A motor unit is a single α-motor neuron and all of the corresponding muscle fibers it innervates; all of these fibers will be of the same type (either fast twitch or slow twitch). 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. Larger motor units have stronger twitch tensions.
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.
Read more about Motor Unit: Motor Unit Types
Other articles related to "motor unit, motor units, motor, motors":
... By stimulating a nerve-muscle motor unit with short sequences of rapid, regular electrical impulses, before and after exercising the motor unit, the ... Two muscle fibers belonging to the same motor unit are identified and the temporal variability in their firing patterns are measured ... of adjacent muscle fibers in the same motor unit ...
... Motor units that consist tens, hundreds or even thousands of motor nerves branches are connected to the muscles ... which are controlled by around 1000 of motor nerves ... Within one motor units which can categorized to type I (slow twitch) or Type II fibers (fast twitch), the composition type of the muscle fiber will be consistent (homogeneous ...
... Motor units possess a range of properties and are generally placed into groups based upon the similarities between those properties ... The typing of motor units has thus gone through many stages and reached a point where it is recognized that muscle fibers contain varying mixtures of several mysosin types that can not easily be ...
... There are at least six techniques that are currently in use to estimate motor unit numbers ... According to Henneman's size principle, motor unit recruitment is always in the same order from smallest to largest motor unit ... Additionally, the motor unit action potential is an all-or-none phenomenon - once the recruitment threshold (the stimulus intensity at which a motor unit begins to fire) is reached ...
... of Transportation Roads Division (Motor Unit) Muckleshoot Indian Tribe Sound Transit Police Snoqualmie Tribe Police (Calls for service based only) King County Court ... The KCSO Motor Unit existed under contract with the King County Department of Transportation Roads Division, which in turn provided funding for S.T.E.P (the Selective Traffic Enforcement Program) which targeted ... The KCSO Motors Unit wore the standard KCSO patch and wears and Class A uniform and rode Honda KCSO marked motorcycles ...
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