along its longitudinal axis into left and right halves. Median or midline sections of the hemispheres are used frequently to study structure immediately adjacent to the midline.
The sagittal plane runs along the longitudinal axis parallel to the median plane. sagittal sections of the hemispheres, brain stem or cerebellum are often employed to study internal structures.
The coronal or transverse plane divides a structure perpendicular to the long axis. Coronal sections (slices) of the hemispheres are frequently used to study internal structure. The term cross section is also applied to transverse sections of the spinal cord and brain stem.
The horizontal plane is perpendicular to both the coronal and sagittal planes and is parallel with the earth's horizon. Horizontal sections of the hemispheres are often employed to study internal structure.
Diamond
Anatomical Position
Upright Bipedal posture of human beings, the four basic reference points of the human body in three dimensional space change through a full 90 degrees. In a standing person in anatomical position, the front is the belly side and the hind end is also the back. The head becomes the upper end, cranial or superior. The tail becomes the lower end, inferior or caudal. The back of the brain and spinal cord is posterior the term dorsal is used synonymously with posterior. although both terms are seen in descriptive anatomy, posterior is gernally preferred. The front of the brain and spinal cord is anterior or rostral. in the case of the brain stem and spinal cord the term ventral is used synonumously with anterior, anterior is generally preferred.
Referring to the human fugure, a few additional terms of direction are shown. The same side as the structural point is ipsilateral, if it is on the opposite side of the reference point it is said to be contralateral. For example, your left hand is initiated by the contralateral hemisphere. When comparing two structures, closer to the midline is said to be medial to the other. Thus the important medial lemniscus of the spinal cord and brain stem is closer to the midline than the lateral lemnisucls
The terms proximal and distal refer to relative distances from a reference point, proximal being closer and distal being farther. In the illustration, proximal is closer to the root of the limb and distal is farther away. For example, damage to the radial nerve of the upper limb is more likley proximal to the elbow than distal.
Anatomical Position
Upright Bipedal posture of human beings, the four basic reference points of the human body in three dimensional space change through a full 90 degrees. In a standing person in anatomical position, the front is the belly side and the hind end is also the back. The head becomes the upper end, cranial or superior. The tail becomes the lower end, inferior or caudal. The back of the brain and spinal cord is posterior the term dorsal is used synonymously with posterior. although both terms are seen in descriptive anatomy, posterior is gernally preferred. The front of the brain and spinal cord is anterior or rostral. in the case of the brain stem and spinal cord the term ventral is used synonumously with anterior, anterior is generally preferred.
Referring to the human fugure, a few additional terms of direction are shown. The same side as the structural point is ipsilateral, if it is on the opposite side of the reference point it is said to be contralateral. For example, your left hand is initiated by the contralateral hemisphere. When comparing two structures, closer to the midline is said to be medial to the other. Thus the important medial lemniscus of the spinal cord and brain stem is closer to the midline than the lateral lemnisucls
The terms proximal and distal refer to relative distances from a reference point, proximal being closer and distal being farther. In the illustration, proximal is closer to the root of the limb and distal is farther away. For example, damage to the radial nerve of the upper limb is more likley proximal to the elbow than distal.
This is why we are here and there is an amazing eloquence and brutality to the field of surgery. Elegant dissection of brain tumor and aneurysm clipping to the brutality of removing bone and placing pedicle screws, rods or corpectomy cages to stabilize a persons spine. A persons life is literally in your hands and the shit can hit the fan quickly causing the inexperienced person to panic. But a well trained person will react with deft speed and purpose to minimize any problem or difficulty to ensure that precious life is protected.
There is a sensitivity to neuromonitoring that should give the surgeon and the patient confidence. It can pick up irritation to the nerves, not just extreme damage.
There is a sensitivity to neuromonitoring that should give the surgeon and the patient confidence. It can pick up irritation to the nerves, not just extreme damage.
Neuroanatomy is important as a window on brain function; neuropathological symptoms, disease of neuronal metabolism with selective distribution and a syndrome of neuronal cell death selective for a specific neural circuit (Parkinson's Disease).
Brain circuitry has at least three levels of organization; serial processing (information transfer from point to point), parallel processing (information is segregated into separate channels for later, higher level analysis or convergence) and local circuits (a few hundred/thousand neurons perform rapid computations).
