Normal Heart Function
In order for the heart to do its work (pumping blood throughout the body), it needs a sort of spark plug or electrical impulse to generate a heartbeat. Normally this electrical impulse begins in the upper right chamber of the heart (in the right atrium) in a place called the sino-atrial (SA) node. The SA node is the natural pacemaker of the heart. The SA node gives off electrical impulses to generate a heartbeat in the range of 60 to 100 times per minute. If you are exercising, doing strenuous work or you are under a lot of stress, your heart rate may be faster. When you rest or sleep your heart rate will slow down. If you take certain medications, your heart rate may be slower. All of this is appropriate.
From the SA node, the electrical impulse is relayed along the heart’s conduction system. It spreads throughout both the right and left atria causing them to contract evenly.
When the impulse spreads over the right atrium it reaches the atrio-ventricular (AV) node. This is a very important structure in the heart because it is the only electrical connection between the top chambers and the bottom chambers. It is therefore the only way in which an electrical impulse can reach the pumping chambers (the ventricles). The impulse spreads through the AV node and down into the lower chambers or ventricles of the heart. This causes them to contract and pump blood to the lungs and body.
The heart is made up of four chambers. The top two chambers are call the Atria and the bottom two chambers are called the Ventricles.
The top and bottom chambers are separated by two valves the Tricuspid Valve and the Mitral Valve.
The Tricuspid Valve separates the Right Atrium from the Right Ventricle
The Mitral Valve separates the Left Atrium from the Left Ventricle
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The top and bottom chambers are separated by two valves the Tricuspid Valve and the Mitral Valve.
The Tricuspid Valve separates the Right Atrium from the Right Ventricle
The Mitral Valve separates the Left Atrium from the Left Ventricle
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1) The normal heart beats starts in the Sino-Atrial Node located in the Right Atrium. This acts as the spark plug to start the heart.
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The normal heart beats starts in the Sino-Atrial Node located in the Right Atrium. This acts as the spark plug to start the heart.
2) Electrical conduction then activates both atria and travels to a structure called the AV-Node. The AV node acts as the ‘gate keeper’ of all electrical impulses to the ventricles.
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2) Electrical conduction then activates both atria and travels to a structure called the AV-Node. The AV node acts as the ‘gate keeper’ of all electrical impulses to the ventricles.
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The normal heart beats starts in the Sinus Node located in the Right Atrium. This acts as the spark plug to start the heart.
Electrical conduction then activates both atria and travels to a structure called the AV-Node. The AV node acts as the ‘gate keeper’ of all electrical impulses to the ventricles.
3) After electrical conduction passes through the AV node it travels down the Left and Right Bundle Branches which activates the Ventricles and tells them to contract.
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Electrical conduction then activates both atria and travels to a structure called the AV-Node. The AV node acts as the ‘gate keeper’ of all electrical impulses to the ventricles.
3) After electrical conduction passes through the AV node it travels down the Left and Right Bundle Branches which activates the Ventricles and tells them to contract.
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The heart's normal contraction can be seen on the ECG. This ECG shows normal sinus rhythm and is made up of a series of waves called the P, QRS and T wave.
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Atrial activation is represented by the ‘P-Wave’ on the ECG.
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Ventricular activation is represented by the ‘QRS’ complex on the ECG. This normally takes less than 120 milliseconds.
During this time the Ventricles contract and blood is pumped from the heart to the lungs and through the aorta to the rest of the body.
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During this time the Ventricles contract and blood is pumped from the heart to the lungs and through the aorta to the rest of the body.
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The final wave is called the T wave. During this phase the Ventricles relax. This normally takes less than 450 milliseconds.
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