Motor Units, Muscle Spindles and Golgi Tendon Organs

Question 1

What does the neural element of the motor system comprise?

Answer 1

Upper motor neurones and lower motor neurones

Question 2

The majority of LMNs are what type of neurone?

Answer 2

Alpha motor neurones

Question 3

What innervates a muscle spindle?

Answer 3

Gamma motor neurones

Question 4

Axons of LMNs exit the spinal cord via ventral/dorsal roots

Answer 4

Ventral

Question 5

In what region of the spinal cord are there a greater number of motor neurones?

Answer 5

Cervical enlargement (C3-T1)
Lumbar enlargement (L1-S3)

Question 6

What is a motor unit?

Answer 6

An alpha motor neurone and all the skeletal muscle fibres it innervates

Question 7

What is a motor neurone pool?

Answer 7

The collection of alpha motor neurones that innervate a single muscle

Question 8

What can regulate an alpha motor neurone?

Answer 8

Dorsal root ganglion cells
Upper motor neurones
Spinal interneurones

Question 9

An increased rate of alpha motor neurone firing causes an increase/decrease in muscle force

Answer 9

Increase

Question 10

Why are smaller motor units recruited more quickly?

Answer 10

As they have smaller cell bodies and are easier to excite

Question 11

Type I muscle fibres are fast and type II are slow contracting. True/false?

Answer 11

False - type I is slow while type II is fast

Question 12

What is the Henneman size principle?

Answer 12

That slower motor units are more easily activated by training that activates the muscle

Question 13

What is the myotatic reflex?

Answer 13

When a skeletal muscle is pulled it pulls back (wouldn’t want to meet it on a night out then lol)

Question 14

The change in length of a muscle is measured by what?

Answer 14

Muscle spindle

Question 15

What does a muscle spindle consist of?

Answer 15

Intrafusal muscle fibres
Sensory afferents
Gamma motor neurone efferents

Question 16

The myotatic reflex can be tested clinically. How?

Answer 16

Striking patellar tendon with a hammer to cause a knee jerk

Question 17

Outline the myotatic reflex

Answer 17

Muscle spindle stretches
Ia afferent activated
Synaptic transmission in spinal cord
Alpha motor neuone activated
Homonymous muscle contracts

Question 18

What innervates the intrafusal fibres of muscle spindles?

Answer 18

Gamma motor neurones

Question 19

What are the two types of intrafusal fibres?

Answer 19

Nuclear bag fibres

Chain fibres

Question 20

Where are golgi tendon organs found?

Answer 20

Junction of muscle and tendon

Question 21

Group Ib afferents enter the spinal cord and synapse onto what?

Answer 21

Inhibitory interneurones

Question 22

What do golgi tendon organs measure?

Answer 22

Force generated in a muscle (via tension in tendon)