11/22 Flashcards
What would expect the osmolarity to be in the PCT in a state of conservation?
What would you expect the renal interstitium around the PCT to be?
300mOsm
water is permeable here to ISF should be the same
300mOsm
What would expect the osmolarity to be in the descending loop of Henle in a state of conservation?
What would you expect the renal interstitium around the descending loop of Henle to be?
1200mOsm
water is permeable here to ISF should be the same
1200mOsm
Which pump is found in the thin ascending loop of Henle?
Is water permeable here?
Na/Cl pump
Not very permeable
Is water permeable in the thick ascending limb?
No. This is why it is called the diluting segment. 25% of solutes get reabsorbed but no water leaves the tubule
what percent of what gets filtered is reabsorbed in the thick ascending limb?
25%
what is an example of what the osmolarity of the thick ascending limb could be in a period of conservation?
100mOsm
Why is the 100mOsm in a period of conservation concentration at the thick ascending loop of Henle interesting?
Because the interstitium is really concentrated in comparison, and even during a period of conservation, the osmolarity in the tubule is getting really low.
Nothing really changes that this segment is the diluting segment, (i.e how much ADH, how much angiotensin II is there). During states of conservation and states of excess it will always be the diluting segment.
The osmolarity of the last part of the distal tubule should be
the same as it is in the interstitium surrounding it.
It is permeable to water and should therefore be in balance.
The osmolarity of the last part of the collecting duct should be
the same as it is in the interstitium surrounding it.
It is permeable to water (under normal circumstances) and should therefore be in balance.
The kidney can’t concentrate the urine any more than it can concentrate the _____
why is this?
renal interstitium
Water permeability is based on osmosis so it will go towards the more concentrated area until it is balancded
What would expect the osmolarity to be in the PCT in a state of excess?
What would you expect the renal interstitium around the PCT to be?
300mOsm
water is permeable here to ISF should be the same
300mOsm
What would expect the osmolarity to be in the descending loop of Henle in a state of conservation?
What would you expect the renal interstitium around the descending loop of Henle to be?
600mOsm
water is permeable here to ISF should be the same
600mOsm
What makes the difference in the concentration of the renal interstitium at the descending loop of Henle in a state of conservation vs. excess?
ADH.
ADH helps us reabsorb water and urea during states of conservation but it is not playing a role during states of excess so that we do not retain as much water
What changes would you see in a nephron in a state of conservation vs a state of excess?
- The renal ISF at the loop of Henle would be a lot more concentrated during conservation
- the distal convoluted tubule will be permeable to water during conservation
- the collecting duct will be permeable to water and urea during conservation
- the urine will be much more dilute during excess
What similarities would you see in a nephron in a state of conservation vs a state of excess?
- the PCT will have similar/same osmolarities in the tube and in the ISF in both states
- The Diluting segment will have similar/same osmolarities in the tube and in the ISF
Why are people put on diuretics?
To lower blood pressure or prevent further heart failure
Diuretics cause an increase in fluid _______ from the body
excretion
Where does the fluid come from that is excreted when using diuretics?
extracellular fluid volume
What happens when you are exposed to a diuretic for the first time?
You dump a lot of urine
what is lost when someone is taking diuretics?
electrolytes and water
If you diurese 1L of fluid, how much of that will come from the plasma?
200cc.
This is enough to lower blood pressure
ECF fluid is made up of what compartments?
1/5 = plasma
4/5 = interstitium
Why do you see an increase in urine when you give a second, third, fourth, etc. dose of a diuretic?
The first time you give the drug you will see an increase in urine d/t the drug “skimming” off the top and taking the extra fluid from the ECF. subsequent doses are only maintaining this new level.
However, you will see an increase in urine output with those doses d/t water building up over the hours between the dose.
If you start off with 1000cc and the initial dose takes off 200cc then the new balance is 800cc. Over the next few hours you gain 200cc and when you take your next dose you lose 200ccs bringing you back down to your new balance.
Why is long term therapy more focused on diuretics than drugs like an alpha receptor blocker?
Long term, the body figures out a way around those drugs by changing ADH, angiotensin, or one of the many other factors that feeds into blood pressure. Assuming the patient is responsive to diuretics, it is a much better long term management strategy.
what effect does salt intake have on angiotensin II?
it decreases it and therefore decreases the amount of salt that we reabsorb
If we have high levels of angiotensin II and we increase salt intake, what will happen?
our bp will increase
What advice can we give to patients with chronically high angiotensin II levels?
decrease salt and water intake and BP should be okay