Fig. 1.

The geometry and equivalent circuit diagram for the microscale model of cardiac conduction in the presence of gap-junctional and ephaptic coupling. We describe cells as active cables connected by resistors and shared cleft potentials. A and B show the potential and gating variables in Eqs. 1–7, respectively. A depicts a continuum of interior points, and B presents its numerical discretization. In the model, clefts are idealized as having zero width. A model without ephaptic conduction is the special case in which the cleft-to-ground resistance is zero.