Electrolytes and Acid-Base Balance in Human Body

The electrolyte balance of the body is studied by determining the electrolyte concentration in blood plasma. Within each fluid compartment the total milli equivalents of cations and anions are balanced, and this maintain the osmotic balance.

Sodium (Na+)-

Sodium is the bulk catione of the extra cellular fluid. It is important for the maintenance of fluid balance, muscle irritability, acid base balance, nerve conduction and osmotic pressure. The main source of sodium in our body is the salt that we use in cooking our food, and some amounts of sodium naturally occurring in foods like egg, fish, nuts and all green leafy vegetables like spinach. The total body content of sodium in an adult man is approximately 42 g expressed as Na+ . The daily intake varies between 2.3 to 9.2 g depending on dietary habits. Common salt is sodium + chloride (NaCl), in which 40% is sodium and 60% chloride. Sodium is lost through sweat, faeces, and urine. The bulk of it is lost in urine.

Regulation of sodium balance:

Because the intake of sodium is controlled by dietary habits rather than by requirements, sodium balance is achieved only by regulating the output. Therefore, kidneys play an important role in the maintenance of sodium balance. Almost 80% of the glomerular filtrate is reabsorbed in the nephrons. The hormone aldosterone plays a role in the re-absorption of Na+.


K+ functions as the major cation of the intercellular fluid, keeping the elector-neutrality