BASICS OF THE HEART
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THE HEART'S ELECTRICAL CIRCUITRY. Have you ever wondered what makes your heart beat, automatically, hour after hour, day after day, year after year, for your entire life? Your heart is an amazing, self-contained, living machine. It works entirely on it's own, without any outside help. It is simply a pump, a pump that re-circulates your blood throughout your body. On one hand it is awesomely simple, but on the other hand it is simply awesome. It's apparent simplicity is actually very complicated. When it is functioning properly, you don't even know it is there but, when it malfunctions, it can cause many different life threatening situations, which can make you so aware of it, that it can become the center of your universe. One of those heart malfunctions is "atrial fibrillation" commonly referred to as, "AFib, or simply AF." It is caused by a malfunction of the heart's electrical system. First, let's see how the heart functions normally and then discuss what happens when AF occurs. Like all pumps, the heart requires a source of energy in order to function. The heart's pumping energy comes from a built-in, electrical, conduction system. Your heart rate, (how many beats per minute), is determined by a simple electrical circuit, controlled by two parts of the heart, the sinoatrial node (SA node) and the atrioventricular node (AV node). |
| STEP 1. The Sinoatrial Node (SA node), the natural pacemaker of the heart, generates an electrical signal. |
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| STEP 2. The electrical signal follows natural electrical pathways, through both atrial chambers, the upper chambers of the heart.
The electricity flowing through those muscles, cause the atrial chambers to contract, which pushes blood into the ventricle chambers, the lower chambers of the heart. |
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| STEP 3. The electrical signal reaches the AV node (the hearts electrical regulator).
There, the signal pauses to give the ventricles time to fill with blood. |
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| STEP 4. After the AV nodes delay time, the electrical signal spreads through the ventricle chambers, the lower chambers of the heart.
The electricity flowing through these muscles cause the ventricles to contract and push blood out to your lungs and body. |
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HEART RATE Your heart rate, how many beats per minute, depends on how long, or short, the Atrioventricular Node (AV node) delays the electrical signal, before sending it to the, ventricle chambers, the lower chambers of the heart. Although the Sinoatrial Node (SA node) creates the electrical impulse that causes the heart to beat, other nerves can change the rate at which the SA node fires and the how strongly the heart contracts. These nerves are part of the Autonomic Nervous System. The Autonomic Nervous System has two parts, (1) the Sympathetic Nervous System, which increases the heart rate and increase the force of contraction and (2) the Parasympathetic Nervous System, which decreases the heart rate and decrease the force of contraction. |
DIFFERENT NORMAL HEART RATES,
DETERMINED BY THE AV NODES DELAY TIME
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SLOW HEART RATE |
MEDIUM HEART RATE |
FAST HEART RATE |
DETAILS OF HOW THE HEART WORKS
The"HeartBasics" picture below is like an interactive minature web page.
It explains all the functions and parts of the heart.
Click on a button, named for the specific function, or parts of the heart
that you wish to see.
The picture will change to show that function or those parts of the heart.
On the new picture, place your mouse pointer over the button that
describes the function or part of the heart that you want to show.
NOTE: To go back to the original "menu" picture,
click on the "back to main page" button.