Pulse generatorThe sealed case. It makes the electrical pulses.
BatteryThe power source, sealed inside the pulse generator.
LeadA thin wire that carries the pulses to the heart.
ElectrodeThe tip of a lead. It senses the heartbeat and delivers pulses.
In the heart 4
VeinThe leads run inside a vein to reach the heart.
Right atriumThe upper right chamber. One lead ends here.
Right ventricleThe lower right chamber. The other lead ends here.
Sinoatrial nodeThe heart's own pacemaker. Each heartbeat signal starts here.
How this list was compiled: Every name checked on 2026-10-02, a name kept only where two of these use it: (1) National Heart, Lung, and Blood Institute (NIH), Pacemakers: How They Work, https://www.nhlbi.nih.gov/health/pacemakers/how-it-works (three main parts: a pulse generator that creates the electrical pulses, wires also called leads, implanted inside the veins, and electrodes that sense the heartbeat and deliver impulses; the generator is placed outside the heart and is connected by wires to electrodes inside one to three heart chambers; single-lead and double-lead pacemakers send pulses to the right side of the heart; the right atrium and the right ventricle), and How the Heart Beats, https://www.nhlbi.nih.gov/health/heart/heart-beats (the signal begins in pacemaker cells in the sinoatrial node in the right atrium); (2) MedlinePlus (US National Library of Medicine), Heart pacemaker, https://medlineplus.gov/ency/article/007369.htm (the generator contains the battery; the leads are wires from the heart to the generator; the generator is placed under the skin of the chest below the collarbone; the leads go into a vein and on into the heart); (3) Wikipedia, Pacemaker, text only, https://en.wikipedia.org/wiki/Pacemaker (a pulse generator, a sealed device with a battery; electrodes; leads placed through a vein to reach the right atrium; right atrial and right ventricular leads; the sinoatrial node as the natural pacemaker); (4) University of Rochester Medical Center, Health Encyclopedia, https://www.urmc.rochester.edu/encyclopedia/content?contenttypeid=92&contentid=P07980 (a pacemaker is made of three parts: a pulse generator, at least one lead, and an electrode per lead; usually implanted in the chest, just under the collarbone). Licence: own work
The drawing: Drawn for this site on 2026-10-01 from plain geometry; nothing traced. Licence: own work
How it works
This diagram of pacemaker in heart gives names only. One drawing shows the device: pulse generator, battery, lead and electrode. The other shows where its leads run inside the heart.
Read the full guide
The device
A pacemaker has a pulse generator, a sealed case that makes electrical pulses and holds the battery. One or more leads, thin wires, carry the pulses, and each lead ends in an electrode.
In the heart
In this heart pacemaker diagram two leads run inside a vein into the right side of the heart. One ends in the right atrium and the other in the right ventricle. The pacemaker of the heart itself is the sinoatrial node: a group of cells in the wall of the right atrium, where each heartbeat signal begins.
Right and left are the heart's own. The right chambers are on the left of the picture.
This page names parts only. It is not medical advice.
Questions and answers
What are the parts of a pacemaker?
A traditional pacemaker has three main parts: a pulse generator, which makes the electrical pulses and holds the battery; leads, the wires that carry the pulses; and electrodes at the ends of the leads.
Where do pacemaker leads go in the heart?
They run inside a vein into the right side of the heart. In a pacemaker with two leads, one lead ends in the right atrium and the other in the right ventricle.
What is the natural pacemaker of the heart?
The sinoatrial node, or SA node. It is a group of cells in the wall of the right atrium, and the electrical signal of each heartbeat begins there.
Where does the pulse generator sit?
Outside the heart, under the skin, most often in the chest below the collarbone. The drawing shows it at the upper right, joined to the heart by its leads.