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Physio II > Tubular Reabsorption & Secretion(B)- Exam 3 > Flashcards

Tubular Reabsorption & Secretion(B)- Exam 3 Flashcards

1
Q

What percent of filtered load of sodium and water is reabsorbed in the proximal tubule?

A

65% (little less percentage for chloride; quantity can be increased or decreased as needed)

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2
Q

What are the cells of the proximal tubule designed for?

A

High reabsorption capacity of sodium and water

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3
Q

What supports the extensive active transport activity in the proximal tubule?

A

Contains a large number of mitochondria

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4
Q

What provides a huge surface area for rapid diffusion in the proximal tubule?

A

Luminal (apical) brush border

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5
Q

What contains extensive number channels in between cells providing huge surface area?

A

Basolateral border

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6
Q

What contains extensive number of protein carrier molecules in the proximal tubule?

A

Luminal border

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7
Q

Why is there an extensive number of protein carrier molecules in the proximal tubule?

A

Co-transport of amino acids and glucose

Counter-transport of hydrogen ions (move a large quantity of hydrogen ions against small hydrogen ion gradient)

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8
Q

What contains an extensive amount of N/K ATPase in the proximal tubule?

A

Basolateral border

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9
Q

What is notable about the first half of the proximal tubule?

A
  1. Extensive co-transport of sodium with glucose and amino acids
  2. Sodium reabsorption carries glucose, bicarb, organic ions leaving chloride resulting in increasing [Cl-]
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10
Q

What is the change in [Cl-] in the early part of the proximal tubule?

A

105 mEq/L increases to 140 mEq/L

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11
Q

What is notable about the second half of the proximal tubule?

A
  1. High chloride concentration favors chloride diffusion (some movement thru Cl- channels)
  2. Most glucose and amino acids have been reabsorbed; sodium reabsorption drives chloride reabsorption (electrochemical gradient)
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12
Q

What changes (quantity/concentration) in the tubule throughout the reabsorption process?

A

Quantity of sodium in tubule changes, but concentration does not change because water reabsorption matches sodium reabsorption

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13
Q

Does osmolarity change during reabsorption?

A

No, water reabsorption matches sodium reabsorption

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14
Q

What happens to glucose and amino acid concentrations as they move through the tubules?

A

Decrease due to extensive reasborption

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15
Q

What happens to creatinine and urea concentrations as they move through the tubule?

A

they become more concentrated because they are not reabsorbed

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16
Q

Total amount of Na+, Cl-, HCO3-, glucose, amino acids in tubules ________(increase/decrease/does not change).

A

Decrease; but Cl- concentration goes up as were in the second half of the proximal tubule

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17
Q

Total amount of creatinine and urea in tubule _________(increase/decrease/does not change)

A

Does not change

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18
Q

What end products of metabolism are secreted by the proximal tubule?

A

Bile salts
Oxalate
Urate
Various catecholamines

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19
Q

What drugs and toxins are secreted?

A

Penicillin

Salicylates

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20
Q

What other acid is also secreted?

A

Para-aminohippuric acid (PAH)

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21
Q

What percent of PAH in the renal blood flow is removed?

A

90%

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22
Q

How can you use PAH to determine renal blood flow?

A

Knowing that 90% of PAH in renal blood flow is removed

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23
Q

What are the three functional segments of hte loop of henle?

A

Thin descending segment
Thin ascending segment
Thick ascending segment

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24
Q

What kind of membrane/characteristics does the thin descending and ascending segments have?

A

Thin epithelial membrane
(No brush border)
Few mitochondria (not a lot of active transport)
Minimal metabolic level

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25
Q

What is the only thing moving in the thin descending and ascending segments?

A

Water is the only thing that’s moving; and solutes through diffusion (no active transport)

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26
Q

What is the thin descending segment highly permeable to? Moderately permeable to?

A

Highly permeable: Water

Moderately permeable: Most solute

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27
Q

What percent of water reabsorption occurs in the loop of henle?

A

20%

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28
Q

What segment of the loop of henle is impermeable to water?

