Chapter

Motion

Thomas M. Brushart

in Nerve Repair

Published on behalf of Oxford University Press

Published in print May 2011 | ISBN: 9780195169904
Published online September 2012 | e-ISBN: 9780199965168 | DOI: http://dx.doi.org/10.1093/med/9780195169904.003.0003
Motion

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  • Sensory and Motor Systems
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Muscle fibers are classified on a physiologic continuum from the fastest, most glycolytic, type IIb, to the slowest, most oxidative, type I. Muscle activity is monitored by proprioceptors; the Golgi tendon organ responds to stretch, while the muscle spindle signals muscle length. The motor unit, the elemental circuit of motor control, consists of a motoneuron and the muscle fibers it serves. Motor units are classified as fast-twitch, fatigable (FF), fast-twitch, intermediate (Fint), fast-twitch, fatigue-resistant (FR), and slow (S). Motor unit size is proportional to the speed with which its fibers contract, with type S units the smallest and type FF the largest. Motoneurons serving individual muscles are grouped together within pools in the anterior horn of the spinal cord. Regulation of motor function is a complex process involving a hierarchical system of controls centered in spinal cord, brainstem, and cortex, each with afferent input and output to the motoneuron pool.

Chapter.  16400 words.  Illustrated.

Subjects: Sensory and Motor Systems ; Rehabilitation Medicine

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