Action Potential

Polarization - Voltage difference of -70mV.

Caused by the sodium potassium pump (gate) - More sodium is pumped out than potassium is pumped in, resulting in a negative charge inside axon of the neuron. 

A threshold stimulus must be applied (a change in pH, pressure, or an electrical stimulus). This causes the sodium potassium pump to cause Na+ gates to open and tons of Na+ rush into the cell, and small amounts of K+ to move out.

Membrane becomes depolarized (+40mV)

After the wave of impulse has moved through Na+ gates close to stop inflow.

Change in electrical potential causes K+ channels to open and K+ ions rush out of the cell.

 Restores the polarized state but now it is hyperpolarized – more positively charged on the outside than the resting state (over shoot).

Ion concentrations are reversed from the resting state.

Resting potential (-70mV) must be restored before the neuron can fire again.

Na+ are pumped out and K+ are pumped back into the cell using ATP energy.