Biology of the Heart
The heart is a hollow organ made of muscle. The heart and blood vessels are part of your cardiovascular system.
Your heart pumps blood through your blood vessels
Blood carries oxygen and nutrients to all parts of your body
Your heart has to beat constantly through your whole life and never gets a rest
Every minute, your heart beats about 70 times and pumps about 1 gallon (4 liters) of blood. Your heart beats faster and pumps harder during exercise, when your body needs more oxygen. When you check your pulse, you're measuring your heart rate, or the number of beats per minute.
Blood traveling through your body delivers oxygen and nutrients to tissues and organs. Waste from those tissues and organs is carried by blood to the lungs and kidneys for removal from the body.
The heart is a pump for blood. It's actually 2 pumps connected together—one on the right side of the heart and one on the left side.
In order to pump blood, your heart has:
The heart has 4 compartments (chambers), two on the right and two on the left. The chambers of your heart relax, fill with blood, and then contract to pump the blood out.
Your heart has 4 valves that control the flow of blood. The valves open to let blood out of one chamber and into the next chamber or blood vessel. The valves close to keep blood from flowing backward into the wrong chamber.
When you put your head on someone's chest and listen to their heartbeat, you're hearing the sound of the heart valves opening and closing.
Your heart should always have a regular, rhythmic beat, like the ticking of a clock:
There are special pacemaker cells in a part of your heart called the SA node. The pacemaker cells have their own natural rhythm of 60 to 100 signals per minute. Nerves from your brain can send messages to the cells telling them to speed up or slow down.
Your heart's conduction system has tiny strips of tissue sort of like electrical wires. The conduction system carries the pacemaker signals to the rest of your heart. The conduction system includes a gateway called the AV node. The AV node controls how signals pass from the upper chambers of your heart (atria) to the lower chambers (ventricles). When the conduction system is working properly, the signals get to each of your heart muscle cells at just the right time. Your heart then gives a good, strong beat that pumps blood properly.
Tracing the Heart's Electrical Pathway
Like all muscles, the heart needs a steady supply of blood to work. You might think that, because the heart is full of blood, it doesn't need a separate blood supply. However, blood that pumps through the heart doesn't feed the heart muscle. Instead the heart muscle is fed by its own blood vessels.
Coronary is a word for heart.
You can have problems with any part of your heart: