exploring how electricity travels inside the heart, from the SA node (the boss) to the AV node (the gatekeeper), all the way through the His-Purkinje system (the super-speed delivery team).

Then we jump into the science behind action potentials in different cardiac cells — pacemaker cells and non-pacemaker cells — explaining every phase (0, 1, 2, 3, 4) in a way that even your mitochondria will understand.:

How Na⁺, K⁺, and Ca⊃2;⁺ ions move across the membrane through specialized channels

Why pacemaker cells don’t behave like ventricular cells

How depolarization and repolarization actually happen

What determines heart rhythm — and how it goes wrong

The key differences in action potentials in SA/AV nodes vs. atrial/ventricular myocytes


And finally—
We put it all together as we decode the ECG: