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An action potential occurs when the membrane potential of a specific cell rapidly rises and falls. [1] This depolarization then causes adjacent locations to similarly depolarize. Action potentials occur in several types of excitable cells, which include animal cells like neurons and muscle cells, as well as some plant cells.
The slope of phase 0 on the action potential waveform (see figure 2) represents the maximum rate of voltage change of the cardiac action potential and is known as dV/dt max. In pacemaker cells (e.g. sinoatrial node cells ), however, the increase in membrane voltage is mainly due to activation of L-type calcium channels.
Phases of a cardiac action potential. The sharp rise in voltage ("0") corresponds to the influx of sodium ions, whereas the two decays ("1" and "3", respectively) correspond to the sodium-channel inactivation and the repolarizing efflux of potassium ions. The characteristic plateau ("2") results from the opening of voltage-sensitive calcium ...
A labeled diagram of an action potential.As seen above, repolarization takes place just after the peak of the action potential, when K + ions rush out of the cell.. In neuroscience, repolarization refers to the change in membrane potential that returns it to a negative value just after the depolarization phase of an action potential which has changed the membrane potential to a positive value.
Artistic interpretation of the major elements in chemical synaptic transmission. An electrochemical wave called an action potential travels along the axon of a neuron.When the action potential reaches the presynaptic terminal, it provokes the release of a synaptic vesicle, secreting its quanta of neurotransmitter molecules.
In electrophysiology, the threshold potential is the critical level to which a membrane potential must be depolarized to initiate an action potential. In neuroscience , threshold potentials are necessary to regulate and propagate signaling in both the central nervous system (CNS) and the peripheral nervous system (PNS).
This image is a derivative work of the following images: File:Action_potential_Class_III.png licensed with Cc-by-sa-3.0-migrated-with-disclaimers, GFDL-en . 2008-06-23T22:27:06Z Rjgalindo 593x319 (11997 Bytes) {{Information |Description=Class Ib antiarrhythmic effect on action potential (with labels) - all languages. |Source=[[:en:Image:Action potential Class III.png|Image:Action potential ...
fix layering, shape of threshold line, alignment of Y-axis labels: 05:50, 14 June 2007: 491 × 485 (13 KB) Tomtheman5 {{Information |Description=Schematic of an en:action potential, drawn by en:User:Diberri in en:Adobe Illustrator. A version with no labels is available at en:Image:Action-potential-nolabels.png. |Source=Self-made, based on [[:en ...