Spinal reflexes

Question 1

What is a myotatic reflex?

Answer 1

A myotatic reflex is stimulated by stretch to the muscle tendon.

1) An impulse is fired down the 1a afferent fibre
2) it excites the motor neurone in the grey matter of the spinal cord.
3) the motor neuron activates the muscle.
4) the 1a afferent neuron also activates an inhibitory inter neurone.
5) the inhibitory inter neurone sends an impulse down the motor neurone fibre to the antagonist muscle and inhibits it.

Question 2

what is the inverse myotatic reflex?

Answer 2

An inverse myotatic reflex is stimulated by tension in the Golgi tendon.

1) an impulse is fired down a 1b afferent fibre
2) excites an inhibitory interneurone , which decreases the activity of the muscle via a motor neurone.
3) the 1b fibre also excites an excitatory interneurone, this increases the activity of the agonist muscle in order to decrease tension.

Question 3

What is the crossed extensor / flexor withdrawal reflex?

Answer 3

1) A nociceptor afferent (A-delta or group C) is activated due to pain stimulus.
2) This activates the ipsilateral flexors via interneurone.
3) Inhibits ipsilateral extensor via inhibitory interneuorne
4) activates contralateral extensors via 2 interneurones.
5) Inhibits contralaterl flexors via 2 interneurones.

EXAMPLE:
standing on a pin:
want the same side flexors to work in order to remove foot from pin.
Want opposite side extensors to work so you can balance on one leg.