(a) Diagram of a biomembrane that separates the inside and outside of the nerve cell. See text for further explanation. (b) Membrane equivalent circuit with k ion channels. are the Nernst potentials for the individual ion species; and represent the resistance of the different ion channels and their currents, respectively. is the current injected. The membrane capacitance and the associated current are and . is the membrane potential. The equation is Kirchhoff’s law applied to the circuit.
