15.6 Osmoregulation Flashcards
define osmoregulation
the balancing and control of the water potential of blood
how is water gained (most to least)
- drink
- food
- cellular respiration
how is water lost (most to least)
- urine
- sweat
- exhaled air
- faeces
describe the mechanism of ADH action
- released from the pituitary gland
- carried in blood to the collecting duct
- binds to receptors on the cell membrane and trigger formation of cyclic AMP(cAMP) as a second messenger
what is the effect of ADH on the distal convoluted tubule and the collecting duct
increases permeability to water
what is a second messenger
a molecule which relays the signal received at cell surface receptors to molecules in cells
explain the cascade of events cAMP caused
- vesicles in cells lining the collecting duct fuse with cell surface membranes on the side in contact with the medulla
- vesicle membranes contain aqauporins making the cell surface membrane permeable to water
- route for water to move into the tissue fluid by osmosis
what are aquaporins
protein-based water channels
if more ADH is released what happens to water channels
- more water channels
- easier for water to leave
- formation of a small amount of concentrated urine
how are water requirements of the body controlled
by a negative feedback system involving osmoreceptors in the hypothalamus which are sensitive to the conc of inorganic ions in the blood
what happens when you are dehydrated
- water content of blood drops = water potential drops
- detected by osmoreceptors
- posterior pituitary gland releases more ADH
- DCT and collecting duct are more permeable so more water is reabsorbed
- small amount of conc urine produced
what happens when you are hydrated
- water content of blood rises = water potential rises
- detected by osmoreceptors
- posterior pituitary gland releases less ADH
- DCT and collecting duct are less permeable so less water is reabsorbed
- large amount of dilute urine produced
