(5) Urine Concentration and Dilution

105 terms by schmidd2 

Create a new folder

Advertisement Upgrade to remove ads

what are the 5 ways we output water?

- kidneys
- lungs
- feces
- sweat
- skin

water is split up into___?

- intracellular fluid
- extracellular fluid
- cell membranes

most water is in ____cellular fluid

intra (28L)

versus extracellular (14L)

extracellular fluid is split up into ____ (3 things)

- plasma (3L)
- capillary membranes
- interstitial fluids (11L)

the lymphatics drain from the ___ to the ____

interstitial fluid to the plasma

sodium is mostly ___cellular

extra

potassium is mostly ____cellular

intra

what is dehydration?

WATER LOSS leading to
- elevation in plasma sodium
- INTRACELLULAR water deficit

what is hypovolemia?

any condition in which the EXTRACELLULAR fluid volume is reduced (e.g. BLOOD LOSS)

TRUE OR FALSE
both dehydration and hypovolemia can occur

true
(e.g. excessive sweating, diarrhea)

what happens when we lose excessive amounts of H2O from the ECF?

- ECF osmotic pressure rises
- cells lose H2O to ECF by OSMOSIS
- cells shrink

what happens when excessive H2O enters the ECF?

- ECF osmotic pressure falls
- H2O moves intro cells by OSMOSIS
- cells swell

TRUE OR FALSE
there is a lack of relation between plasma sodium concentration and volume

true

when you add NaCl to a substance, what happens to:
- plasma osmolality
- plasma sodium
- ECF volume
- ICF volume
- urine sodium

when you add NaCl to a substance, what happens to:
- plasma osmolality INC
- plasma sodium INC
- ECF volume INC
- ICF volume DEC
- urine sodium INC

what hormone will be activated when NaCl is added?

what will the effect be?

renin-aldosterone
- reabsorb less Na
- excrete more Na

when you add water to a substance, what happens to:
- plasma osmolality
- plasma sodium
- ECF volume
- ICF volume
- urine sodium

when you add NaCl to a substance, what happens to:
- plasma osmolality DEC
- plasma sodium DEC
- ECF volume INC
- ICF volume INC
- urine sodium INC

when you add water, what hormone will be affected?

less ADH

when you add isotonic NaCl to a substance, what happens to:
- plasma osmolality
- plasma sodium
- ECF volume
- ICF volume
- urine sodium

when you add isotonic NaCl to a substance, what happens to:
- plasma osmolality doesn't change
- plasma sodium doesn't change
- ECF volume INC
- ICF volume doesn't chance
- urine sodium INC

when you add isotonic NaCl, what hormone will be added?

ANP (stretch due to volume)

the only thing that happens in all 3 scenarios (of adding NaCl, water, isotonic NaCl) is ____

increased urine sodium

what is plasma TONICITY?

balance between extracellular NaCl and H2o

what senses plasma tonicity?

osmoreceptors in hypothalamus

what regulates plasma tonicity?

ADH release

what is plasma volume determined by?

determined by the ABSOLUTE amounts of NaCl and H2O in extracellular space

what is plasma volume sensed by?

macula densa in JGA

what is plasma volume regulated by?

renin release

hypernatremia, when cells shrink, is when you lose water ____ quickly than Na

more

what are 3 general causes of hypernatremia (cell SHRINKAGE)?

- unreplaced water loss
- water loss into cells
- sodium overload

what types of things can cause unreplaced water loss (causing hypernatremia)?

what types of things can cause water loss into cells (causing hypernatremia)?

severe exercise of seizures

what types of things can cause sodium overload (causing hypernatremia)?

intake or administration of hypertronic sodium solutions

hyponatremia (cells welling) is when you lose Na ___ than water

faster

what 2 general things cause hyponatremia?

- disorders in which ADH is high
- disorders in which ADH is appropriately suppressed

what type of things can cause hyponatremia via elevated ADH levels?

what type of things can cause hyponatremia via suppressed ADH levels?

what does edema result from?

- sodium excess
- hypervolemia
- decreased plasma proteins

what 2 diseases causes edema from SODIUM EXCESS and HYPERVOLEMIA?

why?

