Spasticity I: Clinical aspects

L. S. Illis

in Spinal Cord Dysfunction: Volume II: Intervention and Treatment

Published in print December 1991 | ISBN: 9780192617873
Published online March 2012 | e-ISBN: 9780191724312 | DOI:
Spasticity I: Clinical aspects

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Muscle possesses some elasticity, but most of the resting condition of muscle tone or tension is of a reflexive nature and is maintained by afferent impulses which arise in the muscle spindles. The spindles form part of a servomechanism signaling to the CNS information about the length of the muscle. More information which is available to central processors includes information about the speed with which lengthening occurs, and the central nervous system (spinal cord) is also able to adjust the sensitivity of the muscle spindles. The normal resting tone is maintained by the tonic stretch reflex. On moving the limb, the muscle is suddenly stretched, and this elicits the phasic stretch reflex. The difference between the tonic stretch reflex and the phasic stretch reflex is due chiefly to the rapidity of stretching, and the difference between muscle tension is tested by palpation and by passive stretching. Gamma-loop and alpha-motor-neurons collaborate in the execution of movement, and are subject to supraspinal control. Not only are nerve cells organized in columnar and somato-topical arrangements, but dendrites are arranged in specific patterns.

Keywords: elasticity; afferent impulses; muscle spindles; central processors; tonic stretch reflex; phasic stretch reflex

Chapter.  5399 words.  Illustrated.

Subjects: Neuroscience

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