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PSYC 207 (7)


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University of British Columbia
PSYC 207
Michael Souza

Organization of the Motor System 10/15/2012 9:30:00 PM Movement -entire nervous system = motor system = functions to move body 1. visual system must first inspect 2. Information relayed to visual cortex to corticomotor regions (plan and initiate movement) 3. Send instructions to part of spinal cord that controls particular muscles 4. Sensory receptors travel to spinal cord 5. Messages relayed back up to sensory regions that interpret touch *Sensory cortex informs the motor cortex of the event occurring •Basal ganglia (under frontal cortex) = produce appropriate amount of force •Cerebellum = regulate timing & correct errors The Neocortex & Initiation of Movement 1. Posterior Sensory Cortex: -Specify movement goals & send info to … 2. Prefrontal Cortex -Generates plans for movement -Direct routes = execute automatic movement -Indirect routes = movement requiring conscious control 3. Premotor cortex -Contain repertoire of movements to sequence -Recognize movement of others & select similar/different actions 4. Motor cortex -Executes/produces specific, appropriate movement •Movement Hierarchy A) Simple : controlled by motor cortex (push a button) B) Sequence : additionally controlled by premotor cortex C) Complex: controlled by prefrontal, temporal, parietal cortex (maze) Identifying the Motor Cortex with the Use of Electrical Stimulation •Wilder Penfield -Used brief electrical impulses to map cortices of human patients (about to undergo neurosurgery) -Most movements triggered by stimulation of precentral gyrus (primary motor cortex) -Movement can be produced by stimulating dorsal part of premotor cortex (supplementary motor cortex) -Body is symmetrical: each hemisphere contains almost-mirror image of homunculi (found 4 in total) -Homunculi: disproportionate to relative sizes of body parts (Larger brain areas = more complex body functions) Multiple representations in the Motor Cortex -Motor cortex not organized for control of individual muscles but control of movements -Different classes of homunculi represent different classes of movement -Electrical stimulation in a monkey A) Defensive facial expression B) hand to mouth C) manipulation & shaping of hand/digits in central body space D) outward reach with hand E) Climbing & leaping posture *Smooth and coordinated movement! Graziano: *Implies that there are many maps of the body -Motor cortex represents 3 types of organization 1. part of the body that is to be moved 2. spatial location to which the movement is directed 3. function Disorders of Motor Neurons and the Spinal Cord 10/15/2012 9:30:00 PM •Produced by damage to spinal cord or cortical projections to spinal cord Some Movement Disorders Apraxia -Inability to carry out purposeful movements -Or movements on command -Paralysis or other motor/sensory impairments. (Neocortex damage) Ataxia Failure of muscular coordination -Or irregularity of muscular action. (Cerebellar damage) Athetosis -Slow, sinuous (curvy) writhing movement (hands) -Due to abnormal function of extrapyramidal system Brown-Séquard -Unilateral damage to spinal cord Syndrome -Loss of fine touch & pressure sensation on same side of body -Loss of pain & temperature on opposite side of body below body -Different symptoms appear on two sides of body below damage/cut -Walking recovered within 2-3 days = activity bilateral Catalepsy -Muscular rigidity, voluntary movement reduced/absent -Posture still maintained (ft. of Parkinson’s) Cataplexy -Complete loss of movement/posture -Muscle tone absent, consciousness spared Chorea -Jerky movement, seems well coordinated by involuntary Hemiplegia -Complete or partial paralysis to ½ of body -Damage to neocortex & basal ganglia contralateral to motor symptoms -Infancy: fever, epilepsy, birth injury -Young adults: congenital aneurysm/embolism, tumor, or head injury -Older adults: (occur most) hemorrhaging from high blood pressure & blood vessel degeneration -Causes abnormal reflexes: Babinski -Absent reflexes: abdominal (retract when stroked), cremasteric (retraction of testicles when inner thigh stroked in males) Multiple Sclerosis -loss of myelin (in motor & sensory tracts) -Lost in patches (sclerotic plaques=scars) -Loss of sensation in face, limbs, body, limb(s) *Initial symptoms go into remission (appear later again) -Unclear cause, may be hereditary -More common
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