When you hold your breath, which of the following blood gas changes first leads to the urge to breathe?
A) rising O₂
B) falling O₂
C) rising CO₂
D) falling CO₂
E) rising CO₂ and falling O₂

Question

Quizplus · Accepted Answer

The urge to breathe during breath holding is primarily driven by the rise in CO₂ levels in the blood. As CO₂ increases, it forms carbonic acid, which leads to a drop in blood pH, and triggers chemoreceptors in the brain to signal the respiratory muscles to start breathing again. Rising O₂ levels may help alleviate the feeling of breathlessness, but they do not play a significant role in driving the urge to breathe.

When You Hold Your Breath, Which of the Following Blood