PSL301: Water 2 Flashcards Preview

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Flashcards in PSL301: Water 2 Deck (80):
1

- Old man
- MI
- low BP
- Given ACE inhibitor
- Serum creatinine increased 100 -> 200

Why?

- GFR decreased by 50%
- Low BP caused by MI
- Low BP causes decreased afferent arteriole pressure
- Normally would be okay because ANG II will decrease efferent arteriole pressure
- ACE inhibitor stopped ANG II

2

Large volume of plasma is filtered through ___

glomerulus

3

Final urine =

amount filtered - amount reabsorbed + amount secreted

4

fluids & solutes enter the __ lumen

tubule

5

Function of tubules

reabsorb / secrete solute & water

6

Solutes & water is reabsorbed into...

peritubular capillaries

7

The kidney is divided into...

Cortex
Medulla

8

Most of the blood supply to the kidney goes to the...

cortex first

9

Number of nephrons in a kidney?

1 million

10

Where is the bowman's space located?

Between glomerulus and Bowman's capsule

11

What is shared between many nephrons?

The collecting duct

12

Passage of fluid in the nephron

1. Glomerulus / Bowman's capsule
2. Proximal convoluted tubule
3. Loop of Henle (descending & ascending limb)
4. Distal convoluted tubule
5. Collecting duct

13

___% of CO goes to the kidneys

20 - 25

14

The glomerulus is the only place that has...

efferent arteriole (instead of venule)

15

Purpose of the efferent arteriole

Control BP

16

The efferent arterioles flow into...

Peritubular capillaries

17

1 nephron has 2 ___ and 2 sets of ____

arterioles
capillaries

18

The 2 arterioles of the nephron

1. afferent
2. efferent

19

The 2 sets of capillaries of the nephron

1. Glomerulus
2. Peritubular

20

The capillary walls at the glomerulus has more ___ than normal

pores in the endothelium

21

What serves as a barrier to the Bowman's capsule lumen?

Glomerular basement membrane / podocytes

22

The filtered material in the glomerulus goes...

into the Bowman's Capsule lumen through filtration slits

23

Function of the glomerulus

Filter solutes, water into Bowman's space & proximal tubule

24

>90% of renal blood flow goes to ___ first through ___

Glomerulus
afferent tubules

25

What do the peritubular capillaries drain into?

veins

26

Features of glomerular capillaries

- leaky to water
- muscular arterioles put blood in and take blood out
- contraction & dilation of afferent & efferent arterioles regulates GFR

27

The capillaries at the glomerulus is ___x more leaky

10^5

28

What regulates GFR?

contraction & dilation of afferent & efferent arterioles

29

Most important determinant of GFR

Renal blood flow

30

Renal blood flow is determined by...

- arterial BP (at heart)
- resistance (at the renal vessels)

31

Renal blood flow can be kept constant at what BP?

70 - 150 mmHg (systolic arterial pressure)

32

What is the main factor regulating renal blood flow?

myogenic reflex in the afferent arteriole

33

Myogenic reflex sensing decreased BP causes...

afferent arteriole to dilate

34

Myogenic reflex sensing increased BP causes...

afferent arteriole to constrict

35

What other factors are important at low blood pressure?

- ANG II
- Prostagladins

36

Effect of ANG II

Raise blood pressure
- efferent arteriole constrict

37

Effect of prostaglandins

Dilate afferent arteriole

38

What are the renal vasoconstricters?

- ANG II (efferent arteriole)
- Catecholamines (NE)

39

What are the renal vasodilators?

- prostaglandins
- ANP
- Pregnancy
- high protein diet

40

What is one instance in which GFR changes? Why?

During pregnancy
- Both GFR and blood flow increases by 25%

41

What happens to blood pressure during pregnancy?

Goes down

42

Why might high protein diets cause renal arterioles to dilate?

???

43

Afferent arteriole constriction causes... (effect on GFR)

Reduces GFR

44

Decreased ____ = decreased GFR

capillary blood pressure

45

Efferent arteriole constriction causes... (effect on GFR)

Increased GFR (harder to leave capillaries)

46

Filtration fraction

GFR / RBF
Proportion of blood going into glomerulus that is filtered

47

Efferent arteriole constriction prevents...

drop in GFR when BP drops

48

ANG II increases ___

filtration fraction

49

Increased filtration fraction =

increased GFR

50

Role of ANG II in terms of GFR

Keeps it high at lower BP

51

Value: normal GFR

>90 mL/min
125 L/day

52

What is affected during low blood pressure: BP, RBF, GFR, FF?

BP decreases
RBF decreases
GFR unchanged
FF increases

53

Filtration of solutes is determined by...

1. convection (hydrostatic pressure & bulk flow of water)
2. molecular weight

54

Cut offs for which molecular weight can be filtered and whatnot

< 15000 = freely filtered between plasma & Bowman's space

15000 - 60000 = only some are filtered

> 60000 = albumin = not usually filtered

55

What does finding albumin in the urine tell us?

Problems with kidney wall permeability

56

Which solutes are freely filtered?

- Na
- K
- Cl
- Glucose
- Bicarb
- Urea
- Creatinine

57

Which solutes can't be filtered?

- Albumin
- Globulins (antibodies)

58

What is the best measure of kidney function?

GFR

59

Why is GFR such a good measure of kidney function?

- Correlates with clinical consequences of reduced kidney function
- Most kidney diseases affect the glomerulus

60

Units for GFR

mL/min

61

Criteria for solute used to measure GFR

- freely filtered
- not reabsorbed / secreted by tubules
- amount filtered = amount excreted
- GFR = amount found in urine every minute

62

Define: clearance

filtration rate

63

Why is glucose a bad measurement of GFR?

All glucose is reabsorbed

64

Why is urea a bad measurement of GFR?

50% of urea is reabsorbed

65

What is a good marker for GFR? Why?

Insulin (gold standard)
- small
- no reabsorption
- filtration = excretion

Creatinine

66

MW of insulin

5000

67

Problem with using insulin as a marker for GFR

Has to be given using intravenously

68

Formula: filtration

= GFR * [plasma x]

69

Formula: excretion

= urine flow rate * [urine x]

70

Formula: GFR

= urine flow rate * [urine x] / [plasma x]

71

What marker is usually used to measure GFR? How is it usually done?

Creatinine (24h urine sample)

72

Formula: GFR (using creatinine 24h urine sample)

= urine volume * [urine creatinine] / [plasma creatinine]

73

Creatinine is a good estimate for GFR only if...

- accurate urine collection
- production of creatinine = secretion
- serum creatinine is constant

74

If we want to be lazier than 24h urine sample, what can we do to measure GFR?

GFR = 1 / [plasma creatinine]

75

Plasma creatinine depends on...

- GFR
- muscle mass

76

Disadvantage of measuring GFR from plasma creatinine

Differs depending on age, weight, sex...

77

What must we know to calculate GFR from plasma creatinine?

Baseline:
- creatinine
- GFR
(this gives us the constant value)

78

What drug is associated with causing acute kidney failure?

ACE inhibitors

79

GFR is usually autoregulated by...

afferent arteriolar tone

80

When BP is low, which hormones are important?

- prostaglandins
- ANG II