A

Thin ascending segment; part of mechanism for concentration urine

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29
Q

Describe the epithelial cells and mitochondria in the thick ascending segment.

A

Thick epithelial cells

High concentration of mitochondria

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30
Q

Why are there a lot of mitochondria in the thick ascending segment?

A

High level of metabolic activity

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31
Q

Thick ascending segment can absorb what percent of the filtered load?

A

25%; reabsorbs sodium, chloride, potassium.

Also absorbs: calcium, bicarb, magnesium

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32
Q

What is the thick ascending segments permeability to water?

A

Impermeable to water; as solute reabsorb luminal solute concentrations drop especially since water not reabsorbed (dilute fluid)

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33
Q

What drives sodium reabsorption?

A

N/K ATPase in basolateral border of tubule cells

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34
Q

What two transport mechanisms move sodium from the tubule lumen?

A

1 Na-2Cl-1K co-transport mechanism

Na-H Counter-transport mechanism

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35
Q

What is the primary means of moving sodium out of lumen into tubular cells?

A

1 Na-2Cl-1k co-transport mechanism

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36
Q

How does the 1Na-2Cl-1K co-transport mechanism affect electroneutrality?

A

It doesn’t affect it.

37
Q

Potassium is reabsorbed _________(with/against) the potassium concentration gradient in the 1Na-2Cl-1K co-transport mechanism.

A

against

38
Q

In the 1Na-2Cl-1K co-transport mechanism, what two ions diffuse out of the cell into renal interstitial fluid via specific ion channels?

A

Cl- and K+

39
Q

What three diuretics inhibit the action of the 1Na-2Cl-1K co-transport mechanism?

A

Furosemide
Bumetanide
Ethacrynic acid

40
Q

Less sodium reabsorption- ______(more/less) water reabsorption in later segments of the nephron.

A

Less

41
Q

Less sodium reabsorption- ______(more/less) potassium reabsorption with potential loss of potassium.

A

Less

42
Q

What co-transport mechanism is isoelectric?

A

Na-Cl-K co-transport

43
Q

What is able to diffuse back into lumen via channels?

A

Potassium via potassium channels

44
Q

What charge is created when K diffuses back into the lumen?

A

+8 charge in tubule lumen

45
Q

Electrical gradient drives diffusion of what ions? How?

A

Na+, K+, Mg++ and Ca++ into renal interstitial space; via tight junctions (paracellular diffusion)

46
Q

What forms the first part of the distal tubule?

A

Macula densa

47
Q

What is the macula densa? What does it do?

A

Part of the juxtaglomerular complex

Provides feedback control for GFR and blood flow (for this nephron)

48
Q

Describe the segment in the distal tubule past the macula densa.

A

Highly convoluted

49
Q

What kind of reabsorption happens in the distal tubule past the macula densa?

A

Solute reabsorption
No water reabsorption
“diluting segment of the distal tubule”

50
Q

In the early distal tubule, what percent of filtered load for sodium and chloride are reabsorbed?

A

5%

51
Q

Reabsorption of sodium and chloride in the early distal tubule is driven by what?

A

Na-K ATPase in basolateral border of tubular cells

52
Q

What co transport mechanism occurs in the early distal tubule?

A

Na-Cl co-transport mechanisms moves Na+ and Cl- into cell down [Na+]

53
Q

How does chloride diffuse in the early distal tubule?

A

Out of cell via chloride specific channels

54
Q

What inhibits Na-Cl co-transport mechanism in the early distal tubule? How?

A

Thiazide diuretics; reduces sodium and chloride reabsorption and ultimately water reabsorption in later segments of nephron

55
Q

Late Distal Tubule and Cortical Collecting Tubule membranes are impermeable to what?

A

Urea; all urea entering exist to collecting duct to be excreted; some reabsorption will occur in the medullary collecting ducts

56
Q

How is sodium reabsorption controlled in the late distal tubule and cortical collecting ducts?

A

Various hormones; but especially by aldosterone

57
Q

How is potassium secretion controlled in late distal tubule and cortical collecting ducts?

