How the Healthy Heart Works
What Are the Coronary Arteries?
Like all organs, your heart is made of tissue that requires a supply of oxygen and nutrients. Although its chambers are full of blood, the heart receives no nourishment from this blood. The heart receives its own supply of blood from a network of arteries, called the coronary arteries.
Two major coronary arteries branch off of the aorta close to the area where the aorta is connected to the left ventricle.
Right coronary artery: The right coronary artery supplies the right atrium and right ventricle with blood. It branches into the posterior descending artery, which supplies the bottom portion of the left ventricle and back of the septum with blood.
Left main coronary artery: The left main coronary artery branches into the circumflex artery and the left anterior descending artery. The circumflex artery supplies blood to the left atrium and the side and back of the left ventricle while the left anterior descending artery supplies the front and bottom of the left ventricle and the front of the septum with blood.
These arteries and their branches supply all parts of the heart muscle with blood.
How Does the Heart Beat?
The atria and ventricles work together, alternately contracting and relaxing to pump blood through your heart. The electrical system of your heart is the power source that makes this possible.
Your heartbeat is triggered by electrical impulses that travel down a special pathway through your heart.
- The impulse starts in a small bundle of specialized cells called the SA node (sinoatrial node), located in the right atrium. This node is known as the heart's natural pacemaker. The electrical activity spreads through the walls of the atria and causes them to contract.
- A cluster of cells in the center of the heart between the atria and ventricles, the AV node (atrioventricular node) is like a gate that slows the electrical signal before it enters the ventricles. This delay gives the atria time to contract before the ventricles do.
- The His-Purkinje Network is a pathway of fibers that sends the impulse to the muscular walls of the ventricles, causing them to contract.
At rest, a normal heart beats around 60 to 80 times a minute. Exercise, emotions, fever, and some medications can cause your heart to beat faster, sometimes to well over 100 beats per minute.