PSL301: Water 3 Flashcards Preview

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Flashcards in PSL301: Water 3 Deck (100):
1

value: normal GFR

> 90 mL/min or > 125 L/day

2

value: normal urine volume

0.5L - 2 L per day

3

why is there such a big difference between filtered volume and excreted volume?

> 99% of water & solutes are reabsorbed by the tubules

4

function of tubules

- reabsorb solutes & water
- secrete solutes & water
- maintain homeostasis

5

when everything is normal, intake...
What is this called?

intake = secretion
"steady state"

6

steady state

intake = secretion

7

when there is a deficit of something, intake...

intake > excretion
(excretion decreased)

8

when there is an excess of something, intake...

intake < excretion
(excretion increased)

9

How does the kidneys maintain homeostasis?

adjust how much is reabsorbed & secreted

10

What signals do the tubules receive, and what do they do?

- hormones
- nerves
- pH
- electrolyte concentrations
- pressure

signals modify reabsorption / excretion to keep body fluid composition normal

11

Hormone signals to the kidney

- vasopressin / ADH
- aldosterone
- ANG II
- PTH

12

purpose of ADH

water balance

13

purpose of aldosterone

Na & K balance

14

purpose of ANG II

Na & acid-base balance

15

purpose of PTH

Ca++ & phosphate balance

16

main nephron segments

1. proximal tubule
2. loop of Henle
3. distal tubule
4. collecting duct

17

the collecting duct is divided into...

1. cortical collecting duct
2. medulla collecting duct

18

the Loop of Henle is divided into...

1. Thick descending limb
2. descending limb
3. ascending limb
4. thick ascending limb

19

function of tight junctions at the transporting epithelium

- keep cells attached to each other
- prevent movement between adjacent cells (must pass through epithelial cells)

20

The basolateral membrane of the epithelium faces the...

ECF / blood stream

21

The apical membrane of the epithelium faces the...

lumen of kidney / intestines

22

____ increases absorptive surface area on the __ side of the proximal tubule

brush border microvilli
lumen

23

Most of the reabsorption occurs in the...

proximal tubule

24

sites of reabsorption

- proximal tubule
- loop of Henle
- distal convoluted tubule & collecting duct

25

Glucose is reabsorbed in the...

all glucose is reabsorbed in the proximal tubule

26

How is K homeostasis maintained?

by secretion at the distal convoluted tubule & collecting duct

27

Most solutes & water homeostasis is controlled by the...
What is the exception?

distal convoluted tubule & collecting duct

Glucose, controlled by proximal tubule

28

What are the things reabsorbed / secreted by the kidneys? (5)

- water
- Na
- K
- glucose
- bicarb

29

How do transporting epithelial cells work?

Polarized, so have different transport proteins on each side. Solutes must pass through different ones to get to other side.

30

the Na/K ATPase is located on which membrane?

basolateral

31

the Na/K ATPase is next to...

peritubular capillary

32

what does the Na/K ATPase do?

pumps 3 Na out of cell
pumps 2 K into cell

- makes cell negative
- make [Na] in cell low

33

the Na/K ATPase has what effect on Na in the lumen?

can enter cell naturally (down electrochemical gradient) @ apical membrane

Na then leaves through Na/K ATPase @ basolateral membrane

34

What is the purpose of Na movement?

Drives the movement of other solutes by cotransporters and antiporters on the apical membrane

35

cotransporters

transport 2 things in the same direction
- movement of 1 thing down the gradient drives movement of other against the gradient

36

antitransporters

transport 2 things in opposite directions
- movement of 1 thing down the gradient drives movement of other against the gradient

37

movement of water at the proximal tubule

follows Na (moves into capillaries)
- osmotic gradient

38

absorption & secretion t the proximal tubule is ___ because of the movement of sodium

passive

39

define: secondary active transport

an ion can move against the gradient by coupling with another that moves down the gradient

40

the Na/glu transporter is a(n)...

cotransporter

41

reabsorption of glucose

1. Na/glu cotransporter moves glucose into cell (where it is high concentration)
2. glucose moves out of cell on basolateral side using GLUT transporter
3. Na/K ATPase pumps Na out of cell to keep intracellular Na low

42

which ions use sodium co-transport as a method to get through cells?

- glucose
- phosphate
- chloride
...

43

how is paracellular transport achieved (at the renal tubules)?

- through tight junctions
- selective
- have pores
- driven by gradients
- only some ions (Na, Cl, Ca, Mg...) can get through

44

diuretic drugs block...

lumenal Na transporters
- increase Na secretion

specific diuretics target specific transporters

45

common target of diuretics

- loop of Henle
- distal convoluted tubule
- collecting duct

46

how does each nephron segment differ?

