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In biology, depolarization is a decrease in the absolute value of a cell's membrane potential. Thus, changes in membrane voltage in which the membrane potential becomes less positive or less negative are both depolarizations. In neurons and some other cells, a depolarization large enough may result in an action potential. Hyperpolarization is the opposite of depolarization, and inhibits the rise of an action potential. The rising and falling phases of such an action potential are often imprecisely also called depolarization and hyperpolarization, respectively.
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Mechanism
Depolarization is often caused by influx of cations, e.g. Na+ through Na+ channels, or by influx of Ca2+ through Ca2+ channels.
On the other hand, outflux of K+ through K+ channels inhibits depolarization.
If a cell has a resting potential of -70mV and the membrane potential changes to -50mV, then the cell has been depolarized.
Depolarization block
There are drugs, called depolarization blocking agents, that inhibit depolarization, e.g. by blocking the channels responsible for depolarization, or by opening K+ channels. Examples include the nicotinic agonists suxamethonium and decamethonium[1].
References
- ^ Rang, H. P. (2003). Pharmacology. Edinburgh: Churchill Livingstone. ISBN 0-443-07145-4. Page 149
External links
- Neuroscience - online textbook by Purves, et al
- Basic Neurochemistry Molecular, Cellular, and Medical Aspects by Siegel, et al
Wikipedia content modification information:
- This page was last modified on 13 June 2008, at 07:46.
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