Phase 0: rapid depolarisation
- Ion movement: Na+ in
- Ion channels:
- via Fast voltage gated Na channels
- L-type Ca channels open
- Kir K+ channels closed
- Inhibited by tetrodotoxin
Phase 1: early repolarisation
- Ion movement: K+ out, Cl out
- Ion channels:
- fast voltage gated chanenls close
- Kv K+ channels open
- Na/Ca exchanger open
- Ion movement: Ca in, K+ out
Phase 3: final repolarisation
- Ion movement: K+ out
- Ion channels:
- K+ channels open
- Ca channels close
Resting potential is then restored by Na/K ATPase
- ↑ intracellular Na ⇒ ↓ Na-dependent Ca transport out of myocyte ⇒ ↑ intracellular Ca ⇒ ↑ inotropy
