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MED 2031 Wks 7-12 > Kidney physiology > Flashcards

Kidney physiology Flashcards

1
Q

kidney functions in a nutshell

A

removes wastes (urea, creatinine)
electrolyte balnce
secrete EPO, renin, calcitriol

in kidney failure
get wastes off the roof
get electrolyte problems
and get anemia, bone idsease

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2
Q

glomerular filtration rate

A

volume of plasma filtered per min

=125mL per min

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3
Q

filtration fraction

A

the volume of plasma filtered out of all the plasma that runs through the glomerulus in one pass:
GFR/renal plasma flow
= 20%

‘the fraction of the renal plasma flow that is filtered in the glom during a single pass through the kidneys

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4
Q

which part of nephron is in cortex?

A

glom, proximal convuluted tubule, DCT, cortical collecting duct

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5
Q

which part of nephron is in medulla?

A

proximal straight tubule, Loop of henle, medullary collecting duct

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6
Q

GLOMERULAR FILTRATION BARRIER

A
  1. fenestrations of the endothelial capillary cell layer
  2. basement membrane (has neg charge)
  3. slit diaphragms of the podocyte cells layer-epithelial layer
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7
Q

things that can filter through easily at glom

A

small
positive
not bound to proteins

large, neg, bound to proteins= can’t go through!

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8
Q

main thing driving fluid across the glom filtration barrier:

A

hydrostatic pressure of the fluid,(pressure from the heart as well)

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9
Q

GFR formula

A

GFR= Net filtration pressure x Kf

NFP= glomerular hydrostatic pressure - glomerular colloid osmotic pressure – hydrostatic pressure in bowman;s capsule
have net 10 mmHg pressure pushing fluid from cap into bowmans capsule

Kf= glomerular filtration coefficient
= hydraulic conductivity (permeability) X glomerular capillary surface area

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10
Q

o SNGFR=

A

single nephron glomerular filtration rate= NFP x Kf

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11
Q

wen we measure GFR, we normally measure the whole kidney/total GFR=

A

sum of the gfr for each nephron for both kidneys

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12
Q

Kf

A

filtering ability/intergrity of glom filtration barrier. if 
glom fil barrier is damaged, Kf goes down.
u want Kf to be high ie the filteriing ability to be high

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13
Q

GLom hydrostatic pressure determined by

A

ARTERIAL PRESSURE (increase AP=increase GFR)

AFFERENT ARTERIOLAR RESISTANCE
(constriciton=increase AAR= decrease GFR)

EFFERENT ARTERIOLAR RESISTANCE
(constriction=increase EAR= increase GFR. but if constrict too much=decrease GFR)

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14
Q

if GFR too high

if GFR too low

A

too high= not enough time to reabsorb stuff

too low= reabsorb too much=wastes not excreted

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15
Q

auto regulation can keep GFR n renal blood flow constant as long as the arterial pressure is bw

A

70mmHg n 150mmHg

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16
Q

AUTOREGULATION IS DONE VIA 2 MECHANISMS:

A
  1. Myogenic mechanism

2. Tubuloglomerular Feedback (TGF)

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17
Q

myogenic mechanism

A

wen blood pressure increase in a vessel=vessel constricts

So when arterial pressure increases
=stretches the vascular walls
=afferent arterioles constrict
= decreased blood flow to glom

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18
Q

decrease afferent arteriolar resistance

A

=increase GFR

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19
Q

increase efferent arteriolar reistance=

A

increase GFR

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20
Q

tubuloglomerular feedback (TGF)

A

decreased arterial pressure
=decreased GFR

decreased salt sensed by macular densa

  1. dilate afferent arteriole
  2. renin release, constrict efferent arteriole

=increase GFR

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21
Q

creatinine

A

some is secreted, so get overestimation a little bit

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22
Q

to measure GFR, use

A

creatinine

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23
Q

to measure renal plasma flow use

A

PAH

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24
Q

secretion

A 
main things we secrete are:
o	urea
o	K+
o	H+
o	Drugs eg penicillin
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25
Q

TRANSPORT MAXIMUM

A
  • =the maximum rate that the solute can be transported
  • due to the saturation of available protein carriers

eg glucose:
o maximum rate at which glucose can be reabsorbed from the tubules is 320mg/min or 11mol/L
o if filtration rate is more than 320mg/min, =glycosuria

26
Q

reabsorption mechanisms

A
  • Going from across the tubular epithelial cells occurs via ACTIVE OR PASSIVE TRANSPORT
  • Going from renal interstitium into the capillaries is via BULK FLOW/ULTRAFILTRATION
27
Q

antiporters

A

same sign
one gets taken in n one goes out
eg Na+/H+ antiporter

28
Q

symporter

A

different sign
so both gets taken in/or both gets kicked out
eg Na+/K+/2Cl- symport pumps

29
Q

which part is permeable and impermeable to water?

