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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
TRANSPORT MAXIMUM
* =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
reabsorption mechanisms
* 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
antiporters
same sign one gets taken in n one goes out eg Na+/H+ antiporter
28
symporter
different sign so both gets taken in/or both gets kicked out eg Na+/K+/2Cl- symport pumps
29
which part is permeable and impermeable to water?
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
water is filtered n reabsorbed but
NOT SECRETED
31
sodium is filtered and reabsorbed but
NOT SECRETED
32
sodium transport | luminal vs basolateral:
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
where is sodium reabsorbed?
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
the longer the loop vs the shorter loop (nephron
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
which site is thesiteofurineconcentration=waterpreservation
collecting ducts!
36
ADH present=______urine
concentrated urine
37
ADH not present=________urine
dilute urine
38
the amount of blood flowing through the kidneys that is actually filtered (normally 20%) is?
180L/day | this is the filtration fraction
39
what is the normal gfr value?
125mL/min
40
renin
increases blood pressure
41
hormonal control of GFR
Sympathetic stimulation and adrenaline released from the adrenals constrict the AFFERENT arterioles, reducting the GFR and urine output.
42
Endothelin
vasoconstrictor. may thus contribute to renal vasoconstriction and decreased GFR
43
Prostaglandins (PGE2 and PGI2) and bradykinin
vasodilator | increase GFR
44
Endothelial-derived nitric oxide
vasodilator | increases GFR
45
ALDosterone
stimulate sodium reabsorption (n water reabsorption) | n secretion of K
46
bicarbonate regeneration in PCT is mainly from
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
alpha intercalated cells
secrete H+ into tubule secrete HCO3 into blood reabsorb K+ from renal tubule
48
beta intercalated cells
secrete HCO3- into tubule secrete H+ into blood reabsorb Cl- from renal tubule
49
• in alkalosis u get an increase in _____ cell
b interclated cell (cos Beta gets rids of HCO3-
50
in acidosis get an increase in ______
alpha intercalated cell (cos alpha gets rid of H+
51
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
in hypokalaemia, u get more action of this pump | and so get rid of more H+, can lead to alkalosis
52
principal cell
secrete K+ into tubule (from blood-so whole way through cell) reabsorb Na+ into blood (from tubule-so whole way through cell
53
regeneration of Bions in distal tubule n collecting ducts
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
4 factors that control B ion reabsorption | increase in these factors=increase Bion reabsorption
luminal [HCO3-] luminal flow rate arterial pCO2 Ang 2 (stimulates Na+ H+ exchanger in PCT)
55
plasma [HCO3]
24 mM
56
plasma [H+}
40 nM
57
plasma n ph
plasma is not neutral neutral at 37 degrees is 6.8 plasma ph is 7.4
58
buffer
buffer + H Hbuffer any molecule that can hold onto to n let go of H+ reversibly bind to H+
59
main buffer in ECF:
haemoglobin bicarbonate (main buffer in ICF= plasma protein, phosphates)
60
3 basic principles that must be met when determining equation of conc of H+
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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