What happens to ventilation when carbon dioxide levels rise?

• A. Increased respiratory rate and volume
• B. Decreased respiratory rate
• C. No change in breathing
• D. Increased heart rate only

Answer: (A)

Rising carbon dioxide levels trigger the body's chemical sensors to boost breathing. Central chemoreceptors in the brainstem sense the increased acidity from CO2 in the cerebrospinal fluid, while peripheral chemoreceptors in the carotid bodies respond to changes in blood CO2 and pH. This together-arousal of the respiratory centers increases the drive to the muscles used for breathing, raising both how often you breathe and how deeply you breathe. The result is a higher minute ventilation to blow off CO2 and restore pH balance. A higher heart rate can occur with general stress, but it doesn’t fix CO2 levels by itself, and decreasing breathing or not changing breathing would worsen CO2 buildup.