Editing Cardiac pacemaker (section)

===Phase 4{{Dash}}Pacemaker potential===
The key to the rhythmic firing of pacemaker cells is that, unlike [[neuron]]s, these cardiomyocytes will slowly depolarize by themselves and do not need any outside innervation from the autonomic nervous system to fire action potentials.

In all other cells, the [[resting potential]] (-60mV to -70mV) is caused by a continuous outflow or "leak" of [[potassium]] ions through [[ion channel]] [[integral membrane protein|proteins]] in the [[cell membrane|membrane]] that surrounds the cells. However, in pacemaker cells, this potassium permeability (efflux) decreases as time goes on, causing a slow depolarization. In addition, there is a slow, continuous inward flow of [[sodium]], called the funny current, or [[pacemaker current]]. These two relative ion concentration changes slowly depolarize (make more positive) the inside membrane potential (voltage) of the cell, giving these cells their pacemaker potential. When the membrane potential gets depolarized to about -40mV it has reached threshold (cells enter phase 0), allowing an action potential to be generated.