Primary Motor Cortex
The neural control of muscle is smoothly integrated by sensory and motor components through a combination of interaction of multiple levels of the nervous system and local spinal cord processing. The neuromuscular complex is mediated by a mixture of inhibition and excitation and is coordinated with the basal ganglia and cerebellum, action potentials and nicotinic acetylcholine. Basal Ganglia and Cerebellum coordinated an ideal mixture of inhibition, excitation, action potentials powered by nicotinic acetylcholine.
Structural (anatomical) pathways for the subconscious control of posture are the basic elements of the motor system; spinocerebellar tracts, cerebellar and ventrolateral nuclei of the thalamus are the main targets of cerebellar outflow.
The basic elements in the central motor system are pathways for the subconscious control of posture; spinocerebellar tracts, cerebellum and ventrolateral nuclei of the thalamus are the main targets of cerebrellar outflow. The Basal Ganglia have an important role in the initiation of movement and it's continuity. The Reticular formation provides important supplementary feedback via the reticulospinal tract.
The motor cortex serves as the prime conscious influence on muscle that complements cerebellar (subconscious) output. Gamma motoneurons adjust the gain of the 1a system subconsciously by altering spindle excitability. Spinal interneurons propagate reciprocal influences intrasegmentally and propriospinal influence intersegementally. Subconscious elements in the central motor system control posture; spinocerebellar tracts, cerebellum and ventrolateral nuclei of the thalamus are the main target of cerebellar outflow. In addition, the basal ganglia have an important role in the initiation of movement and it's continuity. The reticular formation provides important supplementary feedback via the reticulospinal tract.
The motor system initiates and controls activity in the somatic muscles and functions to control posture and movement. Components of this system include motor cortex and other areas of the frontal lobes (planning, pre-motor). The descending pathways originating at motor cortex traverse the internal capsule, cerebral peduncles, medullary pyramids, and other areas of the brainstem to portions of the spinal cord which include the ventral horns and roots of the spinal cord. The motor system is present throughout the neuraxis and is directly involved in the performance of all motor activity mediated by voluntary muscles. Weakness, paralysis, twitching, jerking, staggering, wasting, shaking, stiffness, spasticity, and incoordination involving the arms, legs, eyes, or muscles of speech are all due to impairments of the motor system.
The motor pathway has three major components, the corticospinal tract from the cortex to the spinal cord, brainstem motor pathways from the brainstem to the spinal cord, and the final common pathway from motor neurons in the ventral horn of the spinal cord (and motor nuclei of the brainstem) to the muscles located in the periphery. The motor neurons receive segmental inputs from the limbs via primary afferents and descending inputs from supraspinal structures. Segmental and supraspinal inputs affect motor neuron activity either directly or, more commonly, via interneurons.,
The descending pathways originate from motor areas of the cerebral cortex and the brainstem. Cortical motor neurons give rise to the corticospinal tract, which controls fine movements of the distal portions of the limbs, particularly the fingers. The descending pathways from the brainstem primarily control postural and reflex movements. The activity of these pathways is regulated by two circuits centered in the basal ganglia and the cerebellum. The basal ganglia are important in the selection and initiation of specific motor programs. The cerebellum controls the execution of the motor actions and motor learning. The cortical motor areas project to both the basal ganglia and the cerebellum. both of these structures project back to the cortex via a relay in the motor nuclei of the thalamus.
Skeletal muscle receives an overlapping pattern of innervation.
Structural (anatomical) pathways for the subconscious control of posture are the basic elements of the motor system; spinocerebellar tracts, cerebellar and ventrolateral nuclei of the thalamus are the main targets of cerebellar outflow.
The basic elements in the central motor system are pathways for the subconscious control of posture; spinocerebellar tracts, cerebellum and ventrolateral nuclei of the thalamus are the main targets of cerebrellar outflow. The Basal Ganglia have an important role in the initiation of movement and it's continuity. The Reticular formation provides important supplementary feedback via the reticulospinal tract.
The motor cortex serves as the prime conscious influence on muscle that complements cerebellar (subconscious) output. Gamma motoneurons adjust the gain of the 1a system subconsciously by altering spindle excitability. Spinal interneurons propagate reciprocal influences intrasegmentally and propriospinal influence intersegementally. Subconscious elements in the central motor system control posture; spinocerebellar tracts, cerebellum and ventrolateral nuclei of the thalamus are the main target of cerebellar outflow. In addition, the basal ganglia have an important role in the initiation of movement and it's continuity. The reticular formation provides important supplementary feedback via the reticulospinal tract.
The motor system initiates and controls activity in the somatic muscles and functions to control posture and movement. Components of this system include motor cortex and other areas of the frontal lobes (planning, pre-motor). The descending pathways originating at motor cortex traverse the internal capsule, cerebral peduncles, medullary pyramids, and other areas of the brainstem to portions of the spinal cord which include the ventral horns and roots of the spinal cord. The motor system is present throughout the neuraxis and is directly involved in the performance of all motor activity mediated by voluntary muscles. Weakness, paralysis, twitching, jerking, staggering, wasting, shaking, stiffness, spasticity, and incoordination involving the arms, legs, eyes, or muscles of speech are all due to impairments of the motor system.
The motor pathway has three major components, the corticospinal tract from the cortex to the spinal cord, brainstem motor pathways from the brainstem to the spinal cord, and the final common pathway from motor neurons in the ventral horn of the spinal cord (and motor nuclei of the brainstem) to the muscles located in the periphery. The motor neurons receive segmental inputs from the limbs via primary afferents and descending inputs from supraspinal structures. Segmental and supraspinal inputs affect motor neuron activity either directly or, more commonly, via interneurons.,
The descending pathways originate from motor areas of the cerebral cortex and the brainstem. Cortical motor neurons give rise to the corticospinal tract, which controls fine movements of the distal portions of the limbs, particularly the fingers. The descending pathways from the brainstem primarily control postural and reflex movements. The activity of these pathways is regulated by two circuits centered in the basal ganglia and the cerebellum. The basal ganglia are important in the selection and initiation of specific motor programs. The cerebellum controls the execution of the motor actions and motor learning. The cortical motor areas project to both the basal ganglia and the cerebellum. both of these structures project back to the cortex via a relay in the motor nuclei of the thalamus.
Skeletal muscle receives an overlapping pattern of innervation.
The Neural Circuit
- involved in the control of coordinated movement, sequences of motor acts
- substantia nigra to striatum in the basal ganglia
- striatum to globus pallidus to motor thalmus to motor cortex
- motor cortex output to the spinal cord and body producing action
- 10,000 excitatory synapses per neuron in the basal ganglia striatum
- each neuron lives at the edge of excitation much of the time
Remember: that the motor cortex programs the contractions of muscles for voluntary power and precision, while the cerebellum controls the subconscious timing and coordination of muscle contraction. Hence cortical damage causes decrements in muscle force and in the accuracy of movement while cerebellar damage affects the timing of muscle contraction, causing the limb to over or undershoot the spider, but has no effect on strength of contraction.***
Question: What effect would damage to the cerebellum have on the organization of your motor response? How would these consequences compare with damage to the motor cortex?
The main descending input from the cerebral cortex enters by way of the pontine nuclei, forming corticopontocerebellar pathways. These allow the motor cortex to affect cerebellar output and since the motor cortex operates consciously, to therefore provide volitional influences upon the cerebellum.