Which heart structures contain pacemaker cells?

Which heart structures contain pacemaker cells?

• A. Atrioventricular nodes only
• B. Sinoatrial and atrioventricular nodes
• C. Purkinje fibers
• D. Bundle of His

Answer: (B)

Pacemaker cells are specialized heart cells that automatically generate electrical impulses, setting the heart’s rhythm. The structures that contain these pacemaker cells are the sinoatrial node, the natural primary pacemaker located in the right atrium, and the atrioventricular node, which also has pacemaker cells and can take over if the SA node fails, though at a slower intrinsic rate. Purkinje fibers and the Bundle of His are mainly conduction pathways, designed to rapidly transmit the impulse rather than start it. So the two nodal tissues—SA node and AV node—are the ones with pacemaker cells.

Pacemaker cells are specialized heart cells that automatically generate electrical impulses, setting the heart’s rhythm. The structures that contain these pacemaker cells are the sinoatrial node, the natural primary pacemaker located in the right atrium, and the atrioventricular node, which also has pacemaker cells and can take over if the SA node fails, though at a slower intrinsic rate. Purkinje fibers and the Bundle of His are mainly conduction pathways, designed to rapidly transmit the impulse rather than start it. So the two nodal tissues—SA node and AV node—are the ones with pacemaker cells.