- chronic renal disease (less NaCl and H2O secretion)
- CHF (inc hydrostatic pressure from backup)

what can cause edema through decreased plasma proteins?

nephrotic syndrome (loss of plasma proteins through leaky glomeruli)

how do we excrete a concentrated urine?

countercurrent mechanism

CONCENTRATED URINE
the renal medullary interstitium is ___osmotic

hyperosmotic

CONCENTRATED URINE
the thick ascending limb of the Loop actively reabsorbs ___

Na

CONCENTRATED URINE
the ascending limbs are ___ to water

impermeable

CONCENTRATED URINE
the ____ are countercurrent exchanges

vasa recta

CONCENTRATED URINE
ADH opens pores in the collecting system to allow ____ to be reabsorbed

water

between the PROX to DISTAL tubules, urine goes from NORMAL conc to ___x conc

4-5x

if we open pores in the collecting duct, H2O will come out because of the _____ (this is default)

concentration gradient

when pores are closed, urine will be ____

dilute

when pores are open, water will be ____

concentrated (more H2O reabsorbed)

our urine is normally ____ by default

diluate

what tubules have active NaCl transport?

- prox
- thick asc
- distal
- collecting

what tubules are permeable to water (with and without ADH)?

- prox
- thin descending loop
- distal tubule (+ADH)
- collecting tubule and duct (+ADH)

what tubules are most permeable to NaCl?

- prox
- thin desc
- thin asc

what tubules are most permeable to urea (with and without ADH)?

- prox
- thin desc
- thin asc
- collecting duct (+ADH)

with ADH, our urine is ____ concentrated

very

without ADH, urine is ____ concentrated

less (it is dilute)

ADH mostly affects what 2 places?

loop of henle
collecting

if countercurrent isn't working, all of the ADH in the world ____

won't help

what detects Na concentration?

osmoreceptors in hypothalamus

osmoreceptors respond to cell ____ (in a water deficit)

shrinkage

when osmoreceptors shrink (due to water deficit), osmoreceptors cause posterior pituitary to release ___

ADH

when osmoreceptors shrink (due to water deficit), the release of ADH causes the kidneys to _____

increase H2O absorption

when osmoreceptors shrink (due to water deficit), ADH is released and causes increased H2O resorption. also, ADH (aka vasopressin) causes ____, therefore ____ BP

V1 vasoconstriction, increasing BP

ADH EFFECT
- inc extracell osm
- ADH secreted
- inc tubular H2O perm
- inc H2O resorption (distal, collecting)
- dec H2O secretion, which causes _____ feedback to the osmoreceptors in the hypothal

negative

picture of ADH effect

ADH EFFECT ON DISTAL/COLLECTING TUBULAR CELLS
- binds to __ receptor
- G protein (gs) activates __
- ___ produced
- __ activated
- intracellular proteins ___
- ___ brought to surface (on luminal side)
- AQP2 fuse together to form ___ channels

on other side
- ___ and ___ permit water to flow out of cell (but not regulated by ADH)

ADH EFFECT ON DISTAL/COLLECTING TUBULAR CELLS
- binds to V2 receptor
- G protein (gs) activates adenylate cyclase
- cAMP produced
- PK activated
- intracellular proteins phosphorylated
- AQP2 brought to surface (on luminal side)
- AQP2 fuse together to form water channels

on other side
- AQP3 and AQP4 permit water to flow out of cell (but not regulated by ADH)

what are the 2 ways to regulate osmolality?

- thirst levels
- ADH

when osmolality of ECF increases, what happens?

- becomes thirsty --> inc water intake
- increased ADH --> water retention
--> dilution of ECF

ADH will be released due to
- ___ plasma osmolality
- ___ blood volume
- ___ blood pressure

which is the biggest contributor?

- inc plasma osmolality (MOSTLY)
- dec blood volume
- dec blood pressure

ADH will be inhibited due to
- ___ plasma osmolality
- ___ blood volume
- ___ blood pressure

- dec plasma osmolality
- inc blood volume
- inc blood pressure

how does thirst regulate plasma osmolality in response to HIGH OSMOLALITY?

- dry mouth (less saliva) and osmoreceptors in hypothalamus
- hypothalamus thirst center
- sensation of thirst
- drinks
- water moistens + absorbed
- dec plasma osmolality

how does thirst regulate plasma osmolality in response to LOW PLASMA VOLUME?

