Motor Units

Question 1

What is a motor unit?

Answer 1

A nerve cell and all of the muscle fibres that the nerve cell is in contact with that it controls (innervates)

Question 2

What is a motor neuron?

Answer 2

A nerve cell in the brain or spinal chord that transmits nerve impulses (electrical signals) to a group of muscle fibres via a motor end plate

Question 3

What is an axon?

Answer 3

An extension of a motor neuron that connects the main nerve cell to the muscle fibre

Question 4

What is the neuromuscular junction?

Answer 4

The point where the axons motor end plates meet the muscle fibre

Question 5

What is the synaptic cleft?

Answer 5

A gap between the motor end plate and the muscle fibre

Question 6

What determines the strength of the contraction?

Answer 6

The number of motor units that are recruited (more = greater strength)

Question 7

What is muscle action potential?

Answer 7

+ve electrical charge inside the nerves and muscle cells which conduct the nerve impulse down the motor neuron and into the muscle fibres

Question 8

What is the ‘all or none’ law

Answer 8

Either all of the muscle fibres in the motor unit will contract or none will (if the charge is high enough)