Final answer:
Chemoreceptors in the aortic and carotid bodies detect changes in blood chemistry such as CO2 levels and signal the brain to adjust the respiratory rate accordingly.
Step-by-step explanation:
The components that detect changes in blood chemistry, such as CO2, PaCO2, and Pao2, are the chemoreceptors located in the aortic and carotid bodies. These sensors are crucial in regulating the respiratory rate by signaling the brain, particularly the respiratory centers in the medulla oblongata, to make immediate adjustments if CO2 levels rise or fall. Therefore, the correct answer to the question is b. Carotid bodies.