The heart is a muscle that has a very specific task in the body. To understand this task, it may be good to start with how a muscle works then proceed to the crucial job the heart does hundreds of times each day.
Muscles receive a signal from the brain, an electrical signal through the nervous system. This message essentially “orders” the muscle to contract. In the involuntary muscles such as the heart, the signal is sent automatically (we don’t have to think about it first). With a voluntary muscle, such as those used to lift, we consciously “tell” the muscle to do its work.
Now that we have established that the heart is one of the “involuntary” muscles we can understand that this muscle keeps us alive by contracting based on a signal sent by our brain. The muscle tissue of the heart acts like a pump to send blood through the blood vessels of the body. While this may seem like a simple process, there is much more to the heart and its work.
The human heart has four chambers or spaces within the overall structure. At the top or two atria, left and right. The bottom two chambers are called ventricles. Large blood vessels go into and out of each of these chambers.
When we breath oxygen comes into the lungs and the small blood vessels of the lungs. This “oxygenated” blood eventually is drawn into the heart by the expanding and contracting that takes place automatically. The oxygen is carried through the blood to all parts of the body. The blood is returned to the lungs by the pumping action of the heart and receives fresh oxygen during the breathing process.
At this point, it might be good to stop for a moment and visualize that the heart is a complex pump that sends blood out to the extremities of the body and brings it back to be refreshed in the lungs.
But how does the blood actually move through the heart? The blood that has left its oxygen in the other parts of the body comes back into the right side of the heart, into the right atrium. The blood goes through a valve into the right ventricle then out to the lungs.
The blood picks up oxygen in the lungs, which also expel the carbon dioxide into the atmosphere. Blood that is rich with oxygen comes into the left atrium, goes through the mitral valve into the left ventricle and then travels out into the body to deliver the new supply of oxygen. Within the heart, the valves between the atria and ventricles keep blood from flowing in reverse. The process continues many, many times each day throughout our lives. What we think of as our heartbeat is the pumping action of this very strong and important muscle.
The heartbeat is triggered by the involuntary electrical signals sent from the brain, as explained earlier. Think of the heart as the source of power for your life and you will begin to understand how the heart works.