Tubular Transport of NaCl and Water

Question 1

What are aquaporins?

Answer 1

water pores formed by proteins

Question 1

What is the proportion of NaCl and water that is ALWAYS absorbed?

Answer 1

65%

Question 1

What does the macula densa do in response to increased NaCl?

Answer 1

it signals the afferent arteriole to contract in order to maintain GFR

Question 3

Nearly all of the obligatory recapture of water and salt occurs in the ______.

Answer 3

“proximal segments” (i.e. proximal tubule and loop of Henle)

Question 4

The primary energetic event occurs when Na+ is actively extruded from the interior of the tubular epithelium by the ______.

Answer 4

basolateral Na+/K+-ATPase ion pump

Question 4

What is another name for ADH?

Answer 4

vasopressin

Question 4

What is another name for vasopressin?

Answer 4

ADH

Question 6

Reabsorption of _____, _____, and _____ are coupled to the active reabsorption of sodium.

Answer 6

• chloride
• water
• other solutes

Question 6

What does aldosterone do in the DCT and collecting duct?

Answer 6

• increases the number of apical sodium channels and basolateral sodium pumps
• increases ATP synthesis

Question 7

What pump is found in the ascending loop of Henle?

Answer 7

Na/K/2Cl cotransporter

Question 8

The filtrate is isotonic in the PCT. What is it like in the Loop of Henle?

Answer 8

hypotonic

Question 10

Most of the filtered load of water and salt is _____, with only a small fraction under homeostatic control.

Answer 10

obligatorily reabsorbed

Question 11

What is the role of the proximal tubule?

Answer 11

obligatory reabsorption of most water, Na, and other important metabolites

Question 11

The main driving force for flow of reabsorbed fluid back into the capillaries is ______.

Answer 11

the osmotic pressure of the capillary plasma

Question 11

______ refers to the ability of the obligatory reabsorption mechanisms in the proximal tubule to compensate for changes in filtered load.

Answer 11

Glomerulotubular balance

Question 12

How fast does aldosterone work? Why?

Answer 12

slower than ADH- takes about 1 hour (bc of gene transcription)

Question 13

Most diuretics tend to increase the urinary excretion rate of ____, _____, and _____ indirectly due to their effect on water flow.

Answer 13

sodium, potassium, and chloride

Question 15

Reabsorption of chloride, water, and other solutes are coupled to the active reabsorption of ______.

Answer 15

sodium

Question 16

What happens to the DCT and collecting duct in the presence of ADH?

Answer 16

aquaporins move to the apical membrane of the tubule to allow water reabsorption

Question 17

How fast does ADH work? Why?

Answer 17

very fast bc the aquaporins are (mostly) already made

Question 19

What is the maximal absorption rate referred to as?

Answer 19

the transport maximum

Question 21

In which part of the Loop of Henle does primary NaCl absorption occur?

Answer 21

in the ascending limb

Question 22

Why doesn’t water follow the NaCl into the interstitium in the ascending Loop of Henle?

Answer 22

the water permeability is low in the ascending limb- it is reabsorbed in the descending limb

Question 23

Why does water follow Na movement?

Answer 23

bc of the osmotic gradient created

Question 24

At the distal tubule, only ___% of the filtered water and ____% of the filtered NaCl remain.

Answer 24

20; 10

Question 25

In the proximal tubule ____% of the filtered water and NaCl is obligatorily reabsorbed.

Answer 25

65

Question 26

What is the transport maximum?

Answer 26

the finite, maximal reabsorption rate in the proximal tubule

Question 27

This is direct regulation of the GFR of each nephron in response to changes in NaCl concentration at the macula densa.

Answer 27

Tubuloglomerular Feedback (TGF)

Question 29

What is glomerulotubular balance?

Answer 29

the ability of the obligatory reabsorption mechanisms in the proximal tubule to compensate for changes in filtered load

Question 30

What is Tubuloglomerular Feedback (TGF)?

Answer 30

direct regulation of the GFR of each nephron in response to changes in NaCl concentration at the macula densa