Flashcards in Renal Deck (116):
Total body water distribution (rule)
60% - total body water
of that: 40%: ICF
20%: ECF (plasma/interstitial fluid)
Cation most prevalent in the ICF
Cation most prevalent in the ECF
What pressure prevails in reabsorption?
Capillary Oncotic Pressure
What pressure prevails in filtration?
Diarrhea is an example of?
Iso-osmotic fluid contraction
decreased ECF volume
Eating a salty ham is an example of?
Hyperosmotic fluid expansion
inc Osm, inc ECF, dec ICF (shrunk cells)
Diabetes insipidus or excessive sweating:
Hyperosmotic fluid contraction
inc Osm, dec ECF, dec ICF
Hypo-osmotic fluid expansion
dec Osm, inc ECF/inc ICF
Hypo-osmotic fluid contraction
dec Osm, inc ICF, dec ECF
Salt wasting occurs when
you have adrenal insufficiency; dec renal NaCl reabsorption; loss of solute from ECf to urine.
the mov't of solutes back into renal lumen.
NEVER SECRETE WATER!
Renal failure begins when GRF <
when GRF < 20ml/min
or a loss of function of 85% of nephrons
What happens to GFR, RPF, and FF when you constrict EFFERENT arteriole?
increase FF, GFR
If macula densa senses more Cl-/flow than usual, it signals___.
vasoconstriction of the AFFERENT arteriole to slow down RPF/GFR.
High levels of Creatinine in the serum suggests______.
That there is a problem with filtration.
A clearance ratio of Substance/Inulin < 1
Na glucose transporter uses what type of mech?
Secondary active; uses Na gradient to co transport glucose against its gradient.
Glucose reabsorption occurs?
ONLY in the proximal tubule.
In glucosuria (seen in pt with diabetes mellitus)...
the filtered load of glucose exceeds the reabsorptive capacity - glucose spills into urine
A decrease in TF/P indicates
reabsorption from the tubular fluid
Antidiuretic hormone (ADH) acts principally on
the collecting ducts
Aldosterone acts principally on
Distal tubule segments
The corticopapillary osmotic gradient is established in the
Loop of Henle
The major titratable acids (TA) excreted in the urine are in the form of:
H2PO4- [Phosphoric acid]
Phosphates make very good buffers in urine because
their pK is near the urine pH
Acquired Fanconi syndrome
a disease of the proximal renal tubules; glucose, amino acids, phosphate and bicarbonate are passed into the urine, instead of being reabsorbed.
the tight junctions linking proximal tubule cells permit passive diffusion of
renal compensatory response to respiratory acidosis
includes an increase in PT HCO3- synthesis
Renal compensatory response to respiratory alkalosis
includes a decrease in PT H+ secretion as NH4+, and an associated decrease in PT HCO3- production
ECF volume contraction causes____________
contraction alkalosis; angiotensin II mechanism specifically stimulates HCO3− reabsorption (along with Na+ and water),
Organic anion secretion involves
active influx across the basolateral membrane against a negative membrane potential
high water/low solute permeability occur here
thin descending limb
relatively impermeable to water. Passive reabsorption of NaCl and urea occur here
thin ascending limb
relatively impermeable to water. Active reabsorption of NaCl and K occur here
Thick ascending limb
(use NaK2Cl symporters)
Counter current multiplication is maintained by:
The thick ascending limb's active reabsorption of Na and Cl w/o water
Notably, the Na/K/2Cl symporters are inhibited by
loop diuretics; like furosemide
loop diuretics act by:
decrease reabsorption of Na, K and Cl while simultaneously increasing their excretion in the urine
ADH is secreted by the posterior pituitary in response to
increased plasma osmolarity
ADH increases the _______ permeability of ____________. This yields ______ urine.
the collecting duct
In situations where ADH is high (______), activity of _____ is increased. This enhances the ____________ effect.
single pass (corticopapillary osmotic gradient)
Decreased ADH release or decreased renal sensitivity to ADH leads to_______________.
central diabetes insipidus
a condition featuring hypernatremia (increased blood sodium concentration), polyuria (excess urine production), and polydipsia (thirst).
corticopapillary osmotic gradient is larger when ADH levels are ______, like in ______.
high (e.g., water deprivation, SIADH)
increased excretion of urine
Urea levels in the interstitium are ~ _____
Urea is decreased in the interstitium: <100mM; it’s being secreted into the collecting ducts.
suppression of secretion of urine by the kidneys/dehydration; stinky and golden yellow urine
For a given inc in plasma osmolarity, more ADH will be secreted when
plasma volume is contracted/hypovolemic (ie: hemorrhage).
