Intrinsic cardiac factors originate from where?

• A. Originate in the brain
• B. Come from within the heart or damage to the heart itself.
• C. Arise from external parts such as the lungs
• D. Are external factors such as blood pressure

Answer: (B)

Intrinsic factors are generated by the heart itself—the heart’s own conduction system and myocardial tissue set the pace and rhythm. The heartbeat starts in the heart's electrical network, with the SA node acting as the natural pacemaker and signals traveling through the AV node and Purkinje system to coordinate contraction. When there’s damage or disease within the heart, such as ischemia, infarction, scar tissue, or dysfunction of the SA/AV nodes, these internal structures alter the rate or rhythm, independent of outside inputs. In contrast, factors from outside the heart—like brain-derived autonomic signals, lung conditions, or overall blood pressure—can modulate heart rate and force but do not originate the beat themselves.