Question

Which of the following is not a stimulus for breathing?

• A. Rising $C{O}_2$ levels
• B. Rising blood pressure
• C. Arterial $p{O}_2$ below $60$mm of Hg
• D. Change in pH of arterial blood

Answer 1

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

An increased concentration of carbon dioxide is the strongest stimulus to breathe more deeply and more frequently. When the carbon dioxide concentration in the blood is low, the brain decreases the frequency and depth of breath.

So the correct answer is 'Rising CO2 levels'.