AEMCA Practice Exam

Which two systems control physiological buffering in the human body?

1. Cardiovascular and immune systems

2. Pulmonary and renal systems

3. Digestive and circulatory systems

4. Nervous and endocrine systems

The correct answer is: Pulmonary and renal systems

The pulmonary and renal systems play a crucial role in maintaining the body's pH balance through physiological buffering. The pulmonary system regulates carbon dioxide levels through ventilation. When carbon dioxide accumulates, it combines with water to form carbonic acid, lowering the pH. By adjusting the rate and depth of breathing, the lungs can either retain carbon dioxide to increase acidity or expel it to raise pH back to normal levels. On the other hand, the renal system contributes to buffering by managing the excretion or reabsorption of bicarbonate and hydrogen ions. The kidneys can adjust the levels of these substances in the blood to either retain bicarbonate, which acts as a base, or excrete hydrogen ions, which adds acidity. This dynamic balance maintained by the pulmonary and renal systems is essential for the body's overall acid-base homeostasis. In contrast, the other systems mentioned do not primarily focus on pH regulation. The cardiovascular and immune systems are more involved in circulation and response to pathogens; the digestive and circulatory systems deal with nutrient absorption and blood flow, respectively, while the nervous and endocrine systems regulate signaling and hormone release rather than direct pH balance.