Exercise Physiology: Theory and Application to Fitness and Performance 9th Edition by Scott Powers, Edward Howley

Exercise 11

Define the terms motor unit and innervation ratio.

Step 1 of 2

A motor unit is the motor neuron and all the muscle fibers it innervates. The muscles are innervated with the axons of the motor neurons that leave the spinal cord and enter them. Once the axon enters the muscle tissue, it splits into collateral branches. Each of these collateral branches innervates a single muscle fiber