An electrical impulse originating anywhere other than the SA node is called what?

• A. SA Node
• B. AV Node
• C. Anywhere other than SA Node
• D. Purkinje fibers

Answer: (C)

When the heart’s electrical impulse starts somewhere other than the sinoatrial (SA) node, that site is called an ectopic pacemaker (or ectopic focus). The SA node is the normal pacemaker, so impulses from other parts of the conduction system—such as the AV node, Purkinje fibers, or other myocardial tissue—are considered ectopic. That’s why describing the origin as “anywhere other than the SA node” is the right concept: it captures the idea of pacemaking arising outside the SA node. The other terms name specific structures or simply restate the normal pacemaker, but they don’t define the concept of pacing coming from outside the SA node.