Introduction to Control of Movement

Question 1

What do alpha motor neurons do?

Answer 1

Release Ach at neuromuscular junctions to innervate skeletal muscle

Question 2

What is a motor unit?

Answer 2

A motor neuron and all the fibres it innervates

Question 3

How does muscle contraction occur?

Answer 3

A motor neuron fires an AP causing a muscle twitch, if firing rate is high enough these twitches fuse to form a continuous contraction.

Question 4

How can contraction strength be increased?

Answer 4

Employing more motor units
Increasing rate of firing of AP’s

Question 5

Are smaller or larger motor neurons activated first?

Answer 5

Small

Question 6

What detects stretching in the stretch reflex?

Answer 6

Muscle spindles

Question 7

Describe the stretch reflex

Answer 7

1- Muscle stretch is picked up by muscle spindle
2 - Activation of spindle afferents
3 - These afferents make monosynaptic connections with alpha motor neurons
4 - These alpha motor neurons innervate the same muscle causing contraction

Question 8

What do gamma motor neurons do in terms of muscle spindles?

Answer 8

They maintain muscle spindle sensitivity during muscle contraction by contracting the spindle fibres

Question 9

Where is the golgi tendon organ found?

Answer 9

The transition between muscle and tendon

Question 10

How do golgi tendon organs fire?

Answer 10

They fire in relation to the force of contraction

Question 11

What is the golgi tendon reflex?

Answer 11

It acts to reduce the strength of muscle contraction when the force is high

Question 12

What are the flexor and crossed extensor reflexes?

Answer 12

Flexion-withdrawal following a painful cutaneous reflex

Question 13

How do Meissner’s corpuscles effect precision grip?

Answer 13

They detect ‘microslips’, this causes a reflex increase in grip strength