- dec plasma volume
- dec BP
- granular cells in kidney sense
- RAA
- inc ATII
- hypothalamus thirst center
- sensation of thirst
- drinks
- water moistens + absorbed
- dec plasma osmolality

INCREASES THIRST
- __ plasma osmolality
- __ blood volume
- __ blood pressure
- __ angiotensin II
- ___ of mouth

INCREASES THIRST
- HIGH plasma osmolality
- LOW blood volume
- LOW blood pressure
- HIGH angiotensin II
- DRYNESS of mouth

DECREASES THIRST
- __ plasma osmolality
- __ blood volume
- __ blood pressure
- __ angiotensin II
- ___ of stomach

DECREASES THIRST
- LOW plasma osmolality
- HIGH blood volume
- HIGH blood pressure
- LOW angiotensin II
- DISTENTION of stomach

what are 3 things that can disrupt urinary concentrating ability?

- inappropriate ADH secretion
- impairment of countercurrent mechanism
- inability of distal/collecting tubules/ducts to respond to ADH

DISORDERS OF URINARY CONCENTRATING ABILITY
inappropriate secretion of ADH:
either too much or too little ADH secretion results in abnormal fluid handling by the ___

kidneys

DISORDERS OF URINARY CONCENTRATING ABILITY
impairment of the coutnercurrent mechanism:
a ____ medullary interstitium is erquired for maximal urine concentrating abiltity; no matter how much ADH is present maximal urine concentration is limited by the degree of this in the medullary interstitium

hyperosmotic

what is DI?

a syndrome of polyuria resulting from inability to concentrate urine

what are the 2 types of DI?

- central
- nephrogenic

what is central DI?

inability to produce or release ADH from posterior pituitary

what causes central DI?

- head injuries
- infections
- congenital

how do you treat central DI in a congenital form?

how does this work?

DESMOPRESSIN (synthetic analog of ADH)

acts selectively on V2 receptors to increase water perm in late distal and collecting tubules

what is nephrogenic DI?

due to either
- failure of the countercurrent mech
- failure of distal/collecting tubules/ducts to respond to ADH

in nephorgenic DI, large volumes of ____ urine are formed, leading to dehydration unless fluid intake is increased by the same amount as urine volume is increased

DILUTE

what medication can cause DI?

lithium

how does DM cause polyuria?

increased glucose in blood increases osmolality of urine (when above threshold)

what are 4 groups of disorders in which water excretion is impaired?

- effective circulation volume depletion
- SIADH
- advanced renal failure
- hormonal changes

what are some examples of effective circulation volume depletion disorders that can cause impaired water excretion?

what are some examples of SIADH disorders that can cause impaired water excretion?

what are some examples of hormonal change disorders that can cause impaired water excretion?

what is SIADH most often seen with (3 things)?

- neurologic disease
- malignancy
- after major surgery

the persistent secretion of ADH in SIADH occurs either in the ___ or _____

- hypothalamus
- ectopically in patients with tumor induced disease

in SIADH
- gradual reduction in plasma ____ (unless water intake is very high)
- urine will be very ____
- most patients are ____

- sodium
- concentrated
- asymptomatic

ACEIs protect the kidneys by _____ glomerular EFFERENT arteriolar resistance

decreasing

ACEIs causes the renal-pressure curve to shift to ____ pressures

lower

ACEIs allows sodium to be secreted at ____ pressures

lower

ACEIs are useful for treating what 2 thigns?

- HF
- MI

there is evidence that ACEIs reduce the incidence of ___ in patients with high cardiovascular risk

DM

CASE 1: exercising on a hot day

Loss of dilute fluid as sweat. The net effect is increased PLASMA TONICITY AND SODIUM, but DEC ECF VOLUME. The rise in plasma tonicity will stimulate both ____ and ____; the ensuing rise in urine tonicity and subsequent water retention eventually return the plasma sodium concentration toward normal. This subject is also volume depleted; consequently, there will be activation of the renin-angiotensin-aldosterone system, resulting in a fall in urinary sodium excretion. The net effect is that the urine will initially be highly concentrated and contain relatively little sodium, an appropriate response to hypertonicity and volume depletion.

