#physiology

7 articles

How Muscles Work: Pulling, Never Pushing

Why muscles can only pull and never push, how they work in antagonistic pairs like the biceps and triceps, and how contraction is filaments sliding past each other.

10 min read·Aug 28, 2026

Medicine

Hormones: The Body's Chemical Messengers

How hormones broadcast slow, body-wide chemical signals through the blood, why only cells with the right receptor respond, and how negative feedback keeps every level in range.

10 min read·Jul 28, 2026

Medicine

Blood Pressure and Circulation

Why a blood-pressure reading has two numbers, how elastic arteries smooth a pulsing heart into steady flow, and why a fourth-power law makes tiny vessels the body's master control valves.

9 min read·Jul 13, 2026

Medicine

The Kidney: The Body's Filter

The nephron filters almost everything out of the blood by size and pressure, then selectively reabsorbs the water and solutes the body needs — a design that lets one filter handle any waste, keeps the blood's chemistry steady, and sets the rate at which many drugs leave the body.

10 min read·Jul 11, 2026

Medicine

Breathing and Gas Exchange

How each breath is a passive physics problem: oxygen diffusing down a partial-pressure gradient across the alveolar membrane, loaded onto hemoglobin by an S-shaped curve built for delivery.

10 min read·Jul 10, 2026

Medicine

Glucose and Insulin: A Feedback Loop

Blood glucose stays inside a startlingly narrow band whether you have just eaten or not eaten for a day. The reason is a negative feedback loop with a sensor, a controller, and an effector — and diabetes is what happens when different parts of that loop fail.

10 min read·Jul 8, 2026

Medicine

How the Heart's Electrical Signal Works

The electrical pulse that makes your heart beat — traced from origin to muscle contraction.

8 min read·Feb 8, 2025