Summary
The distribution of nerve terminals from a single excitatory motor axon has been followed along a fiber from the proximal accessory flexor muscle of the lobster by thin serial sectioning at periodic intervals. The excitatory motor axon provides small axonal branches (diameter 5–12 μm) of varying lengths that travel along the surface of the muscle fiber. Each of these branches gives rise to discrete synaptic terminals which are not uniformly distributed. Individual terminals vary in length from 10–60 μm and the majority possess neuromuscular synapses. The greatest distance between synapses is slightly over 1 mm which is well within the length constant (2.6 mm) of this muscle fiber. Thus the spatial distribution of synapses is such as to ensure adequate depolarization along the entire length of the muscle fiber.
References
Atwood, H.L.: Differences in muscle fibre properties as a factor in “fast” and “slow” contraction in Carcinus. Comp. Biochem. Physiol. 10, 17–31 (1963)
Atwood, H.L., Morin, W.A.: Neuromuscular and axo-axonal synapses of the crayfish opener muscle. J. Ultrastruct. Res. 32, 351–369 (1970)
Atwood, H.L., Govind, C.K., Jahromi, S.S.: Excitatory synapses of blue crab gastric mill muscles. Cell. Tissue Res. 177, 145–158 (1977)
Chiang, R.G.: Quantitative analysis of high and low-output neuromuscular terminals in the lobster. M.Sc. Thesis, University of Toronto, Canada (1977)
DeRosa, R.A., Govind, C.K.: Transmitter output increases in an identifiable lobster motoneuron with growth of its muscle fibers. Nature (Lond.) 273, 676–678 (1978)
Fatt, P., Katz, B.: Distributed “end-plate potentials” of crustacean muscle fibers. J. Exp. Biol. 29, 433–439 (1953)
Govind, C.K., Chiang, R.G.: Correlation between presynaptic dense bodies and transmitter output at lobster neuromuscular terminals by serial section electron microscopy. Brain Res. 161 377–388 (1979)
Govind, C.K., Lang, F.: Neuromuscular analysis of closing in the dimorphic claws of the lobster, Homarus americanus. J. Exp. Zool. 190, 281–288 (1974)
Hoyle, G.: Nervous control of insect muscle. In: Recent Advances in Invertebrate Physiology (B.T. Scheer, ed.). Eugene, USA: University of Oregon Press (1957)
Hoyle, G., McNeil, P.A.: Correlated physiological and ultrastructural studies on specialized muscles. Ic. Neuromuscular junctions in the eyestalk levator muscles of Podopthalmus vigil (Weber). J. Exp. Zool. 167 523–550 (1968)
Katz, B.: Nerve, Muscle and Synapse. New York: McGraw Hill Book Co. (1966)
Thomas, R.C., Wilson, V.J.: Marking single neurons by staining with intracellular recording microelectrodes. Science (Wash.) 151, 1538–1539 (1966)
Tiegs, O.: The flight muscles of insects — their anatomy and physiology; with some observations on the structure of striated muscle in general. Philos. Trans. R. Soc. Lond. (Biol.) 238, 221–348 (1955)
Tisdale, A.D., Nakajima, Y.: Fine structure of synaptic vesicles in two types of nerve terminals in cray-fish stretch receptor organs: influence of fixation methods. J. Comp. Neurol. 165, 369–386 (1976)
Wiersma, C.A.G.: The neuromuscular system. In: The Physiology of Crustacea. Vol. II (T.H. Waterman, ed.). New York: Academic Press (1961)
Wiersma, C.A.G., Ripley, S.H.: Innervation patterns of crustacean limbs. Physiol. Comp. Oecol. 2, 391–405 (1952)
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I thank Professor H.L. Atwood for criticism of the manuscript and R.G. Chiang, R.A. DeRosa, J.A. King and J. Pearce for technical assistance. This work was supported by grants from the National Research Council and Muscular Dystrophy Association of Canada
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Govind, C.K. Spatial distribution of excitatory innervation on a muscle fiber of the lobster (Homarus americanus). Cell Tissue Res. 199, 171–175 (1979). https://doi.org/10.1007/BF00237737
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DOI: https://doi.org/10.1007/BF00237737