Nernst equation is 62mV x log (conc ions outside/conc ions inside) Ion movement through ion channels creates a membrane potential. K+ conc at equilibrium is -90mV but because of the positive charge of Na+ inside, the ways of Na+ is opposite K+ and creates a charge less negative inside the cell. The resting potential reflects the small movement of sodium ions across a few open sodium channels in the resting neuron.