Acid-base homeostasis

Acid-base homeostasis is the part of human homeostasis concerning the proper balance between acids and bases, in other words the pH. The body is very sensitive to its pH level. Outside the range of pH that is compatible with life, proteins are denatured and digested, enzymes lose their ability to function, and the body is unable to sustain itself.

Mechanism

Gains and losses of acid and base must be balanced. The study of the acid-base reactions in the body is acid base physiology.

Buffering agents

Any substance that can reversibly bind hydrogen ions is called a buffering agent. They function to impede any change in pH. Hydrogen ions are buffered by extracellular (e.g., bicarbonate, ammonia) and intracellular buffering agents (including proteins and phosphate). The buffering ability of plasma acts as an immediate defense against pH imbalance. The key buffer system in mammalian blood is the carbonic acid H₂CO₃ and bicarbonate HCO₃^- system.

Active regulation

A short term method of compensating for acid-base imbalance involves regulating ventilation rate. By changing the ventilation rate, the body can alter the concentration of carbon dioxide in the blood, which alters the pH. In the long term, the kidneys maintain acid-base homeostasis by altering the excretion of excess acid or base.

See also

• Acid-base imbalance
• Acid-base physiology
• Acidosis
• Alkalosis
• Mixed disorder of acid-base balance
• Renal physiology

External links

• [ttp://www.anaesthesiamcq.com/AcidBaseBook/ABindex.php On-line text at AnaesthesiaMCQ.com]
• Physiology at MCG 7/7ch12/7ch12lin
• Overview at kumc.edu
• Overview at mcgill.ca