The heart-A2 salters nuffield

how electrical impulses pass through the heart, initiating contraction of the atria and then the ventricles.

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route taken by electrical impulses

Electrical impulses from the SINOATRIAL NODE (SAN) spreads across the atria walls causing contraction.

Impulses pass to the ventricles via the ATRIOVENTRICULAR NODE (VAN).

Impulses pass down the PURKYNE FIBRES to the heart apex.

The impulses spread up through the ventricle walls causing contraction from the apex upwards. Blood is squeezed into the aorta and pulmonary arteries.





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When the impulse travels to the AVN, the impulse is conducted to the ventricles after a delay of about 0.13 seconds.

It is important that the impulse is delayed because the delay ensures that the atria have finished contracting and that the ventricles have filled with blood before they contract.

The purkyne fibres conduct impulses RAPIDLY to the apex (tip) of the ventricles. Right and left fibres and together are called the BUNDLE OF His.

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