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Physio II > Glomerular Filtration&RBF-Exam 2 > Flashcards

Glomerular Filtration&RBF-Exam 2 Flashcards

1
Q

What are the three renal processes?

A

Glomerular filtration
Tubular reabsorption
Tubular secretion

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2
Q

Where is the glomerular filtration process?

A

From glomerular capillaries to Bowman’s capsule

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3
Q

Where is tubular reabsorption?

A

From renal tubules to peritubular capilaries

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4
Q

Where is tubular secretion?

A

From peritubular capillaries to renal tubules

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5
Q

What is the equation for excretion?

A

Excretion = Filtration - Reabsorption + Secretion

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6
Q

How many membranes must be crossed for excretion?

A

2

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7
Q

Increased sodium; increased filtration; decreased reabsorption=

A

Increased excretion

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8
Q

Most substances see _______ filtration and _______ reabsorption rate

A

High; high

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9
Q

Small changes in filtration/reabsorption will produce significant changes in what?

A

Excretion rate

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10
Q

Why is there a high filtration rate?

A
  1. Allows rapid removal of waste products
  2. Allows multiple passes of blood vol. through kidneys/day
  3. Allows rapid and precise control of body fluid volume nad composition
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11
Q

What is the normal GFR?

A

180 L/day or 125 mls/min

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12
Q

How many liters of plasma volume is normal?

A

3-4 L

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13
Q

Plasma volume gets filtered how many times each day?

A

6x/day

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14
Q

Waste products depend on what for adequate removal?

A

Filtration (not reabsorbed or secreted)

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15
Q

What is the filtration fraction equation?

A

Filtration fraction = GFR/ Renal Plasma Flow

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16
Q

What is the normal filtration fraction?

A

20%; Each minute 20% of plasma flowing through the kidneys is filtered

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17
Q

What is normal reabsorption?

A

178.5 L/day (123 mls/min)

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18
Q

What is normal urine output?

A

180-178.5 = 1.5 L/day

125 (GFR) -123 (reabsoprtion) = 2 mls/min

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19
Q

How does the glomerular capillary membrane compare to the normal capillaries?

A

Glomerular capillary filters significantly more volume than normal capillaries; thicker but more porous

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20
Q

How many major layers are in the glomerular capillary membrane?

A

3 layers

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21
Q

What are the major layers of the glomerular capillary membrane?

A
  1. Endothelial cell layer
  2. Basement membrane layer
  3. Epithelial cell layer (podocyets)
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22
Q

What are podocytes

A

surround outer surface of basement membrane

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23
Q

Describe the anatomy of the endothelial layer.

A

Perforated by thousands of fenestrations (small holes)

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24
Q

How is protein passage prevented in the endothelial layer?

A

Negative charge on surface of endothelial cells

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25
Q

The basement membrane allows movement of what?

A

Water and small molecules

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26
Q

How is protein passaged prevented in the basement memebrane?

A

Proteoglycan mesh and negative charge

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27
Q

Describe the anatomy of the epithelial layer

A

Not continuous; slit pores present between adjacent podocytes; allows free movement of water and small solutes

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28
Q

What hinders protein filtration in the epithelial layer?

A

Negative charge surround epithelial cells

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29
Q

What is the overall pore size of the glomerular capillary membrane?

A

8 nm; 80 angstroms

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30
Q

What does a filterability of 1.0 mean?

A

Freely filtered; at the same rate as water (concentration in filtrate will equal plasma)

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31
Q

What does a filterability of 0.75 mean?

A

Filtered 75% as quickly as water; filtrate concentration < plasma concentration

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32
Q

How big is albumin?

A

6nm

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33
Q

What prevents passage of albumin through pores?

A

Negative charge

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34
Q

How does albumin size compare to pore size?

A

Albumin- 6nm

Pore size- 8nm

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35
Q

What type of charge lines the pores?

A

Negative charges; prevents passage of proteins which are also negatively charged

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36
Q

What are dextrans?

A

Polysaccharides that can be made with specific charges

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37
Q

In some renal diseases, what happens first before any histological changes are seen?

A

The negative charge of the basement membrane is lost

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38
Q

What is an early indicator of renal disease?

A

Appearance of albumin in urine; since there is a loss of negative charge in the basement membrane albumin can now pass

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39
Q

What is the equation for GFR?

A

Kf (glomerular capillary filtration coefficient) x Net filtration pressure

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40
Q

Kf

A

glomerular capillary filtration coefficient

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41
Q

What is the normal net filtration pressure?

