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Physiology > renal 3 - filtration > Flashcards

renal 3 - filtration Flashcards

1
Q

which two processes involve entry into renal lumen

A

glomerular filtration and tubular secretion

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2
Q

which two processes involve entry out of the renal lumen

A

tubular reabsorption and excretion of urine

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3
Q

formula for amount excreted

A

amount filtered+amount secreted-amount reabsorbed

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4
Q

what are the 3 layers of the glomerular capillary

A

fenestrated endothelium
basement membrane
podocytes with filtration slits

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5
Q

why cant large proteins or albumin go through filtration (3 reason)

A
  • too large for pores
  • pores&BM are negative, they repel negative proteins
  • podocyte slits remain covered with find semiporous membranes (nephrins podocins)
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6
Q

what are nephrins and podocins

A

proteins that determine what can pass through the podocyte slits

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7
Q

what is the ultrafiltrate

A

the filtrate that passed through the capillary and has nearly identical composition to the plasma (besides RBC and proteins)

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8
Q

what is proteinuria

A

when there is protein in the filtrate

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9
Q

what could cause proteinurea

A

issues with nephrins and podocins

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10
Q

is net glomerular filtration always positive or negative and why

A

always positive because you are pushing things out into the bowmans space

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11
Q

what is PBS and what is its role towards filtration

A

fluid pressure in bowmans space

opposed filtration

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12
Q

what is piBS

A

osmotic force due to proteins in bowmans space

BUT ITS 0 because there are no proteins in the bowmans space

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13
Q

overall, what is the difference with P and pi

A

P is the fluid pressure

pi is the opposing osmotic force

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14
Q

what is PGC and what is its role towards filtration

A

glomerular capillary blood pressure

favors filtration

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15
Q

what is piGC and what is its role towards filtration

A

osmotic force due to proteins in plasma

opposing filtration

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16
Q

what is the net glomerular filtration pressure

A

PGC-PBS-piGC

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17
Q

which direction does PGC go

A

capillary–>bowman

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18
Q

which direction does PBS go

A

bowman–>capillary

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19
Q

which direction does piGC go

A

bowman–>capillary

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20
Q

which direction does piBS go

A

none cause pretty much zero

otherwise it would go towards to bowmans space

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21
Q

which has the highest pressure (PBS PGC piBS piGC)

A

PGC

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22
Q

what does Glomerular filtration pressure initate

A

urine formation by forcing protein ree filtrate from plasma out of the glomerulus into bowmans space

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23
Q

what is filtration fraction (and the %)

A

only 20% of the plasma entering the afferent arteriole is iltered

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24
Q

what % of the filtered volume is excreted

A

less than 1%

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25
Q

what % of the filtered volume is reabsorbed

A

19% (20% filtered, 1% remains)

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26
Q

what is flomerular filtration rate (GFR)

A

the volume of fluid filtered from the glomerulus into the bowmans space per unit time

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27
Q

what is GFR for human

A

125mL/min
180L/day
for 70kg man

28
Q

which 4 factors influence GFR

A
  • net glomerular filtration pressure
  • permeability of corpuscular membrane
  • surface area for filtration
  • neural and endocrine control
29
Q

how does GFR change with changes in arterial pressure or renal blood flow?

A

it remains constant so that you don’t damage the nephrons

30
Q

how do you do autoregulation of GFR

A

change renal blood vessel resistance (compensate for changes in BP)

31
Q

how do you change the arteriol resistance

A

myogenic response of afferent arteriole (smooth muscle)

or the tubuloglomerular feedback effect

32
Q

what is the tubuloglomerular feedback effect

A

increase flow causes constriction of the afferent arteriol to reduce GFR

33
Q

how is the tubuloglomerular feedback effect regulated

A
  • paracrine actions of the juxtaglomerular apparatus (cells close to glomerulus)
  • paracrine control of afferent arteriole resistance
34
Q

what range of blood pressures does autoregulation maintain a nearly constrant GFR

A

80-180mm Hg

35
Q

what is mean arteriol blood pressure formula

A

2/3 diastolic pressure + 1/3 systolic pressure

36
Q

why does autoregulation of glomerular filtration rate take place in a small range of blood pressures

A

it doesnt

it is a wide range so that your body can handle a large fluctuation of blood pressure

37
Q

where does most resistance change occur

A

afferent arterioles

38
Q

what happens (to GFR, capillary BP and blood flow) when you increase resistance in afferent arteriole

A

decrease GFR
decrease capillary BP
decrease renal blood flow
increase flow to other organs

39
Q

what happens (to GFR, capillary BP and blood flow) when you increase resistance in efferent arteriole

A

increase GFR
increase capillary BP
decrease renal blood flow
increase flow to other organs

40
Q

what are two ways to decrease GFR

A

constrict afferent arteriole

dilate efferent arteriole

41
Q

what are two ways to increase GFR

A

dilate afferent arteriole

constrict efferent arteriole

42
Q

what is myogenic response of GFR regulation

A

similar to autoregulation in other systemic arterioles

43
Q

what does autoregulation mean

A

mean arteriole pressure is fluctuating but this helps keep it constant

44
Q

what is a role of the juxtaglomerular apparatus

A

tubuloglomerular feedback

45
Q

what does increased tubular flow cause to afferent arteriole and why

A

constrict afferent to reduce GFR

46
Q

how is tubuloglomerular feedback regulated

A

paracrine control of afferent arterioles by the juxtaglomerular apparatus

47
Q

how does afferent smooth muscle react with an increase in BP

A

smooth muscle cells in the wall of the arteriole are stretched and respond by contracting to resist the pressure, resulting in little change in flow

48
Q

how does afferent smooth muscle react with an decrease in BP

A

smooth muscle cells relax to lower resistance, allowing a continued blood flow

49
Q

what kind of GFR regulation is not autoregulated

A

hormones and autonomic neurons

50
Q

how do hormones and autonomic neurons work

A

not autoregulate

they change resistance in arterioles

51
Q

what are the components of the juxtaglomerular apparatus

A

macula densa and juxtaglomerular cells

52
Q

what/where are the macula densa

A

cells on the wall of the distal convoluted tubule

53
Q

what do macula densa sense

A

can sense increased fluid flow through distal tubule (senses [Na+] and [Cl-])

54
Q

what do macula densa secrete and what does this cause

A

secrete vasoactive compounds with paracrine effects on afferent arteriol resistance
this signals to JG cells (controls GFR)

55
Q

what do juxtaglomerular cells do

A

secrete renin

56
Q

where are juxtaglomerular cells

A

on the wall of the afferent arteriole

57
Q

what are granular cells

A

juxtaglomerular cells

58
Q

what are mesangial cells

A

similar to smooth muscle, help with muscle contraction

59
Q

are mesangial cells part of the juxtaglomerular apparatus

A

noooo

60
Q

what 4 factors control GFR

A
  • myogenic arteriole reflex
  • neuro-endocrine input on arterioles
  • paracrine effects of macula densa
  • mesangial cells
61
Q

what happens with contraction of mesangial cells (surface area and GFR)

A

reduces surface area of glomerular capillaries

GFR decreased

62
Q

what is the definition of filtered load

A

total amount of non protein or non protein bound surface filtered into bowman’s space

63
Q

what is the formula of filtered load

A

GFRx[substance in plasma]

not protein, its stuff like glucose

64
Q

what happens when substance excreted in urine

A

reabsorption

less is released than in the load

65
Q

what happens when substance excreted in urine>filtered load

A

secretion

more is excreted than in the load

Physiology (32 decks)

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