Final answer:
Pacemakers are devices that deliver electrical impulses to the heart muscle to ensure it contracts properly, thereby treating arrhythmias. They can be programmed to stimulate the heart continuously or upon demand and adjust heart rate in response to physical activity.
Step-by-step explanation:
Pacemakers function by delivering electrical impulses to the heart muscle, ensuring that the heart continues to contract and pump blood effectively. These devices are typically used to treat arrhythmias when the heart's rhythm becomes abnormal. Pacemakers have sensors that detect the body's activity level and adjust the heart rate accordingly. For instance, during exercise, when the body needs more blood and oxygen, the pacemaker will increase the heart rate to meet this demand.
The autonomous beating of cardiac muscle cells is regulated by the heart's internal pacemaker via electrical signals. The internal pacemaker starts at the sinoatrial (SA) node and the signal then spreads to the atria, causing them to contract, before being delayed at the atrioventricular (AV) node and finally causing the ventricles to contract. Artificial pacemakers mimic this natural process and can be programmed to provide stimulation both temporarily or continuously, depending on the patient's needs. Some pacemakers also include defibrillators to address serious arrhythmias that can cause the heart to stop.