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109 Cards in this Set

  • Front
  • Back
What is the major function of the early proximal tubule?
Isoosmotic reabsorption of solute and water
What is the major function of the late proximal tubule?
Isoosmotic reabsorption of solute and water
What is the major function of the thick ascending limb of the loop of henle?
Reabsorption of NaCl (Leaves) w/o H2O (stays)
Dilution of tubular fluid
Single effect of countercurrent multiplication
Reabsorption of Ca2+ and Mg+ driven by lumen-positive potential
What is the major function of the early distal tubule?
reabsorption of NaCl w/o water
Dilution of tubular fluid
What is the major function of the late distal tubule and collecting ducts? (Principal cells)
reabsorption of NaCl
K+Secretion
Variable water reabsorption
What is the major function of the late distal tubule and collecting ducts? (a-intercalated cells)
reabsorption ok K+
Secretion of H+
What cellular mechanisms (transporters/etc.) act on the early proximal tubule?
Na+-Glucose exchanger
Na+AAcid Exchanger
Na= Phosphate co-transporter
Na+H exchange
What cellular mechanisms (transporters/etc.) act on the late proximal tubule?
NaCl reabsorption driven by Cl- gradient
What cellular mechanisms (transporters/etc.) act on the thick ascending limb of LOH?
Na+-K+-2Cl- Cotransporter
What cellular mechanisms (transporters/etc.) act on the early distal tubule?
Na+Cl- Co-transport
What cellular mechanisms (transporters/etc.) act on the late distal tubule and collecting ducts (Principal cells)
Na+Channels
K+ Channels
Water Channels
What cellular mechanisms (transporters/etc.) act on the late distal tubule and collecting ducts (a-intercalated cells)?
H+K+ ATPase
H+ATPase
What hormone actions can effect the EPT?
PTH inhibits Na+ phosphate cotransport
Angiotensin II stimulates Na+-H+ Exchange
What hormone actions can effect the LPT?
none
What hormone actions can effec the thick ascending LOH?
ADH stimulates Na+K+Cl2- Transport
What hormone actions can effect the early distal tubule?
PHT Stimulates Ca2+ reabsorption
What hormone actions can effect the late distal tubule and collecting ducts (principal cells)?
Aldosterone stimulates Na+ Reabsorption
Aldosterone stimulates K+ Secretion
ADH stimulates water reabsorbtion
What hormone actions can effect the late distal tubule and collecting ducts (a-intercalated cells)?
aldosterone stimulates H+secretion
What are some common causes of Hyperkalemia? What essentially is happening?
K+ is moving out of the cells and increasing blood K+ concentration
Insulin deficienct
B2 Adernergic ANTAGonists
a-adernergic AGONists
Acidosis
hyperosmolarity
cell lysis
exercise
What are some common causes of Hypokalemia? What essentially is happening?
K+ is moving into the cells and decreases blood K+ concentration.
Insulin
B-Adernergic AGONists
a-adernergeic ANTAGonists
Alkalosis
Hyposmolarity
Constriction of the afferent arteriole has what effect on GFR?
Decreased due to lover Pgc
Constriction of the afferent arteriole has what effect on RPF?
decreased
Constriction of the afferent arteriole has what effect on Filtration fraction?
no change
Constriction of the EFFERENT arteriole has what effect on GFR?
increased due to increased Pgc
Constriction of the EFFERENT arteriole has what effect on RPF?
decreased
Constriction of the EFFERENT arteriole has what effect on filtration fraction?
Increased (Increased GFR/decreaseRPF)
Increase plasma protein has what effect on GFR?
decreased by lower oncotic pressure in gc
Increase plasma protein has what effect on RPF?
nochange
Increase plasma protein has what effect on Filtration Fraction?
decreased (decreased GFR and nc RPF)
What effect would a ureteral stone have on GFR?
decreased (by increasing pressure in bowmans space)
What effect would a ureteral stone have on RPF?
no change
What effect would a ureteral stone have on filtration fraction?
decreased since GFR decreases and RPF has no change
What is the plasma glucose saturation concentration and where does this occur?
250mg all glucose can be absorbed
350 mg.dL saturates
Occurs in the proximal tubule in Na+/glucose cotransport into the cel (re-absorption)
What is splay?
The region of glucose curves between threshold and Tm representing the excretion of glucose in the urine before Tm due to the fact not all nephrons have the same affinity for the Na-glucose carriers
What is a high clearence?
a substance that is both filtered across the capillaries and secrted from the peritubular capillaris into the urine, like PAH
What are low clearance substances?
those that are not filtered or are filtered and subsequently reabsorbed, like proteins, glucose, amino acids. HCO3- and Cl-
List the relative clearences from highest to lowest of the common substances we have learned...
