L6: How do we concentrate urine

Question 1

Label a diagram showing the ascending limb of the loop of henle

Answer 1

z

Question 2

Water deficit ->

Answer 2

Increased ECF osmolarity -> Shrinkage of Osmoreceptor cells -> Stretch-sensitive mechanoreceptors detect change in cell volume -> Impulse sent to posterior pituitary -> AVP release -> Increased total peripheral resistance and water permeability in DCT/Collecting ducuts -> Increased water reabsorption

Question 3

AVP binds to V2 receptor on DCT/CD cell ->

Answer 3

G proteins activate adenylate cyclase -> ATP -> cAMP -> Protein kinase A phosphorylates proteins -> Vesicles containing AQP-2 fuse with apical plasma membrane

Question 4

Diabetes mellitus

Answer 4

Excess urine production due to inability to reabsorb glucose

Question 5

Central diabetes insipidus

Answer 5

Excess urine production due to inability to produce AVP

Question 6

Nephrogenic diabetes insipidus

Answer 6

Excess urine production due to non-functional V2 receptor proteins (ADH receptors)

Question 7

What is a possible cause of hyponatremia?

Answer 7

Persistent leakage of ADH from the neurohypophysis from skull fracture