<unk>  is the homeostatic regulation of the pH of the body's extracellular fluid (ECF). The proper balance between the<unk> s and<unk> s (i.e. the pH) in the ECF is crucial for the normal physiology of the body—and for cellular metabolism. The pH of the intracellular fluid and the extracellular fluid need to be maintained at a constant level. The three dimensional structures of many extracellular proteins, such as the plasma proteins and membrane proteins of the body's cells, are very sensitive to the extracellular pH. Stringent mechanisms therefore exist to maintain the pH within very narrow limits. Outside the acceptable range of pH, proteins are denatured (i.e. their 3D structure is disrupted), causing enzymes and ion channels (among others) to malfunction. An<unk><unk><unk>  imbalance is known as<unk> emia when the pH is<unk> ic, or alkalemia when the pH is alkaline.
Acid–base homeostasis
Gas exchange
Respiratory adaptation
Thermoregulation
Fluid balance
Mechanical properties of biomaterials
Sensory-motor coupling
Fresh gas flow