[Ca2+] curve). We then applied these functions to drive the BK channel Po toward the steady-state Po,ss in response to each [Ca2+] jump (see Materials and methods). Fig. S1 A displays the time course of BK channel currents caused by a step to 6 µM [Ca2+] at three different voltages, and Fig. S1 B shows the activation and decay constants of BK channel currents as a function of voltage and [Ca2+]. A comparison between these simulations and Fig. 9 in Markwardt and Isenberg (1992) confirmed that the model of BK channels we used can reliably replicate the BK channel behavior observed in the experiments in smooth muscle. For example, upon a step to 6 µM Ca2+ from 0 µM Ca2+, τact is 29.3 ms in the simulation and ∼23 ms in the experimental data; upon stepping back to 0 µM Ca2+, τdecay is 25 ms in the simulation and ∼25 ms in the experimental data.
