Question

What means synaptic potential?

Answer 1

Synaptic potential is perhaps another term referring to action potentials.

Action potentials are based on the premise that the resting potential of neurons is usually negative, due to the large amount of potassium ions (where `E_"K" approx -80"mV"`) and negatively charged polypeptides.

The action potential initiates because when voltage-gated sodium channels open due to EPSP summation to threshold, among myriad other factors, there is a large driving force for sodium ions (where `E_"Na" approx 62"mV"`), which results in a brief reversal of the condition (because VGNaC close nearly instantaneously). Voltage-gated potassium channels open when `V_"m" > 0` and drive the membrane potential a bit below its resting potential, where it's in a refractory period, that eventually restores to its resting potential again to initiate another action potential.

This all takes place on the order of fractions of a second.

Said in another way, a depolarization of the membrane potential that results from a large influx of sodium ions that propagates down an axon mainly by saltatory conduction.