Lecture 5

Question 1

To measure GRR, what features do you want in a substance?

Answer 1

Not secreted
Not reabsorbed
Not synthesized or metabolized

Question 2

How is GFR calculated using concentration of substance in urine and plasma?

Answer 2

GFR = urine flow * urine concentration/plasma concentration

Question 3

True or False: Glomerular filtration declines with age

Answer 3

True

Question 4

What are three reasons why glomerular filtration declines with age?

Answer 4

1) less renal blood flow
2) loss of sulfonation (negative charge) on basement membrane
3) elevated glomerular hydrostatic pressure due to injury

Question 5

How does a decline in renal blood flow after ROS and NO production, as wells as afferent arteriola

Answer 5

If you have less renal blood flow, you have greater production of ROS and less NO production. NO preferentially acts on the afferent arteriole. Therefore you will get vasoconstriction of afferent arteriole.

Question 6

How does kidney injury affect glomerular hydrostatic pressure, Kf, and filtration?

Answer 6

Kidney injury results in inappropriate elevation of glomerular hydrostatic pressure, which leads to glomerular sclerosis. Sclerosis can decreased the Kf and reduce SA for filtration.

Question 7

How do you calculate filtration fraction?

Answer 7

Filtration fraction = GFR / RPF (renal plasma flow)

%

Note PAH is used to calculate RPF
PFR = 600 ml/mL

Question 8

_____: rate of removal or clearing of substances from blood

Answer 8

Clearance

Question 9

If 100% of substance enters the tubules and 100% is excreted what is the clearance (%)?

Answer 9

100%

Question 10

True or False: PAH has a 100% clearance

Answer 10

True

Question 11

Under what conditions can can clearance of a substance be used to measure GFR?

Answer 11

1) substance cannot be made or metabolized by kidneys
2) substance is freely filtered
3) neither secreted nor reabsorbed