reflexes

Question 1

How does a stretch reflex work?

Answer 1

1. Monosynaptic reflex: sensory nerve sends stimuli straight to alpha-motorneurones which leads to rapid contraction of agonist muscle
2. Reciprocal inhibition- stimuli sent to interneurons which leads to relax of antagonist muscle
3. stimuli sent to somatosensory cortex- informs about length of muscle

Question 2

How does a clasp-knife/ GTO reflex work

Answer 2

1- alpha-motorneurone of antagonist must stimulated- contracts
2- interneurones of agonist relaxed
3-somatosensory cortex informed.

Prevents excessive contraction and the muscle being torn away from the bone.

Question 3

how does the Flexor/ withdrawal reflex work

Answer 3

1- nocireceptor sends pain stimuli
2-Excitatory interneurones increases activity in flexor muscles
3- extendor muscles relaxed.
4- in contra limb: flexor muscle relaxed and extendor muscles contracted.

Question 4

how can reflexes be overridden?

Answer 4

• by hyper polarisation of alpha-motor neurones in agonist

- activation of gamma-motor neurones which makes the muscle very resistant to stretch.

Question 5

What is meant by monosynaptic reflex?

Answer 5

No interneurons involved

Question 6

Facilitation and inhibition

Answer 6

Facilitation:
-The greater the stimulus, the greater the spinal spread, the greater the response
-Maintains the motor-neurones in their depolarised state
Inhibition:
-Maintains the alpha motor neurones hyperpolarised