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Renal Physio > Glomerular Filtration I > Flashcards

Glomerular Filtration I Flashcards

1
Q

What happens if the body does not filter enough plasma

A

Edema (fluid overload) and azotemic (too much urea), also electrolyte and acid-base disturbances

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2
Q

Glomerular filtration is governed by

A

Starling Forces

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3
Q

Glomerular Capillary Pressure (Pc)

A

largely determines the glomerular filtration rate (GFR)

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4
Q

Glomerular Capillary Pressure (Pc) is largely determined by

A

arterial BP and afferent and efferent arteriolar resistances

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5
Q

What regulates the afferent and efferent arteriolar resistances?

A

Hormones and SNS

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6
Q

Increased afferent arteriolar resistances will have what effect on Pc and GFR?

A

Vasoconstriction of the afferent arteriole causes decreased glomerular capillary pressure and decreased GFR

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7
Q

Increased efferent arteriolar resistances will have what effect on Pc and GFR?

A

Vasoconstriction of the efferent arteriole causes increased glomerular capillary pressure and increased GFR

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8
Q

Intrinsic permeability (Kf) of the glomerular capillary wall effects GFR, increased Kf causes

A

increased GFR

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9
Q

The thick ascending limb is _________ to water

A

impermeable

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10
Q

In the late distal tubule and the collecting duct water permeability depends on

A

presence of ADH

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11
Q

In the proximal tubule and descending limb of hence, water permeability is dependent on

A

waters concentration gradient

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12
Q

Na reabsorption drives the reabsorption of

A

H2O, HCO3, glucose, aa

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13
Q

Na reabsorption drives the secretion of

A

H+

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14
Q

Na/K ATPase drives the reabsorption of other solutes by

A

establishing a concentration gradient of Na, which will drive the reabsorption of Na into the cell which drives the transport of other solutes

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15
Q

If too little ATP is available for the Na/K pump

A

the pump will slow, the concentration gradient will decline and the reabsorption of solutes slows

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16
Q

If the plasma osmolality moves away from its set point then

A

the hypothalamus signals the release of ADH form the posterior pituitary, and ADH changes the permeability of the collecting duct to H2O

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17
Q

Dilution of the urine is dependent on 2 factors

A

ability of the thick ascending limb to transport Na w/o H2O and a low level of ADH

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18
Q

Concentration of the urine is dependent on 2 factors

A

ability of the thick ascending limb to set up a concentration gradient and a high level of ADH

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19
Q

What determines the osmolality of the ECF

A

Na, Cl, and HCO3

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20
Q

Eating salty food (increased Na intake)

A

results in reabsorption of H2O to correct the high osmolality (high BP)

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21
Q

ECF osmolality is corrected for at the expense of

A

ECF volume

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22
Q

How does the body correct for a low ECF? (low Na diet, diuretics)

A

Reabsorb Na, but the kidney’s cannot produce H2O or Na they must be consumed

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23
Q

What signals determine the kidneys Na and water reabsorption

A

BP, neural mechanisms, and hormonal mechanisms

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24
Q

Pressure-Naturiesis

A

Arterial pressure has a DIRECT effect on Na excretion; increased BP = increased excretion of Na via INTRARENAL MECHANISM

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25
Q

How does chronic BP effect pressure-naturiesis

A

Shifts the relationship to the right or has a depressed slope; higher BP at same steady-state Na intake

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26
Q

Na content regulated

A

ECF volume

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27
Q

Body water content regulates

A

plasma osmolarity

28
Q

SNGFR

A

single nephron glomerular filtration rate

29
Q

GFR

A

sum of all the SNGFR for the 2 kidneys

30
Q

GFR =

A

Kf x [(Pgc-Pbs) - (Πgc - Πbs)]

31
Q

Oncotic pressure of Bowman’s Space Πbs =

A

0, since there is virtually no proteins in Bowman’s Space

32
Q

Permeability of the glomerular capillaries is

A

~100X greater than systemic and is the reason for a high filtration rate

33
Q

Renal Clearance

A

amount of solute excreted/ concentration of solute in plasma

34
Q

Input must equal output

A

substance IN = excretion (out1) + return to circulation (out2) *as long as it is not being metabolized

