In fact, this is the voltage of the membrane when the cell is resting, when it's not generating any action potential. And this is known as the resting membrane potential. So the brown section describes the resting membrane potential of the cell for a typical cardiac myoside. This is at around negative 90 millivolts. Now, before we discuss anything else, let's discuss the relative concentrations of four different ions found on the inside and on the outside of the membrane. So when the cell is resting, when it's not generating any action potential, that is, when we are at phase four, these are the relative concentrations.