Figure 9.

Feedback of Na⁺ and Ca²⁺ signals and membrane clock modulates SAM automaticity. (A) Schematic of the relationships linking Na⁺ and Ca²⁺ signaling and SAM automaticity. (B) FR-[Na⁺]_i phase plots showing FR and [Na⁺]_i values predicted over time upon 40%, 60%, and 70% NKA block (blue lines), during quasi-steady-state [Na⁺]_i-clamp simulations in which [Na⁺]_i is slowly (i.e., 0.33 mM/min) increased from 8 to 17 mM and then reduced to 8 mM (orange lines), and at steady-state in voltage-clamp simulations in which the FR is controlled (dotted black lines with dots).