35
Q

How to measure excretion of solute

A

urine concentration of solute x urine flow rate

36
Q

Clearance of a solute (Cx) =

A

(Ux x V) / Px (urine concentration of solute X x urine flow rate) / plasma concentration of solute X

37
Q

Definition of clearance

A

the mL of blood plasma completely cleared of a given substance in 1 minute

38
Q

Clearance of a substance is typically ______ than renal plasma flow

A

LESS; because most solutes are reabsorbed

39
Q

Clearance can estimate

A

GFR and renal plasma flow (RPF)

40
Q

Clearance determines

A

net reabsorption or net or secretion of a filtered substance

41
Q

GRF can be determined by clearance IF

A

the substance is not metabolized, neither secreted or reabsorbed, and freely filtered

42
Q

Filtered load =

A

GFR x plasma concentration of solute

43
Q

Excretion =

A

Urine conc of solute x urine flow rate

44
Q

What substances can be used then to estimate GFR?

A

Inulin, I-iothalamate, creatinine, Iohexol, Iothalamate

45
Q

Inulin for GFR estimation

A

inulin (fructose polymer) infused via IV, gold standard

46
Q

I-iothalamate for GFR estimation

A

can predict GFR via plasma clearance alone

47
Q

Creatinine for GFR estimation

A

ESTIMATES GFR (some is secreted)

48
Q

Plasma clearance used for GFR measurement

A

Give IV bolus of known amount and take plasma samples over time to measure the clearance which = GFR (iohexol, iothalamate)

49
Q

For chronic kidney disease, creatinine clearance _______ GFR

A

OVERESTIMATES; more is SECRETED due to higher serum levels

50
Q

Stage 1 Chronic Kidney Disease, GFR =

A

> 90ml/min/1.73 elevated GFR

51
Q

Stage 2 Chronic Kidney Disease, GFR =

A

60-89 mild decrease in GFR

52
Q

Stage 3 Chronic Kidney Disease, GFR =

A

30-59 moderate decrease in GFR

53
Q

Stage 4 Chronic Kidney Disease, GFR =

A

15-29 severe decrease in GFR

54
Q

Stage 5 Chronic Kidney Disease, GFR =

A

Failure <15

55
Q

With increasing age, GFR

A

decreases

56
Q

Inverse relationship between plasma creatinine concentration and

A

GFR; if GFR decreases then plasma [creatinine] must increase * assuming production is constant 1.8

57
Q

if Pcreatinine increases from 1-2mg then GFR

A

must have decreased

58
Q

In mild to moderate renal insufficiency, creatinine

A

is a poor predictor of GFR because as plasma [creatinine] increases section of creatinine increases

59
Q

plasma creatinine predicts GFR when?

A

when kidney’s are functioning or when there is severe renal insufficiency (saturated creatinine tubular transporters); for the mild and moderate insufficiency secretion of creatinine overestimates GFR

60
Q

What substance is cleared by the kidneys in one pass through?

A

PAH; kidney has HUGE ability to SECRETE PAH without saturation

61
Q

How can PAH be used to measure RPF

A

Since PAH is cleared in one pass through, a bolus of PAH will all be excretion (secretion) = entry of RPF

62
Q

Filtration Fraction

A

GFR/RPF – the portion of plasma that is filtered

63
Q

Higher filtration fraction =

A

greater fraction of plasma that is filtrated

64
Q

If a solute has a clearance > GFR than

A

that substance is also secreted

65
Q

If a solute has a GFR > clearance than

A

that substance must also be reabsorbed

66
Q

A substance CANNOT have a clearance > than

A

RPF

67
Q

How does protein-binding effect the filtration of a substance?

A

DECREASES FILTRATION; If a drug or hormone is protein bound than that substance CANNOT be filtered. If it is partially bound, than the fraction of bound to unbound will determine its filtration rate

Renal Physio (8 decks)

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