Editing Cardiac pacemaker (section)

=== Phase 3{{Dash}}Repolarization ===
The reversal of membrane potential triggers the opening of potassium leak channels, resulting in the rapid loss of potassium ions from the inside of the cell, causing repolarization (V<sub>m</sub> gets more negative). The calcium channels are also inactivated soon after they open. In addition, as sodium channels become inactivated, sodium permeability into the cell is decreased. These ion concentration changes slowly repolarize the cell to resting membrane potential (-60mV). Another important note at this phase is that ionic pumps restore ion concentrations to pre-action potential status. The [[sodium-calcium exchanger]] ionic pump works to pump calcium out of the [[intracellular space]], thus effectively relaxing the cell. The [[sodium/potassium pump]] restores ion concentrations of sodium and potassium ions by pumping sodium out of the cell and pumping (exchanging) potassium into the cell. Restoring these ion concentrations is vital because it enables the cell to reset itself and enables it to repeat the process of spontaneous depolarization leading to activation of an action potential.