Na+ handling Flashcards
Describe the fluid compartments of the body, to include their electrolyte composition the normal composition of the major electrolytes in extracellular fluid (ECF), ICF and urine
what is the biggest effective osmole in blood plasma?
SODIUM
what is the major osmotically effective solute in the ECF?
Na+ ion,
therefore water in the ECF compartment DEPENDS on the Na+ ion content
If sodium in ECF changes then volume of ECF changes
when we’yre talking about the transport of Na+, we r talking about Cl- too, cuz they go togezer
components of sweat?
its hypoosmotic, but still has Na and CL
how is Na+ lost from the body?
Sweat
Faeces
Urine
if we wanted to change plasma volume (ECF), Why cant we just add or remove water to or from the plasma?
what do we do instead?
because that would change the plasma osmolarity!
add isosmotic solution (a solvent and solute) to increase volume!
Osmolarity : The concentration of a solution in terms of osmoles of solute per litre of solution
How do we add or remove an isosmotic solution?
move the osmoles actively and water will follow passively!!!
which 2 common places in nephron is sodium absorbed the most?
proximal tubule and ascending loop of henle!
which area in the nephron is impermeable to water
ascending limb!
how does the Descending & Ascending limb work with water?
Descending limb handles water
Ascending limb reabsorbs Na+
what Effects the change in renal Na+excretion?
Changes in osmotic pressure and hydrostatic pressure alter the proximal tubule Na+ reabsorption (and hence water).
also changes in hydrostatic pressure in the peritubular capillaries effects Na reabsorption.
what happens when renal artery BP INCREASES? how does this effect Na and water?
if pressure increases,
then the hydrostatic p. in the peritubular capillaries will also increase>
things will be harder to move into the capillaries>
we will loose more Na+ and water!
natriuresis ? diuresis
Increased Na+ excretion
Increased water excretion
Increase in BP. actually downregulates the expression of transporters in the proximal tubule!
where r Aquaporin channels located in the kidney ?
Assendinf limb is an asshole, doesnt like water!
Sodium reabsorption is mainly active or passive?
Sodium reabsorption is mainly active
how does Na+ travel transcellularly? paracellulary?
what about Cl-?
Na+ Transcellular process>> driven by 3Na-2K-ATPase pumps on basolateral membrane
Cl- reabsorption is by transcellular (active)
AND
some paracellular (passive)> via a change in the elctrochemical gradient
describe different transporters for Na throughout the whole fucking nephron
what is this?
PCT>> look at its brushborder! lana it reabsorbs the most shit!
describe the different segments of the PCT & how it handles Na+
what drives reabsorption of things from PCT into the peritubular capillaries?
each has a different set of transporters!
the increase of oncotic p. w/in the peritubular capillaries!
- (bc of the protein and albumin we left behind when we were filtering stuff in the glomerulus)*
- so therefore there is an attractive draw in the PCT!*
- the net result of what happens in the PCT is isoosmotic to plasma!*
what does S1 of the PCT contain?
what does S2-S3 of the PCT contain? (how is Na here reabsorbed diffrently)
Sodium and chloride uptake (late proximal tubule)
what is the concentration of Cl- up to this point?
Reabsorption is isosmotic with plasma !!!!
we r taking solute and solvent back into the plasma so we r adding volume straight back
what is the driving force of moving water in the proximal tubule? (3)
– is osmotic gradient established by solute absorption e.g. osmolarity in
interstitial spaces ↑
– hydrostatic force in interstitium ↑
– ↑ Oncotic p. in peritubular capillary due to proteins left in blood
ASK ALAAAA
shnu hatha?
loop on henle
u can see the thick and the thin ones!
explain the distribution of reabsorption of solvent and solute in the loop of Henle
what is occuring in the thin and thick descending limb
as we r going down the loop of henle, there is an increase in osmolality (hyper osmolar!)
this will cause water to be sucked out!
Thin ascending limb reabsorption?
the thin segment of the ascending limb has a much lower reabsoptive capacity
but bc Na+ concentration r high at this point in the lumen,
Sodium ion reabsorption passive at this point
what allows for passive Na+ ion reabsorption in thin ascending limb? (2)
Water reabsorption in descending limb creates a gradient for passive Na+ ion reabsorption in thin ascending limb
AND
Epithelium in thin ascending limb permits passive reabsorption by paracellular route
Thick ascending limb reabsobrtion and importance of K+ here
Role of ROMK channel in the thick ascending?
K+ moves from the cell into the lumen!
it has to be secreted back into the lumen to keep the NA K CL channel working!!
which region of the nephron uses the most energy!
Thick ascending limb
is particularly sensitive to hypoxia !
Tubule fluid leaving loop is ______________ compared to plasma
∴ hypo-osmotic ( more dilute)
shnu hatha
Distal tubule
Distal convoluted Tubule and Late distal tubule
describe the fluid that has reached this point?
By the time the filtrate has reached the end of ascending limb and beginning distal>> filtrate is so dilute!
Late distal tubule & collecting duct
how does Na enter in this portion?
NaCl enters by Na cl cotransporter & ENaC
leaves via 3Na-2K-ATPase in basolateral membrane
which part of the nephron is important in Ca+ reabsorption?
how is is reabsorbed (apical and basolateral side)
different cells of collecting duct
Principle cells & intercalated cells (A & B)
function of principle cells?
Reabsorption of Na+ ions via ENaC on apical membrane
3Na-2K-ATPaseinbasolateral–driving force
produces a lumen(–) charge providing a driving force for Cl- ion uptake via paracellular route
This(-charge) in the lumen has an important role in K+ secretion into the lumen
VariableH20uptakethroughAQP dependent on action of ADH
function of Intercalated cells
TYPE A = Acid-secreting (express H+-ATPase and the H+/K+-ATPase at the apical/luminal membrane,)
TYPE B= Bicarbonate secreting (express the Cl−/HCO3− exchanger at their basolateral membrane)
In the cortical & outer medullary collecting duct,