When in solute balance, eating a high solute diet will lead to __________ clearance.
higher positive free water clearance
Tubular fluid's Osm in the Proximal tubule:
Tubular fluid's Osm along the Loop of Henle
Thin descending: hyper-osmotic (reabsorbs water>solute)
thin/thick ascending: hypo-osmotic (reabsorbs solute>water)
Tubular fluid entering the distal tubule
IS ALWAYS hypo-osmotic (~100-120mOsm).
More ADH secretion does what to thirst?
It increases it!
Effective circulating volume reflects
extent of tissue Perfusion; not the total solute concentrations.
When might effective circulating volume < ECF volume?
CHF, pulmonary edema, liver disease or nephrotic sydrome
How do diuretics help decrease plasma volume?
by forcing the kidney to increase excretion of Na/water.
Angiotensin II promotes _______, by stimulating _______ in the ___________.
Proximal Tubule cells
(overall: inc Na reabsorption)
ANGII constricts what vessel's preferentially?
The efferent, thus GFR is increased.
Secretogogues (agents which increase release of the hormone) for aldosterone include:
ANGII, increased plasma [K+] and ACTH
The functional coupling of _____&______ occurs in the late DT/CD
Na reabsorption and K secretion
Increased Na reabsorption leads to a loss of _____ in the urine; possibly leading to _____
(that's why ppl on diuretics often take K supplements)
Explain Diabetes mellitus
Glucosuria --> excrete large amounts of dilute urine. Dec plasma volume/increased Na concentration.
Central Diabetes insipidus is caused by? results in?
inadequate release of ADH in the face of inc plasma Osm. CD is not sufficiently water permeable. You get polyuria.
Nephrogenic diabetes insipidus is?
excessive water excretion b/c DT/CD can't respond to ADH (levels of ADH are normal/elevated).
Hyperaldosteronism gives you?
more aldo, more Na reabsorption. You get chronic volume expansion.
elevated ADH levels (when plasma Osm is reduced); results in plasma volume expansion.
Hyperkalemia is associated with
Metabolic Acidosis, depolerized membrane potential, muscle hyper-excitability
Hypokalemia is associated with
Metabolic alkalosis, hyperpolerized membrane potential and hypoexcited muscles.
Aldosterone can lead to a(n) ________ in K excretion
How does the body defend against acute Hyperkalemia?
translocation/sequestering K into cells, mediated by NaKATPase is the first line of defense.
What helps induce “de novo” synthesis of Na/K-ATPase to protect against hyperkalemia?
EPI, insulin and Aldosterone
*note: in diabetes, low insulin can lead to poor K excretion. Overall, this can lead to acidosis as ICF dumps H+ into plasma!
Which segment of the nephron is responsible for restoring K+ balance?
The distal tubule.
How is renal handling of Na different from the handling of K?
Na balance is regulated by water reabsorption. K is reabsorbed early, and then secreted back into the tubule based upon body's need. WE DON'T SECRETE Na!!!
80% of K+ reabsorption occurs _______ via ______.
most K reabsorption occurs in the PT paracellularly by solvant drag/passive electro-diffusion.
In the loop of Henle, K is absorbed how?
Active uptake at the luminal membrane (Na/K/2Cl symporters)
In the distal nephron, how is K handled?
α-intercalated cells; transcellular active, concentrative accumulation of K+ across luminal membrane mediated by a K/H-ATPase; actively transports K+ in and H+ out of the cell
If luminal flow increases, what happens to the Concentration of K outside the cells?
it decreases. It's being swept away faster than it can be pumped out. Thus, the gradient appears higher (easier to kick out more K!). Aggravating your hypokalemia/alkalosis).
why is hypokealmeia is a side effect of loop diuretics?
The diuretic “furosemide” blocks the Na/K/2Cl symporters in the Loop of Henle, blocking Na reabsorption. This increases the delivery of Na downstream, which is coupled to inc K secretion
____________ is the primary determinant of long term blood pressure. It's regulated by?
Low serum albumin, high protein in the urine, hyperlipidemia; rotein leaks because the podocytes fuse together and lose their electrical charge
total body edema
Most common cause of death from nephrotic syndrome is
(as well as infections from encapsulated organisms– loss of plasma proteins means loss of Ig)
How do you tell apart primary renal sodium retention edema from edema caused by reduction in oncotic pressure?
