Final answer:
Chemoreceptors in the aortic arch and carotid arteries, as well as in the brain, are responsible for monitoring oxygen and carbon dioxide levels in the blood.
Step-by-step explanation:
The receptors responsible for monitoring oxygen and carbon dioxide levels in the blood are chemoreceptors. These include both peripheral chemoreceptors, which are found in the walls of the aortic arch and carotid arteries, and central chemoreceptors located in the brain.
Peripheral chemoreceptors react to significant changes in blood oxygen levels, especially when they drop to about 60 mm Hg or lower, by stimulating an increase in respiratory activity. They sense dissolved oxygen molecules, not the oxygen bound to hemoglobin. As for CO₂ levels, chemoreceptors signal the brain to adjust respiratory rate accordingly when these levels fluctuate.