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Blood doesn’t automatically flow through your heart

Your heart has its own electrical conduction system that powers it to pump blood. If you’ve ever had a heart test called an electrocardiogram (ECG), then you may have seen your heart’s electrical activity on a graph.

Your heart’s electrical system is made up of three main parts:

  • The sinoatrial (SA) node
  • The atrioventricular (AV) node
  • The His-Purkinje system.

A heartbeat is one cycle in which your heart’s ventricles relax (diastole) and squeeze (systole) to pump blood. This cycle includes the opening and closing of the valves of your heart.

When your heart’s ventricles relax, blood flows from the atria to the ventricles. Your heart’s atria squeeze and pump blood into the ventricles. The atria then relax. Your heart’s ventricles then squeeze, pumping blood out of your heart.

The conduction cycle

In a normal, healthy heart, each heartbeat begins from the SA node in your heart muscle. This node acts as your heart’s own in-built pacemaker. Your heart rate is the number of signals the SA node produces per minute.

Powering the heart to pump

  1. The SA node sends out an electrical signal
  2. The signal makes cells in the atria squeeze, pumping blood into the ventricles
  3. The signal travels to the AV node and slows briefly to allow your ventricles to fill with blood
  4. The signal follows a pathway called the Bundle of His down through the Purkinje fibres to your ventricles
  5. The signal makes cells in the ventricles squeeze, pumping blood out of the heart
  6. The ventricles relax and wait for the next signal.
Did you know?

The heart pumps, on average 4-6 litres of blood around the body every minute!

I never thought much about my heart but now I know it is my engine.Keith
Everything is dependent on my heart, mechanically, electrically, physiologically, emotionally and passionately. Whatever happens it all comes back to how well your heart performs in all areas.Helen Thompson-Carter
Helen Thompson-Carter