The structure of peripheral nerves, and the organization of the myoneural junctions in flight muscle fibers of a beetle is described. The uniaxonal presynaptic nerve branches display the "tunicated" structure reported in the case of other insect nerves and the relationship between the axon and the lemnoblast folds is discussed. The synapsing nerve terminal shows many similarities with that of central and peripheral junctions of other insects and of vertebrates (e.g., the intra-axonal synaptic vesicles) but certain important differences have been noted between this region in Tenebrio flight muscle and in other insect muscles. Firstly, the axon discards the lemnoblast before the junction is established and the axon effects a circumferential synapse with the plasma membrane of the fiber, which alone shows the increased thickness often observed in both pre- and postsynaptic elements. Secondly, in addition to the synaptic vesicles within the axon are present, in the immediately adjacent sarcoplasm, great numbers of larger postsynaptic vesicles which, it is tentatively suggested, may represent the sites of storage of the enzymatic destroyer of the activating substance similarly quantized within the intra-axonal vesicles. The spatial relationship between the peripherally located junctions and the portion of the fiber plasma membrane internalized as circumtracheolar sheaths is considered, and the possible significance of this with respect to impulse conduction is discussed briefly.
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October 01 1960
INNERVATION OF THE FIBRILLAR FLIGHT MUSCLE OF AN INSECT: TENEBRIO MOLITOR (COLEOPTERA)
David S. Smith
David S. Smith
From The Rockefeller Institute
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David S. Smith
From The Rockefeller Institute
Received:
May 16 1960
Copyright 1961 by The Rockefeller Institute Press
1960
J Biophys and Biochem Cytol (1960) 8 (2): 447–466.
Article history
Received:
May 16 1960
Citation
David S. Smith; INNERVATION OF THE FIBRILLAR FLIGHT MUSCLE OF AN INSECT: TENEBRIO MOLITOR (COLEOPTERA) . J Biophys and Biochem Cytol 1 October 1960; 8 (2): 447–466. doi: https://doi.org/10.1083/jcb.8.2.447
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