Reflexes

Question 1

From what type of receptor does the patellar tendon reflex use information from?

Answer 1

Muscle spindles which monitor muscle length and rate of change of muscle length

Question 2

What is meant by a monosynaptic reflex?

Answer 2

A reflex which does not involve interneurons

Question 3

Describe the three pathways which activated spindle sensory afferents can take in the patella tendon reflex.

Answer 3

1. Activate alpha motor neurons of muscle fibre which was stretched, causing it to contract agonist muscle.
2. Indirectly cause antagonist to relax via reciprocal inhibition.
3. Ascend the dorsal column and connect with somatosensory system to inform brain about muscle length.

Question 4

What is meant by reciprocal inhibition in relation to the patellar tendon reflex?

Answer 4

Sensory spindle afferents activate inhibitory interneurons which decrease activation of alpha motor neurons to the antagonist muscle, causing it to relax.

Question 5

What is the function of the inverse stretch reflex?

Answer 5

Prevents muscle contracting to such an extent that the tendon insertion tears away from the bone.

Question 6

Firing of 1b sensory neurons from GTO in the inverse stretch reflex leads to three different pathways. Describe them.

Answer 6

1. Activation of inhibitory interneurons to agonist muscle to decrease strength of contraction.
2. Activation of excitatory interneurons to antagonist muscle to decrease strength of relaxation.
3. Information about muscle tension ascends in the dorsal column to connect with somatosensory system.

Question 7

What is the function of the flexor reflex?

Answer 7

Ipsilateral flexion in response to painful stimulus on nociceptor.

Question 8

Describe the mechanism of the flexor reflex.

Answer 8

Increased firing of action potentials in nociceptors
Activation of flexor muscle in affect part of body via excitatory interneurons.
Inhibition of extensor muscle via inhibitory interneurons.
Excitatory interneurons cross spinal cord and activate contralateral extensors
Inhibitory interneurons cross spinal cord and inhibit contralateral flexors
This helps to maintain body position
Sensory info ascends to brain via contralateral spinothalmic tract.