Question

Contraction Strength Assessment.

Explain how your nerves control skeletal muscle to change the strength of contraction:

Part A. During a weak voluntary movement.

Part B. During a strong voluntary movement

Answer 1

Single motor neuron, its axon terminals and the muscle fibers innervated by it are together called motor unit. Each motor neuron activates a group of muscle fibers through the axon terminals

when a motor neuron is stimulated, it causes contraction of all the muscle fibers innervated by that neuron.

The motor units of the muscles concerned with fine, graded and precise movements (weak voluntary movment )have smaller number of muscle fibers while Muscles concerned with crude or coarse move ments ( strong voluntary movement ) have motor units with large number of muscle fibers

part a- during a weak voluntary movement,only few motor units are involved

partb- during a strong voluntary movement , many motor units are put into action so the force of contraction increases. so it is understood that response of a muscle is directly proportional to the number of motor units involved