chapter 8 notes

chapter 8 notes - CHAPTER 8: Control of Movement...

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Organization of the Motor Cortex: The primary motor cortex lies on the precentral gyrus, just rostral to the central sulcus. It shows somatopic representation; a motor homunculus – like the somatosensory cortex. A disproportionately large amount of cortical area is devoted to movements of the fingers and the muscles used for speech. The commands for movement initiated in the motor cortex are assisted and modified, most notably by the basal ganglia and the cerebellum. Graziano, Aflafo: longer stimulation of certain brain regions in monkey- complex movement The main cortical input to the PMC is the frontal association cortex, which is rostral to it. 2 regions adjacent to the PMC are especially important in control of movement: the supplementary motor cortex and the premotor cortex. Both receive input from the temporal and parietal lobes and send efferent axons to the PMC. The SMA is located on the medial surface of the brain, rostral to the PMC. The premotor cortex is on the lateral surface, also just rostral to the PMC. The PMC also receives info from the adjacent somato cortex. Asanuma and Rosen: found that certain points on the somatopic map of the somatosensory cortex stimulate corresponding points on the somatopic map of the primary motor cortex. Cortical control/ the descending pathways: 2 motor control groups: lateral and ventromedial (for locations in spinal cord white matter). Lateral group consists of the cortiospinal tract, the corticobulbar tract, and the rubrospinal tract. This system is primarily involved in independent limb movement. The (lateral) corticospinal tract originates in the finger, hand, and arm regions of the motor cortex, terminates in the spinal cord gray matter, controls the fingers, hands, and arms, and its function is the grasping and manipulation of objects. The axons leave the cortex and travel through subcortical white matter to the ventral midbrain, where they enter the cerebral peduncles in the medulla and form pyramidal tracts. At the caudal medulla, most axons cross over and form the ventral corticospinal tract; the ones that continue ipsalaterally form the lateral cortico tract. The rubrospinal tract originates in the red nucelus (midbrain), terminates on motor neurons in the spinal cord, controls the hands (not fingers), lower arms, feet, and lower legs, and its function is the movement of forearms and hands independent from that of the trunk. It receives most important inputs from the cerebellum and the corticorubral tract (PMC). The corticobulbar tract originates in the face region of motor cortex, terminates in the motor nuclei of the 5 th , 7 th , 9 th , 10 th , 11 th , and 12 th cranial nerves, controls the face, neck, and tongue muscle group, and its function is face/tongue movements. It projects from the MC to the medulla (similar path to corticospinal tract).
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chapter 8 notes - CHAPTER 8: Control of Movement...

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