Interneuron
As interneurons , also switching neurons or intermediate neurons are nerve cells referred to, with its Endknöpfchen (projections) in a specifically defined region of the central nervous system (CNS) or in ganglia lie and there between two or more nerve cells are connected. In contrast to the projection neurons, they do not have long axons that reach into distant regions of the CNS. They pass on received impulses directly to neighboring nerve cells and serve to spread, align, maintain and modulate an excitation. The propagation of the excitation is realized through branches and plays a role especially with external reflexes . When the neurites of the interneurons make synaptic contact with collaterals of nerve cells , excitation circles are created .
Interneurons are either inhibitory with glycine , γ-aminobutyric acid (GABA) , serotonin or dopamine as neurotransmitters, or excitatory with the neurotransmitters acetylcholine or norepinephrine. The inhibitory interneurons cause either a forward inhibition , a backward inhibition or a presynaptic inhibition . Backward inhibitory interneurons in the spinal cord are called Renshaw cells .
In the narrower sense, interneurons are nerve cells that are connected between sensory and motor neurons in polysynaptic reflex arcs , especially in invertebrates . Several interneurons can be arranged in function chains.
In the brain , the term interneurons is used for nerve cells with relatively short axons (type II Golgi cells). These are compared to the projection neurons with a long axon. Interneurons can be classified into different subgroups according to different properties. Usually, the expression of various polypeptides or electrophysiological properties are used for this. For example, interneurons which contain the polypeptide VIP are referred to as VIP interneurons.
In the enteric nervous system (ENS), too , sensory interneurons occur as descendants of the neural crest and, together with exciting and inhibitory motor neurons and sensory neurons, form a complicated system, the ENS.
Individual evidence
- ^ A b Theodor H. Schiebler, Walter Schmidt: Anatomy: cytology, histology, history of development, macroscopic and microscopic human anatomy . 5th edition, Springer-Verlag, 2013, ISBN 9783662057339 , p. 182.
- ↑ Thomas Rhomberg, Laura Rovira-Esteban, Attila Vikór, Enrica Paradiso, Christian Kremser: Vasoactive Intestinal Polypeptide-Immunoreactive Interneurons within Circuits of the Mouse Basolateral Amygdala . In: Journal of Neuroscience . tape 38 , no. 31 , August 1, 2018, ISSN 0270-6474 , p. 6983–7003 , doi : 10.1523 / JNEUROSCI.2063-17.2018 , PMID 29954847 ( jneurosci.org [accessed May 16, 2020]).