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CPR Exam 2 > 12. Glomerular Function > Flashcards

12. Glomerular Function Flashcards

1
Q

what are the 3 layers of the glomerular filtration barrier

A
  1. capillary endothelium
  2. glomerular basement membrane
  3. podocyte epothelium

(Blood –> urine)

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2
Q

what is the glycocalyx and how does it contribute to filtration

A

= sticky biogel in the glomerular endothelial lumen

leads to net (-) charge –> repel (-) molecules

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3
Q

describe filterability based on charge/size

  • neutral =
  • cationic =
  • anionic =
A
  • neutral = as molecule gets larger, filterabilty decreases
  • cationic = increase filterabilty even if its a larger size bc attraction of (+) charge
  • anionic = decrease filterabilty bc glycocaylx repel (-) charge
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4
Q

what happens to filterabilty of anionic dextrans if there is nephrotoxic serum nephritis

A

barrier messed up - (-) charge removed

more anioinic substance can be filtered ==> proteinuria

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5
Q

what can be freely filtered

A

< 20 A

h2o

small solutes (glu, AA, electrolytes)

  • concentrations on either side of the membrane will be equal
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6
Q

what CANNOT be freely filtered

A

> 42 A

large molecules (proteins)- RBC, WBC

formed elements (cells)

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7
Q

How do you calculate urinary excretion

A

glomerular filtration (Gf) - tubular reabs (Tr) + tubular secretion (Ts)

–> rearrange to solve for others = ex- tubular reabs = Gf - Ue + Ts

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8
Q

if excretion > filtration…

A

then tubular secretion must have occured

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9
Q

what goes in must come out so… equation to describe this =

A

arterial input = venous output + urine outpu

(Px,a * RPFa) = (Px,v * RPFv) + (Ux * V)

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10
Q

how do you calculate urine excretion rate

A

Ux * V

Ux = urinary [X] = [X]/urine vol

V = urine FLOW RATE = urine vol/time –> depend on fluid intake/homeostasis

normal = 0.4 mEq/min

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11
Q

what is renal clearance

A

C = rate at which substance removed from plasma completely by the kidneys

C = Ux*V/Px

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12
Q

what is glomerular filtrate

A

vol of plasma FILTERED across glomerular cap into bowmans space by BOTH kidneys per unit time

should be protein & cell free

aka- plasma ultrafiltrate & isosmotic

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13
Q

what does glomerular filtration rate depend on

A

starlings forces

capillary filtration coeefficient (Kf) = permeabilty * SA

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14
Q

how do you calculate filtration fraction

A

FF = GFR/RPF

= the fraction of RPF that is filtered across glomerulus

change w/ ultrafiltration P, influenced by BP

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15
Q

explain why - when FF inceases - oncotic P of efferent arteriole increases

& what is the result of this

A

as you move from afferent to efferent you filter h2o –> increase concentration in cap –> increase πc

so on efferent side you favor tubular reabs

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16
Q

compare filtered load & FF

A

filtered load = rate in mg/min = GFR * Px

FF = GFR/RBF

17
Q

what % of filter load of X is reabs per day?

how do you calculate

A

filter load = GFR * Px (at glomerular cap)

UE = Ux * V

filter load - UE = reab

reabs/filter load = % reabs

18
Q

when is GFR proportional to renal clearance

A
  1. = freely filtered
  2. ISNT reabs or secreted at renal tubule
  3. NOT synthesized, broken down or accumulated by kidney
  4. phys inert (not toxic & w/o effect on renal fxn)

normal GFR around 125 mL/min

19
Q

what is inulin

A

= freely filtered, not reabs or secreted @ tubular level

so amount excreted = amount filtered

UIn * V = PIn * GFR –> GFR = UIn * V/PIn

20
Q

what is creatinine clearance used for

A

long term monitoring of renal fxn

= endogenous, freely filtered, minimal secreted

but still used to measure GFR compared to inulin bc its endogenous

21
Q

what 3 areas of the of kidney recieve sympathetic stimulation

what is the result

A
  1. arterial resistance vessels (alpha1) –> constrict afferent arterioles
  2. juxtaglomerular granular cells (beta1) - renin + RAAS
  3. tubular epithelial cells (alpha1) - Na/K ATPase- increase Na reabs

==> all lead to increased BP

22
Q

what two forces favor filtratrion

A

PGC & πBC

(πBC should = 0 bc protein shouldnt be filtered)

23
Q

what forces oppose filtration

A

PBC & πGC

24
Q

how do you calculate net filtration P

A

PGC - PBC - πGC

rmr πBC should = 0

25
Q

what 3 factors contribute to GFR

& how do you use these to calculate GFR

A
  1. hydraulic conductivity (permeability) = Lp
  2. SA for filtration = Sf
  3. capillary ultrafiltration P = PUF

ultrafiltration coefficient = Kf = Sf * Lp

==> GFR = Kf * PUF

26
Q

PUF can changed based on PGC. What determines PGC

A

renal arterial BP

afferent arteriolar resistance

efferent arteriolar resistance

27
Q

what are glomerular mesangial cells

A

cells with contractile properties - can change SA of endothelium available for filtration

28
Q

what is hydrostatic P like as it passes from Renal A to Renal V

A
29
Q

How can starling forces change to decrease GFR

& how do each affect RBF

A
  1. constrict afferent arteriole –> decrease PGC & decrease RBF
  2. dilate efferent arterioles –> decrease PGC & increase RBF
30
Q

what starling forces would lead to increased GFR?

& how would each affect RBF

A
  1. dilate afferent arterioles - increase PGC & increase RBF
  2. constrict efferent arterioles - increase PGC​ & decrease RBF
31
Q

vasoconstrictor list =

A
  1. angiotensin II
  2. ATP/adenosine
  3. endothelin
  4. sympathetics (catecholamines)
32
Q

vasodilators list =

A
  1. Prostoglandins
  2. Bradykinin
  3. NO
  4. ANPs
  5. DA
  6. ACE-inhibitor
33
Q

what does angiotensin II do primarily

A

constrict efferent arterioles –> increase GFR

(ACE-inhibitor stops this and decrease GFR)

34
Q

what part of the renal system is innervated by sympathetics

A

renal blood vessels

local sym & circulating Epi/NE activate alpha1 (more on afferent than efferent arterioles)

35
Q

what is glomerulartubular balance

& how is it achieved

A

= increasing reabs rate w/i renal tubules when GFR rises

  1. change P –> increase oncotic P in efferent arterioles & PTC –> increase Na reabs
  2. increase delivery of solute to PCT –> increased filter load –> lot of co-transport of Na into PCT –> increased Na reabs
  3. increase shear strain- bc increase GFR & flow –> upregulate Na transporter insertion –> increase Na reabs
36
Q

what is local myogenic feedback reflex

A

btn vascular sm. m cells

blood vessels resist stretch during periods of high BP –> Sm. M in vessel contract

–> signal Ca –>

afferent arteriolar constriction & efferent dilation

37
Q

what is tubuloglomerular feedback

A

macula densa -sense increased distal tubular NaCl –>

increase ATP/adenosine signaling –> bind thier receptor –>

relase intracell Ca –> stimulate granule cells & then mesangial cells –>

constrict afferent arterioles –> juxtaglomerular cells decrease secretion or renin –> decrease GFR

38
Q

what is fractional excretion and how do you calculate it

A

% of whatever has been filters is actually excreted

=amount X excreted/amount X filtered

can assume GFR = clearance of creatinine for some substances

CPR Exam 2 (20 decks)

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