Ephaptic coupling of cardiac cells

Cardiac cells are electrically coupled through gap junction channels, which allow ionic current to spread intercellularly from one cell to the next. It is clear that gap junctional coupling is the primary mechanism for propagation of action potentials in cardiac tissue. However, recent experimental literature has given rise to questions concerning the nature of electrical coupling of cardiac cells. In addition, certain characteristic of cardiac tissue hint that gap junctions might not be the entire story behind coupling. Because the extracellular junctional cleft space between neighboring cells is very narrow and tortuous, it might act as a microdomain for ionic concentrations and the electric potential. In this microdomain, ionic concentrations and the electric potential might vary drastically and rapidly enough to influence action potential propagation or perhaps conduct an electrical signal from one cell to the next. The aim of this dissertation is to gain a better understanding of these proposed coupling mechanisms and characterize their dependence on certain parameters.