5.3 - .... Flashcards
which nephron segments comprise the distal nephron
- Distal convloluted tubule
(-Cortical collecting tubule - medullary collecting tubule
- papillary cllecting duct)
what fraction of the filtered load of water and sodium remain by the time the tubular fluid arrived at the distal nephron
10% of the filtered load of water
10% of the filtered load of NaCl (180 L)
what two hormones regulate water and sodium re-absorption in the distal nephron
- antiduiretic hormone (ADH)
- Aldasterone
how does ADH make a collecting tubule cell permeable to water
promotes water reabsorption therby generating a small colume of concentreated Urea
in the absence of ADH, why does tubular fluid become even more dilute from the beginning to the end of the distal nephron
Reabsorption of some NaCl in the distaal nephron contunues to dilute the tubular fuid resulting in excretion of a large volume of hypotonic urin. (Diuresis)
how does ADH make a collecting tubule cell permeable to water
ADH stimulates insertion of pre-existing AQP-2 channels into the luminal membrane.
what is the signaling process associated with ADH making a collecting tubule cell permeable to water
Increase AMP —> increase translocation of channel-containing sesicle to luminal membrane—> increase fusion and insertion—-> increase water permeability
where do the water channels reside in low ADH state?
sd
what type of Aquporin are located in the luminal and basolateral membrane of collecting tubule cells
AQP3, (at least 3 different isoforms)
where is the only place aldosterone receptors are found
cortical collecting tubule cells
what is countercurent multiplication
maxiamal NaCl concentreation differenc afross ascending limb ~ 100 mM/mOsm/L
what is essential for the depostion of NaCl in the medullary interstitium
if only isotonic fluid flowed into the ascending limb, it would be impossible to maintain interstitial NaCl concentrations above 150 mM
3 conceptual steps of contercurrent multiplication
1 reabsorption of NaCl by the ascending limb (ASC) retention in interstitium
2 reabsorption of H2O by the descending limb(DES) removeal by the vasa recta
3 isotonic fluid from proximal tubule into loop
How do the eura transport characteristics of the subsection of the collecting tubule differ
with ADH, TF urea concentrations increase (increase ADH —> increase H2O reabsorption—-> increase TF urea)
why is ADH so criticle for urea reabsorption
causes urea to be re-concentrated and reabsorbed
