Question

Explain how and why drinking water affects: (A) Blood plasma (B) Blood plasma osmolarity

Answer 1

Answer:

(A) - The volume of the blood plasma increases on overhydration and decreaes on dehydration.

(B) - Osmolality of blood increases with the dehydration and decreases with the overhydration.

Explanation:

If the levels of drinking water is increased, then the plasma becomes more dilute and the plasma volume increases because the water will be reabsorbed more and which as a result reduces plasma concentration of the solutes and increases volume of plasma.

Plasma osmolality measures electrolyte-water balance of the body. As mentioned, above on overhydration, the plasma concentration of the solutes decraeses which also decreases osmolality. So, Osmolality of blood increases with the dehydration and decreases with the overhydration. Increased osmolality in blood stimulate the secretion of antidiuretic hormone which results in the increased water reabsorption and therefore, more concentrated urine and hence blood plasma with less concentration.