[Reduction in the response threshold to stretching of the afferent nerve of the muscle spindles after stimulation of skeleto- and fusimotor axons]

Abstract

Aftereffects of skeletal- and mixed skeleto-fusimotor stimulation on the dynamic and static sensitivity of the muscle spindle afferents were investigated in anesthetized cats. After the concurrent contraction of both extra and infrafusal fibers resulting from the strong stimulation of the muscle nerve, the dynamic and static thresholds of the primary and secondary endings diminish in the responses of the passive muscle spindle to subsequent stepwise and triangular stretch. The discharge pattern of the afferent is also changed at the beginning of the linear stretch. The increment of the afferent's firing rate caused by the fusimotor stimulation is sometimes in accordance with that of the static response of the same afferent with the static elongation of the m. triceps surae by 10 mm.