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Physio II (Exam 3) > Topic 8 A: Basic Principles Tubular Reabsorption & Secretion > Flashcards

Topic 8 A: Basic Principles Tubular Reabsorption & Secretion Flashcards

1
Q

Excretion = equation?

A

Filtration–Reabsorption + Secretion

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2
Q

Filtration: occurs where?

A

Glomerulus

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3
Q

Reabsorption & Secretion occurs where?

A

Proximal tubule; loop of Henle;

distal tubule; collecting tubule

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4
Q

Filtration Rate = equation?

A

GFR x Plasma concentration

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5
Q

Glucose :(g/day) % of filtered load reabsorbed

A

100 %

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6
Q

Bicarb: mEq % of filtered load reabsorbed

A

99.9 %

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7
Q

Sodium: % of filtered load reabsorbed

A

99.4%

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8
Q

Chloride: % of filtered load reabsorbed

A

99.1%

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9
Q

Potassium: % of filtered load reabsorbed

A

87.8%

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10
Q

Urea: % of filtered load reabsorbed

A

50%

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11
Q

Creatinine: % of filtered load reabsorbed

A

0%

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12
Q

Kidneys has independent control over exertion rate by changing what?

A

appropriate reabsorption rate

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13
Q

Several distinct movements for water and solutes (4)

A

Transcellular path
Paracellular path
From interior of cell into tubular interstitial space
From interstitial space into peritubular capillary

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14
Q

Transcellular path

A

From tubular lumen into tubular cells

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15
Q

Paracellular path

A

From tubular lumen into tubular interstitial space

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16
Q

From interstitial space into peritubular capillary

A

Driven by capillary filtration forces [bulk flow]–net movement into the capillaries

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17
Q

Primary active transport mechanisms of tubular reabsorption (4)

A

Na-K ATPase (basal lateral membrane)
Hydrogen ATPase
H-K ATPase
Ca ATPase

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18
Q

Secondary active transport: Co-transport mechanisms of tubular reabsorption (2)

A

Sodium-glucose

Sodium-amino acids

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19
Q

Secondary active transport: Counter-transport mechanisms of tubular reabsorption

A

Sodium-hydrogen

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20
Q

Pinocytosis mechanisms of tubular reabsorption

A

(requires energy)

Proteins–once in cell broken down to component amino acids and amino acids reabsorbed

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21
Q

Passive mechanisms of tubular reabsorption (2)

A

Osmotic movement of water

Bulk flow into peritubular capillaries

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22
Q

Na reabsorption:
Na-K ATPase on basolateral sides of tubular epithelial cells
Creates membrane potential of what?

A

-70 mV

Na reabsorption

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23
Q

Na reabsorption:

Brush board of proximal tubule luminal membrane creates what?

A

huge surface area for diffusion (20x increase)

part of Na reabsorption

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24
Q

Sodium Rabsorption - Sodium reabsorption also enhanced by carrier proteins through luminal membrane

A

Co-transport & counter-transport proteins

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25
Q

Glucose Reabsorption: Co-transport mechanism so tied to what?

A

tied to sodium gradient from tubular lumen to interior of tubular cells
So efficient that usually removes all filtered glucose
KNOW

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26
Q

Glucose Reabsorption: Two luminal transporters?

A

SGLT2 and SGLT1

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27
Q

SGLT2 what is reabsorbed and where?

A

90% glucose reabsorbed via SGLT2 in early part of proximal tubule

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28
Q

SGLT1 what is reabsorbed and where?

A

10% reabsorbed in later part of proximal tubule

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29
Q

Bulk flow moves what?

A

glucose from interstitial spaces into the peritubular capillaries

30
Q

Amino Acid Reabsorption: Co-transport mechanism tied to what gradient??!?!?

A

sodium gradient from tubular lumen to interior of tubular cells
So efficient that usually removes all filtered amino acids

31
Q

⬆️RBF does what to Glucose Reabsorption?

A

⬆️Glucose Reabsorption

32
Q

Amino Acid Reabsorption:
Luminal co-transporter system pumps the amino acids where???
Amino acids diffuse where??

A

–into the cells

–out of the cells into the interstitial spaces

33
Q

Bulk flow moves the amino acids from where into where?

A

interstitial spaces into the peritubular capillaries

34
Q

Hydrogen Secretion

Counter-transport mechanism tied to what?

A

sodium gradient from tubular lumen to interior of tubular cells

35
Q

Hydrogen Secretion

Sodium-hydrogen exchanger is located where?

A

in brush boarder of the luminal membrane

36
Q

Hydrogen Secretion: can move LRG amounts of H+ but can only do it across a small what?

A

gradient

37
Q

Transport max

A

Max amount of solute that can be reabsorbed (transport max transport)

38
Q

Transport maximum: Occurs when?

