Figure 1. The model cell as a dynamical system undergoing transitions between the low (depolarized, abnormal) and high (hyperpolarized, normal) V_m states.

In this model, the transitions are associated with changes in the biological parameters which determine the electrical rectification characteristics of the voltage-gated channels. The ion channels in the cell membrane are schematically shown. We consider that the inward-rectifying channel (inward arrow) favors the hyperpolarization while the outward-rectifying channel (outward arrow) favors the depolarization.