What is a short-term effect of exercise on the respiratory system?

• A. Breathing quickens and deepens as the heart beats faster to supply oxygen to the body.
• B. Breathing slows to conserve energy.
• C. Lung capacity decreases during activity.
• D. Alveolar sacs contract during breathing.

Answer: (A)

During exercise the body needs more oxygen and must remove more carbon dioxide, so the respiratory system responds by increasing both the rate and depth of breathing. This quickens breathing and makes each breath deeper, while the heart also beats faster to move oxygen-rich blood to the muscles. That combination directly describes the immediate, short-term adjustment the body makes to meet the higher demand for energy, which is why this option is best.

Breathing slowing down would reduce oxygen delivery when it’s needed most. Lung capacity is a fixed anatomical limit and doesn’t decrease during activity. Alveolar sacs don’t actively contract; ventilation is driven by the chest wall and diaphragm expanding and contracting the lungs.