Propagation failure of action potentials at the bifurcation point of the slow axon innervating the extensor tibiae muscle ofDecticus albifrons (Orthoptera)
- 36 Downloads
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.
KeywordsGlial Cell Bifurcation Point SETi Action Motor Nerve Stimulate Frequency
slow extensor tibiae
Unable to display preview. Download preview PDF.
- Bennett RR, Buchan PB, Treherne JE (1975) Sodium and lithium movements and axonal function in cockroach nerve cords. J Exp Biol 62:231–241Google Scholar
- Bittner GD (1968) Differentiation of nerve terminals in the crayfish opener muscle and its functional significance. J Gen Physiol 51:731–758Google Scholar
- Burns MD, Usherwood PNR (1979) The control of walking in Orthoptera. II. Motor neurone activity in normal free-walking animals. J Exp Biol 79:69–98Google Scholar
- Frankenhaeuser B, Hodgkin AL (1956) The after-effects of impulses in the giant nerve fibres of Loligo. J Physiol (Lond) 131:341–376Google Scholar
- Goldstein SS, Rall W (1974) Changes of action potential shape and velocity for changing core conduction geometry. J Biophys 14:731–757Google Scholar
- Grossman Y, Parnas I, Spira ME (1979) Differential conduction block in branches of a bifurcating axon. J Physiol 295:283–305Google Scholar
- Hoyle G (1978) Distribution of nerve and muscle fibre types in locust jumping muscle. J Exp Biol 73:205–233Google Scholar
- Parnas I (1972) Differential block at a high frequency of branches of a single axon innervating two muscles. J Neurophysiol 35:903–914Google Scholar
- Rall W (1959) Branching dendritic trees and motoneuron membrane resistivity. Exp Neurol 1:491–527Google Scholar
- Shofield PK, Treherne JE (1978) Kinetics of sodium and lithium movements across the blood-brain barrier of an insect. J Exp Biol 74:239–251Google Scholar
- Smith DO (1980a) Morphological aspects of the safety factor for action potential propagation at axon branch points in the crayfish. J Physiol 301:261–269Google Scholar
- Smith DO (1980b) Mechanisms of action potential propagation failure at sites of axon branching in the crayfish. J Physiol 301:243–259Google Scholar
- Smith DO, Hatt H (1976) Axon conduction block in a region of dense connective tissue in crayfish. J Neurophysiol 39:794–801Google Scholar
- Theophilidis G (1983) A comparative study of the anatomy and innervation of the metathoracic extensor tibiae muscle in three orthopteran species. Comp Biochem Physiol 75A: 285–292Google Scholar
- Treherne JE (1961) Sodium and potassium fluxes in the abdominal nerve cord of the cock roachPeriplaneta americana L. J Exp Biol 38:315–322Google Scholar
- Treherne JE, Shofield PK, Lane NJ (1982) Physiological and ultrastructural evidence for an extracellular anion matrix in the central nervous system. Brain Res 247:255–267Google Scholar