Nerve network (nervous system)

A nerve network or diffuse nervous system is the simplest known type of nervous system in biological organisms. The individual nerve cells are arranged in nerve networks, not in coordination centers such as ganglia or brains , but concentrations of nerve cells occur, for example in the area of ​​the throat , so they are not completely diffusely distributed. Neural networks are particular to hollow animals on (coelenterates). The simplest representatives are found in polyps of the genus Hydra .

Nerve networks are quite simple in many respects and are very different from higher nervous systems. There are mainly multi- and bipolar nerve cells that usually have no specialized dendrites or axons , i.e. are symmetrically structured. In contrast to those of the higher nervous systems, most of the inter-neuronal connections ( synapses ) are also able to transmit excitations in both directions. This is also due to the fact that these are usually electrical synapses , so the totality of neurons in the diffuse nervous system forms a syncytium . The classic neurotransmitters known from vertebrates also do not appear in nerve networks; instead, it is predominantly neuropeptides that carry out the chemical transmission of information.

literature

• Dudel, Menzel, Schmidt: Neuroscience. From molecule to cognition. 2nd Edition. Springer, Berlin 2001, ISBN 978-3540413356