Glomerular Filtration I

Question 1

What happens if the body does not filter enough plasma

Answer 1

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

Question 2

Glomerular filtration is governed by

Answer 2

Starling Forces

Question 3

Glomerular Capillary Pressure (Pc)

Answer 3

largely determines the glomerular filtration rate (GFR)

Question 4

Glomerular Capillary Pressure (Pc) is largely determined by

Answer 4

arterial BP and afferent and efferent arteriolar resistances

Question 5

What regulates the afferent and efferent arteriolar resistances?

Answer 5

Hormones and SNS

Question 6

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

Answer 6

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

Question 7

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

Answer 7

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

Question 8

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

Answer 8

increased GFR

Question 9

The thick ascending limb is _________ to water

Answer 9

impermeable

Question 10

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

Answer 10

presence of ADH

Question 11

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

Answer 11

waters concentration gradient

Question 12

Na reabsorption drives the reabsorption of

Answer 12

H2O, HCO3, glucose, aa

Question 13

Na reabsorption drives the secretion of

Answer 13

H+

Question 14

Na/K ATPase drives the reabsorption of other solutes by

Answer 14

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

Question 15

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

Answer 15

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

Question 16

If the plasma osmolality moves away from its set point then

Answer 16

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

Question 17

Dilution of the urine is dependent on 2 factors

Answer 17

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

Question 18

Concentration of the urine is dependent on 2 factors

Answer 18

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

Question 19

What determines the osmolality of the ECF

Answer 19

Na, Cl, and HCO3

Question 20

Eating salty food (increased Na intake)

Answer 20

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

Question 21

ECF osmolality is corrected for at the expense of

Answer 21

ECF volume

Question 22

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

Answer 22

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

Question 23

What signals determine the kidneys Na and water reabsorption

Answer 23

BP, neural mechanisms, and hormonal mechanisms

Question 24

Pressure-Naturiesis

Answer 24

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

Question 25

How does chronic BP effect pressure-naturiesis

Answer 25

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

Question 26

Na content regulated

Answer 26

ECF volume

Question 27

Body water content regulates

Answer 27

plasma osmolarity

Question 28

SNGFR

Answer 28

single nephron glomerular filtration rate

Question 29

GFR

Answer 29

sum of all the SNGFR for the 2 kidneys

Question 30

GFR =

Answer 30

Kf x [(Pgc-Pbs) - (Πgc - Πbs)]

Question 31

Oncotic pressure of Bowman's Space Πbs =

Answer 31

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

Question 32

Permeability of the glomerular capillaries is

Answer 32

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

Question 33

Renal Clearance

Answer 33

amount of solute excreted/ concentration of solute in plasma

Question 34

Input must equal output

Answer 34

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

Question 35

How to measure excretion of solute

Answer 35

urine concentration of solute x urine flow rate

Question 36

Clearance of a solute (Cx) =

Answer 36

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

Question 37

Definition of clearance

Answer 37

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

Question 38

Clearance of a substance is typically ______ than renal plasma flow

Answer 38

LESS; because most solutes are reabsorbed

Question 39

Clearance can estimate

Answer 39

GFR and renal plasma flow (RPF)

Question 40

Clearance determines

Answer 40

net reabsorption or net or secretion of a filtered substance

Question 41

GRF can be determined by clearance IF

Answer 41

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

Question 42

Filtered load =

Answer 42

GFR x plasma concentration of solute

Question 43

Excretion =

Answer 43

Urine conc of solute x urine flow rate

Question 44

What substances can be used then to estimate GFR?

Answer 44

Inulin, I-iothalamate, creatinine, Iohexol, Iothalamate

Question 45

Inulin for GFR estimation

Answer 45

inulin (fructose polymer) infused via IV, gold standard

Question 46

I-iothalamate for GFR estimation

Answer 46

can predict GFR via plasma clearance alone

Question 47

Creatinine for GFR estimation

Answer 47

ESTIMATES GFR (some is secreted)

Question 48

Plasma clearance used for GFR measurement

Answer 48

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

Question 49

For chronic kidney disease, creatinine clearance _______ GFR

Answer 49

OVERESTIMATES; more is SECRETED due to higher serum levels

Question 50

Stage 1 Chronic Kidney Disease, GFR =

Answer 50

>90ml/min/1.73 elevated GFR

Question 51

Stage 2 Chronic Kidney Disease, GFR =

Answer 51

60-89 mild decrease in GFR

Question 52

Stage 3 Chronic Kidney Disease, GFR =

Answer 52

30-59 moderate decrease in GFR

Question 53

Stage 4 Chronic Kidney Disease, GFR =

Answer 53

15-29 severe decrease in GFR

Question 54

Stage 5 Chronic Kidney Disease, GFR =

Answer 54

Failure <15

Question 55

With increasing age, GFR

Answer 55

decreases

Question 56

Inverse relationship between plasma creatinine concentration and

Answer 56

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

Question 57

if Pcreatinine increases from 1-2mg then GFR

Answer 57

must have decreased

Question 58

In mild to moderate renal insufficiency, creatinine

Answer 58

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

Question 59

plasma creatinine predicts GFR when?

Answer 59

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

Question 60

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

Answer 60

PAH; kidney has HUGE ability to SECRETE PAH without saturation

Question 61

How can PAH be used to measure RPF

Answer 61

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

Question 62

Filtration Fraction

Answer 62

GFR/RPF -- the portion of plasma that is filtered

Question 63

Higher filtration fraction =

Answer 63

greater fraction of plasma that is filtrated

Question 64

If a solute has a clearance > GFR than

Answer 64

that substance is also secreted

Question 65

If a solute has a GFR > clearance than

Answer 65

that substance must also be reabsorbed

Question 66

A substance CANNOT have a clearance > than

Answer 66

RPF

Question 67

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

Answer 67

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