Kidney and ADH

Question 1

Describe and explain how the secretion of ADH affects urine produced by the kidneys.

Answer 1

Permeability of membrane of the collecting duct is increased; More water absorbed from the collecting duct; smaller volume of urine; Urine becomes more concentrated.

Question 2

Explain how ADH increases the movement of water from the lumen of the collecting duct into the blood.

Answer 2

Permeability of membrane of the collecting duct is increased; More water absorbed from the collecting duct; smaller volume of urine; Urine becomes more concentrated.
ADH causes vesicles containing aquaporins to be inserted into collecting duct wall; water enters cell through aquaporins; by osmosis down a water potential gradient; then it diffuses from cell to capillary; via interstitial fluid;

Question 3

Name the gland that secretes ADH

Answer 3

Pituitary

Question 4

Where are the cells called osmoreceptors found?

Answer 4

The hypothalamus

Question 5

How do osmoreceptors work?

Answer 5

When you are dehydrated, the water potential of the blood is lower, so water moves out of the osmoreceptors, they shrink and this change is detected.

Question 6

Explain the role of ADH in the production of concentrated urine.

Answer 6

When water potential of the blood too low; Detected by receptors in the hypothalamus; Pituitary secretes more ADH; ADH increases the permeability for water in the DCT and collecting duct; More water is reabsorbed into the blood; By osmosis down the water potential gradient;

Question 7

Explain how ADH is involved in the control of the volume of urine produced.

Answer 7

If water potential of blood falls, detected by receptors in hypothalamus; leads to ADH released from pituitary gland; ADH makes cells of collecting duct / distal convoluted tubule permeable to water; water leaves filtrate by osmosis; smaller volume of urine produced;

Question 8

How does the body respond to a rise in water potential of the blood?

Answer 8

Osmoreceptors detect the rise in water potential and the pituitary gland reduces the amount of ADH released. Less ADH via the blood leads to a decrease in the permeability of the collecting duct to water and urea. Less water is reabsorbed from the collecting duct. More dilute urine is produced and the water potential of the blood falls.