Natural Cardiac Pacemaker And Electrical Mechanism Of The Heart

The heart has its own natural cardiac pacemaker responsible for regulating its own heart beats.


This pacemaker is called the SA node (sinus node). It generate its own electricity and it is located in the upper portion of the right atrium.

Sequence of electrical impulses
The electrical impulses start at the SA node and travel to the right and left atria causing them to contract. This contraction allows the atria to empty blood to the ventricles. (P wave in the ECG rhythm strip)



The electrical impulses travels to the AV node (atrioventricular node) which its delayed for a brief moment. This delay is to allow the atria to finish emptying. (The AV node sits just above the ventricles). (PR interval)

The electrical impulses continue to travel down both ventricles via electrical pathways called the right and left bundle branches allowing them to contract pumping the blood into the pulmonary artery and the aorta. (QRS complex)

Electrical System Of The Heart
Electrical System Of The Heart(1)


The ST segment and the T wave are generated when the ventricles recover and the cycle starts all over.



1. MoonDragon, "Common heart problems and procedures." http://www.moondragon.org/health/disorders/cardioproblems.html. Accessed December 7, 2008



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