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23 Cards in this Set
- Front
- Back
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What does the Tubular fluid/ plasma concentration ratio determine?
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Obtaining the TF/P in the Bowman's space and in the late proximal tubule for various substances determines if the substance is reabsorbed and in what concentration relative to water.
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What substances are TF/P ratios measured? How is fraction of solute remaining measured? How is fraction of solute reabsorbed measured?
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Inulin
Solute remaining= (TF/P solute)/ (TF/P inulin) solute reabsorbed= 1-(TF/P solute)/ (TF/P inulin) |
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What substances are reabsorbed in the proximal tubule in the same concentration as water? Which are absorbed quicker? What are less absorbed/ not at all?
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Sodium and potassium are in equal concentration as water.
HCO3-, amino acids and glucose are absorbed quicker than water. Urea and chloride are absorbed slower than water. Inulin and PAH are not absorbed. |
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How is sodium transported from the tubular lumen to the peritubular capillary in the proximal tubule?
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Across the luminal membrane by co-transport of glucose, amino acids and phosphate or antiport with H+.
Across the basolateral membrane by a sodium-potassium ATPase or in a sodium bicarbonate co transporter. |
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How is chloride transported from the tubular lumen to the peritubular capillary in the proximal tubule?
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Across the luminal membrane by active transport via an anion exchanger for a base. The energy comes from the sodium-potassium ATPase.
Across the basolateral membrane via a potassium chloride co-transporter or selective chloride channel. |
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How is water transported from the tubular lumen to the peritubular capillary in the proximal tubule? What pressures drive the movement of water?
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Water travels with sodium across the luminal membrane and the basolateral membrane.
Oncotic pressure of the peritubular capillary and the hydrostatic pressure of the intersitial fluid contribute to reabsorption. |
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What is backleak? How does the volume change?
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Backleak is the sodium and water from the intercellular spaces back into the tubule.
Increased capillary hydrostatic presure or decreased plasma oncotic pressure will decrease the capillary uptake and thus increase the amount of backleak. |
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How is potassium transported in the nephron?
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Passive transport via potassium channels, through intercellular spaces, and via a chloride symporter.
Can be secreted in the distal tubule. |
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How is urea handled in the nephron?
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Half reabsorbed in the PCT; Over half secreted back in the loop of Henle; Most reabsorbed in the collecting duct to leave about 40% excreted.
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How is urea reabsorbed in the proximal tubule?
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Passive diffusion due to sodium and water movement.
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How is amino acid transport handled in the nephron?
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99% reabsorbed in the PCT and the rest in the loop of henle.
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How and where is glucose transported in the nephron?
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All reabsorbed in the proximal tubule, coupled to sodium.
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How is sodium and potassium tranpsorted in the early distal tubule?
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sodium and chloride leave the lumen via a cotransporter. Sodium-potassium ATPase pump sodium out and chloride passes through a channel.
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What type of cell transports sodium and potassium in the late distal tubule/ collecting duct? How does it do so?
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Principal cells
Less negative potential difference across luminal membrane allows potassium to be secreted into the lumen. |
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How does aldosterone affect the principal cells?
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Aldosterone increases activity of basolateral membrane sodium-potassium pump.
Increases potassium permeability across the luminal membrane. Increases sodium permeability across the luminal membrane. |
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What factors other than aldosterone affect the principal cells and increase potassium secretion?
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Increased potassium intake will increase the sodium-potassium pump.
Increased sodium delivery via diuretics, osmotic diuresis or acid-base disorder will elevate potassium secretion. |
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Where and how is calcium reabsorbed in the nephron? What amount is excreted?
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Proximal tubule
Active transport and passive transport Less than 2% excreted |
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Where and how is magnesium reabsorbed in the nephron? What amount is excreted?
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Thick ascending loop of Henle
Unknown 10% filtered |
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Where and how is phosphate reabsorbed in the nephron?
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Proximal tubule
Active transport |
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Which substances are reabsorbed via carrier mediated transport? What will happen when carrier load is passed by filtration?
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glucose, amino acids, phosphate, sulfate.
When the transporters are maximized (Tm), the substance will be excreted in the urine. |
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What is the formula for reabsorption rate?
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(GFR * Pconc)- (V * Uconc)
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What are three factors that may cause osmotic diuresis?
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Excess of normally reabsorbed solute in the tubule
Presence of nonreabsorbed solute Inhibition of solute reabsorption mechanism |
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What susbances are secreted by the renal tubules?
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Potassium, hydrogen, ammonium, uric acid, thiamine, and foreign substances
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