Emergency Medical Technician (EMT) Intermediate Practice Exam

The MOST rapidly acting compensatory mechanism that maintains pH is the:

1. Renal system

2. Bicarbonate buffer system

3. Respiratory system

4. Hepatic system

The correct answer is: Bicarbonate buffer system

The bicarbonate buffer system is the most rapidly acting compensatory mechanism for maintaining pH in the body. This system works through a chemical reaction that involves bicarbonate ions and carbonic acid. When there is an increase in hydrogen ions (H+), which can lower pH, bicarbonate (HCO3-) reacts with these hydrogen ions to form carbonic acid (H2CO3), which can then dissociate into water and carbon dioxide (CO2). The CO2 can be expelled through respiration, thereby removing the excess acid from the system and helping to restore the pH balance quickly. This buffer system operates almost instantaneously, allowing the body to adjust its pH in response to fluctuations, such as during exercise or metabolic changes. Other systems, like the renal and hepatic systems, involve slower responses; the renal system can take hours to days to adjust pH through excretion and reabsorption of acids and bases, while the hepatic system also involves metabolic processes that are not as immediate. The respiratory system can influence pH through changes in CO2 levels via breathing, but this occurs relatively slower compared to the immediate chemical action of the bicarbonate buffer system. Thus, when considering the speed at which these mechanisms can act to regulate p