Registered Cardiovascular Invasive Specialist (RCIS) Practice Test

What is the significance of elevated carbon dioxide levels in respiratory physiology?

1. It lowers heart rate

2. It stimulates breathing in normal individuals

3. It causes drowsiness

4. It reduces blood flow

The correct answer is: It stimulates breathing in normal individuals

Elevated carbon dioxide levels play a critical role in stimulating breathing, particularly in normal individuals. When carbon dioxide levels increase in the blood, it leads to a condition known as hypercapnia. The body monitors the concentration of carbon dioxide through chemoreceptors located in the central nervous system and peripheral arteries. These chemoreceptors detect the rise in carbon dioxide levels and trigger the respiratory center in the brain to increase the rate and depth of breathing. This response enhances the expulsion of carbon dioxide from the lungs, thereby restoring normal levels in the blood and ensuring that oxygen levels can also effectively return to their appropriate range. In healthy individuals, this mechanism is crucial for maintaining homeostasis and ensuring adequate gas exchange during activities that may temporarily elevate carbon dioxide levels, like exercise. This physiological response illustrates the importance of carbon dioxide not just as a waste product but also as a significant regulator of respiratory drive. The other options mentioned do not hold primary significance in the context of respiratory physiology concerning elevated carbon dioxide levels. For instance, while drowsiness may occur in cases of significantly high carbon dioxide leading to other complications, it is not the primary or direct physiological response as is the increased breathing stimulus.