The influence of muscle mechano-receptors on homonymous gamma motoneurones
The predominant theme of this set of papers on the control of fusimotor neurones is the action of muscle afferents at the segmental spinal level. This is surprising since the more potent actions on gamma motoneurones come from skin afferents (Hunt & Paintal, 1958). In particular, the discharge of receptors with the largest myelinated afferents in a skin nerve, such as the sural to the hind limb of the cat, powerfully excites gamma motoneurones (Ellaway & Murphy, 1978; Catley & Pascoe, 1978) but has no segmental action on alpha motoneurones (Rosenberg, 1970). However, the apparent difference in potency between skin and muscle inputs lessens when we examine the effect of afferent discharges arising in actively contracting muscles. Stretch of a muscle within its physiological range does not produce marked changes in gamma efferent discharge to that same muscle whereas contraction can elicit a complex sequence of inhibition and excitation (Ellaway et al., 1981).
KeywordsFatigue Hunt Stim
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