Physiology

Question 1

What substances are used to calculate GFR? Which is more accurate?

Answer 1

Inulin and creatinine. Inulin is more accurate.

Question 2

What substance is used to calculate renal plasma flow (RPF)?

Answer 2

Para-aminohuppuric acid (PAH)

Question 3

Describe the filtration of PAH.

Answer 3

PAH completely filtered at the nephron: freely filtered at the glomerulus (~20%) and the rest is secreted into the tubules (~80%). Thus the urinary excretion of PAH = RPF.

Question 4

Describe the filtration of inulin.

Answer 4

Inulin is freely filtered at the glomerulus, and neither secreted nor absorbed at the tubules. Thus, it can be used to estimate GFR.

Question 5

What is the volume of intracellular water in a 70 kg man? ECF?

Answer 5

28 L, 12 L

Question 6

Volume of interstitial fluid in a 70 kg man?

Answer 6

9 L

Question 7

Volume of plasma in a 70 kg man?

Answer 7

3 L

Question 8

Clearance =

Answer 8

(urine conc/plasma conc) * urine flow rate

Question 9

GFR = (w/ relation to inulin)

Answer 9

(Uinulin/Pinulin) * V

Question 10

What does an increase in BUN indicate?

Answer 10

Decrease in GFR.

Question 11

What is a normal BUN:creatinine ratio?

Answer 11

10:1

Question 12

What does a BUN:creatinine ratio above 20:1 indicate?

Answer 12

Prerenal azotemia (not renal failure)

Question 13

If both BUN and serum creatinine are increased at a ratio of 10:1, where is the problem?

Answer 13

Renal (kidney failure)

Question 14

GFR = (w/ relation to glomerular pressures)

Answer 14

Kf [(Pgc-Pbs) - (πgc-πbs)

Question 15

ERPF = (w/ regard to PAH)

Answer 15

(Upah/Ppah) * V

Question 16

RBF =

Answer 16

RPF/(1-hematocrit)

Question 17

What is the effect of prostaglandins on GFR? RPF? FF?

Answer 17

GFR and RPF up

FF normal

Question 18

PGs’ site of action on the glomerulus?

Answer 18

dilate afferent arteriole

Question 19

Effect of NSAIDs on GFR? RPF? FF?

FF is filtration fraction

Answer 19

GFR and RPF down

FF normal

Question 20

Where is the site of action of Ang II on the glomerulus?

Answer 20

constricts efferent arteriole

Question 21

Effects of Ang II on GFR? RPF? FF?

Answer 21

GFR up
RPF down
FF up

Question 22

At what plasma concentration of glucose does some begin to appear in the urine?

Answer 22

160-200 mg/dL

Question 23

At what plasma glucose concentraion are all renal tubular glucose transporters occupied (Tm)?

Answer 23

350 mg/dL

Question 24

What kind of transporter reabsorbs glucose that is filtered into the Bowman’s capsule? Where is this transporter located?

Answer 24

Na+/glucose cotransporter in the proximal tubule

Question 25

Why must you alkalinize the urine to excrete more of an acidic substance such as sialycylic acid?

Answer 25

The unprotonated, charged form will not back-diffuse from urine into blood.

Question 26

What are the 3 main Sx of pellagra?

Answer 26

Diarrhea, dermatitis, dementia

Question 27

Diagram pathogenesis of Hartnup’s disease.

Answer 27

deficient neutral aa transporter in proximal tubule -> Trp excreted in urine -> niacin (B3) can’t be formed -> pellagra

Question 28

How is Hartnup’s disease different in etiology from Fanconi’s syndrome?

Answer 28

Hartnup’s disease is the deficiency of only one transporter. Fanconi’s syndrome affects the transport of many substances in the proximal tubule.