Your heartbeat is a sign of life itself. Even when you drift off to sleep, your heart continues to beat at a steady rhythm. Why is this process so important that it must keep going even when you sleep?

Each breath you take brings air into your respiratory system. The oxygen in that air is needed by the trillions of cells in your body. Your heart is essential in delivering that oxygen. Its beating produces the force to move oxygen-rich blood through the circulatory system. Interrelationships between the circulatory and respiratory systems supply cells throughout the body with the nutrients and oxygen they need to stay alive.