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. 2014 Apr 23;9(4):e94565. doi: 10.1371/journal.pone.0094565

Figure 7. Importance of a gradient in Na+ conductance in pacemaking and driving.

Figure 7

A, the Kurata-Lindblad 1D model with no gradient in cell type (x 1 = +∞) and a gradient in electrical coupling (x 2 = 1.28 mm) normally exhibits pacemaking but no driving of the atrial muscle (see Fig. 2A) - introduction of a gradient in gNa (red trace in top left panel) alone, without changes in other ionic conductances, enables the SAN to drive the atrial muscle. B, the Kurata-Lindblad 1D model with appropriate gradients in both cell type and electrical coupling (x 1 = 1.2 mm, x 2 = 1.28 mm) exhibits physiological behaviour (pacemaking and driving of atrial muscle; see Figs. 2A and 4A) - elimination of the gradient in g Na (red trace in top left panel) alone from this model, without changes in other ionic conductances, results in a failure to drive the atrial muscle. Left, membrane potential of all cells. Right, C m (top), g j (second panel), activation and repolarization time (open and filled symbols, respectively; third panel) and safety factor (bottom) along length of model. Arrow, leading pacemaker site.