Final answer:
The heart of a brain-dead patient continues to beat because it has its own electrical system that can function independently of brain activity. Life support systems play a crucial role in maintaining circulatory function, allowing a window for organ donation, specifically heart transplants.
Step-by-step explanation:
The heart of a patient who is 'brain-dead' can still beat because the heart has its own intrinsic electrical system, capable of maintaining a beat independent of the brain's function. Brain death occurs when there is irreversible loss of all functions of the brain, including the brainstem, but the heart can continue to function with the help of life support systems that provide oxygen and circulate blood. Brain death can be a sensitive and complex situation, as seen in the cases of Terri Schiavo and others, which raise ethical, legal, and medical questions about life support and organ donation. Patients who are declared brain-dead can be potential organ donors, specifically for heart transplants. The heart must be harvested within a limited time frame after declaration of death due to the importance of maintaining viability. Circulatory functions can be artificially supported even when there is no brain activity, providing a window for organ transplantation. This procedure is crucial for saving other lives, but it involves careful medical and ethical considerations.