AEMCA Practice Exam

What initiates each heartbeat in a normal heart?

1. External nerve impulses

2. Intrinsic electrical impulses

3. Hormonal signals

4. Mechanical stimulation

The correct answer is: Intrinsic electrical impulses

The initiation of each heartbeat in a normal heart is primarily due to intrinsic electrical impulses. The heart has its own specialized electrical conduction system, which includes the sinoatrial (SA) node, also referred to as the natural pacemaker of the heart. The SA node generates electrical impulses that spread through the heart muscle, causing the heart to contract and pump blood. These intrinsic impulses are crucial as they ensure that the heart beats in a coordinated and rhythmic manner. The autonomic nervous system can influence the heart rate by sending external signals, but it does not initiate each heartbeat; the SA node performs this vital role independently. Hormonal signals can also affect heart function and rate but do not initiate the heartbeat itself. Mechanical stimulation of the heart muscle does not serve as the primary trigger for heartbeats either. The intrinsic nature of the electrical impulses generated by the SA node is what fundamentally controls the heartbeat in a normal functioning heart.