The majority of body sodium is present ?
D i.e. Bone- Typical western diet consumption provides approximately 150 mmol of sodium chloride (NaC1) dailyQ.- Normal level of serum sodium is 136 -145 mmol/L (SI unit) or 136- 145 meg/L (conventional unit)Q.Na' - I(' ATP pase pump actively transpos Na+ out of cells. As a result, 85- 90% of all sodium is extracellularQ and ECF volume is a reflection of total body Na+ content(2. And in the same way total body Na+ content is a reflection of ECF volume.Sodium reserve is chiefly stored in stomach wallQ, which makes it alkaline to counter balance the acidic environment. 30-40% sodium is stored in skeletal muscles.- The normal plasma osmolality is 275 - 290 milliosmoles/kg. To maintain it, normally about 600 mosmols/day solute must be excreted. And since maximum urine osmolality is 1200 mosmols/kg a minimum urine out put of 500 mL/ d is required.- Osmoreceptor located in anterolateral hypothalmusQ is stimulated by hypeonicity. Ineffective osmols i.e. solutes that do not contribute to shift water across cell membrane, like urea and glucoseQ do not play a role in stimulating thirst. The average osmotic threshold for thirst is - 295 mosmol/kg. Osmotic adaptation is a defence mechanism of brain cells in chronic hypo & hyper natremia against large water shiftsQ. It is mediated by initialshifts of K' & Na* f/b synthesis, impo or expo of organic solutes (osmolytes) such as inositol, betaine & glutamineQ. In chronic hyponatremia brain cells lose & in chronic hypernatremia gain solutes. Sodium is the principal cation content of ECF. The total body sodium is - 5000 mmol, of which 44% is in extracellular fluid 9% is in intracellular fluid and remaining 47% is in boneQ.98% of potassium (K*) is intracellular & 2% in extracellular fluid. 3/4 of total boy IC+ (- 3500 minol) is found in skeletal muclesQ. Normal adult ingests - 1.0 rnmol/kg of IC+ in food. Fruit, milk & honey are rich in K+.
Extra cellular fluid
Intra cellular fluid
Plasma
Bone