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 -95mV
 * chloride channel: Cl- is approximately -90mV

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