osmoregulation

Question 1

What is osmoregulation? (2)

Answer 1

The process by which the hypothalamus controls the water potential of the blood

An example of homeostasis and negative feedback

Question 2

How is osmoregulation related to water reabsorption? (2)

Answer 2

Water reabsorption occurs via the countercurrent multiplier mechanism

The amount of water reabsorbed is controlled at this stage (by osmoregulation)

Question 3

How do osmoreceptors in the hypothalamus respond to dehydration? (5)

Answer 3

1. When water levels in the blood decrease, osmoreceptors in the hypothalamus shrink
2. Triggering the release of ADH from the posterior pituitary gland
3. ADH increases the number of aquaporins in the DCT and collecting duct
4. Making them more permeable to water, so more water is reabsorbed into the blood\n\n5. This results in less water being lost in urine and the production of small amounts of concentrated urine

Question 4

How do osmoreceptors in the hypothalamus respond to over-hydration? (5)

Answer 4

1. When water levels in the blood increase, the hypothalamus detects this through osmoreceptors
2. The posterior pituitary gland releases less ADH, reducing the number of aquaporins in the DCT and collecting duct
3. Making them less permeable to water
4. Less water is reabsorbed
5. Resulting in more water lost in urine and the production of a large volume of dilute urine