Water retention and balance Flashcards
What is osmolarity? What are the ranges for blood? And Urine?
Depends on number of solutes present-the greater the number of dissolved particles, the greater the osmolality
blood goes from 285-295mosmol, while urine in 5-1400 mosmol
Why does the semi-permeable membranes of cell pause a problem for water retention?
When you increase salt/osmolarity, you HAVE to increase water because we cant stop it from getting out (and same vice-versa). Therefore the salt concentration will determine the volume
What is the most abundant component of plasma and ECF? And the highest conc solute?
Water is the most abundant solvent, and sodium is the main solute
How much water is intercellular and extracellular?
65% intra, 35% extra –and the concentration of solute vary a lot between those
What are the main ways to get rid of water?
Sweat-but isn’t controllable. Faeces-not controllable, respiration-hard to breath, urine-best controlled
Where in the kidney is water reabsorbed?
Everywhere-proximal tubule, descending loop, distant tubule, collecting duct- ALL but ascending loop of henle
About 30% make it to the loop, 20% makes it to collecting tube, and that’s where the last part is absorbed
What is the difference between kidney medulla and cortex for water absorption?
Large osmolarity difference beteween cortex (low) and medulla (high)
How it the shape of the loop of henle helping the gradient be generated?
The shape of the loop of henle-down then up-coiled and they interact with one another
Water goes out on descending, salt comes out in ascending-the salt that comes out from the ascending into the ECF provides force for water to be taken out in descending (equilibrated osm). AND the more you do that, the larger the gradient is (as Ascending loses salt and descending gains-
But length isn’t all, need activity (transport)
How does the kidney reach its highest points of concentration?
In the descending limbs, and the end of collecting duct, as water comes out, urea gets more concentrated> But they communicate. As urea gets more concentrated in collecting duct (water out), then exits to ECF, where it rises to be above the one of loop of henle-then enters there and increases gradient
What different urea transporter exist and where are they?
UTA1-
UTA2-thin descending limb
UTB-descending vasa recta (cycle urea from blood vessels)
How do cells from the loop of henle receive blood?
Vasa recta sit around the loop (for secretion and reabsorption)-but also counter current. As vasa recta goes down to lowest point of loop, high osmolarity. Water dilutes out of descending, and solutes in. in ascending reverse-vasa recta communicate so you get delivery without losing gradient
How does vasopressin/ADH act in water collection?
In the collecting tube, V2 GCPR receptors. increases aquaporin to membrane allowing water to be drawn back in-and also increase expression
What regulates ADH?
Adh is regulated in hypothalamus. Inhbited in response to high blood pressure/lower plasma osmolality (too much water). Also alcohol increases it causing dehydration
Increase fluid loss as osmolality drops, which causes an increase after
Reverse if youre dehydrated (plasma osmolality high/low BP, more ADH, V2 -> AQR2, more water intake etc)
What is the disorder caused by insufficient ADH, no ADH receptor or no aquaporin?
Diabetes INSIPIDUS-large amounts of urine and thirst
SAQ-what are 4 components of making hyperosm
1Countercurrent, Desceinding impermeable to salt but not water, ascending reverse, and urea permeability at bottom
