A Critique of the Hypothesis that the Spindle Secondary Endings Contribute Excitation to the Stretch Reflex
In 1969 I suggested, on indirect evidence, that in the decerebrate cat the group II afferents from the spindle secondary endings contribute excitation to the stretch reflex rather than the classically believed inhibition. This hypothesis has since been vigorously attacked in certain quarters and a variety of alternative explanations offered for the original findings. The present essay reviews the current state of the controversy and concludes that the hypothesis still provides a satisfactory unitary interpretation of a range of experimental findings which would otherwise require a series of ad hoc explanations. The postulated group II autogenetic excitation is, however, unlikely to be mediated by direct action on the motoneurones.
KeywordsMotor Unit Soleus Muscle Muscle Spindle Afferent Fibre Presynaptic Inhibition
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