Cardiac Cycle

Atrial Systole

Sino-atrial node contracts and transmits electrical impulses throughout atria.

These contract and pump blood into ventricles

Ventricular Systole

Electrical impulse passes to ventricles via atrioventricular node, bundle of His and Purkinje fibres.

Fibres do not contract, but pass impulse to base of ventricles.

Ventricle contract shortly after atria, squeezing blood upwards into arteries


Atria and ventricles relax > atria filll with blood


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