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22 Cards in this Set

  • Front
  • Back
What is tubular reabsorption
this is from the tubular lumen to PTC (peritubular capillary)- movement of valuable molecules
What is tubular secretion?
this is from the PTC (peritubular capillary) to the tubular lumen

movement of waste products, metabolites, and toxins
what is excretion?
this is the loss for body in the urine
What is the equation for filtered load?
FL= (GFR)(Px)

filtered load is equal to the glmoerular filtration rate, times the plasma concentration of X
What is the excretion rate?
this is the amount of material lost in urine.

ER= Ux * V
(urinary concentration times Volume of urine produced)
What is the equation for transport rate?
Tx= FL- ER

transport rate= secreted (FL)-excreted (ER)

if it is positive, then some stuff is reabsorbed

if negative, it was secreted
What two membranes must be crossed for transcellular reabsorption?
the luminal membrane

and the basolateral membrane
How is glucose tranpsorted?
by secondary active transport
Where does most reabsoprtion of salt and water take place?
in the Proximal tubule

67% of Na+

and 65% of H2O
What regulates water uptake in the distal/collecting tubule?
What regulates Na+ reabsorption in the distal collecting tubule?
How does water reabsorption occur in the proximal tubule?
Water passively follows the Na+
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
What dose angiotensin 2 do in the Proximal tubule?
this stimulates Na+-H+ exchange across the apical membrane.

increases Na+ reabsorption
What does SNS activity do in the proximal tubule
this stimulates Na+ reabsorption
What does PTH do in the proximal tubule?
this inhibits the Na+-Phosphate cotransport.

increases urinary excretion of phosphate
What does the TF/Px ratio in the proximal tubule represent?
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.
How do you find Tm?
below Tm, all filtered load is reabsorbed,

whatever is above Tm is excreted
(EM=Ux* V)
How does GFR affect the threshold of Tm?
A Slower GFR results in higher blood concentrations (and thus threshold)
What is osmotic diuresis?
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)
How are organic anions transported? what is the organic anion of interest?
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)
Do all organic anions compete for the same transporter?
yes they do, so elevated levels of one anion will inhibit the secretion of others. PAH was used to inhibit the secretion of penicillin