| Axon hillock | |
|---|---|
 Red labeled is pointing directly at the axon hillock. | |
| Details | |
| Part of | Axon of a nerve |
| System | Nervous system |
| Identifiers | |
| Latin | colliculus axonis |
| TH | H2.00.06.1.00006 |
| Anatomical terminology | |
The axon hillock is a specialized part of the cell body (or soma) of a neuron that connects to the axon. It can be identified using light microscopy from its appearance and location in a neuron and from its sparse distribution of Nissl substance.[1]
The axon hillock is the last site in the soma where membrane potentials propagated from synaptic inputs are summated before being transmitted to the axon.[2] For many years, it was believed that the axon hillock was the usual site of initiation of action potentials—the trigger zone. It is now thought that the earliest site of action potential initiation is at the axonal initial segment: just between the peak of the axon hillock and the initial (unmyelinated) segment of the axon.[3] However, the positive point, at which the action potential starts, varies between cells.[citation needed] It can also be altered by hormonal stimulation of the neuron, or by second messenger effects of neurotransmitters.[citation needed]
The axon hillock also delineates separate membrane domains between the cell body and axon.[4] This allows for localization of membrane proteins to either the axonal or somal side of the cell.
- ^ Palay, Sanford L.; Sotelo, Constantino; Peters, Alan; Orkand, Paula M. (1968). "The Axon Hillock and the Initial Segment". The Journal of Cell Biology. 38 (1): 193–201. doi:10.1083/jcb.38.1.193. PMC 2107452. PMID 5691973.
- ^ Hemmings, Hugh C.; Egan, Talmage D. (2012-12-06). Pharmacology and Physiology for Anesthesia E-Book: Foundations and Clinical Application. Elsevier Health Sciences. ISBN 9781455737932.
- ^ Clark BD, Goldberg EM, Rudy B (December 2009). "Electrogenic Tuning of the Axon Initial Segment". Neuroscientist. 15 (6): 651–668. doi:10.1177/1073858409341973. PMC 2951114. PMID 20007821.
- ^ Kobayashi, Toshihide; Storrie, Brian; Simons, Kai; Dotti, Carlos (15 October 1992). "A functional barrier to movement of lipids in polarized neurons". Nature. 359 (6396): 647–650. Bibcode:1992Natur.359..647K. doi:10.1038/359647a0. PMID 1406997. S2CID 4325727.