Question

Choose the correct answer from the alternatives given.
The respiratory centre in the brain which regulates the process of respiration is extremely sensitive to blood concentrations of

• A. $O_2$
• B. $C{O}_2$
• C. hydrogencarbonates
• D. oxyhaemoglobin

Answer 1

The correct option is B $C{O}_2$

There are chemoreceptors in several regions including the medulla oblongata of the brainstem that are sensitive to pH. As carbon dioxide levels increase there is a buildup of carbonic acid, which releases hydrogen ions and lowers pH. The chemoreceptors do not respond to changes in oxygen levels (which actually change much more slowly) but rather responds to pH, which in turn is dependent on plasma carbon dioxide levels. Therefore, CO${}_2$ is the driving force for breathing and the respiratory center is extremely sensitive to blood concentrations of CO${}_2$. So, the correct option is 'CO${}_2$'.