Question

When you hold your breath, which of the following gas changes in blood would first lead to the urge to breathe?

• A. Rising $C{O}_2$ concentration
• B. Falling $C{O}_2$ concentration
• C. Rising $C{O}_2$ and falling $O_2$ concentration
• D. Falling $O_2$ concentration

Answer 1

The correct option is A Rising $C{O}_2$ concentration

Holding of breath leads to the accumulation of carbondioxide in the blood which changes the pH of the blood.
This change in pH, triggers the chemo-sensitive area of the brain, which sends the signals to brain to breathe.
So, the corret answer is 'rising of carbondioxide concentration'.