Threshold potential
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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 mV 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 +60mV
- potassium channel: K+ is approximately -95mV
- chloride channel: Cl- is approximately -70mV
Therefore, resting ion channel for sodium will depolarize and thus excite, while channels for potassium or chloride will hyperpolarize and thus inhibit.