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Propagation failure of action potentials at the bifurcation point of the slow axon innervating the extensor tibiae muscle ofDecticus albifrons (Orthoptera)

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Failure of conduction of nerve impulses has been observed at the bifurcation point of the metathoracic slow extensor tibiae motor axon (SETi) ofDecticus albifrons. Records from the region proximal and distal to the bifurcation point of the axon showed that during prolonged and repetitive stimulation and after a certain number of stimuli, proportional to the stimulating frequency, some SETi action potentials failed to cross this point (Fig. 1).

Cross-sections of the metathoracic extensor motor nerve ofD. albifrons show that at the region of axonal bifurcation, both the neural lamella and the layer of glial cells (the sheath) around the SETi axons became thinner than the region proximal and distal to the bifurcation (Fig. 2).

The possible role of the conduction block in the neuronal control of the muscle has been discussed.

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ETi :

extensor tibiae

SETi :

slow extensor tibiae

PE :

proximal electrode

DE :

distal electrode

SE :

stimulating electrode


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Theophilidis, G. Propagation failure of action potentials at the bifurcation point of the slow axon innervating the extensor tibiae muscle ofDecticus albifrons (Orthoptera). J. Comp. Physiol. 154, 431–434 (1984).

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  • Glial Cell
  • Bifurcation Point
  • SETi Action
  • Motor Nerve
  • Stimulate Frequency