Muscle Fibres as Members of Motor Units
Muscle fibres function only when they are connected to motoneurons. Each motoneuron innervates many muscle fibreswhich together with the nerve cell constitute a “motor unit”. Motor units are the final common pathways of motor activity onto which central and peripheral influences converge. Motor units differ with respect to force, and contractile properties (speed of contraction, fatiguability). All muscle fibres of a given motor unit are of the same histochemical and physiological type. Originally, the definition of a motor unit was a physiological one: all its musclefibres discharge and contract synchronously. First the glycogen depletion method (Sect. D.II.2) made it possible to identify the fibres of a physiologically characterized motor unit using histology.
KeywordsMotor Unit Extensor Digitorum Longus Extraocular Muscle Extensor Digitorum Longus Muscle Motor Unit Potential
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