Regulation of water metabolism.
Answer.
Water is the commonest liquid with the most uncommon properties. Water content of the body changes with age. It is almost 75% in the newborn and decreases to less than 50% in older individuals. Water content is maximum in brain tissue and least in adipose tissue.
Regulation of Water Metabolism
- Antidiuretic hormone or Vasopressin which has got the property to enhance water reabsorption
- Hypothalamus known as a thirst centre. Besides this, osmoconcentration of plasma also stimulates supraoptic and paraventricular nuclei
- Adrenal Cortex. Aldosterone has controll excretion of sodium and potassium by the kidneys
- Rennin-Angiotensin system. Angiotensin II stimulates the synthesis and secretion of aldosterone and the release of vasopressin, and thereby increases renal absorption of Na+ and H2O.
- Prostaglandins. They may also increase urinary loss of water by inhibiting the antidiuretic effect of vasopressin and by increasing the urinary sodium.
- Solutes. Osmotic effect of Na+ helps to retain water in extracellular fluids. Elevation in plasma Na+ raises the ECF volume in primary aldosteronism while an increase in urinary Na+ raises the urinary water output in Addisons disease. K+ helps to retain water in the cells, whereas, plasma proteins do help to retain water in the body by their osmotic effects. Increase in urinary urea or excretion of glucose in urine increases osmotically the urinary loss of water (osmotic diuresis).
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