The Thirst Axis

Question 1

Where is vasopressin synthesised, stored and released? [2]

Answer 1

1. Vasopressin/ADH is synthesised in the supraoptic nuclei of the hypothalamus
2. and stored and released from the posterior pituitary

Question 2

What stimulates the secretion of vasopressin? [4]

Answer 2

1. fall in blood pressure or blood volume / detected by baroreceptors

–> decrease in blood pressure or blood volume = increase in vasopressin

2. increase in plasma osmolality/blood concentration / detected by osmoreceptors

–> increase in plasma osmolality/blood concentration = increase in vasopressin

Question 3

What is the main action of vasopressin in the kidney? [4]

Answer 3

1. acts on principal cells of the distal convoluted tubules and collecting ducts of the kidney
2. binds to G-protein-coupled vasopressin receptors (V2R)
3. kinase action results in the insertion of aquaporin 2 channels into the apical membrane of the DCT and collecting ducts
4. resulting in increased water permeability and increased water reabsorption with very concentration urine

Question 4

What are the other actions of vasopressin? [1]

Answer 4

also causes widespread arteriolar vasoconstriction to increase blood pressure