Figure 1. Electrogenic components of the initial USMC model.

A, Schematic representation of the 14 ion channels/exchangers that contributed to the initial USMC model of myometrial electrical excitability [4]. B-D, this USMC model [4] reproduced different AP forms of short duration but it could not simulate long-lasting APs. B, short bursting-type AP evoked by a 2 s current clamp stimulus (Ist) of -0.2 pA pF⁻¹. C, short plateau-type AP evoked by a 2 s Ist of −0.5 pA pF⁻¹. D, an attempt to simulate a long duration AP with a 50 s Ist of −0.25 pA pF⁻¹ resulted in a plateau-like AP that failed to repolarize at the end of the stimulus. All three simulated APs were initiated from the same initial conditions.