Nervous Control of Muscle Contractions

Question 1

what causes muscle fibres to contract

Answer 1

when an electrical impulse arrives via a neuron at the end plate (or axon terminal)

Question 2

what is innervation

Answer 2

when a group of muscle fibres are recruited by a neuron

Question 3

what is a motor unit

Answer 3

when a group of fibres are together with a neuron

Question 4

what are characteristics of motor units

Answer 4

• all the fibres in a motor unit are the same type
• a muscle are made up of several motor units
• the more motor units are innervated, the greater the force produced

Question 5

what is the all or none law

Answer 5

• an electrical impulse is sent along the neuron
• if the impulse is sufficient, all of the fibres in the motor unit contract
• if the impulse is insufficient, none of the fibres in the motor unit contract

Question 6

what is the pattern of fibre recruitment

Answer 6

type I > type IIa > type IIx

if the type I fibres cant meet the demand force required, type IIa fibres will be recruited, and if that isn’t sufficient, type IIx are recruited