Different parts of the brain are functionally non-equivalent; some functions are specifically localized in one place while others are broadly distributed (hypothalamus and cortical control of hypothalamic output) .
Brain circuitry has at least three levels of organization; serial processing (information transfer from point to point), parallel processing (information is segregated into separate channels for later, higher level analysis or convergence) and local circuits (a few hundred/thousand neurons perform rapid computations).
Different parts of the brain are functionally non-equivalent; some functions are specifically localized in one place while others are broadly distributed (hypothalamus and cortical control of hypothalamic output) .
Make it interesting from everyone from the layman to the professional, lead them up to complex ideas in steps, make it entertaining, memorable.
Serial processing - point to point information transfer
Parallel processing - information is segregated in separate channels for later, higher level analysis or convergence
Local circuits - few hundred/thousand neurons perform rapid computations
Different parts of the brain are functionally non-equivalent
some functions are specifally localized in one place (for example, the hupothalamus) while others are broadly distributed (for examle, across different subdivisions of the cerebral cortex that control hypothalamic output.)
Defining the nervous system: multiple levels for sensory and motor processing
spinal cord - afferent and efferent nerves and fiber tracts
brain stem - cranial nerves, nuclear groups and reticular formation
cerebrum - cerebral hemispheres
coverings of the brain and spinal cord - cerebrospinal fluide, dura, and pia provide mechanical support and hydraulic protection and a matrix for the distribution of the blood supply; the dura guards against desiccation (moisture removal) and reduces mechanical trauma
Pathways within the nervous sytem; an introduction to the major players
receptors: specialized transducers for vision, hearing, touch, taste and other modalities
afferent sensory neurons; ganglion cells convey sensory information to the brain and spinal cord
projection neurons; these interconnect remote regions of the brain with one another
internuncial cells (interneurons): sample the interior milieu and make sensory-motor adjustments that are effected by smooth muscle
Major structural and functional subdivisions
anatomical subdivisions: a picture of increasing level of internal complexity
functional subdivisions
afferent (sensory) nervous sytem: input and integration that precedes higher- level processing
effeent (motor) nervous system: output and coordination that translates central processing into decisions and action, the results of which feed forward onto the afferent system as re-afference
Some principles of neuronal organization
patterns of connections between nerve cells define neural circuits
neural systems as servomechanisms (a powered mechanism producing motion or forces at a higher level of energy than the input level, e.g. in the brakes and steering of large motor vehicles, especially where feedback is employed to make the control automatic): feedback plays an essential role in learning and motor behavior
Parallel processing - information is segregated in separate channels for later, higher level analysis or convergence
Local circuits - few hundred/thousand neurons perform rapid computations
Different parts of the brain are functionally non-equivalent
some functions are specifally localized in one place (for example, the hupothalamus) while others are broadly distributed (for examle, across different subdivisions of the cerebral cortex that control hypothalamic output.)
Defining the nervous system: multiple levels for sensory and motor processing
spinal cord - afferent and efferent nerves and fiber tracts
brain stem - cranial nerves, nuclear groups and reticular formation
cerebrum - cerebral hemispheres
coverings of the brain and spinal cord - cerebrospinal fluide, dura, and pia provide mechanical support and hydraulic protection and a matrix for the distribution of the blood supply; the dura guards against desiccation (moisture removal) and reduces mechanical trauma
Pathways within the nervous sytem; an introduction to the major players
receptors: specialized transducers for vision, hearing, touch, taste and other modalities
afferent sensory neurons; ganglion cells convey sensory information to the brain and spinal cord
projection neurons; these interconnect remote regions of the brain with one another
internuncial cells (interneurons): sample the interior milieu and make sensory-motor adjustments that are effected by smooth muscle
Major structural and functional subdivisions
anatomical subdivisions: a picture of increasing level of internal complexity
functional subdivisions
afferent (sensory) nervous sytem: input and integration that precedes higher- level processing
effeent (motor) nervous system: output and coordination that translates central processing into decisions and action, the results of which feed forward onto the afferent system as re-afference
Some principles of neuronal organization
patterns of connections between nerve cells define neural circuits
neural systems as servomechanisms (a powered mechanism producing motion or forces at a higher level of energy than the input level, e.g. in the brakes and steering of large motor vehicles, especially where feedback is employed to make the control automatic): feedback plays an essential role in learning and motor behavior
Regional neuroanatomy defines the major brain divisions as well as local, neighborhood, relationships within the divisions.
