Ventricular action potential | Ionic basis | Cardiovascular physiology

 Phases of ventricular action potential and its ionic basis

Stable resting membrane potential (phase 4)

Phase of rapid depolarisation (phase 0): Due to opening of voltage gated sodium channels and entry of sodium inside the cells

 Phase of early rapid repolarisation (phase 1): Due to opening of voltage gated potassium channels and exit of potassium outside the cells

 Plateau phase (phase 2) where there is hardly any change in potential: Both voltage gated potassium channels and voltage gated calcium channels are open. Potassium moves out of the cells while calcium moves into the cells. This balances the potenetial and the potential is recorded as a plateau.

Phase of delayed rapid repolarization (phase 3): Calcium channels close while potassium channels remain open. Potassium continues to moves out of the cells causing repolarization.

Total duration of ventricular action potential is approximately 250 ms.