nerve net

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nerve net

n.
A diffuse network of neurons that conducts impulses in all directions from the area stimulated, forming the nervous system in certain invertebrates such as the cnidarians.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.

nerve net

a system of interconnecting nerve cells, in the form of a net, found in those groups of invertebrates which lack a CENTRAL NERVOUS SYSTEM, such as COELENTERATES and ECHINODERMS. In other groups the nerve net is almost nonexistent. Conduction is slow across the net and is often in all directions, as the synapses are not usually unidirectional.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005
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Though the granules in the nerve net and in the colloblasts are presumably functionally distinct, their formaldehyde-induced fluorophores have similar emission spectra, with a major peak near 510 nm and multiple minor peaks at longer emission wavelengths.
Meanwhile, though the function of catecholic molecules in the ctenophore nerve net is unknown, the presence of o-diphenols there suggests that the history of neurotransmitter evolution is potentially more complicated than initially thought.
While the nerve nets are the most conspicuous components of the scyphozoan nervous system, it is much more complex.
This latter property requires the same diffuse conduction as seen in the GFNN, giving the scyphomedusae two parallel nerve nets in the subumbrellar ectoderm, but with a distinct sensory component or sensory inputs.
Neurons in the rhopalia, nerve ring, and nerve nets of all species are immunoreactive to [alpha]- or [beta]-tubulin antibodies and the FMRFamide antibody.
Initial evaluation of the motor nerve nets of the three muscle sheets indicated clear differences in the neuronal density, with the highest density in the frenula and the lowest in the subumbrella (Figs.
This nerve net was particularly dense, however, at the base of the capitate portion of the tentacle, immediately under the cluster of cnidocytes (Fig.
1K) and processes from these merged with the immunoreactive nerve net. The cilia of these sensory cells emerged from the surface of the tentacle, but seemed to extend no further than the mucus layer on the surface.
The Cx43-like protein is localized in the luminescent endoderm and in the mesogleal nerve net
Specific Cx43-like immunoreactivity was present in all tissue layers of autozooid polyps but was more prevalent in the luminescent endoderm and in the mesogleal nerve net. Reactive sites had a predominantly punctate appearance and, in the mesogleal nerve net, a linear dotlike distribution compatible with the labeling of connexon patches (Fraser et al., 1987).
The sulfonated amino acid taurine, which is ubiquitous in animals and prokaryotes and has been implicated as an inhibitory neurotransmitter in both vertebrates (Huxtable, 1989) and invertebrates (Nistri and Constanti, 1976; Hue et al., 1979; Giles and Usherwood, 1985), has recently been shown to depolarize neurons in the motor nerve net (MNN) of the scyphozoan jellyfish Cyanea capillata (Anderson and Trapido-Rosenthal, 1990).
In some preparations the myoepithelium that envelops the MNN neurons was removed to expose the nerve net (Anderson and Schwab, 1984).