Final answer:
An increase in PCO₂ in the blood leads to a decrease in blood pH, making it more acidic. The rate of respiration increases to get rid of excess CO₂ and restore normal pH levels.
Step-by-step explanation:
When there is an increase in PCO₂ (partial pressure of carbon dioxide) in the blood, it leads to a decrease in blood pH, making it more acidic.
This occurs because CO₂ reacts with water to form carbonic acid, and an increase in PCO₂ increases the concentration of carbonic acid in the blood, thus lowering pH.
In response to an increase in PCO₂ and a decrease in blood pH, the rate of respiration increases.
This is the body's way of getting rid of excess CO₂ and reducing the concentration of carbonic acid in the blood, thereby helping to restore normal pH levels.