An electrophysiological study of the giant fiber system of the locust Schistocerca gregaria

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  • WSW. D. Seabrook
    W. D. Seabrook
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Abstract
Electrophysiological studies have indicated that there are three giant fibers activated in the ipsilateral connective and two in the contralateral connective when the cercus is mechanically stimulated. Conduction speeds in these fibers and synaptic delays to the cereal giant synapse have been measured. A second-order interneurone is postulated between the cereal afferent fibers and the contralateral giant fibers. There is a considerable reduction in velocity as the potentials pass through the abdominal ganglia and may be related to a reduction in sheath thickness within the ganglion.Afferent neurones of the lateral branch of the ninth sternal nerve have been shown to synapse with the giant fibers.Though the giant fibers respond to cereal and ninth sternal stimulation there is no evasion response in Schistocerca. This lack of response is correlated with the absence of functional synapses between the giant fibers and the efferent neurones of the metathoracic leg nerve. The giant fibers activated by cereal stimulation terminate within the metathoracic ganglion.