Copyright o The McGraw-Hill Companies, Inc. Permission required for reproduction or display Distribution of major Mobile Ions TABLE 6-2 Across the Plasma Membrane of a Typical Nerve cell Concentration, mmol/L ION EXTRACELLULAR INTRACELLULAR Na 150 15 110 K 150 A more accurate measure of electrical driving force can be obtained using mEq/L, which factors in ion valence. Since all the ions in this table have a valence of 1, the mEq/L is the same as the mmol/L concentration