Fig. 4.

Effect of SR Ca²⁺ load on alternans. SR Ca²⁺ release flux (A), JSR (B) and NSR (C) Ca²⁺ concentrations, and Ca²⁺ transport between the NSR and JSR (D) are shown for the following three simulations: C1 (a combination of β-AR-stimulated downstream effects with high release and no alternans), C2 (a combination of β-AR-stimulated downstream effects with relatively high release, manifesting alternans), and C3 (C2 with NSR Ca²⁺ content changed to that of C1 at the beginning of the plotted period).