Cardiac Arrhythmias: Difference between revisions

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===Phase 1: Early Rapid Repolarization===
===Phase 1: Early Rapid Repolarization===
Immediately following rapid depolarization, the inactivation of the Na<sup>+</sup> channel (I<sub>Na</sub>) and subsequent activation of the outward K<sup>+</sup> channel (I<sub>to</sub>) and the Na<sup>+</sup>/Ca<sup>2+</sup> exchanger (I<sub>Na,Ca</sub>), which exchanges 3 Na<sup>+</sup> for 1 Ca<sup>2+</sup>, produces a early rapid repolarization. Due to the limited role of the Na<sup>+</sup> channel in the upstroke of sinus node and AV node cells and the subsequent slower depolarization, this rapid repolarisation is not visible in their action potentials (Figure 2).
Immediately following rapid depolarization, the inactivation of the Na<sup>+</sup> channel (I<sub>Na</sub>) and subsequent activation of the outward K<sup>+</sup> channel (I<sub>to</sub>) and the Na<sup>+</sup>/Ca<sup>2+</sup> exchanger (I<sub>Na,Ca</sub>), which exchanges 3 Na<sup>+</sup> for 1 Ca<sup>2+</sup>, produces a early rapid repolarization. Due to the limited role of the Na<sup>+</sup> channel in the upstroke of sinus node and AV node cells and the subsequent slower depolarization, this rapid repolarization is not visible in their action potentials (Figure 2).


===Phase 2: Plateau===
===Phase 2: Plateau===
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