Welcome to MedLibrary.org. For best results, we recommend beginning with the navigation links at the top of the page, which can guide you through our collection of over 14,000 medication labels and package inserts. For additional information on other topics which are not covered by our database of medications, just enter your topic in the search box below:
In biology, depolarization is a change in a cell's membrane potential, making it more positive, or less negative. In neurons and some other cells, a large enough depolarization may result in an action potential. Hyperpolarization is the opposite of depolarization, and inhibits the rise of an action potential.
If, for example, a cell has a resting potential of –70mV, once the membrane potential changes to –50mV, then the cell has been depolarized. Depolarization is often caused by influx of cations, e.g. Na+ through Na+ channels, or Ca2+ through Ca2+ channels. On the other hand, efflux of K+ through K+ channels inhibits depolarization, as does influx of Cl– (an anion) through Cl– channels. If a cell has K+ or Cl– currents at rest, then inhibition of those currents will also result in a depolarization.
Because depolarization is a change in membrane voltage, electrophysiologists measure it using current clamp techniques. In voltage clamp, the membrane currents giving rise to depolarization are either an increase in inward current, or a decrease in outward current.
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.
- Purves D, Augustine GJ, Fitzpatrick D, et al., ed. (2001). Neuroscience (2. ed.). Sunderland, Mass: Sinauer Assoc. ISBN 0-87893-742-0 [Amazon-US | Amazon-UK].
- "Depolarization (Animation)". Psychology Department, Hanover College. Retrieved 18 May 2013.