Acid–base homeostasis

[1] The proper balance between the acids and bases (i.e. the pH) in the ECF is crucial for the normal physiology of the body—and for cellular metabolism.

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.

[14] Thus, by manipulating firstly the concentration of the weak acid, and secondly that of its conjugate base, the pH of the extracellular fluid (ECF) can be adjusted very accurately to the correct value.

[13] The most abundant buffer in the ECF consists of a solution of carbonic acid (H2CO3), and the bicarbonate (HCO−3) salt of, usually, sodium (Na+).

[5] The partial pressure of carbon dioxide in the arterial blood is monitored by the central chemoreceptors of the medulla oblongata.

[14][12][20] The central chemoreceptors send their information to the respiratory centers in the medulla oblongata and pons of the brainstem.

[12] The respiratory centres then determine the average rate of ventilation of the alveoli of the lungs, to keep the PCO2 in the arterial blood constant.

[5][21] A rise in the PCO2 in the arterial blood plasma above 5.3 kPa (40 mmHg) reflexly causes an increase in the rate and depth of breathing.

It is very probable that the renal tubular cells of the distal convoluted tubules are themselves sensitive to the pH of the plasma.

H2CO3), thus raising the carbonic acid:bicarbonate ratio in the extracellular fluids, and returning its pH to normal.

[5][22] Acid–base imbalance occurs when a significant insult causes the blood pH to shift out of the normal range (7.32 to 7.42[16]).

[citation needed] Acidemia and alkalemia unambiguously refer to the actual change in the pH of the extracellular fluid (ECF).

For instance, a metabolic acidosis (as in uncontrolled diabetes mellitus) is almost always partially compensated by a respiratory alkalosis (hyperventilation).