The Pacemaker Potential of the SA Node and the AV Node
This video shows how the Pacemaker Potential results in the signal that causes the heart to beat.
It shows how the greater conductance for Sodium ions in the Pacemaker Cells in the S.A. Node cause the cells to depolarize, opening voltage-gated Calcium channels when the membrane potential reaches threshold.
This results in the action potential. Then Potassium channel open, letting Potassium ions leave, repolarizing the cells.