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Histo (VM1 Fall) > Exam 3 - Lecture 37 (Tubular Reabsorption) > Flashcards

Exam 3 - Lecture 37 (Tubular Reabsorption) Flashcards

1
Q

What is reabsorption?

A

Pulling things from the nephron into the bloodstream

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2
Q

How does blood get from the nephron back to the bloodstream?

A

Through peritubular capillaries

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3
Q

What is the opposite of reabsorption?

A

Secretion

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4
Q

What is passive transport?

A

Movement across membrane by random motion down electrochemical gradient without energy (diffusion and facilitated diffusion)

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5
Q

What is active transport?

A

Movement across membrane via carrier protein against electrochemical gradient using energy (primary active and secondary active)

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6
Q

What is the luminal membrane?

A

Side of cell that separates tubular cell from tubular fluid

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7
Q

What is the basolateral membrane?

A

Side of cell that separates cell from peritubular interstitium (blood)

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8
Q

What is transepithelial potential difference?

A

Potential difference between tubular lumen and peritubular interstitium (blood).
- Changes bt tubular sections and contributes to electrochemical gradient

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9
Q

What is the transcellular route?

A

Reabs. thru cytoplasm of tubular cells.

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10
Q

What route does passive transport take?

A

Transcellular and paracellular

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11
Q

What route does active transport take?

A

Transcellular only

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12
Q

What % of reabsorption happens thru the transcellular route?

A

80-90%

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13
Q

What is the paracellular route?

A

Reabs. between tubular cells across tight junctions

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14
Q

What is Na+K+ATPase critical for?

A

Tubular reabsorption

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15
Q

Where is Na+K+ATPase located?

A

Basolateral membrane of all tubular epithelia

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16
Q

What is the role of Na+K+ATPase?

A

Moves 3 Na+ out of the cell and 2 K+ in (to decrease [Na+] inside cell)

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17
Q

What type of transporter is Na+K+ATPase?

A

basolateral antiporter

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18
Q

What type of transport does Na+K+ATPase do?

A

active

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19
Q

Why does Na+K+ATPase maintain low IC Na+?

A

To establish the electrochemical gradient upon which all reabsorption depends.

20
Q

Which molecule’s [ ] is not the same in filtrate as in EC space?

21
Q

Which of the following statements about Na+K+ATPase is correct?

A) It transports Na+ and K+ at the luminal membrane of nephron epithelia
B) It moves 3 Na+ into the cells in exchange for 2 K+ out of the cell
C) Na+ movement is by facilitated diffusion
D) It requires energy in the form of ATP
E) It moves K+ paracellularly

A

D) It requires energy in the form of ATP

22
Q

PT reabsorbs ___% of filtered water, Na+, and solutes.

23
Q

PT reabsorbs ___% of filtered glucose, AAs, and ___% bicarb.

24
Q

What are the 4 steps to tubular reabs. in the 1st half of the PT?

A
  1. Na+K+ATPase generates Na+ gradient (decreases IC [Na+])
  2. Na+ enters down electrochemical gradient via Na+H+ antiporter AND Na+ glucose symporter
  3. Glucose moves down its [ ] gradient into the blood
  4. Water follows Na+ down osmotic gradient
25
Q

What does Na+ enter the cell with during tubular reabs. in the 2nd half of the PT?

26
Q

What does Na+ enter the cell with during tubular reabs. in the 1st half of the PT?

27
Q

What are the 6 steps to tubular reabsorption in the 2nd half of the PT?

A
  1. Na+K+ATPase generates Na+ gradient
  2. Na+ enters down electrochemical gradient via Na+H+ antiporter
  3. Cl- enters down electrochemical gradient via Cl- anion antiporter AND via paracellular route
  4. K+ leaves cell with Cl- symporter
  5. Lumen positive PD drives Na+ down paracellular route
  6. Water follows by osmosis thru aquaporins
28
Q

What happens to proteins that end up being filtered by the glomerulus (3 steps)?

A
  1. Pts partially degraded by enzymes in luminal membrane and reabsorbed by endocytosis
  2. Pts further degraded by enzymes in lysozyme –> AAs and leave via basolateral membrane.
  3. Process can be easily saturated so pts can appear in urine/
29
Q

What is proteinuria?

A

Proteins present in urine

30
Q

The LoH reabsorbs ___% of filtered NaCl and ___% of filtered water.

31
Q

Which limb of the LoH reabsorbs water?

A

descending only

32
Q

Which limb of the LoH reabsorbs NaCl?

A

ascending only (passive transport)

33
Q

Up to this point, which statement about tubular reabsorption is correct?

A) Most water is reabsorbed in the descending Loop of Henle
B) Na+ is reabsorbed actively at the luminal membrane in the proximal tubule
C) Glucose is reabsorbed via facilitated diffusion
D) Cl- reabsorption is both transcellular and paracellular

A

D) Cl- reabsorption is both transcellular and paracellular

34
Q

DT and CT reabsorb ___% of filtered NaCl and ___% of filtered water.

35
Q

DT and CT are _____ to water.

A

impermeable

36
Q

What are the 4 steps to tubular reabsorption in the early distal tubule?

A
  1. Na+K+ATPase generates Na+ gradient
  2. Na+ enters cell via NKCC1 symporter and Na+H+ antiporter.
  3. Positive transmembrane PD means cations move down electrochemical gradient via paracellular route.
  4. Water does NOT follow
37
Q

Loop diuretics (e.g. furosemide) inhibit _____.

38
Q

What is an example of a loop diuretic?

A

Furosemide

39
Q

Why is reabsorption of water in the DT variable?

A

Depends on presence of anti-diuretic hormone

40
Q

What are the 2 steps to tubular reabsorption in the late DT?

A
  1. Na+K+ATPase generates Na+ gradient

2. Na+ enters cell via Na+Cl- symporter.

41
Q

What inhibits NaCl- symporter?

A

Thiazide diuretics

42
Q

When is the only time water is reabsorbed in the DT?

A

In the presence of ADH

43
Q

What two cell types make up the CT epithelium?

A

principal and intercalated cells

44
Q

What are the 5 steps to tubular reabsorption in the CT through principal cells?

A
  1. Na+K+ATPase generates Na+ gradient
  2. Na+ enters cell via amiloride sensitive Na+ channels
  3. Water follows via aquaporins but ONLY with ADH
  4. K+ leaves thru K+ channels down its gradient
  5. Na+ reabs. generates negative PD so Cl- is abs. paracellularly
45
Q

Which of these molecules transports Na+ at the luminal membrane of the late DT?

A) Na-Cl symporter
B) NKCC1
C) Na-glucose symporter
D) Na-H antiporter

A

A) Na-Cl symporter

46
Q

What do intercalated cells secrete during tubular reabsorption?

A

H+ or HCO3-

Maybe important for maintaining acid-base balance

47
Q

Prioritize these tubular sections in terms of Na+ reabsorption: most Na+ reabsorption first, least Na+ reabsorption last:

A) Proximal tubule, Distal tubule, Loop of Henle
B) Loop of Henle, Proximal henle, Distal tubule
C) Distal tubule, Proximal tubule, Loop of Henle
D) Distal tubule, Loop of Henle, Proximal tubule
E) Proximal tubule, Loop of Henle, Distal tubule

A

E) Proximal tubule, Loop of Henle, Distal tubule

Histo (VM1 Fall) (27 decks)

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