General Organization of the Motor Systems

Reflex arc •Neural “wiring” of reflex•Requires 5 functional components: 1. sensory receptor, 2. sensory neuron, 3. intergrating center (SC or BS), 4. motor neuron, & 5. effector

curve A, in a normal muscle, and curve B, in a muscle whose muscle spindles were denervated

Muscle Spindle Reflex

Golgi Tendon Reflex

withdrawal crossedextensor

Myogram of the flexor reflex showing rapid onset of the reflex, an interval of fatigue, and,

finally, afterdischarge after the input stimulus is over.

Myogram of a crossed extensor reflex showing slow onset

but prolonged afterdischarge

Control of voluntary movement

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The somatosensory cortex homunculus & The motor cortex homunculus

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Inputs to motor cortex

SMAPremotor

cortex

Primarymotor cortex

Thalamus

Basalganglia

Cerebellum

Spinal/sensory inputs

Thalamus

Primarysensorycortex

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DECEREBRATIONand DECORTICATION

Plantar Response

Scrape object on sole of foot.Babinski sign indicative of UMN lesion.

Normal in infants up to 1 yr.