The term neuroanatomy is therefore misleading because it implies that knowledge of structure is sufficient to master this discipline.
Develop vocabulary to describe its functional and regional anatomy.
Although derived initially from a single cell (zygote), the cells that make up a given organism undergo differentiation (during embryonic and later development), leading to specialization of the daughter cells. A group of cells that together fulfill some overall function is called tissue. Masses of tissue that are observable to the naked eye are called organs. Groups of organs that function together in achieving broad goals (as perceived by biologists) are called organ systems, for example, the circulatory, digestive, nervous and respiratory systems.
the CNS is interconnected by long nerve tracts.
The term neuroanatomy is therefore misleading because it implies that knowledge of structure is sufficient to master this discipline.
Develop vocabulary to describe its functional and regional anatomy.
Although derived initially from a single cell (zygote), the cells that make up a given organism undergo differentiation (during embryonic and later development), leading to specialization of the daughter cells. A group of cells that together fulfill some overall function is called tissue. Masses of tissue that are observable to the naked eye are called organs. Groups of organs that function together in achieving broad goals (as perceived by biologists) are called organ systems, for example, the circulatory, digestive, nervous and respiratory systems.
the CNS is interconnected by long nerve tracts.
Martin 32
Guidelines for Studying the Regional Anatomy and Interconnections of the Central Nervous System
The rest of this chapter focuses on central nervous system organization from the perspective of it's internal structure. In this and subsequent chapters, myelin stained sections are used to help illustrate the structural and functional organization of the central nervous system. Many structures are distinguished clearly from their neighbors on these sections because of morphological changes at boundaries. For example, the lightly stained dorsal horn of the spinal cord which contains primarily neuronal cell bodies, can be distinguished from the darkly stained white matter, which contains myelinated axons. However, locating other structures on myelin-stained sections can be difficult because neighboring structures stain similarly. this, on a section from a person without corticospinal damage we can localize the corticospinal tract only to a general region in the white matter, because it is surrounded by other myelinated axons that stained the same. As we see in the next section, the location of such a structure in humans is determined by examining tissue from a person who sustained damage to the corticospinal tract during life. This is because after an axon has been damaged, such as by a physical injury or stroke, consistent structural changes occur. The portion of the axon distal to the cut, now isolated from the neuronal cell body, degenerates because it is deprived of nourishment. This process is termed Wallerian (or anterograde) degeneration. In the central nervous system, when a myelinated axon degenerates. The tissue can be stained for the presence of myelin, in which case the territory with the degenerated axons will remain unstained, creating a negative image of their locations. Magnetic resonance imaging is also used to illustrate brain structures, both in healthy patients and in this with neurological disease. Unfortunately, MRI does not provide sufficient detail for learning anatomy We therefore use a combination of radiological and histological images throughout this book. In this chapter, radiological and histological images of the spinal cord, brain stem (five levels), and diencephalon and telencephalon (two levels) are used to illustrate the functions and locations of nuclei tracts.
Guidelines for Studying the Regional Anatomy and Interconnections of the Central Nervous System
The rest of this chapter focuses on central nervous system organization from the perspective of it's internal structure. In this and subsequent chapters, myelin stained sections are used to help illustrate the structural and functional organization of the central nervous system. Many structures are distinguished clearly from their neighbors on these sections because of morphological changes at boundaries. For example, the lightly stained dorsal horn of the spinal cord which contains primarily neuronal cell bodies, can be distinguished from the darkly stained white matter, which contains myelinated axons. However, locating other structures on myelin-stained sections can be difficult because neighboring structures stain similarly. this, on a section from a person without corticospinal damage we can localize the corticospinal tract only to a general region in the white matter, because it is surrounded by other myelinated axons that stained the same. As we see in the next section, the location of such a structure in humans is determined by examining tissue from a person who sustained damage to the corticospinal tract during life. This is because after an axon has been damaged, such as by a physical injury or stroke, consistent structural changes occur. The portion of the axon distal to the cut, now isolated from the neuronal cell body, degenerates because it is deprived of nourishment. This process is termed Wallerian (or anterograde) degeneration. In the central nervous system, when a myelinated axon degenerates. The tissue can be stained for the presence of myelin, in which case the territory with the degenerated axons will remain unstained, creating a negative image of their locations. Magnetic resonance imaging is also used to illustrate brain structures, both in healthy patients and in this with neurological disease. Unfortunately, MRI does not provide sufficient detail for learning anatomy We therefore use a combination of radiological and histological images throughout this book. In this chapter, radiological and histological images of the spinal cord, brain stem (five levels), and diencephalon and telencephalon (two levels) are used to illustrate the functions and locations of nuclei tracts.
