FIG. 7.

(a) Bifurcation diagram of deterministic system when Ca cycling and voltage are positively coupled. When $\gamma =50$, the period 2 and period 4 regimes are expanded, while higher order periodicities are eliminated. (b). Phase diagram of the stochastic map model showing that the dominant behavior is period 2, while stronger coupling is needed to access the period 4 regime. (c) A larger Hill coefficient $(\nu =50)$ introduces higher order period doubling bifurcations in the deterministic dynamics. (d) Phase diagram of the corresponding stochastic map model showing again the expansion of the P2 phase.