where are the chemoreceptors for the breathing rhythm?

Answer 1

there are chemoreceptors in the 4th ventricle of the brain, which detect the pH of the blood, if it gets too low it will increase respiration. note that increasing breathing rhythm doesnt first rely on the lack of oxygen but the excess CO2 in the blood. some CO2 actually travels as bicarbonate ions which is HCO3 +H+, the H+ is what the chemoreceptors actually detect and its what actually makes the blood more acid. when bicarbonate and the hydrogen joins it becomes H2CO3 which then turns into CO2 and H20.

Answer 2

There is one in the brain that is sensitive to carbon dioxide and a secondary in the thoracic aorta that is sensitive to oxygen.