After confirmation of segmental levels, testing of dorsal roots begins, usually starting at L2 and proceeding down to S2 on one side before moving to the other. If enough display channels are available it is useful to display EMG from all muscles on both sides in order to easily detect any bilateral responses. If channels are limited, then a sampling of contralateral levels can be utilized, combining muscles innervated from different levels to obtain maximum coverage, for example, quadriceps-tibialis anterior (L4 & L5) in one channel and gastrocnemius-toe flexors (S1 & S2) in another
At each level the entire dorsal root is stimulated at 1 per second and the channels responding are noted. The root is then separated into typically three to eight rootlets, and each one is tested separately. The threshold for each rootlet is first established with stimulation at 1 per second. Since it is not feasible to record from tall muscles innervated from L2-S3 movement may be perceived before EMG responses are noted; the threshold is thus based on a clear EMG response, typically 200 uV or more in amplitude. It is important to be able to switch easily between single stimuli, delivered at 1 per second for threshold testing, and 50 Hz trains of 1 s duration so that once a threshold is established, a train can be delivered at the same level without significant delay.
Irritation and high level of EMG activity, brief paus and irrigation of the field with warm (body temperature not room temperature saline) will usually quiet the recordings
after threshold is determined a train at 50 Hz is delivered at the same stimulus level and the resulting EMG activity reported. Usually helpful to repeat the train two or three times. Useful to be able to change display gains
figure 5-16 show examples of multichannel traces recorded from a single patient. Rootlets eliciting single twitches, a large twitch followed by constant activity at a lower level, or a constant level response are spared. In contrast, rootlets exhibiting augmenting, clonic, widely diffuse, or bilateral responses are generally transected. In many cases, the “good” rootlets will elicit a barely noticeable movement to train stimulation, while stimulation of the “bad” rootlets will cause the entire leg to flex vigorously and sometimes even end up hanging off the OR table. (this is one of the reasons to have the drapes tented up at the legs and the neurophysiologist sitting at the feet!) helpful to have an addition person log* of the same maximally abnormal electrophysiological response during the second stimulation run.
At each level the entire dorsal root is stimulated at 1 per second and the channels responding are noted. The root is then separated into typically three to eight rootlets, and each one is tested separately. The threshold for each rootlet is first established with stimulation at 1 per second. Since it is not feasible to record from tall muscles innervated from L2-S3 movement may be perceived before EMG responses are noted; the threshold is thus based on a clear EMG response, typically 200 uV or more in amplitude. It is important to be able to switch easily between single stimuli, delivered at 1 per second for threshold testing, and 50 Hz trains of 1 s duration so that once a threshold is established, a train can be delivered at the same level without significant delay.
Irritation and high level of EMG activity, brief paus and irrigation of the field with warm (body temperature not room temperature saline) will usually quiet the recordings
after threshold is determined a train at 50 Hz is delivered at the same stimulus level and the resulting EMG activity reported. Usually helpful to repeat the train two or three times. Useful to be able to change display gains
figure 5-16 show examples of multichannel traces recorded from a single patient. Rootlets eliciting single twitches, a large twitch followed by constant activity at a lower level, or a constant level response are spared. In contrast, rootlets exhibiting augmenting, clonic, widely diffuse, or bilateral responses are generally transected. In many cases, the “good” rootlets will elicit a barely noticeable movement to train stimulation, while stimulation of the “bad” rootlets will cause the entire leg to flex vigorously and sometimes even end up hanging off the OR table. (this is one of the reasons to have the drapes tented up at the legs and the neurophysiologist sitting at the feet!) helpful to have an addition person log* of the same maximally abnormal electrophysiological response during the second stimulation run.
