As said, a less important pathway is for CO2
to activate the peripheral chemoreceptors. These are located in the wall of the aortic arch (= aortic bodies) and in the bifurcation of the carotids (=carotid bodies).
(Don’t confuse them with the carotid and aortic sinus!)
The aortic and carotid sinuses are stretch receptors that are sensitive to the blood pressure and are discussed in the CVS chapter.