Having validated the BK channel model, we simulated STOCs using the spatial relationship between each RYR and its nearby BK channels as identified experimentally (Fig. 5). Each BK cluster was assigned to have 10 channels (see previous section) and exposed to the appropriate spatio-temporal profile of [Ca2+] derived from a reaction-diffusion spark simulation (Bao et al., 2008) based on estimated mean ICa(spark) (i.e., an amplitude of 3.36 pA with a 9-ms rise time and a 12-ms τdecay). Dictated by their distance to RYRs, each BK channel cluster gives rise to a unique time course of IBK. Fig. 7 A displays IBKs from each BK channel cluster as if they were recorded at 0 mV when exposed to a Ca2+ spark that results from the opening of RYRs marked in the insets of Fig. 5 A. By summing IBK from all BK channel clusters that can be activated by this RYR2 cluster, we obtained a STOC with an amplitude of 35 pA, a TTOD of 22 ms, and a τdecay of 31 ms. On average, simulated STOCs had an amplitude of
