Chapter 12, Problem 25RA

Summary Introduction

To review:

The following:

The muscle fibers of a motor unit belong to the same type.

The smaller motor units with slow-twitch fibers are more frequently used than the large motor units with fast-twitch fibers.

Introduction:

Somatic motor neuron branches out their axons that interact with the skeletal muscles to release acetylcholine, which are neurochemicals that depolarize the muscle membrane. The axon is branched out and innervates a number of muscle fibers, which are together called a motor unit. Neurons that innervate less number of fibers are called small motor units, and the neurons that innervate large number of muscle fibers are called large motor units.