Electrical Activity of the Heart: Membrane Resting Potential
Cardiac conduction system cells have a 
membrane
resting
potential such that the outer surface of the resting cell
membrane carries a positive electrical charge and the inner
surface of the membrane carries a negative electrical charge.
During the resting stage, the cardiac conduction system cells are
polarized. The normal resting potential of the cardiac conduction
system is approximately -85 to -95 millivolts (mV).
The changes in electrical potential that occur result from
the movement of sodium and potassium ions across the sarcolemma
of the cell. This movement of charged ions allows for the changes
in electrical potential necessary to propagate the electrical
charge to the next excitable cell. The movement of the sodium and
potassium ions is mediated by the sodium-potassium pump.
Cardiac conduction system cells have a 
membrane
resting
potential such that the outer surface of the resting cell
membrane carries a positive electrical charge and the inner
surface of the membrane carries a negative electrical charge.
During the resting stage, the cardiac conduction system cells are
polarized. The normal resting potential of the cardiac conduction
system is approximately -85 to -95 millivolts (mV).