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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
Q

The higher oncotic pressure in the efferent arteriole ensures what stops as blood exits the glomerular capillaries?

A

filtration stops

26
Q

High concentrations of ATII cause constriction where, leading to what?

A

afferent and efferent arteriole constriction

large drop in RBF

27
Q

lower concentrations of ATII cause constriction where, leading to what?

A

efferent arteriole constriction

decreased RBF

28
Q

When afferent and efferent arteriolar resistances increase (high dose ATII), what happens to Pgc and RBF?

A

no Pgc change

major decrease in RBF

29
Q

When afferent arteriolar resistance increases, what happens to Pgc and RBF?

A

both decrease

30
Q

When efferent arteriolar resistance increases (low dose ATII), what happens to Pgc and RBF?

A

Pgc increases

RBF decreases

31
Q

Why would Pgc increase when the efferent arteriole increases resistance?

A

efferent constriction leads to fluid backup in the glomerulus

32
Q

Why would Pgc stay the same when afferent and efferent arterioles constrict?

A

because the restricted flow into the glomerulus roughly equals the restricted flow out

33
Q

Why would Pgc decrease when afferent arteriole constricts?

A

because there is reduced flow into the glomerulus

34
Q

What measure gives a rough measure of the number of functioning nephrons?

A

GFR

35
Q

What is the equation for filtered load?

A

FLx = (GFR)(Px)

36
Q

Filtered Load (FLx) has a direct relationship with what two variables?

A

GFR and Plasma concentration

37
Q

What are two equations for Excretion Rate?

A

ERx = (Ux)(V)

ERx = FLx + Sx-Rx

38
Q

Excretion rate is directly proportional to what variables?

A

Filtered Load (FLx), net excretion rate (Sx-Rx), Urine Concentration (Ux) and Urine rate (V)

39
Q

What equation is used to measure GFR

A

GFR = (Ux)(V) / Px

40
Q

What molecule is often used to help measure GFR?

A

inulin

41
Q

The perfect GFR marker has what three characteristics?

A

Freely filtered, not absorbed, not excreted

42
Q

What is the gold standard assessment of GFR?

A

inulin clearance

43
Q

What is more commonly used in place of inulin clearance in order to asses GFR?

A

Creatinine clearance and serum creatinine

44
Q

This GFR marker has the following characteristics:

freely filtered, not reabsorbed, slightly secreted

Produced from creatinine phosphate breakdown at constant rate in skeletal muscle

A

Creatinine

45
Q

How do you determine creatinine clearance?

A

Ccr = (Ucr)(V) / Pcr

or

Pcr and standard predictive equation

46
Q

The following are commonly used in combination with Pcr to estimate what?

Cockcroft-Gault

MDRD

CDK-EPI

A

Creatinine Clearance using only plasma creatinine (ED setting)

47
Q

Clearance of any solute can be expressed with what equation?

A

Cx = Ux * V / Px

48
Q

Normal Cr clearance for men…

A

97-140

49
Q

Normal Cr clearance for women…

A

85-125

50
Q

If clearance of a substance is greater than GFR…

A

secretion

51
Q

If clearance of a substance is less than GFR…

A

reabsorbed

52
Q

Glucose has a clearance of ____ because it is _____

A

clearance = 0

completely reabsorbed

53
Q

Clearance of Urea is 65… this means what?

A

1/2 or urea is reabsorbed

54
Q

Cx/Cinulin = 1… this means

A

substance is a GFR marker

55
Q

Cx/Cinulin < 1… this means

A

filtered and reabsorbed

OR

not ever filtered

56
Q

Cx/Cinulin > 1… this means

A

filtered and secreted

57
Q

PAH is used to estimate RPF for what reason?

A

Entire volume of PAH is cleared from blood and excreted

58
Q

What is the value of Cpah…

A

540 mL/min

59
Q

What is the normal value of RPF?

A

600 mL/min

60
Q

What is the equation to estimate RBF?

A

RBF = RPF / (1-Hct)

OR

540 / (1-Hct)

Physiology II (28 decks)

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