Physiology is the study of how living things work. While anatomy focuses on what body parts look like and where they're located, physiology asks: what do those parts actually do, and how do they do it?

A physiologist might study how your heart pumps blood through your body, how your stomach breaks down food, or how your brain sends electrical signals that make your muscles move. They investigate questions like: Why does your heart beat faster when you run? How do your lungs transfer oxygen from the air into your blood? What happens inside your cells when they turn food into energy?

Physiologists work like detectives, uncovering how the machinery of life operates. Some study human physiology, others focus on animals or plants. A plant physiologist might investigate how trees move water from their roots to their highest leaves, while an animal physiologist might study how desert creatures survive extreme heat.

When doctors understand physiology, they can figure out what's going wrong when someone gets sick. If you know how a healthy heart works, you can recognize what's different about a struggling one. That's why medical students spend years studying physiology before they ever treat patients.