PCT Power
What percentage of filtered sodium and water is reabsorbed in the PCT?
~65%
Name the similarities and differences between the descending and ascending limb?
Descending is permeable to water, impermeable to solutes
Ascending is permeable to Na, K, Cl; impermeable to water
Which hormone(s) increases water & Na reabsorption in the collecting duct?
ADH - water
Aldosterone - Na
Where do Thiazides act and what is their MOA?
- DCT
- inhibit Na/Cl transporter
Which hormone increases Na⁺ reabsorption in the PCT?
Angiotensin II
Which transporter is inhibited by loop diuretics?
Na⁺-K⁺-2Cl⁻ cotransporter
What does ANP do to sodium reabsorption?
Decreases it (promotes sodium excretion)
What are consequences of aldosterone deficiency?
- hyperkalemia
- hyponatremia
What happens in the second of half of active Na reabsorption?
Na is transported with Cl (second half)
Na is transported with glucose, AA, HCO3, PO3, lactate (first half)
Describe blood flow in the vasa recta
How does ADH increase water permeability?
Inserts aquaporin-2 channels into collecting duct cells
What is hepcidin and what does it do?
- a peptide hormone produced in the liver
- key mediator for functional iron deficiency
On which membranes are water channels (AQP-1)?
Apical & Basolateral membrane
What is the main function of the LoH?
Generation of medullary hypertonicity
When and where is ANP released?
- released from the atria
- in response to atrial stretch caused by increased atrial pressure due to fluid or Na overload.
In people with CKD, kidney damage is thought to progress due to?
a) a progressive decrease in the level of function of a fixed number of nephrons?
b) progressive destruction of nephrons
c) reduced blood flow to the glomeruli
d) obstruction of renal tubules
e) precipitation of calcium in kidney tissue
b) progressive destruction of nephrons
What is the difference btw SGLT1 & SGLT2?
SGLT1 - high affinity, low capacity
SGLT2 - low affinity, high capacity
Which part of the loop:
a) creates the osmotic gradient
b) is the point where filtrate reaches its highest concentration
a) thick ascending limb
b) bend of the loop
What mediates phosphate excretion in CRF?
- PTH
- FGF-23
What catalyst allows CO2 to diffuse freely across membranes in the nephron?
CA - carbonic anhydrase