Nursing Entrance Exam (NEX) Practice Exam

During exercise, a person's respiratory rate increases due to what?

1. A decrease in CO2 concentration in the blood

2. An increase in hemoglobin in the blood

3. A decrease in O2 concentration in the lungs

4. An increase in CO2 concentration in the blood

The correct answer is: An increase in CO2 concentration in the blood

During exercise, the body requires more oxygen and produces more carbon dioxide as a byproduct of increased metabolism. As the muscles work harder, they consume greater amounts of oxygen and generate more carbon dioxide, which leads to an increase in the concentration of carbon dioxide in the blood. The body detects this rise in carbon dioxide levels through chemoreceptors, which respond to changes in blood gas concentrations. In response to the increased carbon dioxide, the respiratory center in the brainstem stimulates an increase in the respiratory rate. This physiological response is crucial because faster breathing allows for enhanced gas exchange in the lungs, enabling the removal of excess carbon dioxide while taking in more oxygen to meet the demands of the body during exercise. The other choices are not associated directly with the primary trigger for the increase in respiratory rate during physical activity. For instance, a decrease in CO2 concentration would not stimulate increased breathing; rather, it would typically lead to a decrease in respiratory rate. Similarly, while hemoglobin levels are important for oxygen transport, they do not directly cause changes in respiratory rate during exercise. Lastly, a decrease in O2 concentration in the lungs alone does not account for the immediate increase in respiratory rate—it's the build-up of CO2 that is the key factor driving