Electrical activity in the myocardial fibers | Atrial and ventricular muscle action potential
Channel: Decoded Medicine
Date: 2021-12-20

MCQs https://peerr.io/login?refId=drpriya07
Cell Membrane MCQs https://peerr.io/quiz/cell-physiology-cell-biology-eukaryotic-cell-human-cell Watch on 2x speed to save time:)
The atrial and ventricular muscle action potential is characterized by rapid depolarization (phase 0), initial rapid repolarization (phase 1), a plateau (phase 2), and a slow repolarization process (phase 3) that allows return to the resting membrane potential (phase 4).

Phase 0
The initial depolarization is due to Na + influx through rapidly opening Na+ channels (the Na+ current, I Na).
Phase 1
The inactivation of Na+ channels contributes to the rapid repolarization phase. 
Phase 2
Ca2+ influx through more slowly opening Ca2+ channels (the Ca2+ current, I Ca) produces the plateau phase
Phase 3
repolarization is due to net K+ efflux through multiple types of K+channels. 
Phase 4
Return to resting membrane potential

Recorded extracellularly, the summed electrical activity of all the cardiac muscle fibers is the electrocardiogram (ECG).