homeostasis

Question 1

when a person is dehydrated, the cell volume of an osmoreceptors decreases

Explain why

Answer 1

1. Water potential of blood will decrease

2. water moves from osmoreceptors into blood by osmosis

Question 2

stimulation of osmoreceptors can lead to serotonin of the hormone ADH

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

Answer 2

1. Permeability of membrane/ cells to (to water) is increased
2. More water absorbed from/ leaves distal tubule/ collecting duct
3. smaller volume of urine
4. urine becomes

Question 3

long loops of Henle enable the whale to produce very concentrated urine

explain how

Answer 3

there is a high concentration if sodium ions surrounding the loop

active removal of ions from ascending limb which is impermeable to water

with longer loops, there will be a greater gradient/ difference in water potential between the collecting duct and the medulla

therefore greater uptake of water from the collecting duct