Threshold potential

Threshold potential

The threshold potential is the membrane potential to which a membrane must be depolarized to initiate an action potential.

It often can be between −40 and -55 mV, but it can vary based upon several factors. If ion channels are available, that will move the potential in the direction of the equilibrium potential for that ion:

* sodium ion channel: Na+ is approximately +55mV
* potassium channel: K+ is approximately -75mV
* chloride channel: Cl- is approximately -67mV

Therefore, resting ion channel for sodium will depolarize and thus excite, while channels for potassium or chloride will hyperpolarize and thus inhibit.

External links

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* [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]


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