Situations where Ca²⁺ waves do not occure. (A and B) Time course of Ca²⁺ in the cytoplasm (A) and LSR (B) when the main Ca²⁺ buffer concentration in the TSR ([CSQ]) is decreased from 30 to 20 mM. Simulations were for sheep/human RyR2 with uniform RyR2 cluster sizes (black) and exponentially distributed cluster sizes (red) at positions x = 1 μm and y = 1 μm (near the longitudinal axis), z = 25 μm (midpoint of the longitudinal axis). (C and D) z-t fluorescent line scans for uniform clusters (C) and exponentially distributed cluster sizes (D). (E) For the case of exponentially distributed cluster sizes, the mean LSR [Ca²⁺] (green) and the total Ca²⁺ fluxes in the x-y plane at z = 25 μm originating from the initial flux transients from sparks and embers (red) or the subsequent flux plateaus from embers (blue).