The Brain
The brain is a gelatinous mass of protoplasm encased in the protective enclave of the bony skull. It weighs approximately 1300 grams and is constructed of symmetrically complex structural elements combined with microscopic neural circuitry embedded in the cerebral cortex which processes and delivers the human experience.
The cerebrum is the most anterior part of the brain and is grossly divided into two hemispheres separated by the midline, longitudinal fissure in the sagittal plane. The surface of each hemisphere, the cerebral cortex (bark), is convoluted into gyri (folds) separated from one another by sulci (grooves) to compress/increase surface area of the cortex in a confined space. The 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, functionally distinct lobes of function by fissures (deeper grooves). The lobes are named after the cranial bones that are superior to them; frontal, parietal, occipital (from rostral to caudal) and bi-lateral temporal lobes (inferior and lateral). The central sulcus traverses in the coronal plane and separates the pre-central gyrus of the frontal lobe (motor control) from the post-central gyrus of the parietal (somatosensory) lobe. The bilateral Sylvian Fissures demarcate the temporal lobe from the frontal and parietal lobes. The poles define the extremities of the brain.
The frontal lobe extends from the the frontal pole (extreme rostral) to the central sulcus. The pre-frontal cortex and frontal lobe processes long-term, goal-directed planning, behavior and are the architect of personality. Much of the frontal lobe is association cortex that processes complex sensory input to feed higher brain functions (cognition, anticipation, and emotion). The superior middle, and inferior frontal gyri form most of the remaining portion of the frontal lobe, the inferior frontal gyrus (left hemisphere dominant in most people) contains Broca's area, which is essential for the articulation of motor speech. The olfactory nerves (cranial nerve I; L & R) are located at the basal frontal lobes.
Caudal to the frontal lobe is pre-motor cortex, which executes planning and movement sequences which feeds forward directly into the primary motor cortex. The pre-motor areas, which are important in motor decision making and planning movements, are adjacent to the primary motor cortex gyri. The pre-central (rostral central gyrus/posterior frontal lobe) gyrus contains the primary motor cortex, which executes coordinated, mechanical actions of muscular movement. Many neurons in the primary motor cortex project to the spinal cord as the corticospinal tract and have a axons that terminate in the spinal cord. The architecture of the primary motor cortex contains a mapped representation of the entire body image (motor homunculus).
The parietal lobe is caudally separated from the frontal lobe by the central sulcus. The post-central sulcus contains the primary somatic sensory (somatosensory) cortex which processes sensory information for the perception of touch, pain and limb position from input from the periphery. The architecture of the somatic sensory cortex contains a mapped representation of the entire body (sensory homunculus) with gross exaggerations for more sensitive areas.
The parieto-occipital sulcus demarcates the caudal pole (extreme caudal) and occipital lobe which contains the primary visual cortex located in the walls and depth of the Calcarine fissure. There are no distinct boundaries on the lateral and inferior surface of the occipital lobe, only an imaginary line that connects the pre-occiptal notch with the parieto-occipital sulcus. The occipital lobe singular function is processing visual perception. The primary visual cortex is important in the initial stages of visual processing but it is the surrounding, higher-order, associative visual areas that process sensory input into form and color of objects (inferior temporal gyrus).
The lateral sulcus (Sylvian fissure) separates the frontal and parietal lobes and processes memory, emotions and audition. Deep within the lateral sulcus are portions of the frontal, parietal and temporal lobes, this territory is termed the insular cortex. It becomes buried late during prenatal development. Portions of the insular cortex are important in taste, internal body senses, and some aspects of pain.
The primary auditory cortex, located on the superior temporal gyrus, works with surrounding areas (superior temporal gyrus, lateral sulcus, middle temporal gyrus) for processing perception and localization of sounds. The primary auditory cortex has along the superior part of the temporal lobe, hidden deep in the Sylvian sulcus (a valley). The superior temporal gyrus on the left side (in most people) is specialized for motor speech, the posterior portion of this gyrus, Wernicke's area, processes the understanding of speech. The cortex located at the temporal pole together with adjacent portions of the medial temporal lobe and inferior and medial frontal lobes, are important for emotions.
The temporal pole has further visceral functions, (rage, reproduction, aggression, territoriality) that can affect smooth muscle and glands (as opposed to skeletal muscle), causing changes in respiration, heart rate, digestion, sweating, ovulation and reproduction. The temporal lobe inferior and caudal to the auditory cortex is mainly concerned with memory and damage to it can interfere both with the formation of memories or their consolidation from short-term to long-term.
