An increase in carbon dioxide in the body stimulates which physiological response?

• A. Increased heart rate
• B. Increased blood pressure
• C. Increased respirations
• D. Increased digestion

Answer: (C)

Rising carbon dioxide in the blood lowers pH and is detected by central chemoreceptors in the brainstem (and peripheral chemoreceptors in the carotid bodies). In response, the respiratory center increases both the rate and depth of breathing to expel CO2 and restore acid-base balance. This direct chemoreceptor-driven ventilation makes increased respirations the primary response to higher CO2 levels.

While heart rate and blood pressure can rise with activity or stress, and digestion is governed by separate autonomic processes, CO2’s main effect under normal conditions is to boost ventilation rather than these other responses.