Unit 2, L15 Tubular Functions along the Nephron Flashcards
Euvolemia is achieved when
Whenever Na excretion matches Na intake, meaning Na balance leads to steady state ECV
What percentage of Na is reabsorbed in the proximal convoluted tubule
67%
What percentage of Na is reabsorbed in the thin descending limb
0%
What percentage of Na is reabsorbed in the thin ascending limb
0%
What percentage of Na is reabsorbed in the thick ascending limb
25%
What percentage of Na is reabsorbed in the distal convoluted tubule
5%
What percentage of Na is reabsorbed in the collecting duct
3%
Isosmotic reabsorption of Na only happens where
In the proximal tubule
In the early proximal tubule, Na+ is reabsorbed primarily with ___________
HCO3- and organic solutes such as glucose and amino acids
In the late proximal tubule, Na+ is reabsorbed primarily with ________
Cl-
By the time the glomerular filtrate reaches the midpoint of the proximal tubule, what following modifications have been made because of the secondary active transport processes?
100% of the freely filtered glucose and amino acids have been reabsorbed
85% of the filtered HCO3- have been reabsorbed
Most of the filtered phosphate, lactate, and citrate have been reabsorbed
Na+ reabsorption is coupled to each ofhtese transport processes, so its been extensively reabsorbed
In the early proximal convoluted tubule, reabsorption of Na is coupled with HCO3-, what does this do for reabsorption of Cl-
There is a negative transepithelial voltage that provides the driving force for paracellular reabsorption of Cl0
In the late proximal convoluted tubule, Na+ transport is largely accompanied by _____
Cl- reabsorption by both transcellular and paracellular pathways
Concentration of glucose along the PCT
The overall concentration should be the same in Bowman’s space as in the plasma
As it goes through the proximal tubule, it is being reabsorbed
Concentration of Na along the PCT
Concentration is high and its being moved along with water all the way along, so its movement, in terms of concentration, is going to be the same all the way along the proximal tubule. It is isosmotic
Three segments of the loop of Henle
Thin descending limb, thin ascending limb, and thick ascending limb
Thin descending limb permeabilities
Thin descending limb is IMPERMEABLE to Na and Cl, but PERMEABLE to H2O
Thin ascending limb permeabilities
Thin ascending limb is PERMEABLE to Na and Cl but IMPERMEABLE to H2O
Thick ascending limb permeabilities
IMPERMEABLE to water, so Na is being reabsorbed but H2O is not following, so urine is getting more and more diluted (as water is getting left behidn)
In the thick ascending limb, what is the movement and gradients
1) Active pumping by Na/K/ATPase in the basalateral membrane, sends Na out and K in
2) This causes low Na concentration inside the cell
3) This produces a chemical gradient for Na to move from the tubular fluid and into the cell
What part of the nephron is the site of action for diuretics?
Thick ascending limb
At max doses, loop diuretics will inhibit what
Completely inhibit NaCl reabsorption in the TAL and result in excretion of 25% of filtered Na
The early distal tubule reabsorbs what percentage of filtered Na
5%
Permeabilities of the early distal tubule
IMPERMEABLE to water
