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Ned's clinical summaries > Renal- physiology > Flashcards

Renal- physiology Flashcards

1
Q

what units are used for body fluids omolarities

A

mosmol/l

cos body fluids are weak salt solutions

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2
Q

units for osmolality

A

osmol/kg

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3
Q

units for osmolarity

A

osmol/l

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4
Q

what is the tonicity of urea

A

hypotonic

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5
Q

what is the tonicity of sucrose

A

isotonic

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6
Q

where is the majority of water held in our bodies

A

intracellularly (67% of it)

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7
Q

what tracer is used to measure ECF

A

insulin

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8
Q

what tracer is used to measure plasma

A

labelled albumin

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9
Q

what tracer is used to measure TBW

A

^3H20

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10
Q

what are the main ions in ECF

A

Na, Cl, HCO3

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11
Q

main ions in ICF

A

K, Mg and -ivley charged proteins

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12
Q

what are the osmotic concs of both ICF and ECF

A

300mosmol/l

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13
Q

why is K+ so important

A

it plays a key role in establishing membrane potential

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14
Q

what can hypokalaemia cause

A

muscle weakness and cardiac arrhythmias

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15
Q

what do the inner layer of bowman’s capsule contain

A

podocytes

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16
Q

name the layers of the glomerular capillary

A

endothelial cell (nearest lumen of glomerular capillary)

basement membrane

podocytes (nearest lumen of bowman’s capsule)

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17
Q

what are macula densa

A

salt sensitive cells

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18
Q

what percentage of plasma that enters the glomerulus is filtered

A

20% - the glomerular capillaries have massive pores that are pretty leaky

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19
Q

what does rate of excretion +?

A

rate of excretion = rate of filtration + rate of secretion - rate of reabsorption

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20
Q

what way does capillary oncotic pressure push and what causes it

A

pushes back from the filtrate and into the blood vessels

caused by the plasma proteins in blood

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21
Q

what is normal GFR

A

125ml/min

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22
Q

what is the extrinsic regulation of GFR

A

sympathetic control via baroreceptor reflex

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23
Q

what is the (intrinsic) auto regulation of GFR

A

myogenic mechanism - if vascular smooth muscle is stretched, it contracts, constricting the arteriole

tubuloglomerular feedback mechanism –> involves macula densa cells detecting an increased GFR due to increased NaCl in tubule causing vasoconstriction

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24
Q

what is the role of autoregualtion of GFR

A

prevents short term changes in systemic arterial pressure affecting GFR

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25
Q

how does kidney stone reduce the GFR

A

bowman’s capsule fluid pressure is increased

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26
Q

how does diarrhoea cause reduced GFR

A

water loss from blood so the plasma proteins become more concentrated

plasma proteins exert a greater osmotic effect, opposing filtration

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27
Q

how do burns increase GFR

A

plasma proteins are lost through the burn, reducing their concentration in the blood

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28
Q

how much of the urea is reabsorbed

A

50% is reabsorbed

50% is secreted

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29
Q

how is renal plasma flow calculated

A

using para-amino huppuric acid (PAH)

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30
Q

what is the normal renal flow

A

650ml/min

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31
Q

describe the differences in qualities needed between a GFR marker and an RPF marker

A

both need to be filtered freely

GFR - should NOT be secreted or reabsorbed - you need it in the urine

RPF - should be COMPLETELY secreted and not reabsorbed

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32
Q

how do you calculate the filtration fraction

A

GFR/renal plama flow

it should be around 20%

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33
Q

how much of the 125ml of glomerular filtrate is reabsorbed in the proximal tubule

A

80ml/min

34
Q

where is 2/3 of salt and water reabsorbed and 100% of glucose and amino acids

A

the PT

35
Q

what is secreted into the PT

A 
H+
neurotransmitters (ACh) 
uric acid 
drugs 
toxins
36
Q

what ion is the carrier molecule normally coupled to in 2ndary active transport

A

Na

37
Q

where are Na/K ATPase transport mechanisms expressed

A

at the basolateral membrane of epithelial cells

ALWAYS AND EXCLUSIVELY

38
Q

does Na/K ATPase require energy

A

yes - moves the Na and K against their concentration gradients

39
Q

where is Na reabsorbed

A

the proximal tubule

40
Q

the fluid reabsorption across the PT is isometric - true?

A

yeh - the PT epithelium is leaky and allows passive water absorption down NaCl gradient, paracellulary

41
Q

in the PT, Cl moves transcelluary- true?

A

no - it moves paracellulary

the reabsorption of Na sets up a gradient for the reabsorption of Cl

42
Q

normally, where is 100% of the glucose in filtrate reabsorbed from

A

the PT

43
Q

what is the max amount of glucose that can ve absorbed before glycosuria

A

2mmol/min

44
Q

the tubular fluid is iso-osmotic when it leaves the PT - True?

