Question

7 multiple choice 10 points which statement best represents the reason why the cardiovascular system works harder during physical activity than during rest? less oxygen is needed to support increased movement. more oxygen is needed to support increased movement. breathing becomes slower during periods of exercise. breathing becomes quicker during periods of exercise.

Explanation:

During physical activity, the body's cells need more energy. Cellular respiration, which requires oxygen, is the process that provides this energy. So, the cardiovascular system (heart and blood vessels) has to work harder to deliver more oxygen (and nutrients) to the cells to support the increased movement (as more oxygen is needed for enhanced cellular respiration to fuel the activity). The statement "Less oxygen is needed to support increased movement" is incorrect as more oxygen is actually required. "Breathing becomes slower during periods of exercise" is wrong because breathing usually speeds up during exercise to take in more oxygen. While "Breathing becomes quicker during periods of exercise" is a true statement about the respiratory system's response during exercise, the question is about why the cardiovascular system works harder. The key is the increased oxygen demand for movement, which the cardiovascular system has to meet by pumping more blood (carrying oxygen) to the tissues.

Answer:

More oxygen is needed to support increased movement.