Homeostasis is your body’s natural ability to maintain a stable internal environment. When conditions are not in equilibrium (a steady state), your body will fight to fix it. For example, when your body is in an environment that is too cold, it shivers as a physical attempt to warm you up.

Your heart maintains homeostasis, too. It has the important job of pumping oxygenated blood to all of the other organs. If stress is added to your body, then your heart will try to compensate by beating faster to pump more blood. This explains why your heart rate increases when you are frightened. Your body perceives danger and immediately tries to increase blood flow to help you survive.

You can feel your heart rate at various points on your body. These are known as pulses. The two easiest pulses to feel are on your neck (carotid) & on your wrist (radial). In this lab, you will calculate your pulse before and after exercising by counting how fast your heart beats per minute. If your heart beats 100 times in 1 minute, then your pulse is 100 bpm (beats per minute).