Neuromuscular Function and Adaptation

Question 1

What are the two ways in which the CNS can influence the strength of muscle contraction?

Answer 1

1. Spatial Summation - increasing the number of motor units recruited.
2. Temporal summation - increasing the frequency of contraction.

Question 2

What is the “size” principle?

Answer 2

A theory about how muscle fibre types are selected. It theorises that fibre types are selected from smallest to largest i.e. weaker to stronger force of contraction.

Question 3

What are some problems with this theory?

Answer 3

What would be the point of starting off with slow twitch fibres when only fast twitch fibres are needed…

Question 4

What other things may contribute to selection?

Answer 4

Auditory
Visual
Proprioceptive stimuli
Cutaneous mechanoreceptor stimuli
Glycogen depletion

Question 5

What are the categories of muscular fatigue?

Answer 5

Central
Neuromuscular
Peripheral

Question 6

What is the central fatigue hypothesis?

Answer 6

That increased levels of serotonin released during excercise lead to fatigue and a reduction in action potentials/motor unit recruitment.

Question 7

What are the possible causes of neuromuscular fatigue?

Answer 7

Depletion of a neurotransmitter
Problem with post synaptic receptors
Failure of excitation-contraction coupling

Question 8

How might peripheral fatigue come about?

Answer 8

Depletion of things like glycogen, ATP, PCr or…

the accumulation of things like lactic acid.