Unit 4c Flashcards
what is the major way for water to get out the body?
urine
can kidneys both conserve and restore water?
no kidneys can only conserve water added water is from outside the body
where is water reabsorbed in the nephron?
descending loop of henle & distal nephron
At what osmolarity is water conserved and what osmolarity is excess water excreted?
At 1200 mOsM water is conserved and and at 50 mOsM water is excreted
what do antidiuretics do
promotes water reabsorption and conservation
how to produce dilute urine and what is a way to
reabsorb solute without water follow to be reabsorb through
1. reduced expression of aquaporins transporters
how to produce concentrated urine and what are 2 ways ?
reabsorb water but leave solutes in tubules
1. increased expression of aquaporins to let water into interstitial fluid
2. making epithelial more salty than tubular fluid
how is water loss or retention maintained before being excreted
its the changes in osmolarity (how much water or sodium is reabsrobed) in the distal nephron
what are the two ways water crosses membranes to go to blood ?
- leaks through the bilayer
- water channels called aquaporins
how does the epithelial cells become more salty than the tubulular fluid ?
due the medulla being more conentrated which gives us a gradient
what is vasopressin aka ADH
a hormone that has a vasocontrictive effect that prevents diuresis and conserve water
what happens if there is no VP (vasopressin) available ?
in the distal nephron water will not be able to move out leading to dilute urine (diuresis0
what is 4 step vasopressin pathway on the membrane to reabsorbed water
- vasopressin(hormone from blood ) binds to receptrs basal membrane
- second messanger (cAmp)
- AQP2 (Aqua porins) go to the apical surface
4 water is reabsorbed into the blood
where is vasopressin produced and released
vasopressin is produced in the hypothalamus neurons
vasopression is released in the pitiurary gland into blood
what 2 things trigger the release of vasopression?
- increase plasma osmolarity
- decrease in blood pressure/volume
why is osmolarity in the ECF key to regulate ?
osmolarity affects the size of cells and it ionic strength
what are osmoreceptors ?
they are stretch sensitive neurons( mechanorecptors that change shape and. increase their fire rate when osmolarity increased (stimulated by cellular dehydration )
what firing rate are the osmoreceptors when the ECF is hypotonic
no firing of APs
what are the 2 type of osmoreceptors ?
Peripheral Osmoreceptors & Central Osmoreceptors
where are periphery osmoreceptors located?
in mouth and blood vessels
where are central osmoreceptors located?
- in CSF ventricsles 3rd and 4th
- in SON (supraoptic nucleaus) hypothalomus where vasopressis is
where does the trigger for vasopresson release intergrate /
hypothalamus
what leads to bed wetting ?
at night there is a lack of vaspressin to carry out the water in tubules therefore its dilute urine and a high volume and causes you to pee
what is vasopression agonist and what does it do?
it is desmopressin and prevents bed wetting as its a replace for the lack of vp at night
what is the counter current in the renal medulla
the counter current is in the loop of henle and vesa recta travel in opposite direction where the descending limb pushes out water into the blood whilst the ascending limb keeps water and put solutes into the blood .
what transports the solutes from the ascending limb into the blood ?
NKCC symporter that is on the apical membrane and bring in Na+ , K+ , Cl - to membrane and Na+ goes into interstitial fluid via Na/K pump and K+ and Cl- get through via K/Cl symporter and seperate open channels on basal lateral side
what are the 2 reasons why the loop of henle are key ?
- 25% of Na+ & K+ is reabsorbed
- create salt gradient for loop
what is the kidneys response to decrease bood volume/pressume ?
conserve water to minimize blood volume lose
what is the kidney response to increased blood pressule/volume
excrete both salt and water and decrease ECF. volume to decrease blood pressure
