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Physiology II > Renal Physiology: Blood Flow and GFR > Flashcards

Renal Physiology: Blood Flow and GFR Flashcards

1
Q

The renal system receives _______ of cardiac output in order to support filtration.

A

1/4

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2
Q

how many liters of filtrate are formed daily?

A

180L

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3
Q

how many times is the body’s plasma volume filtered each day?

A

65x

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4
Q

Under normal conditions, what is renal blood flow (RBF)?

A

1.1 L/min

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5
Q

Under normal conditions, what is renal plasma flow (RPF)?

A

605 mL/min

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6
Q

Under normal conditions, what is GFR?

A

120-125

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7
Q

What is the equation for filtration fraction?

A

FF = GFR/RPF

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8
Q

How do you calculate RPF?

A

RPF = (1 - Hct) RBF

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9
Q

Angiotensin II acts on both the afferent and efferent arterioles… which of these is more sensitive to ATII?

A

efferent arteriole

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10
Q 
SNS stimulation
ADH
AT II
ATP
Endothelin

These all act as _______ which work to _________ GFR and RBF

A

vasoconstrictors

decrease

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11
Q

ANP
Glucocorticoids
NO
Prostaglandins

These all act as _______ which work to _________ GFR and RBF

A

vasodilators

increase

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12
Q

Autoregulation helps keep renal blood pressure between _______, thereby keeping RBF and GFR fairly constant

A

80-180 mmHg

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13
Q

Severe blood loss has what effect on RBF and GFR and for what reason?

A

decreased RBF and GFR

secondary to hypotension

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14
Q

What two mechanisms are responsible for renal autoregulation?

A

Myogenic

tubuloglomerular feedback

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15
Q

This mechanism for autoregulation occurs when vascular smooth muscle is stretched, therefore causing a proportional response of vasoconstriction

A

myogenic mechanism

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16
Q

This mechanism of autoregulation occurs when an increased GFR causes increased NaCl in the LOH, causing the MD to increase afferent arteriolar resistance

A

tubuloglomerular feedback

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17
Q

Autoregulation acts upon the afferent or efferent arteriole?

A

afferent

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18
Q

filtrate from bowman’s capsule is essentially…

A

protein free blood plasma

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19
Q

Substances are separated in the filter by what two characteristics?

A

size and electrical charge

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20
Q

Why are proteins usually repelled from the basal lamina?

A

Basal lamina and proteins both have a negative charge

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21
Q

What are the two main barriers to protein entry to the urinary space of bowman’s capsule?

A

basal lamina and filtration slits (podocytes)

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22
Q

What is the equation for net filtration pressure?

A

(Pgc - Pbc) - Pigc

(Hydrostatic pressure of glomerulus - Hydrostatic pressure of bowman’s capsulte) - Oncotic pressure of glomerulus

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23
Q

GFR equation is…

A

Kf(NFP)

Kf [(Pgc - Pbc) - Pigc]

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24
Q

Where is oncotic pressure higher, in the afferent arteriole, in the glomerular capillaries, or in the efferent arteriole?

A

efferent arteriole

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25
The higher oncotic pressure in the efferent arteriole ensures what stops as blood exits the glomerular capillaries?
filtration stops
26
High concentrations of ATII cause constriction where, leading to what?
afferent and efferent arteriole constriction large drop in RBF
27
lower concentrations of ATII cause constriction where, leading to what?
efferent arteriole constriction decreased RBF
28
When afferent and efferent arteriolar resistances increase (high dose ATII), what happens to Pgc and RBF?
no Pgc change major decrease in RBF
29
When afferent arteriolar resistance increases, what happens to Pgc and RBF?
both decrease
30
When efferent arteriolar resistance increases (low dose ATII), what happens to Pgc and RBF?
Pgc increases RBF decreases
31
Why would Pgc increase when the efferent arteriole increases resistance?
efferent constriction leads to fluid backup in the glomerulus
32
Why would Pgc stay the same when afferent and efferent arterioles constrict?
because the restricted flow into the glomerulus roughly equals the restricted flow out
33
Why would Pgc decrease when afferent arteriole constricts?
because there is reduced flow into the glomerulus
34
What measure gives a rough measure of the number of functioning nephrons?
GFR
35
What is the equation for filtered load?
FLx = (GFR)(Px)
36
Filtered Load (FLx) has a direct relationship with what two variables?
GFR and Plasma concentration
37
What are two equations for Excretion Rate?
ERx = (Ux)(V) ERx = FLx + Sx-Rx
38
Excretion rate is directly proportional to what variables?
Filtered Load (FLx), net excretion rate (Sx-Rx), Urine Concentration (Ux) and Urine rate (V)
39
What equation is used to measure GFR
GFR = (Ux)(V) / Px
40
What molecule is often used to help measure GFR?
inulin
41
The perfect GFR marker has what three characteristics?
Freely filtered, not absorbed, not excreted
42
What is the gold standard assessment of GFR?
inulin clearance
43
What is more commonly used in place of inulin clearance in order to asses GFR?
Creatinine clearance and serum creatinine
44
This GFR marker has the following characteristics: freely filtered, not reabsorbed, slightly secreted Produced from creatinine phosphate breakdown at constant rate in skeletal muscle
Creatinine
45
How do you determine creatinine clearance?
Ccr = (Ucr)(V) / Pcr or Pcr and standard predictive equation
46
The following are commonly used in combination with Pcr to estimate what? Cockcroft-Gault MDRD CDK-EPI
Creatinine Clearance using only plasma creatinine (ED setting)
47
Clearance of any solute can be expressed with what equation?
Cx = Ux * V / Px
48
Normal Cr clearance for men...
97-140
49
Normal Cr clearance for women...
85-125
50
If clearance of a substance is greater than GFR...
secretion
51
If clearance of a substance is less than GFR...
reabsorbed
52
Glucose has a clearance of ____ because it is _____
clearance = 0 completely reabsorbed
53
Clearance of Urea is 65... this means what?
1/2 or urea is reabsorbed
54
Cx/Cinulin = 1... this means
substance is a GFR marker
55
Cx/Cinulin < 1... this means
filtered and reabsorbed OR not ever filtered
56
Cx/Cinulin > 1... this means
filtered and secreted
57
PAH is used to estimate RPF for what reason?
Entire volume of PAH is cleared from blood and excreted
58
What is the value of Cpah...
540 mL/min
59
What is the normal value of RPF?
600 mL/min
60
What is the equation to estimate RBF?
RBF = RPF / (1-Hct) OR 540 / (1-Hct)

Physiology II (28 decks)

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