Stimulation is delivered through specially designed nerve hooks (Aesculap) which are insulated except for the distal portion, and connected to the monitoring equipment through wires which plug into the end of the handles. Different colored wires are used so that the polarity of the stimulation can be controlled; the surgeon holds the stimulating probes so the cathode is proximal and anode distal, to avoid the possibility of anodal block when stimulating dorsal roots. (When testing ventral roots, the stimulators should be reversed so that the cathode is distal, that is, in the direction of orthodromic conduction.) Stimulation thresholds are typically much lower for ventral roots compared to dorsal roots at the same level. Ventral roots will often exhibit thresholds as low as 0.1 mA or 0.1 while dorsal root thresholds are usually at least three times higher, and often as high as several volts or milliamperes. Constant voltage stimulation is preferred if available, since it is less prone to shifting thresholds due to shunting from cerebrospinal fluid (CSF) or saline.
General anesthesia can be maintained with any common agents, as long as no neuromuscular blockade remains by the time stimulation is necessary. A relatively light plane of surgical anesthesia is desirable so as to not overly suppress reflex responses. Ankle clonus is a good indicator of approximate anesthetic depth; almost all patients with spasticity secondary to cerebral palsy will exhibit marked clonus, and its presence under anesthesia indicates conditions that will be favorable for neurophysiological monitoring.
Spontaneous EMG should be quiet, although clonic EMG will of course be seen when testing the ankle reflexes.
Regardless of the surgical exposure, monitoring begins in earnest after completion of the laminectomy. We have typically used an exposure from L2 to S2, to allow visualization of the nerves as they exit the foramina at these levels.
The first step is to confirm these levels by stimulation. The S1 root is usually the largest, and stimulation at 1 per second will produce responses that are largest in the biceps femoris and gastrocnemius muscles, although smaller responses may be seen in muscles innervated from higher and lower levels (i.e. tibialis anterior or toe flexors) It should be noted that many patients who are candidates for selective dorsal rhizotomy may exhibit anomalous innervation patterns; in one first such cases I monitored, the gastrocnemius was primarily innervated from L5 on the L but from S3 on the R!
Spontaneous EMG should be quiet, although clonic EMG will of course be seen when testing the ankle reflexes.
Regardless of the surgical exposure, monitoring begins in earnest after completion of the laminectomy. We have typically used an exposure from L2 to S2, to allow visualization of the nerves as they exit the foramina at these levels.
The first step is to confirm these levels by stimulation. The S1 root is usually the largest, and stimulation at 1 per second will produce responses that are largest in the biceps femoris and gastrocnemius muscles, although smaller responses may be seen in muscles innervated from higher and lower levels (i.e. tibialis anterior or toe flexors) It should be noted that many patients who are candidates for selective dorsal rhizotomy may exhibit anomalous innervation patterns; in one first such cases I monitored, the gastrocnemius was primarily innervated from L5 on the L but from S3 on the R!
The patient is positioned prone so that the feet are at the bottom of the operating table, and the neurophysiologist sits at the foot of the table so as to be able to palpate the muscles of the legs
A transparent drape is used over the legs, so the surgeon can see movements elicited by stimulation. This drape is tented up to IV poles placed at each side so the legs are accessible to the neurophysiologist during the procedure. Clonus image should be in prone position; foot tends to vibrate to show clonus
A transparent drape is used over the legs, so the surgeon can see movements elicited by stimulation. This drape is tented up to IV poles placed at each side so the legs are accessible to the neurophysiologist during the procedure. Clonus image should be in prone position; foot tends to vibrate to show clonus
Our typical setup involves recording with twisted pair needle electrodes from the following muscles in each leg: quadriceps (vastus medialis-vastus lateralis), adductor magnus, tibialis anterior, biceps femoris, gastrocnemius, and intrinsic toe flexors, as well as the external anal sphincter. (***show muscles via bourgery***)
Most of the leads are placed while the patient is supine, before positioning prone for the procedure. Since flexion at the knee is a common occurrence with stimulation, the leads are all brought together at the knee before being led to the amplifier inputs; this allows free movement of the leg without dislodging the electrodes (***wrapped electrodes joined at knee***)
After placement in the prone position, the final electrodes (i.e. anal sphincter, biceps femoris) are placed, connected to the amplifiers, and a “tap test” is performed by watching free running EMG while tapping each electrode in turn to elicit movement artifacts. This confirms that all electrodes are connected correctly and that all components of the recording system, both hardware and software, are intact from electrode to display.