ADH release and THIRST

CASE 2: infuse a liter of isotonic saline

An infusion of isotonic saline will cause volume expansion, with no alteration in the plasma tonicity. ADH release and thirst are therefore not significantly altered, since there is no change in the plasma tonicity. In this setting, only volume regulation is activated as the associated volume expansion diminishes the release of aldosterone and increases that of ____. The net effect is excretion of the excess sodium and water in a relatively isotonic urine.

atrial natriuretic peptide (ANP)

CASE 3: viral gastroenteritis

lead to the physical findings of volume depletion (eg, decreased skin turgor and orthostatic hypotension and tachycardia) and an elevated plasma sodium concentration. Such patients have both dehydration (ie, unreplaced insensible losses leading to hypernatremia) and salt and water loss from the diarrhea. The hormonal profile would consist of elevations of _____ and _____, and decreased _____. This scenario is most likely to occur in infants, young children, or nursing home patients with impaired mental status who are unable to express the normal intense stimulation of thirst induced by hypernatremia.

elevations in ADH and renin and a reduction in ANP

CASE 4:

A 53- year- old man has been feeling tired and weak for several weeks and now presents with several days of vomiting. He has a 60- pack- year history of smoking. Physical examination shows an ill- appearing man in no acute distress. Vital signs reveal a blood pressure of 120/ 80 with a 10 mm Hg decline after assumption of the upright posture. The skin turgor is moderately reduced and the estimated jugular venous pressure is less than 5 cm H2O. These findings plus the orthostatic fall in blood pressure are compatible with volume depletion, presumably induced by the vomiting. A left lower lobe mass is noted on chest x- ray. Further evaluation shows the mass to be an oat cell carcinoma. Initial blood and urine tests reveal the following: BUN = 42 mg/ dL ( 9- 25) Creatinine = 1.2 mg/ dL ( 0.8- 1.4) Na = 107 mEq/ L ( 136- 142) K = 3.9 mEq/ L ( 3.5- 5) Cl = 75 mEq/ L ( 98- 108) Total CO2 = 22 mEq/ L ( 21- 30) Urine Na = 8 mEq/ L ( variable) Osmolality = 553 mOsm/ kg ( variable)
what is this?

could be
- bleed
- SIADH (oat cell)

CASE 4:

A 53- year- old man has been feeling tired and weak for several weeks and now presents with several days of vomiting. He has a 60- pack- year history of smoking. Physical examination shows an ill- appearing man in no acute distress. Vital signs reveal a blood pressure of 120/ 80 with a 10 mm Hg decline after assumption of the upright posture. The skin turgor is moderately reduced and the estimated jugular venous pressure is less than 5 cm H2O. These findings plus the orthostatic fall in blood pressure are compatible with volume depletion, presumably induced by the vomiting. A left lower lobe mass is noted on chest x- ray. Further evaluation shows the mass to be an oat cell carcinoma. Initial blood and urine tests reveal the following: BUN = 42 mg/ dL ( 9- 25) Creatinine = 1.2 mg/ dL ( 0.8- 1.4) Na = 107 mEq/ L ( 136- 142) K = 3.9 mEq/ L ( 3.5- 5) Cl = 75 mEq/ L ( 98- 108) Total CO2 = 22 mEq/ L ( 21- 30) Urine Na = 8 mEq/ L ( variable) Osmolality = 553 mOsm/ kg ( variable)


why isn't this DI?

should have decreased osmo if DI

what hormone changes in
DECREASED VOLUME?

renin

what hormone changes in
INCREASED VOLUME?

ANP

what hormone changes in
DEC/INC OSMOLALITY?

ADH

Please allow access to your computer’s microphone to use Voice Recording.

Having trouble? Click here for help.

We can’t access your microphone!

Click the icon above to update your browser permissions above and try again

Example:

Reload the page to try again!

Reload

Press Cmd-0 to reset your zoom

Press Ctrl-0 to reset your zoom

It looks like your browser might be zoomed in or out. Your browser needs to be zoomed to a normal size to record audio.

Please upgrade Flash or install Chrome
to use Voice Recording.

For more help, see our troubleshooting page.

Your microphone is muted

For help fixing this issue, see this FAQ.

Star this term

You can study starred terms together

NEW! Voice Recording

Create Set