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Physiology > Renal 3- Glomerular Filtration, Renal blood flow, and their control > Flashcards

Renal 3- Glomerular Filtration, Renal blood flow, and their control Flashcards

1
Q

what is GFR (number)

A

125 ml/min or 180 L/day

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2
Q

entire plasma volume is filtered every ____

A

24 minutes

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3
Q

how does GFR occur

A

via bulk flow

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4
Q

what is GFR selective for

A

cells, proteins, Ca2+, fatty acids and other protein bound substances

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5
Q

what is filtration fraction

A

GFR/RPF

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6
Q

what does filtration fraction average

A

20% of renal plasma flow

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7
Q

what does the renal corpuscle contain

A

-bowmans capsule -parietal and visceral layers
-glomerular capillaries - glomerulus
- bowmans space

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8
Q

where is protein free fluid filtered into in glomerular filtration

A

filtered out of glomerulus into bowmans space

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9
Q

where does protein free fluid flow into

A

proximal tubule

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10
Q

what is blood in glomerular capillaries separated from bowmans space by

A

a filtration barrier

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11
Q

what are the 3 layers of the glomerulus

A
  • capillary endothelium: fenestrated
  • basal lamina: basement membrane
  • podocytes: visceral layer of bowmans capsule
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12
Q

what are podocytes and what do they do

A
  • foot processes that cover outside of basal lamina
  • creates filtration slits
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13
Q

what are mesangial cells and where are they found

A
  • modified smooth muscle cells
  • surround glomerular capillary loops
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14
Q

what do mesiangial cells do

A
  • modify size of filtration slits and alter rate of filtrate production
  • not a part of filtration barrier
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15
Q

what do substances have to be small enough to fit through to be filtered

A

filtration pores

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16
Q

is protein lost in excretion

A

no

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17
Q

what are the determinants of the ability of a solute to penetrate the glomerular membrane

A

-molecular size (small molecules filter better than large
- ionic charge (cations filter better than anions)
- proteins are both large and negatively charged and do not filter well

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18
Q

in minimal change nephropathy ____

A

-loss of negative charge on GBM
- proteins filtered through GBM
- proteinuria

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19
Q

what is the formula for GFR involving starlings forces

A

GFR = Kf x NFP

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20
Q

what is capillary filtration coefficient (Kf)

A

product of the permeability and surface area of the capillaries

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21
Q

what is NFP

A

balance of hydrostatic and colloid osmotic forces acting across the capillary membrane

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22
Q

what starlings forces would cause GFR to be high

A

high hydrostatic pressure and high Kf

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23
Q

what is NFP (number)

A

10mmHg, 125 ml/min or 180 L/day

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24
Q

describe the glomerular capillary filtration coefficient Kf

A

-400x higher than any other capillary bed
- normally not highly variable
- alterations in Kf not used to regulate GFR

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25
Q

how can diseases lower Kf

A
  • thickened basement membrane: hypertension, DM
  • decreased capillary surface area: glomerulonephritis
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26
Q

what are the two hydrostatic pressures that regulate GFR

A
  • glomerular
    -bowmans capsule
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27
Q

what is the primary control point for GFR

A

glomerular hydrostatic pressure

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28
Q

which hydrostatic pressure is a physiological controller of GFR: glomerular or bowmans

A

glomerular

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29
Q

what are the factors that influence glomerular hydrostatic pressure (Pg)

A

-arterial pressure (effect is buffered by autoregulation)
- afferent arteriolar resistance
-efferent arteriolar resistance

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30
Q

what diseases can affect GFR via PB (hydrostatic pressure of Bowmans capsule)

A

-tubular obstruction (stones, tubular necrosis)
-urinary tract obstruction (prostate hypertrophy/cancer)

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31
Q

what does glomerular capillary colloid osmotic pressure increase along

A

length of glomerular capillary
-affected by filtration fraction

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32
Q

what does glomerular capillary colloid osmotic pressure oppose

A

hydrostatic pressure

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33
Q

what happens to GFR along the length of the capillary

A

decreases
-factors that affect PiG

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34
Q

what is piG proportional to

A

[protein] plasma and FF (fraction of blood flow filtered in nephron)

35
Q

how can hydrostatic pressure in glomerular capillaries be altered

A

by altering the resistance of the afferent and efferent arterioles leading to changes in GFR

36
Q

what happens to PG and GFR when you constrict the efferent arteriole

A

PG: decreases
GFR: decreases

37
Q

what happens to PG and GFR when you dilate the efferent arteriole

A

PG: decrease
GFR: decrease

38
Q

what happens to PG and GFR when you constrict the efferent arteriole

A

PG: increase
GFR: increase

39
Q

what happens to PG and GFR when you dilate the afferent arteriole

A

PG: increase
GFR: increase

40
Q

an increase in efferent arteriolar resistance causes an increase in GFR only until a certain point where GFR then decreases. why?

