Which is responsible for respiratory drive:September 2007

Ans. C: CO2Although the body requires oxygen for metabolism, low oxygen levels do not stimulate breathing. Rather, respiratory centre is directly stimulated by higher carbon dioxide levels or excess hydrogen ions in the blood. As a result, breathing low-pressure air or a gas mixture with no oxygen at all (such as pure nitrogen) can lead to loss of consciousness without ever experiencing air hunger.The respiratory centers try to maintain an aerial CO2 pressure of 40 mm Hg. With intentional hyperventilation, the CO2 content of aerial blood may be lowered to 10-20 mm Hg (the oxygen content of the blood is little affected), and the respiratory drive is diminished.