During short-term respiratory responses to exercise, why does breathing quicken and deepen?

During short-term respiratory responses to exercise, why does breathing quicken and deepen?

• A. Because the heart beats faster and the lungs need to supply more oxygen to the body.
• B. Because the lungs reduce air flow to conserve energy.
• C. Because the brain slows down the breathing rate.
• D. Because the air becomes thinner.

Answer: (A)

During short-term exercise, working muscles need more oxygen and produce more carbon dioxide. To meet this demand, ventilation increases: breathing becomes faster and deeper so more air, and thus more oxygen, reaches the lungs each minute, while more CO2 can be removed. The heart also speeds up to transport the increased oxygen to the muscles and return CO2 to the lungs more quickly, supporting the greater metabolic rate. The other options don’t fit because breathing isn’t reduced, the brain doesn’t slow the rate, and thinner air isn’t the immediate cause in normal conditions.

During short-term exercise, working muscles need more oxygen and produce more carbon dioxide. To meet this demand, ventilation increases: breathing becomes faster and deeper so more air, and thus more oxygen, reaches the lungs each minute, while more CO2 can be removed. The heart also speeds up to transport the increased oxygen to the muscles and return CO2 to the lungs more quickly, supporting the greater metabolic rate. The other options don’t fit because breathing isn’t reduced, the brain doesn’t slow the rate, and thinner air isn’t the immediate cause in normal conditions.