Motor control: reflexes

Question 1

how does the higher centers of the brain impact reflexes

Answer 1

often seen to be inhibitory of the reflexes (via nociceptor mechanoreceptors)

but also will provide excitatory input as well

Question 2

What is spinal shock

Answer 2

transection of the spinal cord that will affect the neurons producing the reflexes even though they are below the level of the transection (therefore intact) but the reflex fails to occur

Question 3

How are reflexes recovered after spinal shock

Answer 3

believed to result from:
axonal sprouting below the level of the transection
or
expression of receptor phenotypes that are self activating (5HTC receptor)

Question 4

rigidity

Answer 4

resists motion in all directions
results from maintained muscle contraction (extensors)
continual activation of alpha motor neurons via the brainstem ganglia usually

Question 5

spasticity

Answer 5

resists motion in a given direction
myotic reflex hyperactive
continual activation of gamma motorneurons (increases the sensitivity of the reflexes)

region in cortex that supplies communicates with the brainstem inhibitor complex of the gamma motor neurons
region in brainstem that activates the gamma motor neurons (no cortical input)
-therefore cortex damage leads to spasticity