Spinal reflexes Flashcards Preview

Year 1 Neuroanatomy > Spinal reflexes > Flashcards

Flashcards in Spinal reflexes Deck (21)
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1
Q

which neurons are involved in reflexes?

A

alpha and gamma motor neurons

2
Q

what do alpha motor neurons innervate?

A

skeletal muscle fibers (extrafusal fibers)

3
Q

what do gamma motor neurons innervate?

A

contractile (polar) portion of intrafusal fibers of muscle spindles

4
Q

what forms the sensory (afferent) limb of a reflex arc?

A
  1. pseudounipolar (sensory) neuron whose cell body is housed in a DRG 2. peripheral process is in skin / skeletal muscle / tendon / joint capsule; central process synapses in spinal cord gray matter
5
Q

what forms the motor (efferent) limb of a reflex arc?

A
  1. motor neuron whose cell body is usually located in the ventral horn of the spinal cord 2. axon synapses in skeletal muscle
6
Q

what is the receptor in the muscle stretch reflex?

A

muscle spindle

7
Q

what is the receptor in reciprocal inhibition?

A

muscle spindle at peripheral end of 1a fiber

8
Q

what is the receptor in autogenic inhibition?

A

GTO

9
Q

what is the stimulus in autogenic inhibition?

A

muscle contraction triggers sensory endings innervating tendons to fire

10
Q

what does autogenic inhibition inhibit?

A

muscle over-contraction

11
Q

what does the autogenic inhibition reflex protect?

A

tendon

12
Q

where are the receptors in the flexor reflex (withdrawal reflex, nociceptive reflex)?

A

cutaneous

13
Q

what type of fibers make up the afferent limb of the flexor reflex (withdrawal reflex, nociceptive reflex)?

A

lightly myelinated Ad fibers, or unmyelinated C fibers of pseudounipolar neurons whose cell bodies are in a DRG

14
Q

where does the central process of a pseudounipolar neuron involved in the flexor reflex enter the spinal cord?

A

enters the dorsolateral tract of Lissauer and branches into short ascending and descending fibers

15
Q

what neurons are involved in the crossed extension reflex?

A

commissural interneurons whose axons cross the midline to synapse with excitatory and inhibitory interneurons located in the ventral horn of the spinal cord on the opposite side

16
Q

gamma motor neurons are under what type of control?

A

supraspinal (from the brain)

17
Q

what do gamma motor neurons stimulate in maintenance of muscle tone?

A

polar (contractile) portions of intrafusal fibers

18
Q

what triggers the slight contraction of gross muscle during muscle tone maintenance?

A

stretch reflex

19
Q

what does stimulation of gamma motor neurons do to muscle tone? inhibition of gamma motor neurons?

A
  1. increase 2. decrease
20
Q

the gamma loop contains what five components?

A
  1. gamma motor neurons 2. intrafusal fibers 3. 1a fibers 4. alpha motor neurons 5. extrafusal fibers
21
Q

what is the purpose of alpha gamma coactivation?

A

a way to maintaining sensitivity to stretch during gross muscle contraction