Your Heart


Lt Col Reynolds
Your heart’s job is to circulate blood throughout your body in order to supply oxygen and nutrients to all your organs and tissues. Let’s hear from Dr. Patel to learn how the heart accomplishes such a big job.

Dr. Patel
A healthy heart is a muscle about the size of an average adult fist. Every time your heart beats, it contracts, sending blood into your arteries. Blood returns to your heart through your veins.

Your heart has four chambers: the right and left atria, and the right and left ventricles. The atria are the upper chambers, and they receive blood that is being returned to the heart. The right atrium receives blood low in oxygen because it receives blood that has just circulated throughout your body releasing oxygen and delivering nutrients. The left atrium fills with newly oxygenated blood returning from your lungs. When the atria pump, they push the blood through one-way flaps called valves into the relaxed ventricles. When the ventricles contract, the right ventricle pumps blood to your lungs. The left ventricle pumps blood through the aorta to the rest of the body. It also supplies blood to the heart muscle itself through the coronary arteries.

Your heart is controlled by its own electrical system. Each beat of your heart starts with an electrical signal from the sinoatrial, or SA, node in the right atrium. The signal causes the atria to contract and push blood into the ventricles. This electrical signal then travels through a series of nodes and fibers into the cells of the ventricle walls, causing the ventricles to contract and send blood to your lungs and the rest of your body.

Your pulse is the number of signals produced by the SA node per minute. When you’re resting, your pulse is approximately 60 to 100 beats per minute. When you exercise, your muscles require more oxygen and nutrients to work harder, so your heart beats faster and your pulse goes up.