Your Heart's Electrical System
Did you know that your heart has an electrical system? It is a bit like the electrical wiring in your home. The heart's electrical system creates the signals that tell your heart when to beat. And your heartbeat is what pumps blood throughout your body. The heart's electrical system is also called the cardiac conduction system.
Parts of the Electrical System
Your heart's electrical system includes three important parts:
S-A node (sinoatrial node) — known as the heart's natural pacemaker, the S-A node has special cells that create the electricity that makes your heart beat.
A-V node (atrioventricular node) — the A-V node is the bridge between the atria and ventricles. Electrical signals pass from the atria down to the ventricles through the A-V node.
His-Purkinje system — the His-Purkinje system carries the electrical signals throughout the ventricles to make them contract. The parts of the His-Purkinje system include:
o His Bundle (the start of the system)
o Right bundle branch
o Left bundle branch
o Purkinje fibers (the end of the system)
Electrical Signals and Blood Flow
The S-A node normally produces 60-100 electrical signals per minute — this is your heart rate, or pulse. With each pulse, signals from the S-A node follow a natural electrical pathway through your heart walls. The movement of the electrical signals causes your heart's chambers to contract and relax.
In a healthy heart, the chambers contract and relax in a coordinated way, or in rhythm. When your heart beats in rhythm at a normal rate, it is called sinus rhythm.
When working well, your conduction system automatically responds to your body's changing need for oxygen:
When you climb stairs, carry heavy groceries, or take a walk, you need more oxygen; therefore, your heart beats at a faster heart rate.
When you are sitting or sleeping, you need less oxygen; therefore, your heart beats at a slower rate.
Your conduction system senses your need for oxygen and responds with the proper heart rate.
A problem in your heart's electrical system can disrupt your heart's normal rhythm. Any kind of abnormal rhythm or heart rate is called an arrhythmia. It is normal and healthy for your heartbeat to speed up or slow down during the day as your activity level changes. But it is not normal for your heart to beat out of rhythm. When your heart beats out of rhythm, it may not deliver enough blood to your body.
Play the animation to see the cardiac cycle in action. You'll see blood flow plus the movement of the heart's chambers and valves.
You can click the Step Through button repeatedly to see the animation play one step at a time.
Next: When Your Heart Has Problems >>