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22 Cards in this Set
- Front
- Back
What is tubular reabsorption
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this is from the tubular lumen to PTC (peritubular capillary)- movement of valuable molecules
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What is tubular secretion?
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this is from the PTC (peritubular capillary) to the tubular lumen
movement of waste products, metabolites, and toxins |
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what is excretion?
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this is the loss for body in the urine
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What is the equation for filtered load?
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FL= (GFR)(Px)
filtered load is equal to the glmoerular filtration rate, times the plasma concentration of X |
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What is the excretion rate?
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this is the amount of material lost in urine.
ER= Ux * V (urinary concentration times Volume of urine produced) |
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What is the equation for transport rate?
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Tx= FL- ER
transport rate= secreted (FL)-excreted (ER) if it is positive, then some stuff is reabsorbed if negative, it was secreted |
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What two membranes must be crossed for transcellular reabsorption?
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the luminal membrane
and the basolateral membrane |
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How is glucose tranpsorted?
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by secondary active transport
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Where does most reabsoprtion of salt and water take place?
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in the Proximal tubule
67% of Na+ and 65% of H2O |
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What regulates water uptake in the distal/collecting tubule?
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ADH
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What regulates Na+ reabsorption in the distal collecting tubule?
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Aldosterone
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How does water reabsorption occur in the proximal tubule?
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Water passively follows the Na+
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How does Na+ resorption occur in the proximal tubule?
(along with glucose, phosphate, citrate, lactate, AA's) |
Na+ enters the PT via contransport with organics.
This is done by Na/H+ antiporter. Cl- enters via paracellular routes |
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What dose angiotensin 2 do in the Proximal tubule?
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this stimulates Na+-H+ exchange across the apical membrane.
increases Na+ reabsorption |
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What does SNS activity do in the proximal tubule
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this stimulates Na+ reabsorption
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What does PTH do in the proximal tubule?
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this inhibits the Na+-Phosphate cotransport.
increases urinary excretion of phosphate |
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What does the TF/Px ratio in the proximal tubule represent?
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this represents the rate of reabsoprtion in the proximal tubule
(tubular fluid/ plasma concentration. So if more concentrated in tubular fluid, so there is a loss realtive to water, or secretion) If TF/P is less than 1, then this is more reabsorbed than water if TF/P is greater than 1, then reabsorption is less than water, or there has been net secretion. |
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How do you find Tm?
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below Tm, all filtered load is reabsorbed,
whatever is above Tm is excreted (EM=Ux* V) |
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How does GFR affect the threshold of Tm?
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A Slower GFR results in higher blood concentrations (and thus threshold)
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What is osmotic diuresis?
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excess unreabsorbed solute (like mannitol)- INHIBITS osmotic flow of water from lumen of Proximal tubule.
results in lots of fluid being put into urine. (polyuria in diabetics, or mannitol to induce it) |
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How are organic anions transported? what is the organic anion of interest?
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Organic anions are secreted via tertiary active transport.
PAH is the example (PAH is exhanged for a-KG). ALL PAH is secreted, used to estimate RPF (using RBF= RPF (1-htc)) (and RPF= UpahV/Ppah) |
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Do all organic anions compete for the same transporter?
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yes they do, so elevated levels of one anion will inhibit the secretion of others. PAH was used to inhibit the secretion of penicillin
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