Which organ system can alter the amount of CO₂ in the blood?

The respiratory system directly regulates the level of carbon dioxide (CO₂) in the blood. CO₂ is a waste product of cellular respiration and is removed from the body through exhalation. When breathing rate increases, more CO₂ is expelled, lowering blood CO₂ levels. When breathing slows, CO₂ levels rise. While the cardiovascular system transports CO₂, it does not regulate its concentration. The urinary system regulates pH and fluid balance but does not directly remove CO₂. The endocrine system controls hormones, not gas exchange. The NEX Science exam frequently emphasizes the role of the respiratory system in maintaining acid–base balance through CO₂ regulation.

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