Topic 9 Flashcards
Solute concentration & osmolarity determined by what?
Total amount of solute / Volume of extracellular fluid
Changing extracellular water has significant effect on what?
solute concentration and osmolarity
Body water determined by what 2 things?
- Fluid intake (controlled by thirst)
2. Renal excretion of water (controlled by changing GFR and tubular reabsorption
If ECF solute concentration increases, what ultimately happens?
kidneys hold onto water so ECF volume increases diluting ECF solutes
If ECF solute concentration decreases, what ultimately happens?
kidneys excrete more water so ECF volume decreases concentrating ECF solutes
Assuming normal solute intake and metabolic production: What will remain relatively constant each day
Solute excretion
–Total amount of solute in ECF relatively constant as well
Assuming normal solute intake and metabolic production: What is adjusted to keep solute concentration of ECF constant?
Quantity of water excreted each day
With Increased ECF [solute]/osmolarity: The Normal amount of solute dissolved is in ____ water
less
With Increased ECF [solute]/osmolarity: Holding onto water will spread the total amount of solute over larger volume of water thus…
decreasing solute concentration of ECF
With Decreased ECF [solute]/osmolarity: The Normal amount of solute dissolved is in ______ water
too much
With Decreased ECF [solute]/osmolarity: Getting rid of water will spread the total amount of solute over smaller volume of water thus…
increasing solute concentration of ECF
Posterior pituitary responds to changes in ECF osmolarity by changing what?
ADH release
Increased ECF osmolarity results in an
increased release of ADH
Decreased ECF osmolarity results in a
decreased release of ADH
Quantity of water excreted controlled by what?
[ADH]
What part of the kidney does ADH act on and influence water reabsorption?
distal tubule & collecting duct
Decreased [ADH] results in a decrease in what?
decrease in water
–reverse is true
Changes in water reabsorption controls what 2 things?
urine volume and urine solute concentration
Increased water reabsorption means ___ water enters collecting duct _____ overall volume of urine - Normal amount of excreted solutes now dissolved in ____ volume –> production of small amount of very _____ urine
less
decreasing
less
concentrated
max concentration of urine: mls/day and osmolarity
KNOW
500 mls/day with osmolarity of 1200 to 1400 mOsm/Liter
— so its a little urine that is very concentrated
Decreased water reabsorption means ____ water enters collecting duct _____ overall volume of urine – Normal amount of excreted solutes now dissolved in ____ volume –> production of large amount of very ____ urine
more
increasing
more
dilute
min concentration of urine: L/day and osmolarity
KNOW
20 Liters/day with osmolarity of 50 mOsm/Liter
— so its diluted urine with a small concentration
An Increase in ECF solute does what to osmolarity?
Increase
Posterior pituitary increases release of what?
ADH
Increase in [ADH] produces an increase in _____ in distal tubule and collecting duct
water permeability
Increase in water permeability increases amount of what?
water reabsorbed
Increase in water reabsorption increases water volume in ECF so total ECF solute spread out over larger water volume returning ECF osmolarity to what level?
normal level
Increase in water reabsorption decreases water volume in urine so total excreted solute spread out over less water volume which increases what?
increases urine osmolarity (less urine with higher osmolarity)
For dilute urine, what is the max L/day and the osmolarity? KNOW
Can excrete 20 liters/day with minimal concentration of 50 mOsm/Liter
Excretion of dilute urine means you have high or low ADH?
Low
For dilute urine, what amounts of solutes have been reabsorbed?
normals amounts
For dilute urine, what section do you Limit water reabsorption?
late distal tubule and collecting ducts
If you Drink 1 liter of water, Changes begin to occur in how many minutes?
45 min
After you drink 1 liter of water and wait 45 minutes for the changes, you get a Slight increase in
solute excretion
After you drink 1 liter of water and wait 45 minutes for the changes, you get a Slight decrease in
plasma osmolarity
After you drink 1 liter of water and wait 45 minutes for the changes, you get a Large decrease in
urine osmolarity [600 mOsm/L to 100 mOsm/L]
After you drink 1 liter of water and wait 45 minutes for the changes, you get a Large increase in
urine output [1 ml/min to 6 mls/min]
For dilute urine production,
Filtrate osmolarity = Plasma osmolarity… which is about?
≈ 300 mOsm/L
To produce dilute urine, solute has to be reabsorbed at a ____ rate than water
faster
To produce dilute urine (PROXIMAL TUBULE): Solute & water reabsorbed at what rate? Whats the change is osmolarity?
same rate
No change osmolarity
To produce dilute urine (DESCENDING LOOP): Water reabsorbed following gradient into what? Whats the change is osmolarity?
hypertonic interstitial fluid
Osmolarity increases 2 to 4 times osmolarity of plasma
To produce dilute urine (ASCENDING LOOP): What is reabsorbed? Whats the change is osmolarity?
Sodium, potassium, chloride reabsorbed
–No water reabsorbed regardless of [ADH]
Tubular osmolarity decreases to 100 mOsm/L
–1/3 osmolarity of plasma