Fig. 1.

The coupled V_m/Ca²⁺-oscillator system in SAN cells and its modulation by the mechanical environment. SAN (A) V_m and (B) intracellular free Ca²⁺ concentration ([Ca²⁺]_i) under normal conditions (solid line) and during stretch (dashed line). Time intervals of spontaneous DD and spontaneous Ca²⁺ release (CR) are indicated. (C) ‘Standard’ transmembrane ionic currents associated with the V_m/Ca²⁺-oscillator system. Shaded currents (I_f, I_Ca,T) and the SAC_NS current (I_SAC,NS) refer to the 20 pA scale, while solid currents (I_NCX, I_Ca,L, I_K) refer to the 200 pA scale. V_m, [Ca²⁺]_i, and ionic currents generated from (Maltsev and Lakatta, 2008), except for I_SAC,NS, which is from (Cooper et al., 2000), and stretch-induced increases in I_f (I_f,stretch) and I_Ca,L (I_Ca,L,stretch), which represent theoretical predictions.