Renal 3- Glomerular Filtration, Renal blood flow, and their control Flashcards
(83 cards)
1
Q
what is GFR (number)
A
125 ml/min or 180 L/day
2
Q
entire plasma volume is filtered every ____
A
24 minutes
3
Q
how does GFR occur
A
via bulk flow
4
Q
what is GFR selective for
A
cells, proteins, Ca2+, fatty acids and other protein bound substances
5
Q
what is filtration fraction
A
GFR/RPF
6
Q
what does filtration fraction average
A
20% of renal plasma flow
7
Q
what does the renal corpuscle contain
A
-bowmans capsule -parietal and visceral layers
-glomerular capillaries - glomerulus
- bowmans space
8
Q
where is protein free fluid filtered into in glomerular filtration
A
filtered out of glomerulus into bowmans space
9
Q
where does protein free fluid flow into
A
proximal tubule
10
Q
what is blood in glomerular capillaries separated from bowmans space by
A
a filtration barrier
11
Q
what are the 3 layers of the glomerulus
A
- capillary endothelium: fenestrated
- basal lamina: basement membrane
- podocytes: visceral layer of bowmans capsule
12
Q
what are podocytes and what do they do
A
- foot processes that cover outside of basal lamina
- creates filtration slits
13
Q
what are mesangial cells and where are they found
A
- modified smooth muscle cells
- surround glomerular capillary loops
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
15
Q
what do substances have to be small enough to fit through to be filtered
A
filtration pores
16
Q
is protein lost in excretion
A
no
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
18
Q
in minimal change nephropathy ____
A
-loss of negative charge on GBM
- proteins filtered through GBM
- proteinuria
19
Q
what is the formula for GFR involving starlings forces
A
GFR = Kf x NFP
20
Q
what is capillary filtration coefficient (Kf)
A
product of the permeability and surface area of the capillaries
21
Q
what is NFP
A
balance of hydrostatic and colloid osmotic forces acting across the capillary membrane
22
Q
what starlings forces would cause GFR to be high
A
high hydrostatic pressure and high Kf
23
Q
what is NFP (number)
A
10mmHg, 125 ml/min or 180 L/day
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
25
how can diseases lower Kf
- thickened basement membrane: hypertension, DM
- decreased capillary surface area: glomerulonephritis
26
what are the two hydrostatic pressures that regulate GFR
- glomerular
-bowmans capsule
27
what is the primary control point for GFR
glomerular hydrostatic pressure
28
which hydrostatic pressure is a physiological controller of GFR: glomerular or bowmans
glomerular
29
what are the factors that influence glomerular hydrostatic pressure (Pg)
-arterial pressure (effect is buffered by autoregulation)
- afferent arteriolar resistance
-efferent arteriolar resistance
30
what diseases can affect GFR via PB (hydrostatic pressure of Bowmans capsule)
-tubular obstruction (stones, tubular necrosis)
-urinary tract obstruction (prostate hypertrophy/cancer)
31
what does glomerular capillary colloid osmotic pressure increase along
length of glomerular capillary
-affected by filtration fraction
32
what does glomerular capillary colloid osmotic pressure oppose
hydrostatic pressure
33
what happens to GFR along the length of the capillary
decreases
-factors that affect PiG
34
what is piG proportional to
[protein] plasma and FF (fraction of blood flow filtered in nephron)
35
how can hydrostatic pressure in glomerular capillaries be altered
by altering the resistance of the afferent and efferent arterioles leading to changes in GFR
36
what happens to PG and GFR when you constrict the efferent arteriole
PG: decreases
GFR: decreases
37
what happens to PG and GFR when you dilate the efferent arteriole
PG: decrease
GFR: decrease
38
what happens to PG and GFR when you constrict the efferent arteriole
PG: increase
GFR: increase
39
what happens to PG and GFR when you dilate the afferent arteriole
PG: increase
GFR: increase
40
an increase in efferent arteriolar resistance causes an increase in GFR only until a certain point where GFR then decreases. why?
