Electrochemical difference between the two sides of a nerve or cardiac cell membrane when the cell is not conducting an impulse. In most nerve and cardiac cells, the resting potential is negative— the interior of the cell is negatively charged as compared to the extracellular space. The resting potential in cardiac cells is about -90 mV (millivolts), and in nerve cells, -60 mV. This potential is determined by the selective permeability of the cell membrane to potassium (K+) and sodium (Na+) ions. At rest, nerve and cardiac cell membranes are permeable to K+, but they are relatively impermeable to other ions. The resting membrane potential is therefore determined by the K+ gradient across the cell membrane. The gradient is maintained by various ion pumps and ion exchange mechanisms.
Base condition of the nerve due to unequal distribution of ions inside and outside the cell, typically -70 millivolts (mV).