PAH>K+inulin>urea>glucose,aa &HCO3-
True or False-Why
Most of the sodium reabsorbed by the nephron
True
67% in the PCT
25% in Thick Ascending LOH
5% in DCT
3% in CD
How is sodium reabsorbed in the PCT?
Cotransport with Glucose, AA, Phosphate and Lactate and via a countertransport exchanger with Na+/H+
Where and how do carbonic andhydrase inhibitors work? What is an example of one?
Acetazolamide is a diuetic that acts in the PCT by inhibiting the reabsorption of filtered HCO3-
How is Na+ absorbed int he late PCT?
It is reaborbed with Cl-
What is the filtrate like in the PCT?
Isoosmotic
What are the effects of ECF volume on proximal tubular reabsorption?
ECF volume contraction increases reabsorption
ECF volume expansion decreases reabsorption
describe Na+ transport in the LOH
In the THICK ASCENDING limb, 25% of filtered Na+ is reabsorbed with the Na+2Cl-K+ transporter
Is the PCT permiable to water
Yes. It keeps filtrate isoosmotic with all the Na+ it reabsorbs
Is the LOH permeable to water?
The THICK ASCENDING limb is NOT. This is why it is called the diluting segment
Where do loop diuetics worK? What are some of their names?
they work in the thick ascending LOH to block the nakcl cotrasporter.
Furozimide (Lasix) bumetanide, ethacrynic acid)
What are the special features of the early distial tubule? (3)
Rabsorbs NaCl by cotransporter
impermeable to H2o so called the "cortical diluting segment"
Site of action for thiazide diuretics
Describe the features of principal cells. Where are they found?
In the late distal tubule and collecting duct:
1) Reabsorbe Na & H20
2) Sectere K
3) Aldosterone, ADH, and K Sparing Diuretics act here
What role does aldosterone play in urine formation?
It increase Na+ reabsorption and increases K+ SECRETION in to the urine in the principal cells.
stimulates H+(ATPase) secretion in a-intercalated cells
What role does ADH play in the kidneys?
It increases H20 permeability by directly inserting aquaporins in the apical (luminal) membrane
Are principal cells permeable to water?
generally no, unless ADH is present, the yes
What are K+ sparing diuretics?
Spirinolactone, trimterene, amiloride: they decrease K+ secretion in the late distal tubule
how does spirinolactone work?
It is an aldosterone receptor antagonists. It causes the kidneys to eliminate unneeded water and sodium from the body into the urine, but reduces the loss of potassium from the body.
Describe the alpha intercalted cells...
Also found in the DCT and CD.
They secrete H+ via ATPase transporter that is stimulated by aldosterone and reabsorb K+ by a h/k-Atpase transporter
What is hyperkalemia?
shift of K+ out of the cells
(From ICF->ECF, ECF is now high, ICF usually has high K+)
What is hypokalemia?
shift of K+ into the cells
(From ECF->ICF, ECF is now lower than usual)
Where is most of the K+ reabsorbed?
PCT
What role does K+ have on chemical and elecrical driving forces?
It moves passivly into the lumen so its secretion is based on chemical and electical forces
disucss aldosterone and k+
Aldosterones goal is to increase Na+ into the cell using a Na+/K+ pump. The increase K+ bulds an intracellular K+ gradient and is the driving force for its secretion. Aldosterone also increases the number of luminal K+ Channels
Describe the effect of HYPERaldosteronism and K+
It increase K+ secretion and causes hypokalemia
Describe the effect of HYPOraldosteronism and K+
It DECREASES K+ secretion and causes hyperkalemia
What is acid/base relation to K+
Acidosis decreases K+ secretion
(H+ enters the cell and K+ leaves, makes the cell think there isn't a lot of K+ and secretion is decreased)
Alkalosos increases K+ secretion
(H+ in short supply and leaves the cell to enter the blood, K+ exchanges and enters the cell. Cell thinks there is enough K+ and simulates secretion)
What are the components of the JGA?
- Macula densa (MD)
– Extraglomerular mesangial cells (EGM)
– Granular cells (G), a.k.a.
juxtaglomerular cells
What is the role of the JGA?
– Helps control GFR
– Controls renin secretion
(blood pressure & vol.)
What are Mesangial cells?
Cells of the JGA – Found between capillary loops; contract in response to angiotensin II
Describe the renal vasculature...
– Glomerular & Peritubular:

Preitubular is further divided into » Cortical (in cortex) and Vasa Recta which follows the LOH into the medulla (or also jugtgolmerular nephrons into the medulla)
What vasuclature supplies the nephron?How is it arranged?
The peritubular capillaries which carry blood from efferent arterioles.
Arranged in SERIES
What is the job of the Vasa Recta?
Soecialize peritubular capillaries for the long/deep juxtaglomerular nephorons that is responsible for Supplying nutrients to medullary tissue and important for recovery of water.
What is the innervation to the kidnesy?
