Kaplan Nursing Entrance Practice Exam

What structure is responsible for monitoring carbon dioxide levels in the blood to control breathing rate?

1. Cerebellum

2. Medulla oblongata

3. Pons

4. Cortex

The correct answer is: Medulla oblongata

The medulla oblongata plays a crucial role in regulating the body's respiratory rate by monitoring carbon dioxide levels in the blood. This structure is part of the brainstem and contains chemoreceptors that detect changes in the concentration of carbon dioxide. When levels rise, the medulla responds by signaling the respiratory muscles to increase breathing rate and depth, facilitating the expulsion of carbon dioxide and the intake of oxygen. This automated response helps maintain the acid-base balance in the body, critical for overall homeostasis. The functions of the other structures mentioned differ from this specific regulatory role. The cerebellum primarily coordinates voluntary movements and maintains balance and posture. The pons also contributes to the regulation of breathing but mainly serves as a relay between different parts of the brain, rather than directly monitoring carbon dioxide levels. The cortex, particularly the cerebral cortex, is involved in higher-order functions such as decision-making and voluntary control of breathing but is not responsible for the automatic regulation based on carbon dioxide levels.