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R6
Basic Renal Processes for Sodium, Chloride and Water
23
Physiology
Professional
02/24/2013

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Cards

Term
Where is the filtered sodium reabsorbed?
Definition
65% in the proximal tubule, 25% in the loop of Henle, 10% in the distal nephron
Term
What is the major route of sodium excretion from the body?
Definition
urine
Term
What portion of the nephron is salt impermeable?
Definition
Descending thin limb of loop of Henle
Term
What portion of the nephron is water impermeable?
Definition
Ascending thick and thin limbs of loop of Henle and distal convoluted tubule
Term
What are the ranges of reabsorption of water in the collecting duct?
Definition
5 to >24% depending on hydration status
Term
What ion does chloride compete with for reabsorption in the proximal tubule?
Definition
bicarbonate
Term
How much bicarbonate is reabsorbed by the end of the proximal tubule? How much chloride?
Definition
80% bicarbonate; 60% chloride
Term
How does the charge of the proximal tubule with respect to the blood change as you go down the proximal tubule?
Definition

The first half is negatively charged with respect to the blood (-4 mV) The second half is positively charged (+4 mV)

 

*This is because chloride is preferentially reabsorbed in the second half of the proximal tubule

Term
Where do we see isoosmotic reabsorption in the nephron?
Definition
proximal tubule
Term
Does sodium help reabsorption of organic nutrients, phosphate, and sulfate by cotransport or countertransport?
Definition
Cotransport
Term
Does sodium help secretion of hydrogen ion by cotransport or countertransport?
Definition
Countertransport
Term
Which part of the loop of Henle has active transporters?
Definition
The thick limb
Term
Which part of the loop of Henle is freely permeable to water but not salts?
Definition
The thin descending limb
Term
Which part of the loop of Henle is freely permeable to salts but not water?
Definition
The thin ascending limb
Term
Which part of the nephron is called the diluting segment?
Definition
The thick ascending limb because it actively pumps salts out via the Na-K-2Cl symporter but it is impermeable to water
Term
What is the target for inhibition by loop diuretics like Furosemide?
Definition
NKCC = Na-K-2Cl symporter in the thick ascending limb
Term
How does the osmolarity of the kidney change from the cortex to the deep medulla?
Definition
It goes from 300 to 1200 mosm/l
Term
What ions and molecules make us the 1200 mosm/l osmolarity of the deep medulla?
Definition
25% Cl-, 25% Na+, 50% urea
Term
Why is urea an ineffective osmole?
Definition
It follows water, not leads water
Term
What does ADH do?
Definition
It causes the insertion of aquaporin water channels into the APICAL membrane of the collecting duct, increasing the water permeability.

*basolateral membrane is always freely permeable to water
Term
What portion of the nephron contains NCCs (Na-Cl symporter) and ENaCs (apical sodium channels)?
Definition
Distal convoluted tubule
Term
What is the major type of cell in the cortical collecting duct?
Definition
Principal cells
Term
Where does ADH work?
Definition
Solely on the cortical and medullary collecting duct – not on the proximal nephron
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