Sympathetic only a-1 receptors present PRIMARIILY on afferent arteriols which
What is the net effect of the sympathetics on the kidneys?
timulation by the SNS tends to reduce RBF and GFR,
but the simultaneous release of PGE 2 and PGI 2 opposes the effect. Reductions in RBF and GFR are minimized.
What cells of the JGA are innervated by sympathetics? What is the effect?
Granular cells (JGA) innervated by SNS; renin released upon stimulation of beta receptors.
Wht is the production of Glomerular filtration?
Protein free filtrate
What is Tubular reabsorption ?
from tubular lumen to PTC
What is Tubular secretion ?
from PTC to tubular lumen
How much of the cardia output do the kidneys get? For what purpose?
25%, for filtration, not metabolism
How much filtrate is formed a day?
180 Liters
What 4 Factors (besides sympatheics) will decrease GFR and RBF?
Angiotensin II (Ang II),
ADH,
ATP
endothelin
What effect does angiotensis II have on the renal vasuclature
Ang II constricts both the afferent and efferent arterioles,
however, the efferent arteriole is more sensitive.
Vasoconstrictors do what to GFR & RBF?
Decrease
Vasodialators do what to GFR & RBF?
» increase RBF and GFR.
What are the 4 common Vasodialators of the kidney?
Atrial natriuretic peptide (ANP), glucocorticoids,
NO,
prostaglandins
What is autoregulation?
basically the mechanism that insulates renal excretory function from fluctuations in BP
What are the ways the kidneys autoregualte?
Myogenic mechanism: intrinsic to VSMC; contract in response to stretch.
and
Tubuloglomerular feedback:
What is Tubuloglomerular feedback?
Flow Dependent Feedback: Increasing GFR increases NaCl delivery to LOH;
sensed by the macula densa which causes the
resistance of the afferent arteriole (R A ) to increase
thereby decreasing RBF & GFR (next panel).
Possible by thromboxane A2 or adenosine
How does the composition of Plasma compare to glomular filtrate?
Essentialy the same with the exception of protein in the pasma, but not in the filtrate
What is the charge of the basal lamina?
Negative
Which of the following is more permiable: Mygloobin or hemoglobin?
Myoglobin

Hemoglobin is too large to easily permiate
How does the Kf for glomerular capillaries compare to that for capillaries in skin and muscle.
is 50-100 times greater
What is Kf?
What can change it?
the filtration rate produced by
each mmHg of net filtration pressure

mesangial cells (AII reduces K f )
What does iiGC = (oncotic pressure) do to GFR?
Slows GFR
What can GFR Clinically Tell you?
a rough measure of the number of
functioning nephrons.
if there renal disease and if its progressing
grading of chronic renal disease
Drug dosaging based on kidney function
What is the perfect GFR marker criteria?
freely filtered, but neither reabsorbed nor secreted. Perfect is Inulin, but we use creatin and PAH
What is normal BUN range?
Normal Range: 9-18 mg/dL
What is a normal BUN-Creatin ratio?
BUN:Cr ratio should
be 10 - 15.
How is glucose transported across the cell membrane?
Secondary Active Transport
Is Na+ Reabsorption active or passive?
Almost always active requiring ATPase at BL membrane
What is the effect of Parathyroid hormone in the proximal tubule?
inhibits Na + -phosphate cotransport & increases urinary excretion of phosphate
What is "Threshold?"
[In the plasma:] amount
where glucose first
appears in urine.
Depends on GFR.
How are GFR and threshold related?
Decreasing GFR
Increases Threshold
What other soultes besides glucose have Tm's?
Prettymuch anything els reabsorbed in the PCT:
 Other sugars (fructose, galactose)
 Amino acids
 Metabolic Intermediates:
– lactate
– ketone bodies
– Kreb’s cycle intermediates
 Phosphate ions
 Water-soluble vitamins
 Proteins and peptides
What is osmotic diuresis?
Urination caused by diuresis resulting from the presence of certain nonabsorbable substances in tubules of the kidney, such as mannitol, urea, or glucose. It results in the increase loss of electrolytes in urine
(Particularly Sodium, chloride, potassium as seen in diabetics)
What substance is used clinically to induce osmotic diuresis?
Mannitol vis IV
How are organic anions secreted?
via tertiary active transport in a very nonspecific manner.
What is normal plasma osmolarity?
Normal plasma osmolarity is 285-­295 mOsm/L.
What type of solution is normal urine?
Generally slightly hypertonic
What are the ranges for urine concentration output?
dilute urine (as low as 50
mOsm/L ²water diuresis)
concentrated urine (to 1400
mOsm/L -­antidiuresis)
True or False
The kidneys can regulate water excretion independently of solute excretion?
True
Fill in the hormone:
_______ controls sodium reabsorption while ______ controls water reabsorption.
Aldosterone (Na)
ADH (H20)