Inhibitory Synapses Operating by Electrical Transmission

Abstract

In most species of fish the two large Mauthner cells (M-cells) are the most conspicuous neurones in the brain. As illustrated in Fig. 89A several distinct types of synapse cover the two large dendrites; but of particular interest is the helicoidal feltwork of fine fibres (s.p.) that is embedded in the so-called axon cap (Bartelmez 1915; Bodian 1937, 1942, 1952; Retzlaff 1954). The axon cap is an approximately spherical structure of glial and nervous elements surrounding the axon of the M-cell from its axon-hillock origin to the beginning of its myelination (see broken line of Fig. 89A). The axon of each M-cell then expands to about 40 µ in diameter, decussates with its fellow, and runs down the spinal cord (Fig. 97A).