Walter F. Boron
Acid-base physiology is really the study of the proton, or hydrogen ion (H+). Although they are present in exceedingly low concentrations in most intracellular and extracellular fluids, protons nevertheless have a major impact on biochemical reactions and on a variety of physiological processes that are critical for the homeostasis of the entire body and individual cells. Not surprisingly, the body has evolved sophisticated systems to maintain [H+] values within narrow and precise ranges in the blood plasma, intracellular fluid, and other compartments.
This chapter provides the introduction to acid-base physiology, including the chemistry of buffers, the buffer system, the competition between the buffer system and other buffers, and the regulation of intracellular pH. In other chapters, we discuss how blood pH—and, by extension, the pH of extracellular fluid—is under the dual control of the respiratory system, which regulates plasma [CO2] (see Chapter 31), and the kidneys, which regulate plasma  (see Chapter 39). In addition, we discuss the control of cerebrospinal fluid pH in Chapter 32.