Flashcards in 5.3 Kidneys & Osmoregulation Deck (35):
what is osmoregulation?
controlling water potential of blood within very narrow boundaries
what sorts of things can put the osmotic stress on the body?
drinking a lot
what could happen is kPa was not kept stable?
damage or even death
what is crucial to maintaining kPa, regardless of water sources is taken in or lost?
changing the concentration of urine
amount of water lost in urine is controlled by which hormone? in what sort of system?
negative feedback system
ADH is produced by the hypothalamus and secreted where?
posterior pituitary where it is stored
what does ADH do to the collecting duct and distal convoluted tubule?
changes their permeability to water
ADH is released from pituitary and travels in the blood till it binds to receptors where?
on cell membrane of tubule cells
when ADH binds it triggers the formation of what?
Cyclic AMP is a second messenger, what is this?
a molecule relaying signals received at cell surface to molecules inside the cell
cAMP causes vesicles in the cells lining the collecting duct to do what?
fuse with cell surface membranes in contact with tissue fluid of medulla
membranes of the vesicles contain what?
what are aquaporins?
protein based water channels which are inserted into the cell surface membrane making it permeable to water
what do aquaporins provide?
a route for water to move out of tubule cells into tissue fluid of medulla and blood capillaries by osmosis
the more ADH released, the more aquaporins inserted making what easier?
water to leave tubule cells by osmosis resulting in a small amount of concentrated urine
when water is returned to tissue fluid and blood capillaries what does it maintain?
what happens when ADH levels fall?
levels of cAMP fall
aquaporins removed from tubule membrane and are enclosed in vesicles
collecting duct impermeable to water
large amounts of dilute urine
control of ADH levels is done by a negative feedback system involving which receptors?
osmoreceptors in the hypothalamus
what are osmoreceptors sensitive to?
the concentrations of inorganic ions in the blood
(little water) when concentration of inorganic ions in the blood increases what happens to its kPa?
it becomes more negative
(little water) what detects the change in kPa?
(little water) what do the osmoreceptors do?
send nerve impulses to posterior pituitary which releases ADH
(little water) ADH binds to receptors on collecting duct and has what effect?
increases permeability to water
(little water) water leaves filtrate and diffuses into blood by osmosis producing what?
small amount of concentrated urine
(excess of water) blood becomes more dilute with an excess of water, what effect does this have on kPa?
(excess of water) the change is detected by what?
(excess of water) what happens to the nerve impulses to the posterior pituitary?
reduced or stopped and release of ADH inhibited
(excess of water) what happens to the walls of the collecting duct?
remain impermeable to water little reabsorption takes place
(excess of water) what is produced?
large amount of dilute urine
what other receptors control ADH release?
baroreceptors in the aortic and carotid arteries detect changes in what?
blood pressure which can stimulate or inhibit ADH release
(baroreceptors) increase in blood pressure can be caused by a rise in what?
(baroreceptors) increase in blood pressure is detected by baroreceptors which do what?
prevent release of ADH
(baroreceptors) less ADH increases the amount of water lost in urine which has what effect?
reduced blood volume
reduced blood pressure