15.6 The kidney and osmoregulation

Question 1

Describe the mechanism of ADH action

Answer 1

ADH SECRETED by posterior PITUITARY GLAND in hypothalamus into the BLOODSTREAM.
ADH is then carried to cells of collecting duct where it BINDS to RECEPTORS on plasma membrane of collecting duct cells.
- Triggers formation of secondary messenger, cAMP which causes a cascade of events:
In tubule cells, VESICLES FUSE with plasma membrane.
These vesicles contain AQUAPORINS which are inserted into plasma membrane.
Aquaporins INCREASE PERMEABILITY of plasma membrane to water.
Water moves OUT of tubule cells in tissue fluid by OSMOSIS

Question 2

What’s osmoregulation

Answer 2

The Balance & control of blood water potential

Question 3

What does ADH control

Answer 3

PERMEABILITY of collecting duct walls
￬
volume of water reabsorbed
￬
volume & concentration of urine