A

10 mmHg

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42
Q

What forces promote filtration?

A

Glomerular hydrostatic pressure (60 mmHg)

Bowman’s capsule oncotic pressure (0mmHg)- factor with disease

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43
Q

What forces inhibit filtration?

A

Glomerular oncotic pressure (32 mmHg)

Bowman’s capsule hydrostatic pressure (18 mmHg)

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44
Q

How do you get a net filtration pressure of 10 mmHg?

A

Glomerular hydrostatic P(60) - Bowman’s capsule P (18)- Glomerular oncotic pressure (32)

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45
Q

What is glomerular capillary filtration coefficient affected by?

A

Overall hydraulic conductivity and surface area of glomerular capillaries

46
Q

Can glomerular capillary filtration coefficient be measured directly?

A

No

47
Q

What is the normal Kf?

A

125 mls/min / 10 mmHg = 12.5 mls/min/mmHg

4.2 mls/min/mmHg / 100 gm tissue

48
Q

Normal Kf other capillaries

A

0.01 mls/min/mmHg/100gm

49
Q

What is the relationship between filtration coefficient and GFR?

A

Direct positive relationship; usually not part of day-to-day control of GFR

50
Q

What do HTN and diabetes mellitus do to glomerular membrane?

A

Increasing thickness of membrane (decreased hydraulic conductivity)

51
Q

What are examples of how disease can affect filtration coefficient and GFR?

A

Decreasing number of functional glomerular capillaries (decreased surface area)

52
Q

What are some of the major factors affecting GFR?

A

Colloid osmotic pressure & filtration fraction

Hydrostatic pressure

53
Q

Increased glomerular oncotic pressure does what to GFR?

A

Decreases GFR

54
Q

Decreased glomerular oncotic pressure does what to GFR

A

Increases GFR

55
Q

As blood passes through glomerulus, plasma oncotic pressure will increase by how much?

A

20% (20% of fluid is filtered producing increased protein)

56
Q

What is the plasma oncotic pressure entering the glomerulus?

A

28 mmHg

57
Q

What is the glomerular oncotic pressure as blood leaves glomerulus?

A

36 mmHg

58
Q

What is the average pressure in the glomerulus

A

32 mmhg average (28 mmHg in and 36 mmHg out)

59
Q

What are two major factors affecting glomerular oncotic pressure?

A

Plasma protein concentration of arterial blood

Fraction of plasma being filtered (filtration fraction)

60
Q

Increased plasma protein concentration will __________ glomerular oncotic pressure, which will _________ GFR

A

increase; decrease

61
Q

What does increased filtration fraction mean?

A

More plasma is being filtered from each ml of blood in the glomerulus

62
Q

As blood is concentrated, the oncotic pressure of blood remaining in the glomerulus ________ which will _________ GFR

A

increases; decrease

63
Q

A decrease in RBF ( no initial change in GFR) will do what to filtration fraction and GFR?

A

Increase the filtration fraction

Decrease in GFR

64
Q

Changing RBF with constant glomerular hydrostatic pressure will have what effect on GFR

A

Increased RBF
Decreased fraction
Decreased glomerular oncotic pressure
increased GFR

65
Q

Increased pressure = _________ GFR

A

increased

66
Q

Decreased pressure =__________ GFR

A

decreased

67
Q

What are the primary means for controlling GFR?

A
  1. Arterial pressure
  2. Afferent arteriole resistance
  3. Efferent arteriole resistnace
68
Q

Increased MAP = ___________ GFR

A

increased

69
Q

How is MAP/GFR relationship buffered?

A

Autoregulation of flow to keep consistent glomerular pressure

70
Q

How does increased afferent arteriole constriction affect pressure and GFR?

A

Decreased pressure, decreased GFR

71
Q

How does decreased afferent arteriole constriction affect pressure and GFR?

A

increased pressure; increased GFR

72
Q

As afferent arteriole constriction increases, what does RBF do?

A

It also decreases

73
Q

As afferent arteriole constriction increases, what does GFR do?

A

Decreases; at a faster rate than RBF decreases

74
Q

As efferent arteriole resistance increases constriction, what happens to pressure and GFR?

A

Increased pressure

Increased GFR

75
Q

As efferent arteriole resistance decreases, what happens to pressure and GFR?

A

decreased pressure

decreased GFR

76
Q

As efferent arteriole resistance constriction increases, what happens with RBF/glomerular pressure?

