Figure 2.

Major currents participating in the action potential (AP) plateau. Late I_Na is very effective at modulating the action potential duration (APD) because the other participating currents are relatively small and balance each other out, increasing membrane resistance and reducing the magnitude of dV_m/dt_max.¹⁴² Representations of the cardiac Na⁺ current (I_Na), the L-type Ca²⁺ channel (I_Ca,L), the rapid and slow delayed rectifier K⁺ channels (I_Kr and I_Ks), the inward rectifier K⁺ channel (I_K1), and current generated by the Na⁺-Ca²⁺ exchanger are shown during the AP.