Florida State Paramedic Practice Exam

The term 'automaticity' in cardiac physiology refers specifically to the heart's intrinsic ability to generate its own electrical impulses without requiring external stimuli. This property is primarily associated with the pacemaker cells found in the sinoatrial (SA) node, which discharges electrical signals at regular intervals. These impulses initiate the contraction of the heart muscle, allowing it to maintain a natural rhythm.

Automaticity is crucial for the normal functioning of the heart, ensuring that it can continue to beat and pump blood efficiently, even in the absence of nervous system input. While other aspects, such as rhythmic contraction and the heart rate, are related to cardiac function, they do not define automaticity. External electrical stimulation pertains to how the heart responds to external signals rather than its ability to generate impulses independently. Thus, the correct understanding of automaticity emphasizes the heart's self-sufficiency in generating these electrical impulses.