Tubular Transport of NaCl and Water Flashcards
(30 cards)
What are aquaporins?
water pores formed by proteins
What is the proportion of NaCl and water that is ALWAYS absorbed?
65%
What does the macula densa do in response to increased NaCl?
it signals the afferent arteriole to contract in order to maintain GFR
Nearly all of the obligatory recapture of water and salt occurs in the ______.
“proximal segments” (i.e. proximal tubule and loop of Henle)
The primary energetic event occurs when Na+ is actively extruded from the interior of the tubular epithelium by the ______.
basolateral Na+/K+-ATPase ion pump
What is another name for ADH?
vasopressin
What is another name for vasopressin?
ADH
Reabsorption of _____, _____, and _____ are coupled to the active reabsorption of sodium.
- chloride
- water
- other solutes
What does aldosterone do in the DCT and collecting duct?
- increases the number of apical sodium channels and basolateral sodium pumps
- increases ATP synthesis
What pump is found in the ascending loop of Henle?
Na/K/2Cl cotransporter
The filtrate is isotonic in the PCT. What is it like in the Loop of Henle?
hypotonic
Most of the filtered load of water and salt is _____, with only a small fraction under homeostatic control.
obligatorily reabsorbed
What is the role of the proximal tubule?
obligatory reabsorption of most water, Na, and other important metabolites
The main driving force for flow of reabsorbed fluid back into the capillaries is ______.
the osmotic pressure of the capillary plasma
______ refers to the ability of the obligatory reabsorption mechanisms in the proximal tubule to compensate for changes in filtered load.
Glomerulotubular balance
How fast does aldosterone work? Why?
slower than ADH- takes about 1 hour (bc of gene transcription)
Most diuretics tend to increase the urinary excretion rate of ____, _____, and _____ indirectly due to their effect on water flow.
sodium, potassium, and chloride
Reabsorption of chloride, water, and other solutes are coupled to the active reabsorption of ______.
sodium
What happens to the DCT and collecting duct in the presence of ADH?
aquaporins move to the apical membrane of the tubule to allow water reabsorption
How fast does ADH work? Why?
very fast bc the aquaporins are (mostly) already made
What is the maximal absorption rate referred to as?
the transport maximum
In which part of the Loop of Henle does primary NaCl absorption occur?
in the ascending limb
Why doesn’t water follow the NaCl into the interstitium in the ascending Loop of Henle?
the water permeability is low in the ascending limb- it is reabsorbed in the descending limb
Why does water follow Na movement?
bc of the osmotic gradient created