A

Various hormones, especially by aldosterone

58
Q

What happens with hydrogen in the late distal tubule and cortical collecting ducts?

A

Able to secrete hydrogen ions against a large concentration gradient (1000:1)

59
Q

Proximal tubule moves hydrogen ions against what gradient?

A

(4 to 10) :1

60
Q

What controls water permeability in the late distal tubule and cortical collecting ducts?

A

Concentration of ADH, aka vasopressin

61
Q

What happens in late distal tubule and cortical collecting ducts if there’s no ADH?

A

No water permeability; excrete dilute urine

62
Q

What happens in late distal tubule and cortical collecting ducts w/ increased ADH?

A

Increased permeability of water and decrease in volume of urine and increase the concentration of urine

63
Q

What happens if aldosterone is increased?

A

Sodium reabsorption goes up

64
Q

What are the two types of cells in the late distal tubule and cortical collecting ducts?

A

Principal cells

Intercalated cells

65
Q

Principal cells reabsorb and secrete what

A

reabsorb sodium and water

secrete potassium

66
Q

Intercalated cells reabsorb and secrete what

A

Reabsorb potassium

Secerete hydrogen

67
Q

What drives the activity of principle cells?

A

Na-K ATPase in basolateral borders of tubule cells

68
Q

Describe the gradients of Na and K in principle cells.

A

Sodium follows concentration gradient-diffuses through sodium specific channels

Potassium- follows concentration gradient out of cell into tubular lumen via potassium specific channels

69
Q

Aldosterone antagonists are also called what?

A

Mineralcorticoid receptor antagonists

70
Q

How do aldosterone antagonists work?

A

Compete with aldosterone receptor sites which inhibits sodium reabsorption and potassium secretion

71
Q

What are some examples of aldosterone antagonists?

A

Spironolactone

Epleronone

72
Q

What is a potassium sparing diuretic?

A

Sodium channel blockers; amiloride, triamterene

73
Q

How do sodium channel blockers work?

A

Inhibit entry of sodium into cell which reduces amount of sodium transported by Na-K ATPase; reduces secretion of potassium as action of Na-K ATPase decreases

74
Q

What ions have intercalated cell activity?

A

Hydrogen ions

75
Q

Secretion of H+ are controlled by what?

A

H-ATPase transporter

76
Q

Presence of what allows conversion of CO2 and H2O to hydrogen ions and bicarb?

A

Carbonic anhydrase

77
Q

What is also secreted from cell with H+ ions?

A

Chloride; following electrochemical gradient

78
Q

What happens to bicarb (intercalated cell activity)? What else has this same action?

A

Reabsorbed using Cl- HCO3- counter transport mechanism following the Cl- gradient into the cell

Potassium is also reabsorbed.

79
Q

What happens with CO2?

A

Moves freely between cell and interstitial fluid

80
Q

Medullary collecting ducts reabsorb what percent of filtered water and sodium?

A

<10%

81
Q

What determines final concentration of solutes and urine concentration?

A

Medullary collecting ducts

82
Q

Describe the epithelial cells and mitochondria in medullary collecting ducts.

A

Epithelial cells smooth with few mitochondria

83
Q

What controls water permeability in medullary collecting duct?

A

ADH

84
Q

How is urea reabsorbed in medullary collecting duct?

A

Specific urea transporters which moves urea into the interstitial space thus affecting osmolarity

85
Q

What happens to hydrogen ions in the medullary collecting duct?

A

Secretes hydrogen ions (like cortical collecting tubule)

86
Q

Change in solute concentration depends on what?

A

Rate of absorption (secretion) vs rate of water absorption

87
Q

What happens to inulin? What does it indicate?

A

neither secreted or reabsorbed provides indication of water reabsorption

88
Q

What does an inulin concentration of 3 mean?

A

1/3 of water remains in tubule (2/3 have been reabsorbed)

89
Q

What does an inulin concentration of 125 mean?

A

1/125 of water remains in tubule 124/125 has been reabsorbed

Physio II (14 decks)

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