Threshold potential
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2008-06-10T19:12:11Z
Bradv
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Reverted to revision 166016627 by [[Special:Contributions/Richard001|Richard001]]; Restoring older version. ([[WP:TW|TW]])
[[Image:Action potential vert.png|thumb|350px|'''A.''' A schematic view of an idealized action potential illustrates its various phases as the action potential passes a point on a [[cell membrane]]. '''B.''' Actual recordings of action potentials are often distorted compared to the schematic view because of variations in [[electrophysiology|electrophysiological]] techniques used to make the recording.]]
The [[threshold potential]] is the [[membrane potential]] to which a membrane must be [[depolarization|depolarized]] to initiate an [[action potential]].
It often can be between −40 and -55 [[volt|mV]], but it can vary based upon several factors. If [[ion channel]]s are available, that will move the potential in the direction of the equilibrium potential for that ion:
* [[sodium ion channel]]: Na+ is approximately +60mV
* [[potassium channel]]: K+ is approximately -95mV
* [[chloride channel]]: Cl- is approximately -70mV
Therefore, [[resting ion channel]] for sodium will [[depolarization|depolarize]] and thus excite, while channels for potassium or chloride will [[hyperpolarization (biology)|hyperpolarize]] and thus inhibit.
==External links==
* {{eMedicineDictionary|threshold+stimulus}}
* {{GeorgiaPhysiology|1/1ch4/s1ch4_8}}
* [http://www.cameron.edu/~gabrielr/PHYCH4/sld013.htm Description at cameron.edu]
* [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=mcb.figgrp.6213 Diagram at nih.gov]
{{neuro-stub}}
[[Category:Electrophysiology]]
[[de:Schwellenpotential]]
[[pl:Potencjał progowy]]