Lecture 5 - Motor Units in Movement

Question 1

What three stages make up a reflex arc

Answer 1

1. receptor
2. integration centre
3. effector

Question 2

What are the two types of proprioceptors in muscles

Answer 2

1. muscle spindles
2. golgi tendon organs

Question 3

Where are muscle spindles located

Answer 3

Within the extrafusal muscle fibres

Question 4

What does primary endings in muscle spindles detect

Answer 4

stretch and muscle length

Question 5

What does secondary endings in muscle spindles detect

Answer 5

Muscle length

Question 6

How are muscle spindles innervated

Answer 6

by gamma motor neurons split into group I and II

Question 7

What is the monosynaptic stretch reflex

Answer 7

When the involuntary stretching of a muscle triggers contraction i.e hammer to patellar tendon

Question 8

What are the stages in a monosynaptic stretch reflex

Answer 8

1. tendon stretched
2. muscle stretched
3. stretch detected by muscle spindle and AP generated
4. AP travels to motor neuron in spinal cord
5. aMN depolarised and AP generated
6. AP travels to muscle

Question 9

What is reciprocal inhibition

Answer 9

when a muscle is stretched their antagonist is inhibited by activating interneurons that inhibit the aMN for the antagonist muscle

Question 10

What is the autogenic inhibition reflex

Answer 10

excessive load on the muscle triggers the golgi tendon organ to fire and inhibit the motor neuron causing muscle to relax

Question 11

How does the stretch reflex influence work generated

Answer 11

muscles can generate more positive work when they are stretched before the contraction