Myocardial cell action potentials have three phases: depolarization via Na+ influx, a plateau phase due to balanced Ca2+ influx and slow K+ efflux, and repolarization caused by Ca2+ channel closure and increased K+ efflux.
1. Depolarization by Na influx 2. Plateau phase is caused by Ca influx which matches slow efflux of K+ through some VG channels 3. Repolarization phase is due to closure of Ca channels and opening of many more K channels; exit of K ions repolarizes cell back to RMP <img src="paste-8d5e1df5d448be33b7690920ced776de888f5e4f.jpg"> <br>
| Front | What are the phases of AP in the myocardial cells? |
|---|---|
| Back | 1. Depolarization by Na influx 2. Plateau phase is caused by Ca influx which matches slow efflux of K+ through some VG channels 3. Repolarization is due to closure of Ca channels and opening of many more K channels; exit of K ions repolarizes cell back to RMP |
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