Cardiac Action Potential Breakdown || EMS Cardiology

When tackling cardiac pharmacology 💊 (Na, K, Ca channel blockers, etc.) it is vital to have a basic understanding of cardiac 🫀 action potential and what is occurring within each phase. If you have a grasp on this, everything will begin to fall into place. Sooooo let’s talk about it!

Take a look at the illustration above and remember the following.

Phase 0 - Depolarization (aka contraction) occurs here and sodium channels open and Na rushes into the cell.

Phase 1 - Sodium channels close & Calcium channels open

Phase 2 - Calcium enters slowly & Potassium exits slowly causing a plateau

Phase 3 - Repolarization (aka relaxation) occurs as Calcium channels close & Potassium finishes exiting the cell.

Phase 4 - Potassium channels close and resting potential is achieved.

Also, don’t forget your cardiac basics.

P wave = Atrial depolarization (contraction)

QRS complex = Ventricular depolarization (contraction)

T wave = The end of ventricular depolarization and beginning of ventricular repolarization (relaxation)

U wave (if it’s there and not due to an electrolyte imbalance) = Most likely the repolarization of the purkinje fibers

🚨 Disclaimer: This is not meant to be used as or in the place of professional medical advice. 🚨

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