State-space dynamics and model regimes as a function of Δ<i>V</i>_1/2.

<p>These bifurcation diagrams illustrate the FP’s and PO’s of the <i>V</i> and <i>h</i> model states as a function of Δ<i>V</i>_1/2. <i>Thin black line</i>: stable FP’s; <i>thick cyan</i>: the unstable-FP branches (with one or two (real or complex) positive-real eigenvalues. <i>LP</i>1 and <i>LP</i>2: lower and upper limits of the middle branch. HB: Hopf bifurcation. See the text for more details. Thin and thick dashed lines: minimum and maximum model-state value for the stable and unstable cycles respectively. Unstable cycles are born from FP’s at a <i>subcritical</i> HB and metamorphose to stable at a cycle saddle-node (fold).