Motor units

Question 1

What is a motor unit?

Answer 1

A motor unit plus all the muscle fibres it innervates

Question 2

What is a motor unit function?

Answer 2

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

Question 3

What effects the number of motor units created?

Answer 3

The greater the strength of the stimulus from the central nervous system the greater the number of motor units recruited and the greater the force of contraction in the muscle

Question 4

What effects the type of motor unit recruited

Answer 4

Type 1: small and produce a low force of contraction over a long period of time.
Type 2a: the force and time of contraction is between type 1 and 2b.
Type 2b: are large and produce the greatest force over the shortest period of time.

Question 5

What effects the synchronisation of motor units recruited?

Answer 5

Not all fibres are recruited at the same time. 1st motor units recruited are type 1-force of contraction is low. 2nd motor units recruited are type 2a-force of contraction increases. 3rd motor units recruited are type 2b-force of contraction increases further

Question 6

What is a neuron?

Answer 6

A nerve cell

Question 7

What is an axon?

Answer 7

Carries the electrical impulse from cell body to neuromuscular junction

Question 8

What is a neuromuscular junction?

Answer 8

The point

where neuron communicates with muscle fibre across a space called the synapse

Question 9

What is a synapse

Answer 9

The space between a motor neuron and skeletal muscle

Question 10

What is a motor end plate

Answer 10

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

Question 11

What is resting potential?

Answer 11

The neuron at rest. There is a lower charge inside the neutron than outside

Question 12

What is action potential?

Answer 12

The electrical activity carried down the axon

Question 13

What is a neurotransmitter?

Answer 13

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

Question 14

What is acetyl choline?

Answer 14

The neurotransmitter released at neurotransmitter junction that travels across synapse

Question 15

What is the all or none law?

Answer 15

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

Question 16

What is the physiology of a motor unit?

Answer 16

Resting potential has a low charge and a high charge outside neuron. Action potential threshold is reached, high charge inside and low charge outside neuron. Electrical impulse carried down axon to the neurotransmitter junction. The neurotransmitter acetyl choline is released that carries electrical impulse across synapse. Acetyl choline recurved by receptors on motor end plate to initiate muscular contraction.