![cover image](https://wikiwandv2-19431.kxcdn.com/_next/image?url=https://upload.wikimedia.org/wikipedia/commons/thumb/9/95/Action_Potential.gif/640px-Action_Potential.gif&w=640&q=50)
Aktionspotential
En signalmekanisme mellem levende celler / From Wikipedia, the free encyclopedia
Et aktionspotential (undertiden skrevet aktionspotentiale[1]) er en signalmekanisme mellem levende celler. Ved et aktionspotential stiger cellens elektriske membranpotentiale brat for hurtigt at falde igen, hvilket efterfølges af en stilstandsperiode. Aktionspotentialer forekommer i mange typer dyreceller, under ét kaldt excitable celler, herunder neuroner, muskelceller og kirtelceller, samt visse planteceller. I neuroner spiller aktionspotentialet en central rolle i celle-celle-kommunikationen. I andre typer celler har det til formål at aktivere intracellulære processer. I muskelceller er aktionspotentialet eksempelvis det første skridt i en kæde af begivenheder, der i sidste ende fører til kontraktion (sammentrækning). I bugspytkirtlens betaceller udløser de frigivelsen af insulin.[2] Aktionspotentialer i neuroner kaldes også for ”nerveimpulser”, og en serie af aktionspotentialer udløst af et neuron kaldes et ”impulstog”. Et neuron, der udsender et aktionspotential, siges at ”fyre”.
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![Two plots of the membrane potential (measured in mV) versus time (ms). Top: idealized plot where the membrane potential starts out at -70 mV at time zero. A stimulus is applied at time = 1 ms, which raises the membrane potential above -55 mV (the threshold potential). After the stimulus is applied, the membrane potential rapidly rises to a peak potential of +40 mV at time = 2 ms. Just as quickly, the potential then drops and overshoots to -90 mV at time = 3 ms, and finally the resting potential of -70 mV is reestablished at time = 5 ms. Bottom: a plot of an experimentally determined action potential that is very similar in appearance to the idealized plot, except that the peak is much sharper and the initial drop is to -50 mV increasing to -30 mV before dropping back to the resting potential of -70 mV.](http://upload.wikimedia.org/wikipedia/commons/thumb/c/cc/Action_potential_vert.png/640px-Action_potential_vert.png)