By applying Po(d) to the spatial relationship between BK channel puncta and RYR puncta (Fig. 5 B), we finally arrived at a relationship between an RYR punctum and the number of BK channel puncta being activated (Fig. 6, B and C). Because the Po of each BK punctum depends on its distance from the RYR, we calculated the number of activated BK channel puncta by weighting each nearby BK channel punctum by its Po, as shown by the red lines in Fig. 6 (B and C; see the legend for calculation). With this calculation, on average, an RYR2 punctum activated 1.26 ± 0.04 BK channel puncta, and an RYR1 punctum activated 1.92 ± 0.07 BK channel puncta (n = 5 cells for RYR1 and 6 cells for RYR2).
