Which of the following is NOT a component of the cardio-electro-conductive pathway?

• A. Sinoatrial node
• B. Atrioventricular node
• C. Bundle of His
• D. Left atrial appendage

Answer: (D)

The electrical conduction system coordinates heart rhythm through specialized tissue: the sinoatrial node sets the pace, the atrioventricular node controls the delay between atrial and ventricular contraction, and the His-Purkinje pathway (bundle of His, bundle branches, and Purkinje fibers) carrying impulses to the ventricles. The left atrial appendage, however, is an anatomical extension of the left atrium that does not generate or transmit electrical impulses. It participates in atrial contraction as part of the atrial anatomy and is notable as a potential site for thrombus in atrial fibrillation, but it does not belong to the conduction pathway. That’s why it’s not a component of cardio-electro-conductive tissue.