Which system is responsible for changes in carbon dioxide levels affecting serum pH?

The respiratory system plays a crucial role in regulating carbon dioxide levels in the blood, which in turn affects serum pH. The primary mechanism involves the removal of carbon dioxide (CO2) from the body through breathing. When CO2 is produced as a metabolic byproduct, it dissolves in the blood and forms carbonic acid, which can decrease the pH, making the blood more acidic.

When the respiratory system increases the rate of breathing (hyperventilation), it expels more CO2, leading to a reduction in carbonic acid and an increase in blood pH (making it more alkaline). Conversely, if breathing slows down (hypoventilation), CO2 levels rise, increasing carbonic acid concentration and decreasing pH (making it more acidic).

This balance is crucial for maintaining homeostasis within the body, as blood pH must remain within a narrow range for optimal enzymatic activity and physiological functions. Thus, the respiratory system is directly involved in adjusting CO2 levels to maintain proper pH balance in the serum, making it the correct answer.