AEMCA Practice Exam

Which physiological response occurs due to high levels of carbon dioxide?

1. Increased heart rate

2. Vasodilation of blood vessels

3. Decreased blood pH

4. Decreased oxygen affinity in hemoglobin

The correct answer is: Decreased blood pH

High levels of carbon dioxide in the bloodstream lead to a physiological response that includes the phenomenon of decreased blood pH. This occurs because carbon dioxide (CO2) reacts with water in the body to form carbonic acid (H2CO3), which dissociates into bicarbonate (HCO3-) and hydrogen ions (H+). The increase in hydrogen ions results in a lower pH, causing the blood to become more acidic. This response is crucial as it plays a significant role in the body’s ability to regulate respiration. When CO2 levels rise, the decrease in pH serves as a signal for the respiratory center in the brain to increase the rate and depth of breathing. This helps to remove excess CO2 from the body, thereby restoring acid-base balance. In contrast, increased heart rate, vasodilation of blood vessels, and decreased oxygen affinity in hemoglobin, while they may be related to other physiological responses, are not directly caused by elevated carbon dioxide levels. Specifically, increased heart rate would occur in response to a variety of factors, such as physical exertion or stress, rather than solely from high CO2. Vasodilation is often a result of various factors including heat, and decreased oxygen affinity in hemoglobin typically relates