Depolarization 531587 219034346 2008-06-13T07:46:40Z BeardWand 7283361 /* Depolarization block */ fix redlink {{otheruses}} 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 (biology)|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. ==Mechanism== Depolarization is often caused by influx of cations, e.g. [[sodium|Na<sup>+</sup>]] through [[sodium channel|Na<sup>+</sup> channels]], or by influx of [[Calcium|Ca<sup>2+</sup>]] through [[Calcium channel|Ca<sup>2+</sup> channels]]. On the other hand, outflux of [[potassium|K<sup>+</sup>]] through [[potassium channel|K<sup>+</sup> 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== <!--Depolarization block redirects here--> There are drugs, called [[Neuromuscular-blocking drugs#Depolarizing blocking agents|depolarization blocking agents]], that inhibit depolarization, e.g. by blocking the channels responsible for depolarization, or by opening K<sup>+</sup> channels. Examples include the [[nicotinic agonist]]s [[suxamethonium]] and [[decamethonium]]<ref name=Rang149> {{cite book |author=Rang, H. P. |title=Pharmacology |publisher=Churchill Livingstone |location=Edinburgh |year=2003 |pages= |isbn=0-443-07145-4 |oclc= |doi=}} Page 149 </ref>. ==References== {{reflist}} ==External links== *[http://www.ncbi.nlm.nih.gov/books/bv.fcgi?call=bv.View..ShowTOC&rid=neurosci.TOC&depth=2 Neuroscience] - online textbook by Purves, et al * [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?call=bv.View..ShowTOC&rid=bnchm.TOC&depth=2 Basic Neurochemistry] Molecular, Cellular, and Medical Aspects by Siegel, et al [[Category:Membrane biology]] [[de:Depolarisation (Physiologie)]] [[fr:Dépolarisation]] [[is:Afskautun]] [[lt:Depoliarizacija]] [[pl:Depolaryzacja (biologia)]] [[fi:Depolarisaatio]] [[sv:Depolarisering]] [[ur:زوال تقطیب]]