A

RBF decreases

Glomerular pressure increases

77
Q

Initially in efferent arteriole resistance, what has more effect than decrease in RBF?

A

The change in glomerular pressure; which produces an overall increase in GFR

78
Q

Increase in glomerular pressure is _________ (greater/less) than decrease in RBF

A

greater

79
Q

As efferent arteriole resistnace continues to increase, what beings to play a role?

A

Filtration fraction change

80
Q

What does increased filtration fraction result in?

A

(Decreased BF, increased GFR)

Higher glomerular colloid oncotic pressure which decreases GFR

81
Q

When the effect of the increase in glomerular oncotic pressure exceeds the effect of the hydrostatic pressure, what will happen to GFR?

A

Decrease

82
Q

Increased hydrostatic pressure = ________ GFR

A

Decreased

83
Q

Decreased hyrostatic pressure = ________ GFR

A

Increased

84
Q

Does hydrostatic pressure (bowman’s capsule) normally play a primary role in controlling GFR?

A

No

85
Q

Obstruction of the urinary tract could produce what?

A

Big increase in pressure with big decrease in GFR

86
Q

RBF provides flow for basic metabolic needs of what?

A

kidneys and excess flow for plasma filtration

87
Q

Renal O2 consumption is how many x that of the brain?

A

2x

88
Q

RBF is how many x that of the brain?

A

7x

89
Q

Most of O2 consumed in kidneys supports what?

A

Sodium reabsorption ( direct relationship)

90
Q

What is the equation for RBF?

A

(Renal artery pressure - Renal vein pressure)/ Total renal resistance
Arterial: 100 mmHg; Vein 4 mmHg

91
Q

Percentage of renal vascular resistance: afferent arterial

A

26%

92
Q

Percentage of renal vascular resistance: Efferent arterial

A

43%

93
Q

Percentage of renal vascular resistance: interlobar, arcuate, interlobular arteries

A

16%

94
Q

Resistance of afferent arterial, efferent arterial, & interlobar/arcuate/interlobular arteries are controlled by what?

A

Sympathetic nervous system, hormones, local control within kidneys

95
Q

Increased resistance of 3 areas tends to do what to RBF?

A

Reduce RBF

96
Q

Decreased resistance of 3 areas tends to do what to RBF?

A

increase RBF (assume no change in arterial or venous pressures)

97
Q

What percent of RBF goes to renal cortex?

A

98-99%

98
Q

What percent of RBF goes to renal medulla vai the vasa recta?

A

1-2% (key part of ability to concentrate urine)

99
Q

Which vessels receive sympathetic activation?

A

All vessels

100
Q

Strong activation of sympathetic system results in what?

A

Constriction; decrease RBF and GFR

101
Q

Mild to moderate activation of sympathtic system results in what?

A

moderate decrease in BP with corresponding baroreceptor response; little effect on RBF or GFR

102
Q

When is sympathethic activation most important?

A

When body face with life threating problem ex. severe hemhorrage; very little effect in healthy normal person

103
Q

What kind of effect do epinephrine and norepinehprine have

A

similar to effect of SNS

104
Q

Endothelin is released by what?

A

release by damaged vascular endothelial cells of kidneys and other tissue; plays role in hemostasis

105
Q

When is the concentration of endothelin increased?

A

during toxemia of pregnancy; acute renal failure; chronic uremia; powerful vasoconstrictor

106
Q

Angiotensin II

A

potent vasoconstrictor; noramlly circulating and produced locally

107
Q

What vessels show weak if any response to angiotensin II?

A

Preglomerular vessels; bc of simultaneous release of vasodilators such as nitric oxide and prostaglandins

108
Q

What does angiotensin II have a strong effect on?

A

Efference arterial producing increased glomerular pressure and decreased renal blood flow

109
Q

What does giving nitric oxide inhibitor do?

A

Increases renal vascular resistance
Decresaes GFR and urinary excretion of sodium
If continued will result in an increase in MAP due to the increased sodium levles

110
Q

Bradykinin & Prostaglandins

A

Potent vasodilators
Tend to increase RBF and GFR
Dampen effect of sympathetic nerves and angiotensin II; may help prevent excessive decreases in RBF and GFR

111
Q

What are bradykinin and prostaglandins inhibited by?

A

Administration of nonsteroidal anti-inflammatory agents

112
Q

What is the purpose of autoregultaion of RBF and GFR?

A

maintain noraml GFR and allow control of renal excretion of water and solutes; prevents big changes in water/solute excretion with normal changes in BP

Physio II (14 decks)

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