Question

Which one of the following statements is correct with respect to kidney function regulation?

• A. During summer when body loses lot of water by evaporation, the release of ADH is suppressed.
• B. When someone drinks lot of water, ADH release is suppressed.
• C. Exposure to cold temperature blood flow stimulates formation of Angiotensin II.
• D. An increase in glomerular blood flow stimulates formation of Angiotensin II.

Answer 1

Answer: (B)

Antidiuretic hormone or vasopressin is secreted from neurohypophysis or the posterior pituitary. ADH stimulates reabsorption of water from last part of DCT and entire collecting duct by increasing the permeability of cells. This leads to reduction in urine volume and decrease in osmolarity of blood.
Once the osmolarity of blood comes to normal, activity of certain osmoreceptor cells decreases leading to decrease in ADH secretion. This is called negative feedback.
In absence of ADH, diuresis or dilution of urine takes place and person tends to excrete large amount of dilute urine. This condition called as diabetes insipidus.
If more water is consumed, the chemoreceptors are deactivated and there is eventual decrease in ADH production.