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Renal Phys 6: Regulation of extracellular fluids
Pasley 4/27/11 lecture 1 hr
66
Physiology
Undergraduate 4
04/20/2011

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Term
900 mOsm/L, you have to get out at least 600 mOsm
Definition
what is the average solute excretion rate?
Term
900 mOsm/day / 50 mOsm/kg = 18 L/day
Definition
if you are excreting solutes at the average solute excretion rate of 900 mOsm/L and you can only concentrate your urine to 50 mOsm/L, how much urine do you have to excrete to get rid of all the solutes you need to?
Term
hot weather: decrease water out by 100 mL
heavy excercise: increase water lost by 300 mL
Definition
what happens to water loss in the lungs during hot weather? during heavy excercise compared to normal loss?
Term
hot weather: 1300 more mL's lost
heavy excercise: lose 4900 more mLs H2O
Definition
what happens to water loss in the sweat during hot weather? during heavy excercise compared to normal loss?
Term
No, even in heavy exercise or hot weather, the skin and feces water loss remains at 350 mL and 200 mL respectively
Definition
does the amount of water loss change in the feces or from the skin depending on environmental conditions changing?
Term
hot weather: retain 300 mL's (normally lose 1500, in hot weather lost 1200)
heavy excercise: retain 1000 more mLs H2O
Definition
how does water loss in the urine change in hot weather? heavy exercise?
Term
1) ECFV: increases
2) Plasma Osm: decreases
3) urine flow rate: increases
4) sodium lost in the urine: decreases
Definition
what does drinking a hypotonic solution do to the following:
1) ECFV
2) Plasma Osm
3) urine flow rate
4) sodium lost in the urine
Term
1) ECFV: increases
2) Plasma Osm: increases
3) urine flow rate: increases a lot
4) sodium lost in the urine: increases
Definition
what does drinking a hypertonic solution do to the following:
1) ECFV
2) Plasma Osm
3) urine flow rate
4) sodium lost in the urine
Term
1) ECFV: increases
2) Plasma Osm: stays the same
3) urine flow rate: increases
4) sodium lost in the urine: increases
Definition
what does drinking a isotonic solution do to the following:
1) ECFV
2) Plasma Osm
3) urine flow rate
4) sodium lost in the urine
Term
1) ECFV: decreases
2) Plasma Osm: increases
3) urine flow rate: decreases
4) sodium lost in the urine: decreases
Definition
what does dying of thirst do to the following:
1) ECFV
2) Plasma Osm
3) urine flow rate
4) sodium lost in the urine
Term
P Na (plasma sodium concentration)
Definition
Posm = 2.1 x ?
Term
142 x 2.1 = 298 mOsm/L
Definition
if plasma sodium concentration = 142 mEq/ml, what is the plasma osmolarity?
Term
increased extracellular osmolarity (NaCl) stimulates ADH release which increases H2O reabsorption and stimulates thirst(H2O intake)
Definition
what is the thirst mechanism?
Term
ADH - Thirst Osmoreceptor system
Definition
what is the name of the thirst system?
Term
magnocellular neurons of the hypothalmus make it, then it is released from the posterior pituitary
Definition
what neurons synthesize ADH?
Term
1) water deficit which causes
2) increased Extracellular osmolarity
3) osmoreceptors detect that and cause ADH secretion
4) which increases plasma ADH
5) which increase H2O permeability in the DCT & collecting ducts
6) water is reabsorbed
7) and less water is excreted
Definition
describe the osmoreceptor-ADH feedback mechanism flow chart
Term
1) increased osmolarity!!
2) decreased blood volume
3) decreased blood pressure
4) other: fear, angiotensin 2, nausea, nicotine, morphine
Definition
what are the stimuli for ADH secretion?
Term
small changes(increase) in osmolarity or big change(decrease) in blood volume
Definition
___ changes in osmolarity cause ADH release, whereas ____ changes in blood volume cause ADH release
Term
they shrink due to increased osmolarity
Definition
what happens to the osmoreceptor cells to cause ADH release?
Term
ADH decreases water excretion, and decreases urine volume, however it does not affect solute excretion, so the urine is more concentrated
Definition
what does ADH do to water excreted? solutes excreted?
Term
causes them to swell and decrease ADH, so there is a lot of dilute urine released
Definition
what does excess water do to the osmoreceptor cells?
Term
1) decreased osmolarity
2) increased blood volume
3) increased BP
4) other: alcohol, clonidine, haloperidol
Definition
what 4 things DECREASE ADH secretion?
Term
eat salty food to counteract inhibition of ethanol and being up your osmolarity
Definition
what do you do to counteract the effects of alcohol blocking your ADH secretion (making you pee a lot?)
Term
1) high osmolarity (shrink the osmoreceptors)
2) decreased blood volume
3) decreased BP
4) angiotensin 2 (aldosterone and salt reabsorption)
5) low h2O -> decreased salivary gland excretion so dry mouth (and gastric distention = variable effect)
Definition
what 5 things stimulate thirst?
Term
small changes in GFR can cause BIG changes in renal excretion (which is why the body tries to maintain the GFR)
Definition
how does GFR affect renal excretion?
Term
GFR or tubular resorption
Definition
ALL feedback mechanisms that control renal excretion of Na & H2O alter either ___ or ___
Term
causes increased sodium excretion
Definition
what does a increased BP do in pressure natiuresis?
Term
increased urine volume
Definition
what does a increased BP do in pressure diuresis?
