Define Sodium, Potassium and Chloride - Minerals?
Claude Bernard was the first to draw attention to the internal environment (milieu interior), referring to the extracellular fluid (ECF)-a medium in which all cells are bathed. Homer Smith presented a convincing argument that the extracellular compartment contains constituents and concentrations similar to the precambrian seas, which presumably bathed the earliest piimordial unicellular organisms". As we know that the total body water (TBW) in a 70 kg man is 60% of the body's weight 1.e. about 40 litres. Two-thirds of this resides inside the cells, i.e. the intracellular fluid (ICF), while one-third is in the extracellular compartment (ECF) that bathes the cells. A
minor portion about 1 litre is present in the intestines and anterior chambers of the eyes. The most important electrolytes in the ECF are sodium (135- 145 millimoles/L and chloride (98- 108 millimoles/ L). The concentration of potassium in the ECF is very low, 3.5-4.5 millimoles/L, however, potassium is the predominant cation (K+) in the ICF, whereas sodium and chloride in the ICF are negligible. Muscle cells have much higher water content than the others and therefore ICF and TBW are closely related to lean body mass. The three macro minerals, Na, K and C1 are related to each other and hence will be discussed together, which makes it easier to appreciate their roles in metabolism. You know that Na and K are monovalent cations (ions that carry a positive charge) while Cl is a monovalent anion (ions that carry a net negative charge). All three are known as electrolytes as their ions are used for generating electric charge differences across the plasma membrane of most cells. Na constitutes 2%; K 5% and C1 3% of the total mineral content of the body. These minerals exist as ions in the body fluids and are principal electrolytes in the body. K is a major intracellular electrolyte while Na and C1 are present in the extracellular fluids.