Figure 7.

Increasing the discontinuity in Gj at the heterogeneity increases the range of coupling intervals for which single premature impulses block at a structural heterogeneity when initiated close (2.5 mm away) to the heterogeneity. (A) Changes in I_Na current peak for single premature impulses, with different coupling intervals (S1S2), as the impulses propagate away from the stimulation site (x = 0 mm), in a preparation with a structural heterogeneity with average cell-to-cell coupling Gj = 0.31 μS in the proximal side and Gj = 4.95 μS in the distal side. The dashed vertical line indicates the location of the heterogeneity. (B) Action potentials calculated in the proximal side (1.5 mm from the border), at the border and in the distal side (2.5 mm from the border). Horizontal dashed line indicates a transmembrane potential of 0 mV. The dashed plot (S1S2 = 198 ms) is the shortest coupling that resulted in a propagated response (in the proximal side). Size of the preparation: 7.5 × 2.5 mm (proximal side: 2.5 mm; distal side: 5 mm). Note that single premature impulses with S1S2 = 198–202 ms block at the structural heterogeneity.