Final answer:
The respiratory system can increase blood pH by a hyperventilation-induced decrease in PCO₂, which leads to reduced carbonic acid levels and a more alkaline condition.
Step-by-step explanation:
The activity of the respiratory system can increase pH by a hyperventilation-induced decrease in PCO₂. When the respiratory system responds to high levels of carbon dioxide (CO₂) in the blood, it can do so by increasing ventilation. This leads to the exhalation of more CO₂, which in turn reduces the level of carbonic acid in the blood. The decrease in carbonic acid shifts the acid-base balance, increasing pH, a more alkaline condition. Essentially, higher respiratory rates during hyperventilation remove excess CO₂, thus reducing hydrogen ion (H+) concentration and increasing systemic pH. This biological phenomenon is a part of respiratory compensation for metabolic acidosis and helps prevent acidosis caused by exercise or other metabolic activities.