Spinal Reflexes

Question 1

where do the cell bodies of lower motor neurons reside

Answer 1

ventral horn of spinal hord

Question 2

innervate typical skeletal muscle fibers

Answer 2

alpha motor neurons

Question 3

smaller: gamma or alpha motor neuron

Answer 3

gamma

Question 4

innervate the contractile portion of intrafusal fibers of muscle spindles

Answer 4

gamma motor neurons

Question 5

involve of affect only a single spinal cord level

Answer 5

intrasegmental

Question 6

they involve or affect numerous spinal cord leels

Answer 6

intersegmental

Question 7

they are influenced by neurons residing in the cerebral hemisphere or brainstema nd through their connection influence reflex activity occurring at the spinal cord level

Answer 7

suprasegmental

Question 8

biceps reflex

Answer 8

C5/6

Question 9

triceps reflex

Answer 9

C6-8

Question 10

quadriceps reflex “knee jerk”

Answer 10

L2-4

Question 11

gastrocnemius reflex “ankle jerk”

Answer 11

S1-2

Question 12

how many neurons in muscle stretch reflex

Answer 12

2 neurons (sensory and motor)

Question 13

describe quadriceps stretch reflex

Answer 13

displaces patella slightl
stretches extrafusal fibers, and therefore stretch muscle spindles –> fire
signal down their annulospiral neurons to alpha motor neuron to quadricep

Question 14

how does reciprocal inhibition happen

Answer 14

central process of sensory neuron bifurcates to excite an alpha neuron one way and via an interneuron inhibit a different alpha motor neuron

Question 15

what does autogenic inhibition limit?

Answer 15

muscle over contraction via activation of GTO

Question 16

stimulation of muscle spindle –>

stimulation of GTO –>

Answer 16

spindle: muscle contraction

GTO: muscle relaxation

Question 17

body responds by withdrawing of affected body part

Answer 17

flexor reflex

Question 18

uses dorsolateral tract of lissauer

Answer 18

flexor reflex

Question 19

when standing or walking, one of the limbs contact a noxious stimulus

Answer 19

crossed extension reflex

happens in unaffected limb so the weight of the body can be shifted to it

Question 20

commissural interneurons cross midline to synapse with excitatory and inhbitory interneurons located in ventral horn of spinal cord on opposite side

Answer 20

crossed extension reflex

Question 21

muscle tone results from stimulation of…

Answer 21

gamma motor neurons and the stretch reflex

Question 22

gamma motor neurons are under ______ control

Answer 22

supraspinal control, not under the control of the sneory fiber innervating intrafusal fibers

There are NO signals relayed back from the muscle spindles to the gamma motor neurons

Question 23

how do gamma motor neurons initiate the stretch reflex

Answer 23

gamma motor neurons stimulate contractile portions of intrafusal fibers –> they contract and cause firing of stretch reflex

Question 24

it is the _________ that triggers slight contraction of the gross muscle, generating a normal amount of muscle tone so that gross muscle is not flaccid

Answer 24

stretch reflec

Question 25

5 components of the gamma loop

Answer 25

gamma motor neurons

intrafusal fibers

Ialpha fibers

alpha motor neurons

extrafusal fibers

Question 26

during voluntary movement, axons of descending mtoor tracts converge on both alpha and gamma motor neurons to stimulate them simultaneously

Answer 26

alpha-gamma coactivation

causes contraction of extrafusal and intrafusal fibers

Question 27

lesion involving alpha and gamma motor neurons results in … (4)

Answer 27

flaccid parlaysis

atrophy

hypotonia

hyporeflexia/areflexia

Question 28

overstretching

Answer 28

muscle stretch reflec

Question 29

over contraction

Answer 29

autogenic inhibition