Question

When you hold your breath which of the following gas changes in blood would first lead to the urge to breathe?
A. Falling CO2 concentration
B. Rising CO2 and falling O2 concentration
C. Falling O2 concentration
D. Rising CO2 concentration

Answer 1

Hint: Difference in The partial pressure of CO2 as compared to O2 – as the solubility of CO2 is 20-25 times higher than that of O2, the amount of CO2 that can diffuse through the diffusion membrane per unit partial pressure is much higher to that of O2.

Complete answer:When lungs become concentrated with the same CO2 as in blood, it no longer leaves the blood and keeps rising. One breathes in CO2 diffuse out of lungs and oxygen is taken in. When you hold your breath there is an accumulation of carbon dioxide in your cells, in your blood and lungs it will irritate and trigger the impulses from the respiratory center part of your brain due to a rise in CO2 concentration, it signals the body to breathe and respiration. This rise in CO2 concentration also makes us sleepy. The effect of rising CO2 tension is to decrease the affinity of Hb for O2. Thus, when CO2 concentration in blood increases, breathing becomes faster and deeper.
So, here the option D, i.e., rising CO2 concentration is the correct answer.

Note: While holding the breath you give your cells more time to both absorb oxygen and produce carbon dioxide. Due to this, holding the breath sometimes can increase the amount of carbon dioxide in the cells and be a lifesaver in case of hyperventilation.