Fig. 5.

Simulated action potential and ionic currents of SA node cells. Simulated action potential and changes in I_Kr current, I_CaL current, and sum of I_Kr and I_CaL accompanying the spontaneous action potential are indicated. BCL of the action potential was 382 ms, which was shorter than that of early embryonic ventricular cells (492 ms). The MDP was approximately the same in the SA node cells (−62.17 mV) and early embryonic ventricular cells (−62.86 mV). The overshoot was 16.14 mV in the SA node cells: this value was more positive than that in the early embryonic ventricular cells (3.13 mV)