FIGURE 1.
Characteristics of the fast sodium current (INa) of the Fabbri-Severi model of a human SA nodal pacemaker cell. (A) Steady-state activation and inactivation curves (blue and red curves, respectively) of INa (left) and associated “window” of overlap (shaded area) in the voltage range between -60 and -40 mV (right). (B) Current–voltage relationship of steady-state INa. (C) Effect of full block of INa in the absence of acetylcholine (ACh). Spontaneous action potentials (top) and associated net membrane current (Inet) and INa (bottom). Horizontal arrow indicates increase in cycle length. (D) Effect of full block of INa during simulated administration of 10 nM ACh. Spontaneous action potentials (top) and associated Inet and INa (bottom). Horizontal arrow indicates increase in cycle length.