due to increased [plasma protein] caused by increased filtration fraction
41
what are factors than can decrease GFR directly and what are the physiologic causes of those
-decreased Kf: renal disease, DM, HTN
- increased PB: urinary tract obstruction
- increased piG; increased [proteins]plasma, dehydration
-decreased Pg
42
what are factors that decrease GFR by decreasing PG and what are the physiological causes of those
- decreased MAP: low arterial pressure
- decreased RE: low ANG II
-increased RA: increased sympathetic activity, vasoconstrictor hormones
43
what is the formula for renal blood flow
RBF = (Pa-Pv)/total renal vascular resistance
44
how do kidneys tightly control RBF
renal autoregulation
45
what is vascular resistance in renal blood flow regulated by
factors acting on afferent and/or efferent arterioles (70% of total intrarenal resistance)
46
what percentage of blood flow into medulla makes up total RBF
less than 10%
47
what does a very low flow in vasa recta contribute to
concentrated urine
48
what does high RBF reflect in terms of energy
high energy cost of active transport
49
what are the primary active transporters in renal blood flow
- Na+ K+ ATPase
- H+ ATPase
- H+ K+ ATPase
- Ca2+ ATPase
50
what are the 3 levels of control of RBF
-autoregulation
- local control
-systemic control
51
what does autoregulation do
prevents moment to moment changes in GFR
52
what is the function of myogenic autoregulation
keeps RBF and GFR relatively constant in spite of changes in MAP
53
what is myogenic autoregulation
used in autoregulation
- reflex vessel constriction in response to increased MAP
- intrinsic to blood vessels
54
what is a transient drop in GFR and RBF as a result in a decrease in renal artery pressure followed by
vasodilation
55
what is a transient increase in GFR and RBF as a result of an increase in renal artery pressure followed by
vasoconstriction
56
what is the function of tubuloglomerular feedback (TGF)
-helps ensure a nearly constant delivery of Na+ and Cl- to the distal nephron
- prevents spurious fluctuations in renal excretion
57
what does the JGA do
mediates the TGF response
58
what is the JGA composed of
-juxtaglomerular cells (granular cells)
-macula densa cells in the wall of the thick ascending loop of henle
59
where are JG cells located and what do they do
-primarily in walls of afferent arterioles
-secrete renin
60
what do macula densa cells do
sense [Na+] and [Cl-] in filtrate
61
what is the mechanism of action of JGA
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
what are the stimuli for renin release
-low BP
- low RBF
- low NaCl delivery to macula densa
63
describe the TGF response
-low arterial pressure -> low glomerular hydrostatic pressure -> low GFR -> macula densa ->decreased RA and increased renin and ANGII to increase RE
64
what feedback effect do increased RE and decreased RA have on the TGF repsonse
negative feedback on the glomerular hydrostatic pressure
65
what are the vasoconstrictors in local control
-endothelin
- dopamine in high concentrations
66
what are the vasodilators in local control
-prostaglandins
- NO
- bradykinin
-dopamine in low concentrations
67
what is involved in sympathetic control of RBF and are they vasoconstrictors or dilators
-sympathetic NS (vasoconstrictor)
- epinephrine (vasoconstrictor)
- renin-angiotensin system (vasoconstrictor)
- ANP (vasodilates afferent and vasoconstricts efferent arterioles)
68
what role does SNS and EPI play in regulation RBF in normal state
minor role
69
when does SNS activation alter RBF
stress such as blood loss, cardiac events
70
what does NE/E do to RA, RE, RBF, and GFR
RA: increase
RE: increase
RBF: decrease
GFR: decrease
71
what does endothelin do to RA, RE, RBF, and GFR
RA: increase
RE: increase
RBF: decrease
GFR: decrease
72
what does angiotensin II do to RA, RE, RBF, and GFR
- mainly just increases RE
- RBF: decrease
-GFR: increase
73
what does ANP do to RA, RE, RBF, and GFR
RA:decrease
RE: increase
RBF: increase
GFR: increase
74
what does PGE2 and PGI2 do to RA, RE, RBF, and GFR
RA: decrease
RBF: increase
GFR: increase
75
what does bradykinin do to RA, RE, RBF, and GFR
RA: decrease
RBF: increase
GFR: increase
76
what does NO do to RA, RE, RBF and GFR
RA: decrease
RE: decrease
RBF: increase
GFR: increase
77
what are other factors that increase GFR and RBF
high protein diet
high blood glucose levels
78
what is the mechanism of protein ingestion
-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
what is the filtered load (Fx) of a substance and how is it calculated
-rate at which substances enter the nephron
- Fx= GFR ([X] plasma)
80
what is the excretion rate of a substance and how is it calculated
-rate at which substances are excreted
-Ex = (Uv)([X]urine) where Uv = urine flow rate
81
what is the clearance rate of a substance and how is it calculated
- determines the volume of blood cleared of a substance in a given amount of time
-Clx = Ex/[X]plasma
82
the clearance rate of what 2 substances are used as an index of GFR
inulin and creatinine
83
the clearance rate of what substance is used as an index of RBF
PAH
