Figure 8.

(A) Diagram of two cells sharing a cleft. The two cells are not autorhythmic when they do not share a cleft and F_IK = 0.65 in cell 1 and F_IK = 0.25 in cell 2. (B) Autorhythmic activity is initiated when they share a cleft with cleft width factor w_f = 1. (C) Heterogeneous F_IK in cells 1 and 2 results in multiphasic potassium cycling resulting from temporally shifted [K]_cl dynamics. The action potential of cell 1 increases [K]_cl, and activation of cell 2 further increases [K]_cl to create a second peak in [K]_cl. (D) I_K,cl is phase shifted, and the peak amplitudes are different for the two apposing cell ends sharing the cleft. I_K,cl for both cells 1 and 2 are biphasic during the respective action potentials, but the outward amplitude is reduced in cell 2 concurrent with the inward I_K,cl of cell 1.