Unit 2: Functional Diagnostics and Imaging Techniques

Excess carbon dioxide in the blood from breathing reacts with water to produce carbonic acid. This lowers the blood pH and increases the depth of respiration as shown in the following reaction:

CO₂ + H₂O ⇌ H₂CO₃ ⇌ H⁺ + HCO₃^-

The respiratory system can therefore participate in acid-base balance by removing CO2 from the body. The central nervous system has sensors for CO2 and hydrogen ion levels (H+) in the arterial blood and in the cerebrospinal fluid that send information to the body's controllers of breathing.