ABSTRACT
Various types of K+ channels drive cell membrane repolarization. e transient outward currents (Ito, Figure 39.1c, and ICl(Ca)), carried by K+ and Cl−, respectively, determine the early AP repolarization (notch) that follows the upstroke, whereas the components of the delayed rectier K+ current (IKr and IKs, Figure 39.1c) contribute to AP repolarization. e inward rectier current (IK1, Figure 39.1c) maintains and stabilizes the resting potential. Another important player in shaping cardiac AP properties is the Na+/K+ pump (NKA), which generates an outward current (Figure 39.1d) by extruding three Na+ ions and importing two K+ ions on each cycle and contributes to AP repolarization.
