After-effects following responses of a muscle stretch receptor of the shore crab, Carcinus maenas.

Stretch evoked responses of the thoracic-coxal muscle receptor organ in the crab are shown to be time dependent. Thus, by varying the interstretch interval, the duration of the T fibre dynamic component of the response to a ramp-and-hold stretch was found to be directly related to the inter-stretch interval. With long interstretch intervals (e.g. 10 min), the T fibre dynamic component of the response to stretch was undistinguishable from the response when pre-conditioned with stimulation of the receptor motor nerve. These observations are consistent with the hypothesis of spontaneous cross-bridge formation when the receptor is quiescent. Such properties lead to a source of ambiguity of the muscle afferent response, which are presumably overcome by maintaining tonic efferent activation of the receptor.