Figure 3

Transverse propagation of simulated action potentials (APs; rising phase) for cardiac muscle (5 × 5 models) with stimulation of one cell only (cell A1; first cell of the A-chain). A: R_gj = ∞ (0 channels). R_ol2 = 200 KΩ. Standard conditions. All 25 cells responded. B: R_gj = 1.0 MΩ (10,000 channels). R_ol2 kept unchanged. The last 2 chains (D, E) failed to respond. All 5 cells of each chain that responded (A, B, C) fired simultaneously because of the strong cell coupling. C: With R_gj held at 1.0 MΩ, raising R_ol2 to 10 MΩ (representing tighter packing of the parallel chains) now allowed all 5 chains to respond. Thus, adding gj-channels inhibited transverse propagation, but this inhibition could be overcome by raising R_ol2.