Spinal Level Reflexes

Question 1

What is the stimulus for stretch reflex

Answer 1

muscle stretch

Question 2

Stretch reflex - reflex arc

Answer 2

afferent Ia fiver from muscle spindle to alpha motor neurons projecting back to muscle of origin

Question 3

stretch reflex- function

Answer 3

maintenance of muscle tone, support agonist muscle contraction, and provide feedback about muscle length

Question 4

reciprocal inhibition

Answer 4

via an inhibitory interneuron, the same stretch stimulus inhibits the antagonist muscle

Question 5

reciprocal innervation

Answer 5

describes the effects of a stretch stimulus on agonist (autogenic facilitation), antagonist (reciprocal inhibition), and synergistic muscles (facilitation)

Question 6

Inverse Stretch (myotatic) reflex

Answer 6

• stimulus: muscle contraction
• Reflex arc: multiple sensory receptors and corresponding fiber types activate inhibitory interneuron to muscle of origin
• Functions to provide agonist inhibition, diminution of force of agonist contraction, stretch-protection reflex

Question 7

Gamma reflex loop

Answer 7

• stretch reflex forms part of this loop
• allows muscle tension to come under control of descending pathways
• descending pathways excite gamma motor neurons, causing contraction of muscle spindle, and in turn increased stretch sensitivity and increased rate of firing from spindle afferents, impulses are then conveyed to alpha motor neurons

Question 8

flexor withdrawal reflex

Answer 8

• stimulus: cutaneous sensory stimuli
• reflex arc: cutaneous receptors via interneurons to largely flexor muscles; multisegmental response involving groups of muscles
• functions as a protective withdrawal mechanism to remove body from harmful stimuli

Question 9

crossed extension reflex - stimulus

Answer 9

noxious stimuli and reciprocal action of antagonists; flexors of one side are excited, causing extensors on same side to be inhibited; opposite responses occur in opposite limb

Question 10

crossed extension reflex- reflex arc

Answer 10

• cutaneous and muscle receptors diverging to many spinal cord motor neurons on same and opposite side

Question 11

crossed extension reflex- function

Answer 11

coordinates reciprocal limb activities such as gait