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Heart's Electrical System
The muscular pumping action of the heart is triggered by electrical signals which are sent through the heart muscle telling it when to contract and relax.
The electrical signal starts in the right atrium where the heart's natural 'pacemaker', called the sino–atrial node, is situated. This signal crosses the atria, making them contract. Blood is then pumped through the valves into the ventricles.
Where the atria meet the ventricles there is an area of special cells, called the atrio–ventricular node.
These cells act as a 'junction box' and pass the electrical signals throughout the heart muscle by a system of electrical pathways, known as the conducting system.
This makes the muscles of the ventricles contract. Blood is then pumped through the pulmonary and aortic valves into the main arteries.
The 'pacemaker' produces another electrical signal and the cycle starts again.
What can go wrong with the electrical system?
Normally the heart will beat between 60 – 80 times per minute. This regular rhythmic beating is dependent upon electrical signals being conducted throughout the whole heart.
If the electrical signals within the heart are interrupted, or disturbed, the heart can beat too quickly (tachycardia), too slowly (bradycardia) and / or in an irregular way. This is called an arrhythmia.
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