Figure 9.

(A) Oscillatory solutions for the dual cell model with cells coupled via a common diffusion-limited cleft domain (w_f = 1), fractional potassium cleft current F_IK = 0.65 for both cells, cell 2 with standard sodium channel density (solid curves), and g_Na=0 (dashed curves), hence inexcitable. Neither cell 1 nor 2 are autorhythmic on their own. Excitable cell 1 gains automaticity when sharing a cleft with an inexcitable cell 2 (dashed traces). Making cell 2 excitable confers automaticity to cell 2 that is synchronized with cell 1 and increases the autorhythmic frequency of cell 1. (B) Cleft potassium currents corresponding to the V_m oscillations in (A). (C) Peak [K]_cl is modestly reduced in the electrophysiologically heterogeneous cell pairs because the integral of outward I_K,cl is partially balanced by the small inward current into cell 2.