S3 Spinal reflexes

Question 1

Define a spinal reflex:

Answer 1

Fast, predictable automatic response to a change in the environment or stimulus.

Question 2

What are the five functional components of a spinal reflex?

Answer 2

Sensory neuron recieves pain signal.
Action potential fires.
Integration - monosynaptic or polysynaptic.
Activation fo a motor neuron.
Contraction of muscle/gland.

Question 3

Myotatic (stretch) reflex -
Type of fibre:
Stimulus:
Function:

Answer 3

1a.
Change in muscle length (muscle spindle)
Antigravity, posture, movement.

Question 4

What happens during the myotatic (stretch) reflex?

Answer 4

Muscle stretch increases 1a firing.
Monosynaptic excitation results in contraction of the muscle the signal arose from (homonymous agonist).
Polysynaptic integration via inhibitory neurone results in relaxation of heteronymous antagonist.

Question 5

When the patella tendon is stretched, what happens?

Answer 5

Quad contraction.

Hamstring relaxation.

Question 6

When the biceps brachii muscle is stretched, who happens?

Answer 6

Bicep contraction.

Tricep relaxation.

Question 7

Inverse myotatic reflex -
Type of fibre:
Stimulus:
Function:

Answer 7

1b.
Change in muscle tension (golgi tendon).
Tension feedback, overload protection.

Question 8

What happens during the inverse myotatic reflex?

Answer 8

Golgi tendon stretches, 1b firing increases.
Indirect inhibitory neuron relaxes the homonymous muscle (agonist).
Indirect excitatory neuron contracts heteronymous muscle (antagonist).

Question 9

Flexor withdrawal reflex -
Type of fibre:
Stimulus:
Function:

Answer 9

A-delta, C, Group III/IV.
Painful/damaging stimuli.
Damage limitation/avoidance, maintained balance after withdrawal.

Question 10

What happens during the flexor withdrawal reflex?

Answer 10

Increased activity in A-delta/C fibres.
Polysnaptic: activation of ipsilateral flexors + inhibit of ipsilateral extensors.
Polysynaptic: inhibition of contralateral flexors and excitation of contralateral extensors.