Fig. 5
From: Integrative and theoretical research on the architecture of a biological system and its disorder
Bifurcation phenomena and tetra-stable action potential (AP) dynamics observed in a human ventricular myocyte model. a A one-parameter bifurcation diagram of the sampled membrane potential (Vm) in each AP response as a function of the maximum conductance (%GKr) of rapid components (IKr) of the delayed-rectifier K+ channel currents in the Kurata model with 100%GKs. The maximum conductances of the slow component (IKs) and IKr of the delayed-rectifier K+ channel currents are expressed as a percentage of the control values. The solid and dashed lines represent stable and unstable AP responses, respectively. EAD Early afterdepolarization, SN saddle-node bifurcation. b An example of multi-stable AP dynamics. Simulated tetra-stable AP trains and changes in intracellular Na+ concentration ([Na+]i) observed in the Kurata model at 39%GKr with 70%GKs. The arrows (values in mM) indicate each [Na+]i perturbation at appropriate times during the simulated AP trains. Colored and gray lines indicate the steady-state and transient responses, respectively. Dots indicate the application of current pulses. Pacing cycle length = 2 s. Each panel was modified based on Tsumoto et al. [57]