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PSL301 > PSL301: Water 2 > Flashcards

PSL301: Water 2 Flashcards

Glomerular function

1
Q
  • Old man
  • MI
  • low BP
  • Given ACE inhibitor
  • Serum creatinine increased 100 -> 200

Why?

A
  • 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
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2
Q

Large volume of plasma is filtered through ___

A

glomerulus

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3
Q

Final urine =

A

amount filtered - amount reabsorbed + amount secreted

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4
Q

fluids & solutes enter the __ lumen

A

tubule

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5
Q

Function of tubules

A

reabsorb / secrete solute & water

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6
Q

Solutes & water is reabsorbed into…

A

peritubular capillaries

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7
Q

The kidney is divided into…

A

Cortex

Medulla

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8
Q

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

A

cortex first

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9
Q

Number of nephrons in a kidney?

A

1 million

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10
Q

Where is the bowman’s space located?

A

Between glomerulus and Bowman’s capsule

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11
Q

What is shared between many nephrons?

A

The collecting duct

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12
Q

Passage of fluid in the nephron

A
  1. Glomerulus / Bowman’s capsule
  2. Proximal convoluted tubule
  3. Loop of Henle (descending & ascending limb)
  4. Distal convoluted tubule
  5. Collecting duct
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13
Q

___% of CO goes to the kidneys

A

20 - 25

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14
Q

The glomerulus is the only place that has…

A

efferent arteriole (instead of venule)

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15
Q

Purpose of the efferent arteriole

A

Control BP

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16
Q

The efferent arterioles flow into…

A

Peritubular capillaries

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17
Q

1 nephron has 2 ___ and 2 sets of ____

A

arterioles

capillaries

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18
Q

The 2 arterioles of the nephron

A
  1. afferent

2. efferent

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19
Q

The 2 sets of capillaries of the nephron

A
  1. Glomerulus

2. Peritubular

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20
Q

The capillary walls at the glomerulus has more ___ than normal

A

pores in the endothelium

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21
Q

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

A

Glomerular basement membrane / podocytes

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22
Q

The filtered material in the glomerulus goes…

A

into the Bowman’s Capsule lumen through filtration slits

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23
Q

Function of the glomerulus

A

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

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24
Q

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

A

Glomerulus

afferent tubules

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25
Q

What do the peritubular capillaries drain into?

A

veins

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26
Q

Features of glomerular capillaries

A
  • leaky to water
  • muscular arterioles put blood in and take blood out
  • contraction & dilation of afferent & efferent arterioles regulates GFR
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27
Q

The capillaries at the glomerulus is ___x more leaky

A

10^5

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28
Q

What regulates GFR?

A

contraction & dilation of afferent & efferent arterioles

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29
Q

Most important determinant of GFR

A

Renal blood flow

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30
Q

Renal blood flow is determined by…

A
  • arterial BP (at heart)

- resistance (at the renal vessels)

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31
Q

Renal blood flow can be kept constant at what BP?

A

70 - 150 mmHg (systolic arterial pressure)

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32
Q

What is the main factor regulating renal blood flow?

A

myogenic reflex in the afferent arteriole

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33
Q

Myogenic reflex sensing decreased BP causes…

A

afferent arteriole to dilate

34
Q

Myogenic reflex sensing increased BP causes…

A

afferent arteriole to constrict

35
Q

What other factors are important at low blood pressure?

A
  • ANG II

- Prostagladins

36
Q

Effect of ANG II

A

Raise blood pressure

- efferent arteriole constrict

37
Q

Effect of prostaglandins

A

Dilate afferent arteriole

38
Q

What are the renal vasoconstricters?

A
  • ANG II (efferent arteriole)

- Catecholamines (NE)

39
Q

What are the renal vasodilators?

A
  • prostaglandins
  • ANP
  • Pregnancy
  • high protein diet
40
Q

What is one instance in which GFR changes? Why?

A

During pregnancy

- Both GFR and blood flow increases by 25%

41
Q

What happens to blood pressure during pregnancy?

A

Goes down

42
Q

Why might high protein diets cause renal arterioles to dilate?

A

???

43
Q

Afferent arteriole constriction causes… (effect on GFR)

A

Reduces GFR

44
Q

Decreased ____ = decreased GFR

A

capillary blood pressure

45
Q

Efferent arteriole constriction causes… (effect on GFR)

A

Increased GFR (harder to leave capillaries)

46
Q

Filtration fraction

A

GFR / RBF

Proportion of blood going into glomerulus that is filtered

47
Q

Efferent arteriole constriction prevents…

A

drop in GFR when BP drops

48
Q

ANG II increases ___

A

filtration fraction

49
Q

Increased filtration fraction =

A

increased GFR

50
Q

Role of ANG II in terms of GFR

A

Keeps it high at lower BP

51
Q

Value: normal GFR

A

> 90 mL/min

125 L/day

52
Q

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

A

BP decreases
RBF decreases
GFR unchanged
FF increases

53
Q

Filtration of solutes is determined by…

A
  1. convection (hydrostatic pressure & bulk flow of water)

2. molecular weight

54
Q

Cut offs for which molecular weight can be filtered and whatnot

A

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

15000 - 60000 = only some are filtered

> 60000 = albumin = not usually filtered

55
Q

What does finding albumin in the urine tell us?

A

Problems with kidney wall permeability

56
Q

Which solutes are freely filtered?

A
  • Na
  • K
  • Cl
  • Glucose
  • Bicarb
  • Urea
  • Creatinine
57
Q

Which solutes can’t be filtered?

A
  • Albumin

- Globulins (antibodies)

58
Q

What is the best measure of kidney function?

A

GFR

59
Q

Why is GFR such a good measure of kidney function?

A
  • Correlates with clinical consequences of reduced kidney function
  • Most kidney diseases affect the glomerulus
60
Q

Units for GFR

A

mL/min

61
Q

Criteria for solute used to measure GFR

A
  • freely filtered
  • not reabsorbed / secreted by tubules
  • amount filtered = amount excreted
  • GFR = amount found in urine every minute
62
Q

Define: clearance

A

filtration rate

63
Q

Why is glucose a bad measurement of GFR?

A

All glucose is reabsorbed

64
Q

Why is urea a bad measurement of GFR?

A

50% of urea is reabsorbed

65
Q

What is a good marker for GFR? Why?

A

Insulin (gold standard)

  • small
  • no reabsorption
  • filtration = excretion

Creatinine

66
Q

MW of insulin

A

5000

67
Q

Problem with using insulin as a marker for GFR

A

Has to be given using intravenously

68
Q

Formula: filtration

A

= GFR * [plasma x]

69
Q

Formula: excretion

A

= urine flow rate * [urine x]

70
Q

Formula: GFR

A

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

71
Q

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

A

Creatinine (24h urine sample)

72
Q

Formula: GFR (using creatinine 24h urine sample)

A

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

73
Q

Creatinine is a good estimate for GFR only if…

A
  • accurate urine collection
  • production of creatinine = secretion
  • serum creatinine is constant
74
Q

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

A

GFR = 1 / [plasma creatinine]

75
Q

Plasma creatinine depends on…

A
  • GFR

- muscle mass

76
Q

Disadvantage of measuring GFR from plasma creatinine

A

Differs depending on age, weight, sex…

77
Q

What must we know to calculate GFR from plasma creatinine?

A

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

78
Q

What drug is associated with causing acute kidney failure?

A

ACE inhibitors

79
Q

GFR is usually autoregulated by…

A

afferent arteriolar tone

80
Q

When BP is low, which hormones are important?

A
  • prostaglandins

- ANG II

PSL301 (29 decks)

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