, Volume 121, Issue 1, pp 99-113

Sense organs in the femur of the stick insect and their relevance to the control of position of the femur-tibia-joint

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Summary

The sensory innervation pattern is described for the femur of the middle and the hind legs ofCarausius morosus. — In one of the nerves (F121) extracellular recordings show a unit which mirrors the tension of the flexor tibiae muscle (tension receptor). The tension receptor increases the firing rate of the slow extensor tibiae motoneuron. It measures the tension of one or more muscle fibres of the anterior side near the distal end of the muscle. The anatomical basis of this receptor is uncertain. — Another receptor was found on the ventral side of the distal end of the apodeme of the extensor tibiae muscle (apodeme receptor). Recordings from this receptor could not be obtained inCarausius. But inExtatosoma tiaratum it responded to stretching of the nerve. In the natural position it shows a minimum of excitation in the 90°-position of the femur-tibia-joint and an increase in firing rate for both flexion and extension. — Tactile hairs react phasically and have no special sensitivity for one direction. Two receptors at the dorsal side of the femur-tibia-joint (RDAL and RDPL), which are situated in the same position as inSchistocerca hind legs, react phasically to extension movements and fire tonically in the most extended position of the joint. — The influence of these receptors on the position of the femur-tibia-joint is only weak.

Supported by Deutsche Forschungsgemeinschaft