The cerebrum is the most anterior part of the brain and is grossly divided into two hemispheres separated by the midline, longitudinal fissure in the sagittal plane. The surface of each hemisphere, the cerebral cortex (bark), is convoluted into gyri (folds) separated from one another by sulci (grooves) to compress/increase surface area of the cortex in a confined space. The 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, functionally distinct lobes of function by fissures (deeper grooves). The lobes are named after the cranial bones that are superior to them; frontal, parietal, occipital (from rostral to caudal) and bi-lateral temporal lobes (inferior and lateral). The central sulcus traverses in the coronal plane and separates the pre-central gyrus of the frontal lobe (motor control) from the post-central gyrus of the parietal (somatosensory) lobe. The bilateral Sylvian Fissures demarcate the temporal lobe from the frontal and parietal lobes. The poles define the extremities of the brain.
The frontal lobe extends from the the frontal pole (extreme rostral) to the central sulcus. The pre-frontal cortex and frontal lobe processes long-term, goal-directed planning, behavior and are the architect of personality. Much of the frontal lobe is association cortex that processes complex sensory input to feed higher brain functions (cognition, anticipation, and emotion). The superior middle, and inferior frontal gyri form most of the remaining portion of the frontal lobe, the inferior frontal gyrus (left hemisphere dominant in most people) contains Broca's area, which is essential for the articulation of motor speech. The olfactory nerves (cranial nerve I; L & R) are located at the basal frontal lobes.
Caudal to the frontal lobe is pre-motor cortex, which executes planning and movement sequences which feeds forward directly into the primary motor cortex. The pre-motor areas, which are important in motor decision making and planning movements, are adjacent to the primary motor cortex gyri. The pre-central (rostral central gyrus/posterior frontal lobe) gyrus contains the primary motor cortex, which executes coordinated, mechanical actions of muscular movement. Many neurons in the primary motor cortex project to the spinal cord as the corticospinal tract and have a axons that terminate in the spinal cord. The architecture of the primary motor cortex contains a mapped representation of the entire body image (motor homunculus).
The parietal lobe is caudally separated from the frontal lobe by the central sulcus. The post-central sulcus contains the primary somatic sensory (somatosensory) cortex which processes sensory information for the perception of touch, pain and limb position from input from the periphery. The architecture of the somatic sensory cortex contains a mapped representation of the entire body (sensory homunculus) with gross exaggerations for more sensitive areas.
The parieto-occipital sulcus demarcates the caudal pole (extreme caudal) and occipital lobe which contains the primary visual cortex located in the walls and depth of the Calcarine fissure. There are no distinct boundaries on the lateral and inferior surface of the occipital lobe, only an imaginary line that connects the pre-occiptal notch with the parieto-occipital sulcus. The occipital lobe singular function is processing visual perception. The primary visual cortex is important in the initial stages of visual processing but it is the surrounding, higher-order, associative visual areas that process sensory input into form and color of objects (inferior temporal gyrus).
The lateral sulcus (Sylvian fissure) separates the frontal and parietal lobes and processes memory, emotions and audition. Deep within the lateral sulcus are portions of the frontal, parietal and temporal lobes, this territory is termed the insular cortex. It becomes buried late during prenatal development. Portions of the insular cortex are important in taste, internal body senses, and some aspects of pain.
The primary auditory cortex, located on the superior temporal gyrus, works with surrounding areas (superior temporal gyrus, lateral sulcus, middle temporal gyrus) for processing perception and localization of sounds. The primary auditory cortex has along the superior part of the temporal lobe, hidden deep in the Sylvian sulcus (a valley). The superior temporal gyrus on the left side (in most people) is specialized for motor speech, the posterior portion of this gyrus, Wernicke's area, processes the understanding of speech. The cortex located at the temporal pole together with adjacent portions of the medial temporal lobe and inferior and medial frontal lobes, are important for emotions.
The temporal pole has further visceral functions, (rage, reproduction, aggression, territoriality) that can affect smooth muscle and glands (as opposed to skeletal muscle), causing changes in respiration, heart rate, digestion, sweating, ovulation and reproduction. The temporal lobe inferior and caudal to the auditory cortex is mainly concerned with memory and damage to it can interfere both with the formation of memories or their consolidation from short-term to long-term.