Lecture 5: Muscle spindle II

Question 1

Gamma motor units are located:

Answer 1

On the polar endings of muscle spindles

Question 2

When muscle stretches over time, _____ frequency increases:

Answer 2

AP

Question 3

In unstretched muscle, how is AP frequency?

Answer 3

Constant

Question 4

During alpha and gamma neuron coactivation, how is AP frequency?

Answer 4

Constant

Question 5

During alpha motor neuron stimulation only, how is AP frequency?

Answer 5

There are no APs, unable to signal length changes

Question 6

Characteristics of alpha motor neurons:

Answer 6

The largest and innervate extrafusal fibres

Question 7

Characteristics of gamma motor neurons:

Answer 7

The smallest and connect exclusively to intrafusal muscle fibres

Question 8

Characteristics of beta motor neurons:

Answer 8

Intermediate in size and innervate both extrafusal and intrafusal muscle fibres

Question 9

Stimulation of ______ fibres increases the dynamic response:

Answer 9

Dynamic efferent

Question 10

Stimulation of ______ fibres increases the length response:

Answer 10

Static

Question 11

The monosynaptic reflex facilitates:

Answer 11

A fast contraction of the stretched muscle

Question 12

What activates Ia afferents in the monosynaptic reflex?

Answer 12

An unexpected stretch (small or large)

Question 13

Ia synapse onto ___% on homonymous and ___% of synergist alpha MNs:

Answer 13

100, 60

Question 14

Reciprocal inhibition of the monosynaptic reflex:

Answer 14

Stimulus stretches muscle, stretching spindles
- Ia afferent fires
- Ia synapses with Ia inhibitory interneuron (Ia IN)
- The synapse reduces excitability of antagonist alpha MN
- Relaxes muscle on other side of joint