5.2.8 Osmoregulation

Question 1

How is ADH activated? (Osmoregulation)

Answer 1

• Osmoreceptors in hypothalamus detect water potential of blood
• If low, pituitary gland stimulated
• Released ADH
• ADH causes kidneys to selectively reabsorb more water
• Reduces water loss in urine

Question 2

Effect of ADH on kidneys

Answer 2

• ADH binds to receptors which trigger chemical cascade phosphorylating aquaporins
• Activates them
• Increases permeability of collecting duct to water
• So more water selectively reabsorbed
• Smaller volume of urine