A

due to increased [plasma protein] caused by increased filtration fraction

41
Q

what are factors than can decrease GFR directly and what are the physiologic causes of those

A

-decreased Kf: renal disease, DM, HTN
- increased PB: urinary tract obstruction
- increased piG; increased [proteins]plasma, dehydration
-decreased Pg

42
Q

what are factors that decrease GFR by decreasing PG and what are the physiological causes of those

A
  • decreased MAP: low arterial pressure
  • decreased RE: low ANG II
    -increased RA: increased sympathetic activity, vasoconstrictor hormones
43
Q

what is the formula for renal blood flow

A

RBF = (Pa-Pv)/total renal vascular resistance

44
Q

how do kidneys tightly control RBF

A

renal autoregulation

45
Q

what is vascular resistance in renal blood flow regulated by

A

factors acting on afferent and/or efferent arterioles (70% of total intrarenal resistance)

46
Q

what percentage of blood flow into medulla makes up total RBF

A

less than 10%

47
Q

what does a very low flow in vasa recta contribute to

A

concentrated urine

48
Q

what does high RBF reflect in terms of energy

A

high energy cost of active transport

49
Q

what are the primary active transporters in renal blood flow

A
  • Na+ K+ ATPase
  • H+ ATPase
  • H+ K+ ATPase
  • Ca2+ ATPase
50
Q

what are the 3 levels of control of RBF

A

-autoregulation
- local control
-systemic control

51
Q

what does autoregulation do

A

prevents moment to moment changes in GFR

52
Q

what is the function of myogenic autoregulation

A

keeps RBF and GFR relatively constant in spite of changes in MAP

53
Q

what is myogenic autoregulation

A

used in autoregulation
- reflex vessel constriction in response to increased MAP
- intrinsic to blood vessels

54
Q

what is a transient drop in GFR and RBF as a result in a decrease in renal artery pressure followed by

A

vasodilation

55
Q

what is a transient increase in GFR and RBF as a result of an increase in renal artery pressure followed by

A

vasoconstriction

56
Q

what is the function of tubuloglomerular feedback (TGF)

A

-helps ensure a nearly constant delivery of Na+ and Cl- to the distal nephron
- prevents spurious fluctuations in renal excretion

57
Q

what does the JGA do

A

mediates the TGF response

58
Q

what is the JGA composed of

A

-juxtaglomerular cells (granular cells)
-macula densa cells in the wall of the thick ascending loop of henle

59
Q

where are JG cells located and what do they do

A

-primarily in walls of afferent arterioles
-secrete renin

60
Q

what do macula densa cells do

A

sense [Na+] and [Cl-] in filtrate

61
Q

what is the mechanism of action of JGA

A

decreased GFR -> decrease rate of filtrate flow in nephron -> increased Na+/Cl- reabsorption -> decreased Na+/Cl- delivery to MD -> sensed by MD -> signals sent to JG cells -> increased renin secretion and other paracrines -> increased ANGII production and other paracrines -> increased RE and decreased RA -> increased PG -> increased GFR

62
Q

what are the stimuli for renin release

A

-low BP
- low RBF
- low NaCl delivery to macula densa

63
Q

describe the TGF response

A

-low arterial pressure -> low glomerular hydrostatic pressure -> low GFR -> macula densa ->decreased RA and increased renin and ANGII to increase RE

64
Q

what feedback effect do increased RE and decreased RA have on the TGF repsonse

A

negative feedback on the glomerular hydrostatic pressure

65
Q

what are the vasoconstrictors in local control

A

-endothelin
- dopamine in high concentrations

66
Q

what are the vasodilators in local control

A

-prostaglandins
- NO
- bradykinin
-dopamine in low concentrations

67
Q

what is involved in sympathetic control of RBF and are they vasoconstrictors or dilators

A

-sympathetic NS (vasoconstrictor)
- epinephrine (vasoconstrictor)
- renin-angiotensin system (vasoconstrictor)
- ANP (vasodilates afferent and vasoconstricts efferent arterioles)

68
Q

what role does SNS and EPI play in regulation RBF in normal state

A

minor role

69
Q

when does SNS activation alter RBF

A

stress such as blood loss, cardiac events

70
Q

what does NE/E do to RA, RE, RBF, and GFR

A

RA: increase
RE: increase
RBF: decrease
GFR: decrease

71
Q

what does endothelin do to RA, RE, RBF, and GFR

A

RA: increase
RE: increase
RBF: decrease
GFR: decrease

72
Q

what does angiotensin II do to RA, RE, RBF, and GFR

A
  • mainly just increases RE
  • RBF: decrease
    -GFR: increase
73
Q

what does ANP do to RA, RE, RBF, and GFR

A

RA:decrease
RE: increase
RBF: increase
GFR: increase

74
Q

what does PGE2 and PGI2 do to RA, RE, RBF, and GFR

A

RA: decrease
RBF: increase
GFR: increase

75
Q

what does bradykinin do to RA, RE, RBF, and GFR

A

RA: decrease
RBF: increase
GFR: increase

76
Q

what does NO do to RA, RE, RBF and GFR

A

RA: decrease
RE: decrease
RBF: increase
GFR: increase

77
Q

what are other factors that increase GFR and RBF

A

high protein diet
high blood glucose levels

78
Q

what is the mechanism of protein ingestion

A

-increased amino acids -> increased PCT amino acid reabsorption ->PCT NaCl reabsorption -> decreased macula densa NaCl -> decreased afferent arteriolar resistance -> high GFR which does negative feedback on macula densa

79
Q

what is the filtered load (Fx) of a substance and how is it calculated

A

-rate at which substances enter the nephron
- Fx= GFR ([X] plasma)

80
Q

what is the excretion rate of a substance and how is it calculated

A

-rate at which substances are excreted
-Ex = (Uv)([X]urine) where Uv = urine flow rate

81
Q

what is the clearance rate of a substance and how is it calculated

A
  • determines the volume of blood cleared of a substance in a given amount of time
    -Clx = Ex/[X]plasma
82
Q

the clearance rate of what 2 substances are used as an index of GFR

A

inulin and creatinine

83
Q

the clearance rate of what substance is used as an index of RBF

A

PAH

Physiology (41 decks)

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