C12 - Osmoregulation Flashcards
What is osmoregulation
a homeostatic function that maintains concentrations of enzymes and metabolites.
So that the reactions within cells occur at a constant and appropriate rate to maintain the osmotic properties of their tissues and fluids.
How does osmoregulation operate
Negative feedback loop
What acts as the receptor in osmoregulation
The hypothalamus that is located at the base of the brain,
as its osmoreceptors monitor the solute potential of the blood
What is the co-ordinator
Also the hypothalamus
As it signals the effector
What is the effector
The posterior lobe of the pituitary gland to release stored ADH (antidiuretic hormone)
What does ADH do
N.b Jamie additional note from MUM
It returns the system to normal if it deviates too far by changing the behavior of the walls of the distal convoluted tubule and the collecting duct
The action of ADH is to CONSERVE WATER
What is ADH
The hormone produced in the hypothalamus
and secreted by the posterior pituitary gland
it increases the permeability of the cells of the distal convoluted tubule and collecting duct walls to water increasing water reabsorption
What is diuresis
production of a large volume of dilute urine
what is a diuretic
e.g. alcohol
a compound that causes the production of a large volume of urine
ADH causes….
The production of a small volume of concentrated urine
makes the walls of the collecting duct and DCT more permeable to water
so that more is reabsorbed from the filtrate back into the blood
what does negative feedback control
the volume of water reabsorbed.
restores the normal water potential if the blood is diluted or becomes more concentrated
a fall in water potential of the blood may be caused
3 FACTORS TO REMEMBER
- reduced water intake
- sweating
- intake of large amounts of salt
ADH is caried to the kidneys where…
ADH increases the permeability of the walls of the distal convoluted tubule and the collecting duct to water
more water is reabsrbed from there into the region of high solute concentration, low water potential in the medulla
more water is reabsorbed from the medulla into the blood in the vasa recta
the water potential of the blood is restored to normal
the small volume of urine produced is relatively concentrated
its concentration is close to the concentration of the tissues near the apex of the loop of Henle
Near the apex of the loop of Henle and it is hyper tonic to the body fluids
Describe the ADH mechanism
ADH binds to the membrane receptors
Adenyl cyclase catalyzes the production of cyclic AMP(the second messenger)
Vesicles containing aquaporins in the cytoplasm to move to and fuse with the cell membrane
Aquaporins are incorporated into the membrane
Water molecules move in single file through their pores into the cell
down a water potential gradient
What is an Aquaporins
Intrinsic membrane proteins with a pore through which water molecules move through
