Motor unit

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A motor unit is a single α-motor neuron and all of the corresponding muscle fibers it 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.

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 (muscle pathology/diseases)
• motor unit number estimation

v • d • e Histology: muscle tissue
skeletal muscle/general	epimysium, fascicle, perimysium, endomysium, muscle fiber (intrafusal, extrafusal), myofibril sarcomere (a, i, and h bands; z and m lines), myofilaments (thin filament/actin, thick filament/myosin, elastic filament/titin, nebulin), tropomyosin, troponin (T, C, I) costamere (dystrophin, α,β-dystrobrevin, syncoilin, synemin/desmuslin, dysbindin, sarcoglycan, dystroglycan, sarcospan), desmin neuromuscular junction, motor unit, muscle spindle, excitation-contraction coupling, sliding filament mechanism myoblast, satellite cell, sarcoplasm, sarcolemma, sarcoplasmic reticulum, T-tubule
cardiac muscle	myocardium, intercalated disc, nebulette
smooth muscle	calmodulin, vascular smooth muscle

de:Motorische Einheitfi:Motorinen yksikkö he:יחידה תנועתית