Loop of HENLE Flashcards
What is the loop of henle
a hair pin like structure that is responsible for water being reabsorbed from the collecting duct
what does it do to the urine
it concentrates it so it has a lower water potential compared to the blood
where is it found
cortex extending into the medula of the kidney
describe the descending limb
thin narrow long and very permeable to water
describe the ascending limb,
thick and impermeable to water
what happens first to the sodium ion
they are actively transported using atp in the walls of the ascending limb, from the acending limb into the interistial space between the asc/desc
what does this do
create a lower water potential in the interestrial space increase the water potential in the distant convulated tubulr
what happnes in the descending limb
as a result of the low water potential water moves out of the descending limb via ososmosis decreasing water potential in the filtrate
what happens to the water
it enter the space and then enters the blood capillaires which take water away
how does filtrate travel down the descending tube
as it goes down progressively loses water potential becoming more negative and reaches most negative at the tip
what happens at the base of the ascending limb
sodium ion start to diffuse out of the filtrate into the interistrial space
what happens as we go up the ascending limb
the sodium ions start getting actively transported out using active transport
what does it do the space
the interestrial space between the collecting duct and the ascending limb decreases in water potential
what exist in the interestrial space
there is a water potential gradient high water potential in the cortex and then water potential decreases further into the medulla as the ion concentration increases
what is the collecting duct
permeable to water so water moves out via ososmosis into the blood vessels in the space and carried away
how is flow of water maintained
although filtrate loses water as it moves down the collecting duct it always meet the interestrial space fluid with a lower water potential so water continues to move out throughout the whole length
what does the counter current multiplier ensure
water is always being removed out of the tubule
how does the water pass out
out of the collecting duct through aquapourins , which is controlled by adh
how is urine compared to the blood
the urine has a lower water potential compared to the blood
what is the role of the distal convulated tube
make final adjustment to the water level and salt levels, and reabsorption of any ions to maintain the ph
how are the walls of the convulated tube adapted
contain many mitochomdria and microvilli to allow blood to reabsorb any material from the blood rapidly
how does homeostatic control exist
achieved by hormones that act on the distal convulated tubule and the collecting duct
what is the water potential of the blood dependent on
the concentration of the glucose, ions, protiencs
why is the water potential lowered 3 reasons
an increase in sweating, increase in salt consumption, little water drinking
what is the first step of osmoregulation
the osmorecptors in the hypothalumus detect a fall in the water potential cause these cells to shrink as a result of loss of water via ososmosis
what does this shrinkage do
it leads to the production of the hormone adh which travels to the posterior pituitry gland
what happens here
the adh is released into capillaries where it travels in the blood to the collecting duct
what does it do in general to the distal convulated tube and collecting duct
increaes permeability to water so more water is reabsorbed into the blood
how does this occur
specific proteins in the cell surface membrane bind adh which activates the enzyme phosphorylase
what does phosphorylase do
causes the vesicle to bind to the cell membrane surface
what does the vescicle contain
pieces of plasma membrane that have aquapourins
what happens when they fuse
lead to the increase of aquarpourins on the cell surface membrane making the cell surface membrane much permeable to water
what does this do to water
more water leaves the collecting duct by osomosis down a concentration gradient , and reneter the blood making urine more concentrated
what also happens in the osmorecptors
sen nerve impulse to the thirst centre to encourage person to drink water
what happens when water levels increase
the osmorecepttors detect an increase in water and cause less nerve impulse to the pitutity and less adh released and less permeability to water
when does water level become too high
when large volumes of water is consumed
salts used in metabolism is not replaced in the diet
what does the osmorecptors do when water is too high
increase the impulses sent to the pitutitry gland to decrease the secretion of adh
what happens when there is less adh
less via the blood, leads to a decrease in the permeability of water in the collecting duct , less water reabsorbed and more diluted urine
what happens to the water potential
the water potential in the blood falls and returns to normal and adh release is increases
