Varicosity
As Varicose veins is called multiple bubble swellings on the extension ( dendrite or axon ) of a neuron . Such varicosities occur, for example, in nerve tracts of the autonomic nervous system and in non-pyramidal cells in the cerebral cortex .
In the autonomic nervous system, varicosities are special contact devices between nerve fibers and target tissue. The specialty is that this contact point not only occurs at the end of the nerve fiber, but that many contact points are strung together like a string of pearls along the course of the nerve. The varicose veins have no myelin sheath and contain synaptic vesicles. Unlike other synapses, these vesicles do not empty into a synaptic gap, but into the interstitium (surrounding tissue) and thus into the vicinity of their target cells. This type of synapse is also called synapse en passant . Due to the large surface area of the varicosities and the large area of directly accessible effector cells, a quick reaction to external influences is possible. For example, the activation of the Fight & Flight reaction by the sympathetic nervous system is favored by the release of noradrenaline through this transmission path.
literature
- Robert F. Schmidt, Florian Lang, Manfred Heckmann (eds.): Physiology of humans . 31st edition. Springer, Berlin / Heidelberg 2011, ISBN 978-3-642-01650-9 .
Individual evidence
- ↑ Rainer Schandry: Biological Psychology: A Textbook . 2., revised. Edition. Beltz, PVU, Weinheim 2006, ISBN 978-3-621-27590-3 , pp. 167 .
- ↑ Karl Zilles, Bernhard Tillmann (Ed.): Anatomie . Springer-Verlag, Berlin / Heidelberg 2011, ISBN 978-3-540-69483-0 , p. 604 ( limited preview in Google Book search).