- type of transport protein
- leakiness
- type of hormone receptors present

47

things that will affect leakiness in tubules

- nature of the tight junction
- presence of channels (e.g. aquaporins)

48

Trend of leakiness at the nephron tubules

Start off very leaky (proximal tubule)
Get tighter as you go on (collecting duct)

49

proximal tubule is the site of...

most reabsorption (Na, Cl, K, bicarb, water)

50

the most important lumenal Na transport protein at the proximal tubule is...

NHE3 (sodium-hydrogen exchanger)

51

NHE3 works by...

pump Na into the cell
pump H+ out of the cell

52

Purpose of NHE3

bicarb reabsorption

53

which cotransporters are only found on the proximal tubule?

- glucose
- phosphate
- amino acid

54

the proximal tubule is very leaky -> ____ reabsorption of Na. What does this mean?

isotonic
[Na] in lumen is the same as [Na] in plasma due to water moving with Na

55

The thick ascending limb reabsorbs ___% of ___

20 - 30%
filtered Na

56

what is the lumenal transport at the thick ascending limb?

Na/K/2Cl cotransporter (NKCC2)

57

NKCC2 is inhibited by...

furosemide (diuretic)

58

how permeable is the thick ascending limb to water?

not at all

59

fluid leaving the thick ascending limb is ____

hypotonic
(less concentrated than plasma because water in tubule cannot get out)

60

What concentrates the medullary interstitium? What is the necessary for?

Add salt without water

Necessary for urine concentration

61

the thick ascending limb has a ___ lumen and a ___ ISF

dilute
concentrated

62

the distal convoluted tubule reabsorbs ___% of _____

5 - 10%
filtered Na and water

63

what is the lumenal Na transporter in the distal convoluted tubule?

NCC (sodium chloride cotransporter)

64

NCC is inhibited by which diuretic?

thiazides

65

Which is more potent: thiazides or furosemides? Why?

furosemide.
thick ascending loop reabsorb more Na than the distal convoluted tubule

66

the distal convoluted tubule is important for...

urine dilution

67

when are thiazides used? furosemides?

furosemides used when you want a lot of Na+ lost in the urine.
thiazides used when you only want a bit more Na+ lost in the urine.

68

the collecting duct reabsorbs ____% of ____

1-3%
filtered Na

69

reabsorption at the collecting duct depends on...

body's needs

70

what is the lumenal transport protein at the collecting duct?

ENaC (epithelial sodium channel)

71

the collecting duct has receptors for...

- aldosterone
- vasopressin

72

effect of aldosterone binding to the collecting duct

increase Na reabsorption
- increase amount of Na channels
- open more Na channels

73

effect of ADH binding to the collecting duct

increase water reabsoprtion
- increase aquaporin2

74

Effect of drugs on the collecting duct

collecting duct has low capacity, so it is easily affected by drugs

75

why is the collecting duct important?

- can generate large [ ] gradients
- establish final urine composition / concentration

76

the collecting duct is less permeable to ___ than Na. What does this cause?

Cl-
Causes lumen to be neg, so K+ will be secreted (down charge gradient)

77

the collecting duct is the site of regulation for the secretion of...

- Na
- K
- water
- ammonium

78

ammonium is secreted to regulate...

acid-base balance

79

There are __ transporters for glucose. They are...

2
in series: proximal and distal

80

Properties of the proximal glucose transporter

- low affinity
- high capacity

81

Properties of the distal glucose transporter

- high affinity
- low capacity

82

How does the SGLT protein work?

1. Na+ binds
2. creates a site for glucose
3. glucose binding changes SGLT conformation
4. Na+ released, glucose follows

83

what does "high affinity for glucose" mean?

can transport glucose even if the glucose gradient is very opposing

84

what is the proximal glucose transporter called?

SGLT2

85

what is the distal glucose transporter called?

SGLT1

86

How does SGLT1 have a higher affinity for glucose?

exchanges 2 Na for 1 glucose
2 Na creates a higher drive into the cell

87

SGLT2 is located...

S1 segment of the proximal tubule / early proximal tubule

88

SGLT1 is located...

S3 segment of the proximal tubule / late proximal tubule

89

job of SGLT1

remove all glucose from the lumen

90

glucose (in) : glucose (out) ratio for SGLT2

70:1

91

glucose (in) : glucose (out) ratio for SGLT1

5000:1

92

What happens when someone has glucose in the urine with normal blood glucose?

- problem with SGLT2
- no problem as long as they get enough calories

93

___ can be possible treatment for hyperglycemia and diabetes. What effect might this have?

SGLT2 inhibitor drugs.
- lower blood glucose
- lower weight

94

lumenal Na transport proteins

- Na cotransporters
- Na antiporters
- Na channels

95

___ has no large gradients because of ____

proximal tubule.
very leaky

96

___ has large gradients because of ____

collecting duct.
tight

97

Organic solute transporters are all...

proximal

98

water reabsorption is...

passive (osmotic gradient)

99

water reabsorption at the proximal tubule

follows Na isotonically

100

water reabsorption at the collecting duct

dependson the presence of ADH (aquaporin2)