Motor units

Question 1

The stimulation of motor units initiates and controls what?

Answer 1

the activity of muscles

Question 2

A motor unit is made up of what? (2)

Answer 2

1. a motor neuron and
2. the muscle fibres it innervates or communicates with.

Question 3

There are two types of motor unit, which are?

Answer 3

1. Slow twitch motor units
2. Fast twitch motor units

Question 4

All of the muscles fibres within a motor unit are what?

Answer 4

of the same type

Question 5

The motor neuron in a slow twitch motor unit has what size cell body?

Answer 5

A small cell body

Question 6

The motor neuron in a slow twitch motor unit typically innervates how many muscle fibres?

Answer 6

Typically innervates 10–180 muscle fibres

Question 7

The motor neuron in a fast twitch motor unit has what size cell body and has how many axons?

Answer 7

a large cell body & has many axons

Question 8

The motor neuron in a fast twitch motor unit typically innervates how many muscle fibres?

Answer 8

Innervates 300–800 muscle fibres

Question 9

Which type of motor unit reaches peak tension quicker and generates more force?

Answer 9

Fast twitch motor units

Question 10

Each motor neuron innervates from a few, to several thousand muscle fibres depending on what? Give an example!

Answer 10

the function of the muscle.

For example, muscles used for fine control, such as movement of the eye, may have one motor neuron innervating only fifteen fibres.

Question 11

Muscles involved in more general movement, such as the gastrocnemius calf muscle, can have how many motor neurons innervating how many fibres?

Answer 11

one motor neuron innervating almost two thousand fibres.

Question 12

In order for our muscles to produce force, motor units have to be what?

Answer 12

activated, or recruited

Question 13

Describe how motor units work

Answer 13

they work in an all or none fashion

Question 14

What happens if the threshold for stimulation isn’t met?

Answer 14

no fibres in the unit act

Question 15

When perfoming tasks such as lifting weights, motor units are recruited in a what?

Answer 15

specific order

Question 16

The order in which motor units are recruited is directly related to what?

Answer 16

the size of the motor neuron

Question 17

What is the order of motor unit recruitment?

Answer 17

1. slow twitch motor units are recruited first (which have small neurons)
2. as the force needed to lift the weight increases fast twitch (a) units are recruited
3. followed by fast twitch (b) at higher intensity’s

Question 18

Is the pattern of motor unit recruitment the same in all activities? give an example

Answer 18

as in lifting weights, the recruitment is the same for endurance exercises such as running a marathon

as the slow twitch units fatigue, fast twitch units are recruited

Question 19

Motor units are recruited in the order:

Answer 19

1. Slow twitch
2. Fast twitch type a
3. Fast twitch type b