Diagrams of equivalent circuits representing ion channels. (a) A two branch equivalent circuit for a linearized potassium channel. The potassium channel has properties similar to an inductor. A change in current flowing through an inductor creates a time-varying magnetic field inside the coil; this induces a potential that opposes the change in current that created it. In the potassium channel, a change of K+ current is opposed by the change in membrane potential and the associated change in K+-conductance caused by the current. (b) Equivalent circuit for linearized sodium activation and inactivation. (c) A part of the linearized membrane model for the sodium channel with negative values for both and (c1) and its equivalent RC circuit (c2).
