Our heart is a pump. As it performs its pumping action, it sends blood to the entire body, thus enabling us to live. A heart-beat* is the contracting and relaxing of the heart. A human heart-beats around 60-100 times per minute approximately 1,00,000 times per day. As the heart contracts, blood is pumped out and when it relaxes, new blood enters the heart. A small electric impulse generated by the natural pacemaker present in the heart is what makes the heart-beat. There are two natural pacemakers present in the heart: the SA node which helps contract the atria and the AV node which helps control the contraction of ventricles. These pacemakers are the lifelines of the heart.