Where are the pacemaker cells located in the heart?

Inner wall of the right atrium, both ventricles and septum

The pacemaker cells of the heart with location are:

Sinoatrial node (SA node): Wall of the right atrium near the opening of the superior vena cava

Atrioventricular node (AV node): Between the left atrium and the right ventricle within the atrial septum

Bundle of His: Along the interventricular septum

Purkinje fibers: In the inner ventricular walls of the heart, just beneath the endocardium