Foundations

How Blood Pressure Is Controlled: Cardiac Output, Resistance & the Levers Drugs Pull

Every blood-pressure pill ever made pulls on one of just two levers — how hard the heart pumps, or how tight the vessels squeeze. Master a single equation and the entire cardiovascular pharmacy suddenly makes sense: you'll know why a water pill, a beta blocker, and a vessel-relaxer all lower the same number by completely different routes. This is the master map for everything that follows.

The Renin–Angiotensin–Aldosterone System (RAAS): The Body's Pressure Thermostat

Why does a common blood-pressure pill give some people a nagging dry cough? The answer is a single hormone cascade that the body uses to defend its blood pressure — and that four of the most important drug classes in medicine are built to block. Follow the chain from kidney to blood vessel and you'll understand hypertension, heart failure, and kidney protection all at once.

The Cardiac Action Potential, Pacemakers & the ECG

That steady beep on a hospital monitor is the sound of an electrical wave sweeping through the heart, sixty times a minute, for a lifetime. Understand the ion channels that make that wave — and the natural pacemaker that fires it — and every anti-arrhythmic drug becomes obvious: each one simply blocks one of those channels. This is the wiring diagram behind the entire rhythm section.