Motor unit
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2008-06-09T23:15:25Z
Neuroskills
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/* See also */
A '''motor unit''' is a single [[α-motor neuron]] and all of the corresponding [[muscle fiber|muscle fibers]] it [[Innervate|innervates]]. When a motor unit is activated, all of its fibers contract. Groups of motor units often work together to coordinate the contractions of a single [[muscle]]; all of the motor units that subserve a single muscle are considered a ''motor unit pool''.
The number of muscle fibers within each unit can vary: [[thigh]] muscles can have a thousand fibers in each unit, [[eye]] muscles might have ten. In general, the number of muscle fibers innervated by a motor unit is a function of a muscle's need for refined motion. The smaller the motor unit, the more precise the action of the muscle. Muscles requiring more refined motion are innervated by motor units that [[synapse]] with fewer muscle fibers.
Nerve cell [[axons]] are very thin, about 1 micrometer. However, they are extraordinarily long. For many motor neurons the axon is over a meter long, extending from the spinal column to a muscle cell. They stretch the spinal column to increase height.
In medical [[electrodiagnostic testing]] for a patient with weakness, careful analysis of the "motor unit action potential" (MUAP) size, shape, and recruitment pattern can help in distinguishing a [[myopathy]] from a [[neuropathy]].
==See also==
* [[motor unit recruitment]]
* [[tetanic contraction]]
* [[Myopathy|myopathy (muscle pathology/diseases)]]
* [[motor unit number estimation]]
* [[Tonic and Phasic Inputs]]
==External links==
*[http://www.siumed.edu/~dking2/ssb/neuron.htm/ Neurons and Support Cells]
[[Category:Somatic motor system]]
{{muscle-stub}}
{{Muscle tissue}}
[[de:Motorische Einheit]]
[[fr:Unité motrice]]
[[fi:Motorinen yksikkö]]
[[he:יחידה תנועתית]]
[[no:Motorisk enhet]]
[[pt:Unidade motora]]