Term
increase in blood pressure
Definition
what happens in chronic HTN when the kidneys fail to successfully excrete salt and water at normal pressures?
Term
natriuretics and diuretics to decrease blood volume and BP by decreasing salt and water retention
Definition
what is a common treatment of HTN, what does it do?
Term
1) high ADH
2) high osmolarity of renal interstitium
Definition
what are the basic requirements for secretion of concentrated urine?
Term
initially the blood volume increases, but after a few days (8ish) the body adjusts and lowers the blood volume by excreting more sodium
Definition
if you increase your sodium intake what happens to blood volume initially? after about 8 days?
Term
it will lower the concentration slightly, but it doesn't play a huge, role in regulating it (unlike ADH)
Definition
if aldosterone/AngII is blocked, what effect will it have on plasma sodium concentration as more sodium is taken in?
Term
2 mEq > normal
Definition
what concentration of sodium in the ECF activates the thirst mechanism?
Term
right next to each other on the 3rd ventricle
Definition
where in the brain are the thirst and ADH centers?
Term
both are elicited (increased)
Definition
if there is a decrease in extracelluar sodium and decreased blood volume, what happens to thirst and salt appetite?
Term
it sky rockets because ADH is a major regulator of plasma sodium concentration
Definition
what happens to plasma concentration of sodium when ADH is blocked and sodium intake increases?
Term
there is increased blood volume, causing you to have low ADH and excrete water
Definition
baroreceptors and volume receptors firing tonically inhibit SON (supraoptic nucleus) and PVN(paraventricular nucleus) when ??
Term
elevate plasma osmolarity, causes you to then retain and drink water
Definition
what stimulates the osmoreceptors to increase ADH in the plasma?
Term
decrease it
Definition
in severe dehydration, what can ADH do to EC sodium?
Term
increases, this is what happens when you drink beer because it inhibits ADH
Definition
as you have less Plasma ADH, collecting duct reabsorbtion declines and urinary flow ______
Term
1 L/hour
Definition
if you take in 3 beers/hour (1 L), what does your urinary flow become to maintain water balance?
Term
1) ECF volume increases
2) MABP increases
3) these inhibit ADH
4) POsm increases (due to ethanol)
5) ethanol inhibits ADH secretion
Definition
how does beer drinking make your urinary flow increase?
Term
diabetes insipidus
Definition
what disease is caused by a decrease in ADH production?
Term
inability of the posterior petuitary to secrete ADH (head injuries)
Definition
what causes CENTRAL diabetes indipidus?
Term
PU & PD, large volume of dilute urine
Definition
what are the clinical signs of diabetes insipidus
Term
1) inability of the renal tubules to respond to ADH
2) impariment of the counter-current mechanism
Definition
what causes nephrogenic diabetes insipidus
Term
special atrial cells when the atria are distended
Definition
when/where is ANP secreted?
Term
causes increased GFR to increase sodium and H2O excretion
Definition
what does ANP do?
Term
inappropriate ADH syndrome
Definition
what disorder is characterized by excess ADH leading to
1) excess water reabsorption and
2) decreased plasma osmolarity
3) hyponatremia
Term
inappropriate ADH syndrome
Definition
what disorder is characterized by excess ADH leading to
1) excess water reabsorption and
2) decreased plasma osmolarity
3) hyponatremia
Term
central diabetes insipidus
Definition
what disorder is characterized by insufficient ADH leading to
1) increased plasma osmolarity
2) hypernatremia
3) excess thirst
Term
1) ADH deficiency (central diabetes insipidus)
2) failure to respond to ADH (nephrogenic diabetes insipidus)
-defect in ADH action
-impaired loop NaCl reabsorption
- drug induced renal damage(lithium, analgesics)
- malnutrition (decreased urea concentration)
- kidney disease: pyelonephritis, hydronephrosis, chronic renal falure
-
Definition
what things cause problems concentrating the urine?
Term
hypothalamic or Cenral DI
Definition
name the diabetes type: defect in ADH sythesis or released (depresses PADH)
Term
nephrogenic DI
Definition
name the diabetes type:
defect in ADH action, failure to maintain hyperosmotic medullary gradient
Term
polydypsic DI
Definition
name the diabetes type:
compulsive water drinking
Term
Diabetes mellitus (H2O out with the glucose)
Definition
name the diabetes type:
elevated blood glucose leads to osmotic diuresis
Term
central: hypernatremia, with LOW plasma ADH
neprhogenic: hypernatremia with elevated plasma ADH
Definition
what happens when you restrict fluid to a central DI patient? with a nephrogenic DI patient?
Term
central DI
Definition
which patient will respond to ADH administration with reduced urine output and urine osmolarity? central DI or nephrogenic DI
Term
water access and ADH
Definition
what is the treatment of central DI?
Term
1)1st correct the underlying renal disorder if possible
2) low sodium diet
3) diuretic to enhance Na+ excretion
Definition
what is the treatment of nephrogenic DI?
Term
fluid restriction normalizes the situation
Definition
what will fix a patiendt with polydipsic DI with polyuria and hyponatremia?
Term
total GFR: decreases
GFR/nephron: increases
urine flow rate: stays the same
volume excreted: increases (more dilute urine)
Definition
if you lose 75% of your nephrons, what happens to total GFR? GFR/nephron? urine flow rate? urine volume excreted?
Term
20 million or 1 in 9 US adults
Definition
how many americans have chronic kidney disease?
Term
early detection
Definition
what can help prevent the progression of kidney disease to kidney failure?
Term
GFR
Definition
what is the best estimate of kidney function?
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