ISSN:
1432-0878
Keywords:
Crustacean muscle
;
Nerve terminals
;
Synapses
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary The innervation pattern of distal muscle fibers of the opener muscle of walking legs of crayfish (Astacus leptodactylus) was investigated using methylene-blue staining, cobalt infiltration, and electron microscopy. A quantitative analysis of the entire innervation of single muscle fibers was attempted. It was found that instead of the generally assumed parallel array of numerous excitatory and inhibitory terminals, innervation consists of only a few branched terminals. The branches of excitatory and inhibitory terminals lie side-by-side. Both types are characterized by numerous varicosities (see Fig. 9B). The aggregate length of excitatory as well as inhibitory terminals on one muscle fiber is, on the average, about 1,500 μm with a total of 152 varicosities spaced about 10 μm apart. The average diameter of the varicosities is 4.26 μm, that of the connecting thin segments about 0.5 μm. Total terminal surface of motor or inhibitory terminals amounts to about 10,000 μm2 per muscle fiber. There are approximately 2,000 motor synapses on each muscle fiber, but their average total area is only about 6% of the terminal membrane area, or 0.06% of the (idealized) muscle fiber surface. There are conspicuous differences in the postsynaptic specializations associated with excitatory and inhibitory terminals; these are described in detail. The results are discussed in a functional context and with regard to design and results of electrophysiological experiments.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00213750
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