A

PCT n descending loop of henle -permeable (has aquaporins 1)

ascending limb-impermeable

distal tubule n collecting ducts- variable (depends on ADH)-which ADH=permeable, without ADH=impermeable

30
Q

water is filtered n reabsorbed but

A

NOT SECRETED

31
Q

sodium is filtered and reabsorbed but

A

NOT SECRETED

32
Q

sodium transport

luminal vs basolateral:

A

luminal-transport is passive via some form of diffusion/fasciliated diffusion

basolateral -transport is active via Na+/K+ATPase- active pump ensures sodium is low inside cell to promote passive entry at luminal side

diffusion into peritubular cap- via bulk transport

33
Q

where is sodium reabsorbed?

A

proximal tubule-yes

thick descending limb- according to slides=impermeable. according to guyton- moderately permeable

ascending limb-yes

distal tubule n collecting duct=fine control via aldosterone

34
Q

the longer the loop vs the shorter loop (nephron

A

when ur dehydrated, shift to longer loop, so u can concentrate more urine

the longer the loop, the ghiher the conc we can make
the more water we can reabsorb

35
Q

which site is thesiteofurineconcentration=waterpreservation

A

collecting ducts!

36
Q

ADH present=______urine

A

concentrated urine

37
Q

ADH not present=________urine

A

dilute urine

38
Q

the amount of blood flowing through the kidneys that is actually filtered (normally 20%) is?

A

180L/day

this is the filtration fraction

39
Q

what is the normal gfr value?

A

125mL/min

40
Q

renin

A

increases blood pressure

41
Q

hormonal control of GFR

A

Sympathetic stimulation and adrenaline released from the adrenals constrict the AFFERENT arterioles, reducting the GFR and urine output.

42
Q

Endothelin

A

vasoconstrictor.

may thus contribute to renal vasoconstriction and decreased GFR

43
Q

Prostaglandins (PGE2 and PGI2) and bradykinin

A

vasodilator

increase GFR

44
Q

Endothelial-derived nitric oxide

A

vasodilator

increases GFR

45
Q

ALDosterone

A

stimulate sodium reabsorption (n water reabsorption)

n secretion of K

46
Q

bicarbonate regeneration in PCT is mainly from

A

glutamine (that comes from iiver)

this glutamine goes to tubular cells n makes ammonia, as it does this, it makes alpha ketoglutarate. A-ketoglutarate makes B ions, which go back into blood.

47
Q

alpha intercalated cells

A

secrete H+ into tubule
secrete HCO3 into blood
reabsorb K+ from renal tubule

48
Q

beta intercalated cells

A

secrete HCO3- into tubule
secrete H+ into blood
reabsorb Cl- from renal tubule

49
Q

• in alkalosis u get an increase in _____ cell

A

b interclated cell (cos Beta gets rids of HCO3-

50
Q

in acidosis get an increase in ______

A

alpha intercalated cell (cos alpha gets rid of H+

51
Q

on the luminal membrane of alpha intercalated cell there is a K+/H+ antiporter
with H+ going into tubule n K+ getting reabsorbed into alpha cell

A

in hypokalaemia, u get more action of this pump

and so get rid of more H+, can lead to alkalosis

52
Q

principal cell

A

secrete K+ into tubule (from blood-so whole way through cell)
reabsorb Na+ into blood (from tubule-so whole way through cell

53
Q

regeneration of Bions in distal tubule n collecting ducts

A

via TITRATABLE ACIDS
in acidosis, end up with lots of CO2 inside the tubular cells.

CO2 combination with water etc makes B ions n H+. Bions go into blood, H+ goes into renal tubule lumen.

In lumen, H+ joins with PHOSPHATE, UREA or Titratable acids (ketoacids or creatinine) to makes these things that can somehow make B ions.
so if u have acidosis, this method can make some B ions for u. But this method is limited-it is limited by the amoung of urea and phosphate u have in the yellow space

54
Q

4 factors that control B ion reabsorption

increase in these factors=increase Bion reabsorption

A

luminal [HCO3-]
luminal flow rate
arterial pCO2
Ang 2 (stimulates Na+ H+ exchanger in PCT)

55
Q

plasma [HCO3]

A

24 mM

56
Q

plasma [H+}

A

40 nM

57
Q

plasma n ph

A

plasma is not neutral
neutral at 37 degrees is 6.8
plasma ph is 7.4

58
Q

buffer

A

buffer + H Hbuffer

any molecule that can hold onto to n let go of H+
reversibly bind to H+

59
Q

main buffer in ECF:

A

haemoglobin
bicarbonate

(main buffer in ICF= plasma protein, phosphates)

60
Q

3 basic principles that must be met when determining equation of conc of H+

A

electroneutrality must be conserved
mass must be conserved
all dissociation eqns must be met

MED 2031 Wks 7-12 (13 decks)

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