Final answer:
Chemoreceptors, including peripheral blood sensors and those in the brain, are involved in detecting changes in carbon dioxide levels in the blood.
Step-by-step explanation:
Carbon dioxide levels in the blood are primarily detected by chemoreceptors, specifically the peripheral blood sensors found in the walls of the aorta and carotid arteries.
These chemoreceptors signal the brain to make immediate adjustments to the respiratory rate if CO₂ levels rise or fall. Additionally, chemoreceptors in the brain itself detect changes in the pH of the cerebrospinal fluid, which can directly modulate the breathing rate to bring the pH back into the normal range.