Motor Unit

Question 1

What is a motor unit?

Answer 1

A motor neuron plus all the muscle fibres it innervates

Question 2

What is the motor units function?

Answer 2

To carry impulses from the central nervous system to the muscle fibres to initiate muscular contraction

Question 3

What happens when there is a greater number of motor units recruited?

Answer 3

There is a greater force of contraction in the muscle

Question 4

What are the 3 types of motor units in muscles and their characteristics?

Answer 4

Type 1- small, low force of contraction over a long period of time
Type 2a- force and time of contraction in between type 1 and 2b
Type 2b- large, produce greatest force over shortest period of time

Question 5

What order are the motor units recruited?

Answer 5

1st motor units recruited are type 1- low force
2nd motor units recruited are type 2a- increased force
3rd motor units recruited are type 2b- increases further

Question 6

What is the order of the nervous stimulation of the motor unit (anatomy)?

Answer 6

Neuron, axon, neuromuscular junction, synapse, motor end plate

Question 7

What is a neuron?

Answer 7

A nerve cell

Question 8

What is the function of an axon?

Answer 8

It carries the electrical impulse from cell body to neuromuscular junction

Question 9

What is the neuromuscular junction?

Answer 9

The point where motor neuron communicates with muscle fibre across the synapse

Question 10

What is the synapse?

Answer 10

The space between a motor neuron and skeletal muscle

Question 11

What is the motor end plate?

Answer 11

The area of muscle fibre that establishes synaptic contact with motor neuron

Question 12

What is the order of the nervous stimulation of the motor unit (physiology)?

Answer 12

Resting potential, action potential, neurotransmitter, acetyl choline, all or none law

Question 13

What is resting potential?

Answer 13

The neuron is at rest, the charge inside the neuron is lower than outside

Question 14

What is action potential?

Answer 14

The electrical activity carried down the axon

Question 15

What is the neurotransmitter?

Answer 15

The chemical messenger that transmits across synapse and binds to muscle fibres to initiate contraction

Question 16

What is acetyl choline?

Answer 16

The neurotransmitter released at neuromuscular junction that travels across the synapse

Question 17

What is the all or none law?

Answer 17

If the action potential threshold is reached, all muscle fibres in the motor unit are activated, if it’s not reached no muscle fibres are activated

Question 18

What is the order of the motor unit?

Answer 18

Resting potential- low charge inside and high charge outside neuron
Action potential- threshold reached, voltage changes, high charge inside and low charge outside neuron
(All or none law)
Electrical impulse carried along axon to neuromuscular junction
Neurotransmitter acetyl choline released carrying electrical impulse across synapse
Acetyl choline received by receptors on motor end plate to initiate muscular contraction