Role of ADH in Osmoregulation Flashcards
What does ADH do?
Controls permeability of kidney tubule cells which results in increased or decreased blood water potential.
What are osmoreceptors?
Cells in the hypothalamus that detect a fall in blood water potential.
What can osmoreceptor cells do to try and raise blood water potential?
They lose water from their cells and it enters the blood
What happens to the shape of osmoreceptor cells when water is lost?
They shrink
When ADH is released, permeability of what 3 parts of the kidney to water is increased?
Kidney walls, distal convoluted tubule and collecting duct
ADH is secreted when…
Blood water potential is low
Describe how phosphorylase enzymes are activated.
ADH binds to receptors on kidney cells activating phosphorylase.
What are aquaporins?
Channel proteins designed to increase water absorbed
Describe how activation of phosphorylase enzymes causes permeability of the cell to water to increase.
Activation of phosphorylase causes vesicles containing pieces of plasma membrane rich in aquaporins to fuse with the kidney cell membranes, increasing permeability to water.
ADH increases permeability of the collecting duct to what 2 substances?
Urea and water
How does urea entering the collecting duct and then leaving cause water to be reabsorbed from the collecting duct into blood vessels?
Urea leaving the duct causes a lower water potential around the duct.
This causes water to leave the duct by osmosis into blood vessels.
As water re enters blood, why does it not raise the water potential?
It does not raise the water potential of blood because the water came from the blood originally. Instead, it prevents the water potential from lowering.
Osmoreceptors send impulses to the brain that instruct the organism to do what?
Drink more water.
Once an organism consumes more water, what do osmoreceptors start to do less?
They send fewer impulses to the pituitary gland so less ADH is released.
Give 3 things that raise the water potential of blood.
Consume large volume of water
Salts used up in metabolism
Salts excreted and not replaced by diet