Most of the leads are placed while the patient is supine, before positioning prone for the procedure. Since flexion at the knee is a common occurrence with stimulation, the leads are all brought together at the knee before being led to the amplifier inputs; this allows free movement of the leg without dislodging the electrodes (***wrapped electrodes joined at knee***)
After placement in the prone position, the final electrodes (i.e. anal sphincter, biceps femoris) are placed, connected to the amplifiers, and a “tap test” is performed by watching free running EMG while tapping each electrode in turn to elicit movement artifacts. This confirms that all electrodes are connected correctly and that all components of the recording system, both hardware and software, are intact from electrode to display.
The Procedure: The key to successful utilization of intraoperative monitoring to select rootlets for sectioning is to recognize that individual patterns differ greatly in the extend to which they demonstrate the different EMG patterns to train stimulation described above. In some patients most responses will be in the “normal” range and the least normal will be candidates for section. Other patients will exhibit almost all “abnormal” responses and the least abnormal will be the ones to be left intact. Finally, some patients will exhibit the complete range of responses described above, and in these patients the decisions are more straightforward. In other words, there is no fixed set of criteria that will work for all patients. Rather, the criteria must be adjusted in the light of each individual's characteristic pattern of responses to train stimulation
Selective Dorsal Rhizotomy: Electrically stimulate lumbar and sacral dorsal roots or rootlets with two electrodes 1cm apart, and recorded electromyographic (EMG) responses from (unspecified target muscles). Beginning at 1Hz, they first established a threshold for each dorsal root, and then progressively increased the stimulation from 1 to 50Hz. The above image are representative examples of the variety of responses elicited by 50 Hz train stimulation for 1 s
Cerebral Palsy primarily manifests as a disruption of motor function characterized by increased limb rigidity primarily in the lower extremities. Charles Sherrington (1898) first reported that spasticity could be relieved by segmental dorsal rhizotomy in decerebrate animals, indicating that the underlying mechanism was hyperactive reflexes due to loss of descending inhibitory inputs
Even if one recognizes the superiority of teaching the basic principles, how is this to be accomplished in practice? This website is for students, in contrast to many textbooks that seem to have been written for the authors' peers and have little regard for the "teachability" of the result.
From the microscopic to macroscopic approach and from principles to specifics.
The main purpose of the evoked potential course is to make clear those ideas that are of fundamental importance in neurophysiology.
Followers should remember that the "facts" presented in textbooks are merely conclusions based on experimental evidence, which may change when more accurate (or more complete) studies are made.
From the microscopic to macroscopic approach and from principles to specifics.
The main purpose of the evoked potential course is to make clear those ideas that are of fundamental importance in neurophysiology.
Followers should remember that the "facts" presented in textbooks are merely conclusions based on experimental evidence, which may change when more accurate (or more complete) studies are made.
This page provides essential terminology, particularly in neuroanatomy. Those who are familiar with these ideas may still find it of some interest as the approach used here is different from the usual viewpoint of neuroanatomy.
Classically, anatomy is the study of form, while physiology is the study of function. A consultation in histology and neuroanatomy should be followed to appreciate the full range of anatomic knowledge.
Classically, anatomy is the study of form, while physiology is the study of function. A consultation in histology and neuroanatomy should be followed to appreciate the full range of anatomic knowledge.
Dimensions related to the Meter Standard
Dimensions in common neurophysiological Use
Units of Time in common neurophysiological use
1 ms = 10^-3 second
1 us = 10^-6 second
1 Hz = 1 cycle/second
Units of Volume
1 mL = 10^-3L
1 uL = 10^-6L
1 nL = 10^-9L
Dimensions in common neurophysiological Use
Units of Time in common neurophysiological use
1 ms = 10^-3 second
1 us = 10^-6 second
1 Hz = 1 cycle/second
Units of Volume
1 mL = 10^-3L
1 uL = 10^-6L
1 nL = 10^-9L
In more down-to-earth language, the nervous system's job is to organize the four F;s of an animal's behavior relative to its environment; Feeding, Fighting, Fleeing, and reproductive behavior.)
This course provides you with a basic understanding of the interdisciplinary nature associated with the principles of neurophysiology as applies to evoked potentials. This class will prepare you for the advanced preparation necessary to pass the Certificate of Neurophysiologic Intraoperatiive Monitoring Exam that is an essential part of becoming a surgical neurophysiologist. We will study aspects of neurophysiology, neurochemistry, neuropathology and recovery of function after neurological trauma. These are essential ingredients for a global perspective on modern surgical
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IOM is a method to protect patients from neurologic injury during surgery.