A

yes - around 300mosmol/l

45
Q

how does the loop of hence enable the formation of hypertonic urine

A

it generates a corticomedulalry solute conc gradient

the loop functions as a countercurrent multiplier

46
Q

what is the descending limb permeable to and what is it not permeable to

A

highly permeable to water

NOT reabsorb NaCl

47
Q

what are being reabsorbed in the ascending limb

A

Na and Cl are being reabsorbed

ascending limb is impermeable to water

48
Q

where is the Na/K/Cl triple co transporter located

A

the thick (upper) ascending loop of Henle

49
Q

other than the PT, where else is Na reabsorbed

A

the thick ascending loop of henle

this part is impermeable to water

50
Q

what do loop diuretics block

A

the triple co transporter at the thick ascending loop of Henle

51
Q

in the ascending limb of LOH, what happens to the osmolality off the interstitial fluif

A

it is raised - ions are moving into it from the filtrate and water is not moving in, making it more concentrated

52
Q

fluid in the descending limb is concentrated - true?

A

yes - water is lost but the ions are not

53
Q

is the fluid iso-osmotic in as it leaves the ascending tubule and moves into the DT?

A

no- it is hypo-osmotic - around 100mosmol/l

means there is more osmotically active particles in the interstitial fluid than than filtrate

54
Q

what 2 structures form the countercurrent system

A

the loop of Henle and vasa recta

55
Q

where in the nephron do hormones usually work

A

the distal tubule - the remaining ions at this point are v important for salt and water balance of the urine

56
Q

ADH causes reabsorption of water only - true?

A

yeah

57
Q

what 2 things does DT have a low permeability to

A

water and urea

58
Q

what does the early DT reabsorb

A

it has Na/K/Cl transporters

NaCl reabsorption

59
Q

what does the late tubule reabsorb

A

Ca, Na and K reabsorption

H+ secretion

60
Q

which part of the collecting duct has a permeability to water, influenced by ADH

A

the late collecting duct

61
Q

ADH is stored in the ant pit - true ?

A

no - in the post pituitary

62
Q

what type of hormone is ADH

A

peptide - short half life

63
Q

which vasopressin receptor will the vasopressin bind to

A

type 2!!

64
Q

what does vasopressin cause

A

recruitment of aquaporins to the apical membrane due to increased intracellular cAMP

65
Q

what do type 1 vasopressin receptors cause

A

smooth muscle contractions and vasoconstriction

66
Q

high ADH causes hypotonic urine - true?

A

false - causes hypERtonic urine - its more concentrated due to less water init

67
Q

how do you treat nephrogenic DI

A

thiazide diuretics

68
Q

90% of K+ is absorbed in the proximal tubule - where is the other 10% reabsorbed

A

in the absence of aldosterone, K+ reabsorbed in the distil tubule

69
Q

how does an increase in plasma conc of K+ stimulate adrenal cortex to release aldosterone

A

directly stimulates it

70
Q

how does a decrease in the plasma conc of Na promote secretion of aldosterone

A

indirectly

71
Q

what does renin do

A

converts angiotensinogen to angiotensin 1

72
Q

what’s the action of ANP

A

promotes excretion of Na and diuresis, reducing plasma vol

73
Q

what’s the difference between water and osmotic diuresis

A

both cause an increased urine flow

water dieresis doesn’t cause an increased solute excretion

osmotic diuresis is due to a primary increases of salt excretion

74
Q

what effect do acidosis and alkalosis have on CNS

A

acidosis = depression of CNS

alkalosis = over excitability of peripheral and CNS

75
Q

what catalyses the production of carbonic acid from co2 and h20

A

carbonic anhydrase

76
Q

what does the plasma concentration of bicarbonate rely on

A

relies entirely on H+ secretion into the tubule

77
Q

in order to reabsorb bicarbonate ions from the filtrate, what do we need

A

hydrogen ions!

the hydrogen ion combines with the bicarbonate to make it carbonic acid

78
Q

how does the bicarbonate ion pass back across into the epithelial cell

A

it has to be made into carbonic acid, then broken down to co2 and h20 - then it can get across to the pother side

79
Q

how is new bicarbonate formed by the kidneys

A

in the filtrate, H+ combines with phosphate (the 2nd most plentiful buffer in the filtrate)

for every one hydrogen ion secreted in urine, one new bicarbonate ion is made by kidneys

80
Q

what’s the difference between compensation and correction

A

both aim to restore the pH

compensation = restores pH irrespective of plasma conc of bicarbonate and CO2

correction= restores pH and also the partial pressure of CO2

Ned's clinical summaries (3 decks)

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