A

Occurs when tubular load (amount of solute delivered to tubule exceeds transport capacity of carrier proteins

39
Q

Glucose transport max mg/min?

on that line graph

A

375 mg/min

40
Q

Glucose filtered load = equation (normal amount)

A

GFR x [Glu] = 125 mls/min x 1 mg/ml = 125 mg/min

41
Q

concentration where glucose first appears in urine?

on line graph thing

A

Threshold concentration (approx. 250 mg/dL)

42
Q

Why is Threshold concentration is less than transport max?

A

Less than T max because each individual nephron is different–chart represents action of both kidneys so Tmax reached when ALL nephrons have reached their max

43
Q

Glucose Transport Max

A

375 mg/min

44
Q

Amino Acids transport max

A

1.5 mM/min

45
Q

Plasma protein transport max

A

30 mg/min

46
Q

Two excretion rates?

A
  • -Before secretion Tmax is reached the amount excreted is sum of amount filtered and amount secreted (steepest slope of excretion curve)
  • -After secretion Tmax is reached rate of excretion parallels filtration rate (slope of excretion curve matches slope of filtration curve)
47
Q

Two excretion rates: steepest slope of excretion curve

A

Before secretion Tmax is reached the amount excreted is sum of amount filtered and amount secreted

48
Q

Two excretion rates: slope of excretion curve matches slope of filtration curve

A

After secretion Tmax is reached rate of excretion parallels filtration rate

49
Q

Change in GFR would change the slope of what line on the transport max secretion graph?

A

Filtered line

50
Q

Creatinine Transport Max (mg/min)

A

16 mg/min

actively secreted

51
Q

Rate of transport depends on: what 3 things ?

A
  • Electrochemical gradient for solute
  • Membrane permeability for solute
  • Time fluid containing solute remains in tubule
    - Transport rate inversely related tubular flow rate
52
Q

⬆️GFR ⬆️ Tubular Flow - does what to Na reabsorption?

A

⬇️Na reabsorption

53
Q

Sodium transport max? in Proximal Tubule

A

does not show a transport maximum even though it is actively reabsorbed

54
Q

Proximal Tubule: Significant amount of transported sodium leaks back into the tubular lumen affected by what? (2)

A
  • Permeability of tight junctions between cells

- Forces controlling bulk flow of water & solute into peritubular capillaries

55
Q

Na reabsorption:

As plasma concentration of sodium increases, what happens in the Proximal Tubule and toreabsorption?

A

sodium concentration in proximal tubule increases and sodium reabsorption increases
A decrease in tubular flow rate will also increase sodium reabsorption

56
Q

Na reabsorption: Proximal Tubule: A decrease in tubular flow rate will_____ sodium reabsorption?

A

increase

57
Q

Na reabsorption: Distal Tubule: Sodium reabsorption shows classic what?

A

tubular max transport

58
Q

Na reabsorption: Distal Tubule: Capacity of Na-K ATPase does not exceed rate of what?

A

net sodium reabsorption

Minimal back leak of sodium into tubular lumen
Tighter (less permeable tight junctions) coupled transport of much smaller amount of sodium

59
Q

Na reabsorption: Distal Tubule: Minimal back leak of Na into where? and why?

A

Minimal back leak of sodium into tubular lumen

Tighter (less permeable tight junctions) coupled transport of much smaller amount of sodium

60
Q

Na reabsorption in Distal Tubule: what increases the Threshhold max level?

A

Aldosterone

61
Q

Passive Reabsorption of water driven by what?

A

Driven by osmotic differences created by movement of solute (mainly sodium) from tubular lumen to the tubular interstitial spaces

62
Q

Passive Reabsorption of water affected by what?

A

Affected by cellular permeability (cell membranes and tight junctions)
Increased permeability

63
Q

Passive Reabsorption of water Increased permeability means what for reabsorption and excretion?

A

means increased reabsorption and decreased water excretion

64
Q

Passive Reabsorption of water in proximal tubule?

A

Highly permeable
Rapid movement so overall solute gradient across cell is minimal
Solvent drag–water carries significant amount of sodium, chloride, potassium, calcium, magnesium because of high permeability

65
Q

Passive Reabsorption of water Loop of Henle (ascending loop) permeability?

A

Low permeability

Little movement of water even though there is a large osmotic gradient

66
Q

Passive Reabsorption of water Distal tubule / Collecting tubules / Collecting ducts: permeability?

A

Variable permeability
Cellular permeability depends on presence of antidiuretic hormone (ADH)
Permeability directly related to [ADH]
Changing water permeability only affects amount of water reabsorbed not the amount of solute due to low solute permeability

67
Q

⬆️ADH = does what to permeability of H2O

A

⬆️H2O Urine permeability (reabsortion)

68
Q

Passive Reabsorption: Chloride & Urea
Sodium diffusion into cells creates electrical
gradient that pulls what ions into the cell?

A

negative chloride ions into the cell

69
Q

Passive Reabsorption: Chloride & Urea
Movement of water into cells concentrates
urea creating??

A

concentration gradient into cell but urea not nearly as permeable as water

70
Q

What % of filtered urea is reabsorbed ?

A

Only 50% of filtered urea is reabsorbed

Physio II (Exam 3) (6 decks)

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