Fig. 8. Effects of the force produced by the action of individual flexor motor neurons on the activity of sensory neurons from the lump receptor. A pulse of depolarising current was injected into the cell body of a motor neuron to evoke spikes. (A) Spikes in a slow flexor motor neuron innervating the proximal muscle bundles did not elicit spikes in the lump receptor. (B) Similarly a high frequency of spikes in another slow motor neuron innervating distal muscle bundles did not evoke sensory spikes. A later burst of spikes in fast flexor motor neurons, not directly related to the applied depolarisation, caused muscle activity and sensory spikes. The bridge is unbalanced in the intracellular recordings.