Breathing and Exchange of Gases Question 20
20. When you hold your breath, which of the following gas changes in blood would first lead to the urge to breathe?
[2015 RS]
(a) rising $CO_2$ concentration
(b) falling $CO_2$ concentration
(c) rising $CO_2$ and falling $O_2$ concentration
(d) falling $O_2$ concentration
Show Answer
Answer : a
Hints & Solution
(a) Chemoreceptors in the medulla get stimulated by increase in $CO_2$ concentration in the blood of arteries. Decrease in $O_2$ concentration has no significant effect on chemoreceptors.
