Level 3 Unit 2 Part 21: The motor unit

The term motor unit refers to one lower motor neuron and all the skeletal muscle cells that it innervates. Usually, each time a lower motor neuron fires an axon potential, all the skeletal muscle cells in its motor unit contract. The lower motor neurons are in the brainstem or the spinal cord, and their axons travel in cranial or spinal nerves, and in their subsequent branches, until they reach and synapse on skeletal muscle cells.

3.2.21.1

This type of synapse is called a neuromuscular junction. Small muscles that need rapid, fine control, like those that move the eyes and fingers, have small motor units, meaning that each lower motor neuron synapses on a small number of skeletal muscle cells. Large muscles that do not need rapid, fine control, like those those of the torso and proximal limbs, have large motor units with each lower motor neuron synapsing on a large number of skeletal muscle cells.

Next:

Level 3 Unit 2 Part 22: Muscle stretch reflex

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s