Dec oncotic = increased renin
Inc hydrostatic = decreased renin
Hyponatremia, a disease of excess water, presents with what type of urine?
what disease is associated with this?
SIADH! too much ADH, so too much water reabsorbed.
Explain Motrin (NSAID) induced acute renal failure
NSAIDs block prostaglandins, which work at the afferent nephron to dilate them. No PGs, no dilation, can drop GFR/RPF dramatically.
Low sodium with CHF is a bad diagnostic finding. It means the kidneys are not seeing enough blood. (they interpret this as
low blood volume, so they try to hold onto salt (dec its excretion) and thus hold on water to increase blood volume. This can lead to volume overload and further damage the heart.
A substance known to be freely filtered has a certain concentration in the afferent arteriole. What can we predict about its concentration in the efferent arteriole
close to the value in the afferent arteriole; They are in equilibrium with the ultrafiltrate.
efferent arteriole dilation would cause:
decrease in GFR, dec in FF and an increase in renal blood flow.
If the clearance of a freely filtered substance is Less than the C of inulin, the substance underwent net:
Filtration fraction is defined as
FF= (GFR) / (RPF).
RPF = [RBF x (1-hematocrit)]
Which glomerular structures normally prevents cells from entering the tubule?
Capillary endothelial cells
Increases in both renal blood flow and glomerular filtration rate (GFR) are caused by which of the following?
Dilation of afferent arterioles
Antidiuretic hormone (ADH)-sensitive water channels (aquaporins) are located in the
Na+-K+-2Cl- co transporters on the thick ascending limb of Henle; solute-free water reabsorption in the descending limb of Henle and urea recycling all play a role in?
establishing/maintaining the medullary interstitial concentration gradient.
NOTE: distal tubule is not involved.
thick ascending limb's function in a healthy adult is?
extracts Na+, K+ and Cl- from lumen; here they help form the corticopapillary osmotic gradient. TAL has a low water permeability, so the tubule fluid becomes relatively dilute
If the thick ascending limb stopped reabsorbing sodium, then the final urine would be
isosmotic with plasma in all conditions
Urea is secreted into the tubules where?
in the thin descending limbs, where the interstitial concentrations are high.
Angiotensin II has two direct actions on the kidneys
inc PT sodium reabsorption and to constrict renal afferent and efferent arterioles.
This increases sodium and water reabsorption
Renin is secreted from the juxtaglomerular cells in response to
Renin is secreted from the granular cells in the juxtaglomerular apparatus
Aldosterone stimulates sodium reabsorption in the
late distal tubules and collecting ducts.
Aldosterone secretion by the adrenal gland is stimulated by? Inhibited by?
hyperkalemia and angiotensin II
inhibited by ANP.
Increasing sodium intake would ______renin secretion
A large increase in aldosterone secretion combined with a high sodium intake would cause severe
Aldosterone stimulates ___________secretion
Patients with Addison's disease have a deficiency of aldosterone secretion and therefore tend to have
When a woman who has been on a low-sodium diet for 8 days is given an ACE inhibitor, one would expect
Blood pressure to fall, b/c periphreal resistance would also fall.
High plasma creatinine is most likely to indicate a decrease in
[Creatinine levels are not affected by ADH or acid-base status]
a renin-secreting tumor might present with:
elevated plasma Aldosterone, depressed plasma [K+]/RBF and no change in sodium excretion rates.
Increased aldosterone concentration would cause________ whereas high levels of angiotensin II would cause _______.
hypokalemia (dec plasma K)
renal vasoconstriction/dec RBF.
Respiratory alkalosis involves:
inc pH, dec PCO2
Renal response to respiratory alkalosis is
decreasing Bicarb reabsorption and retaining H+ (decreasing excretion of NH4Cl/titratable acids
In metabolic Alkalosis, you have
increased pH, inc bicarb
When can you see metabolic alkalosis?
Pt with diuretics/HT (kidneys secrete H)
Dehydration leading to K def
What is a compensatory mechanism of the kidney to metabolic alkalosis?
decreasing bicarb reabsorption
In metabolic acidosis, you have
dec pH, dec bicarb
A decrease in sodium chloride concentration initiates a signal from the macula densa that has two effects:
1) dec resistance in afferent arterioles via vasodilation, (increases glomerular hydrostatic pressure and helps return GFR to normal)
(2) inc renin release from juxtaglomerular cells