Receptor Potentials and Impulse Generation in the Isolated Spindle During Controlled Extension

In the paper preceding this (Shepherd and Ottoson), the responses of the isolated spindle to different rates of controlled stretches were described. For any given velocity and amplitude of stretch the spindle gives rise to a characteristic impulse pattern. The discharge of the afferent nerve is initiated by a local graded potential in the sensory terminals (Katz, 1950). It is likely that the impulse pattern in response to a given stretch is closely related to the time course and magnitude of the potential changes in the spindle and that these in turn are closely related to the parameters of the mechanical stimulus. The present paper describes the results of experiments which were carried out to compare and analyze the composite potential and the pure receptor response obtained with controlled stretches.