Question

What are the most powerful stimuli for breathing?

• A. high pH; high CO₂
• B. low pH; low CO₂
• C. low pH; high CO₂
• D. high pH; low CO₂

Answer 1

The correct option is C

low pH; high CO₂

Normally, an increased concentration of carbon dioxide is the strongest stimulus to breathe more deeply and more frequently. Conversely, when the carbon dioxide concentration in the blood is low, the brain decreases the frequency and depth of breaths.