In heart pumping action the atria and ventricle are contract rhythmically . The wave impulse of contraction begins every time from sa node  present in the right atrium. Which means the sa  node controls the heartbeat.  Pacemaker is the rhythmic center of pace activity.So it is known as natural pacemaker. In some cases the impulse conduction system is interrupted  , which  cause irregularity in heart beat like failure of receiving the atrial impulse by ventricle and the contraction and relaxation of atria and ventricles may change.such type of patients are provided with an artificial electronic device which is known as pacemaker. The artificial pacemaker can generate electrical pulses. . the pacemaker is placed in the upper thoracic region and having a connection with the heart. This pacemaker have a pulse generator and lithium battery. The pulse generator produces electrical pulses, a wire lead which transmits the impulse .