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Glossary Term

Motor Unit

A motor unit is a single nerve fiber and all the muscle fibers it innervates. The number and size of motor units recruited to determine the force output of a muscle. Synonyms include motor neuron unit, , motor nerve unit, and motor endplate unit.

Motor Unit: One nerve fiber (nerve cell axon) and all of the muscles cells (fibers) it innervates. For example, although a single muscle cell must fire completely or not at all, force output can be calibrated by the number and size of motor units recruited.

  • Saladin, K. (2012). Anatomy & Physiology: The unity of form and function. (6th ed.). New York: McGraw-Hill.




  1. Motor neuron unit
  2. Motor nerve unit
  3. Motor endplate unit