Fig. 5. Effect of manipulating the actions of the extensor and flexor muscles on the signalling by the lump receptor. (A,B) The extensor tendon was cut in the distal femur so that stimulation of the extensor muscle exerted no direct force on the joint. Instead the stimulus activated flexor tibiae motor neurons through the central, monosynaptic connections that the fast extensor tibiae motor neuron (FETi) makes with them, and caused a contraction of the flexor muscle. (A) With the tibia held in the fully flexed position and the flexor tendon free to move, a burst of spikes from the lump receptor followed the stimulus. (B) The tibia in the same locust was held in a partially extended position, and the stimulus now did not lead to sensory spikes. (C,D) A second locust in which the extensor tendon was intact. (C) The flexor tendon exerted force on the joint fixed in the fully flexed position. The stimulus was accompanied by a burst of sensory spikes. (D) The flexor tendon was clamped so that force could not be transmitted through it to the joint. No sensory spikes followed the stimulus. The inset diagrams show the experimental arrangement. The solid arrows show the flow of effects from the evoked FETi spike; the open arrows, the movement of the flexor tendon. The recording during the stimulus has been truncated.

Return to article