Final answer:
Increased CO2 levels or a decrease in pH stimulates chemoreceptors, leading to an increased respiratory rate to normalize blood gas and pH levels.
Step-by-step explanation:
The regulation of respiratory rate is primarily controlled by the levels of carbon dioxide (CO2) and the pH of the blood. Increased levels of CO2 or a decrease in pH stimulates chemoreceptors which in turn signal the respiratory centers in the brain to increase the rate and depth of respiration. This mechanism allows the body to expel more CO2, thereby reducing hydrogen ion concentration and normalizing the pH. When chemoreceptors detect lowered CO2 levels, the respiratory rate slows down. Hence, an increased respiratory rate can be a result of a decrease in cerebrospinal fluid oxygen partial pressure (PO2), an increase in CO2, a decrease in cerebrospinal fluid pH, and increased levels of hydrogen ions following activities such as strenuous exercise.