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The first part of this article considers the Nernst potential of a particular species of ions as the difference in electrical potential between two regions that exactly balances the difference in chemical potential energy between these two regions, brought about by a difference in concentrations. If the cell membrane is permeable to only one species of ions, the membrane potential at which there is no net ion current to or from the membrane, i.e. the resting membrane potential, equals the Nernst potential for the given species of ions. If the cell membrane is permeable to different species of ions, an expression for the resting membrane potential can be derived from several different models. In the second part of this paper, we present one of the two most commonly used models, which predicts that ions obey the Ohm’s law and is thus coined the ohmic model. According to the ohmic model, the resting membrane potential is a weighted sum of Nernst potentials of all ionic species to which the membrane is permeable, the weights being the relative contributions of each ionic species to the total membrane conductance. In the third and last part, the role of Na+/K+-ATPase in ensuring constancy of concentrations as well as its contribution to the resting membrane potential are presented in a quantitative manner.