If you are a small animal with many predators in your environment you'd better react quickly to the earliest sign of danger. Startle reflexes have evolved as one way to deal with such situations. Input from sensory organs is rapidly transmitted to efferent systems, usually the muscles that are involved in flight responses. One such reflex is the backward tailflip response in crayfish. The coincident arrival of synaptic inputs is crucial because only when enough synapses fire simultaneously will they be able to activate the giant fiber system; however, the medial giant fibers receive input from widely differing distances along the crayfish antennules. Mellon and Christison-Lagay found that sensillar axons have precisely calibrated conduction velocities. Axon diameters near the flagellum tip were very small, and axon diameters increased continuously toward more proximal locations along the flagellar axis.
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