Motor unit 422470 218283247 2008-06-09T23:15:25Z Neuroskills 7279153 /* 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]]