Relative Refractoriness and Patterned Discharge of Locust Flight Motor Neurons

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Abstract
The threshold recovery after impulse propagation in locust peripheral motor axons to flight muscles is described. The refractoriness is large enough to have functional significance for at least 10 msec, and may be detected after 50-100 msec. The refractoriness to successive impulses accumulates. Ganglionic and axonal preparations demonstrate frequency division, apparently due to the refractoriness of the motor neuron. Accumulating refractoriness gives rise to non-integral division. Behaviour of the locust preparations is compared to that of an electronic model. Antidromic stimulation during flight shows that refractory oscillation may regulate the interval between the closer spaced pairs of impulses in the motor units during flight, but that the wingbeat cycle must have another cause.