During exercise, the cardiovascular system must supply muscles with large amounts of oxygen and fuel and get rid of a lot of wastes. How do the cardiovascular systems of athletes respond to prolonged exercise? Athletes are not the only people with enlarged hearts. Many patients with cardiovascular disease also have enlarged hearts. Suggest a cause of this enlargement.

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1. 1. During prolonged exercise, the cardiovascular system of athletes responds by increasing the heart rate and stroke volume. This is to ensure that more blood, and therefore more oxygen and nutrients, are delivered to the working muscles. The blood vessels in the muscles also dilate to allow for increased blood flow. Additionally, the body increases its rate of respiration to take in more oxygen and expel more carbon dioxide, a waste product of cellular respiration.
2. 2. The heart, like any other muscle, adapts to the increased workload by becoming larger and stronger. This is known as cardiac hypertrophy. In athletes, this is a healthy adaptation as it allows the heart to pump more blood with each beat, increasing the efficiency of oxygen and nutrient delivery to the muscles.
3. 3. However, in patients with cardiovascular disease, an enlarged heart, or pathological cardiac hypertrophy, is often a sign of an underlying problem. This could be due to high blood pressure (hypertension), heart valve disease, or heart attack. These conditions force the heart to work harder to pump blood, leading to the enlargement of the heart muscle.
4. 4. In pathological cardiac hypertrophy, the heart muscle becomes thicker, which can decrease the heart's ability to pump blood effectively. This can lead to further complications such as heart failure.
5. 5. Therefore, while an enlarged heart in athletes is a healthy adaptation to increased physical demand, an enlarged heart in patients with cardiovascular disease is a sign of an underlying problem and can lead to serious health complications.