Resting membrane potential: resting membrane potential, goldman equation ion in the equation. Membrane permeable to a variety of ions, so can"t use the nernst equation. Each ion affects the rmp depending on its permeability & concentration gradient. No valence in the equation because the charge is taken into account based on the position of the. Important ions (k, na, and cl) and their concentration gradients. Degree of importance of each ion at a particular time is proportional to membrane: rmp = -70mv (can vary from cell to cell) permeability. This potential maintains the concentration gradient of chloride. Some potassium will leak out because the rmp isn"t strong enough to counter the movement of potassium. Potassium moved back in using the na/k pump. Sodium (whose equilibrium potential is much higher than the rmp) theoretically should move down its gradient, but membrane is less permeable to sodium than potassium. Cells in the heart don"t have an rmp.