1. Warns the surgeon of serious complication in time to intervene and correct the problem before it becomes permanent.
2. Sometimes, it identifies a serious systemic problem that needs to be corrected
3. the surgeon can feel comfortable about the patient's neurologic safety to that point in the case, and therefore go forward to provide a more thorough procedure
4. with IOM the surgeons can feel more confident about a procedure's safety, allowing a surgery on a high-risk patient who might otherwise be turned away
5. the patient and his or her family can take comfort that the very real neurologic risks of surgery are lessened by IOM.
problems of the techniques itself? The difficulty of obtaining good quality tracings from some patients or as a result of anesthetic changes.
deep brain stimulation is now in the realm, functional intervention of which involve prompting the expression of neural plasticity
Deep Brain Stimulation selectively lesions brain tissue for treating movement disorders and severe pain. treatment is directed specifically to structures that are involved in producing the symptoms, whereas other general medical treatment is much less specific. this will expand to include disorders that are treated with medication alone.
Provides an opportunity for research and study of the normal function of the human nervous system as well as the function of the diseased nervous system. intracranial recordings are possible. study pathophysiology of disease processes basic research and applied research. results are directly applicable to humans. a human can respond to tell you how they feel.
The termination pattern of large-diameter and small-diameter afferent fibers are illustrated. Large-diameter fibers terminate in the deeper portion of the gray matter whereas the small diameter fibers terminate superficially. Branches of the small-diameter fibers ascend and descend for a few segments in the tract of Lissauer, whereas the major branch of larger diameter fibers ascend to the brain in the dorsal column.
IOM is a method to protect patients from neurologic injury during surgery.
1. Warns the surgeon of serious complication in time to intervene and correct the problem before it becomes permanent.
2. Sometimes, it identifies a serious systemic problem that needs to be corrected
3. the surgeon can feel comfortable about the patient's neurologic safety to that point in the case, and therefore go forward to provide a more thorough procedure
4. with IOM the surgeons can feel more confident about a procedure's safety, allowing a surgery on a high-risk patient who might otherwise be turned away
5. the patient and his or her family can take comfort that the very real neurologic risks of surgery are lessened by IOM.
problems of the techniques itself? The difficulty of obtaining good quality tracings from some patients or as a result of anesthetic changes.
deep brain stimulation is now in the realm, functional intervention of which involve prompting the expression of neural plasticity
Deep Brain Stimulation selectively lesions brain tissue for treating movement disorders and severe pain. treatment is directed specifically to structures that are involved in producing the symptoms, whereas other general medical treatment is much less specific. this will expand to include disorders that are treated with medication alone.
Provides an opportunity for research and study of the normal function of the human nervous system as well as the function of the diseased nervous system. intracranial recordings are possible. study pathophysiology of disease processes basic research and applied research. results are directly applicable to humans. a human can respond to tell you how they feel.
The termination pattern of large-diameter and small-diameter afferent fibers are illustrated. Large-diameter fibers terminate in the deeper portion of the gray matter whereas the small diameter fibers terminate superficially. Branches of the small-diameter fibers ascend and descend for a few segments in the tract of Lissauer, whereas the major branch of larger diameter fibers ascend to the brain in the dorsal column.
Cell theory, the microscopic world of building blocks that constructs our environment and now we will move to the macroscopic, structural elements of support; the muscles and tissue that surround and attach to nervous tissue. Following that, we will take a deep dive into pertinent functional neuroanatomy as it interacts with the structural system as it is crucial to understand how the integrity of the structure and nervous system coexists so we may protect it and our patients can live an enriched life without pain and with maximum function for their condition.
In this module we will discuss the bones of the body and bones of the skull, the muscles of the body and muscles of the skull and will move into the nervous system as it applies to the main modalities of sensory and motor and their innervation (attachment) at the neuromuscular junction and specific landmarks required for our precise technique.
In this module we will discuss the bones of the body and bones of the skull, the muscles of the body and muscles of the skull and will move into the nervous system as it applies to the main modalities of sensory and motor and their innervation (attachment) at the neuromuscular junction and specific landmarks required for our precise technique.