GFR/RBF

Question 1

PGC
PBC
piGC
piBC
And how much pressure exists from these forces?

Answer 1

Out of capillary into BC. (60)
Out of BC into the capillary. (18)
Out of BC into the capillary. (32)
Out of the capillary into the BC. (0)

Question 2

Net filtration pressure =

Answer 2

PGC - PGC - piGC

Question 3

What 3 factors contribute to GFR?

Answer 3

1. Hydraulic conductivity (permeability of the fenestrated epithelium). (Lp)
2. Surface area for filtration. (Sf)
3. Capillary ultrafiltration pressure. (PUF)
   GFR is the product of these 3 factors.

Question 4

What is the main way to alter PUF?

How can you do that? (3)

Answer 4

Changing PGC.

Adjust renal arterial BP.
Afferent arteriolar resistance
Efferent arteriolar resistance

Question 5

Ultrafiltration coefficient (Kf) =

Answer 5

Lp x Sf

hydraulic conductivity x surface area

Question 6

What 2 sites in the renal vasculature are regulated? Why?

Answer 6

At the afferent and efferent arterioles, because there is the greatest change in hydrostatic pressures there.

Question 7

How does the PGC and piGC change from the afferent arteriole to the efferent arteriole?

Answer 7

PGC goes down slightly as filtrate leaves the vasculature. As a result, the piGC increases due to an increase in plasma protein conc.

Question 8

What happens to PGC, RBF and GFR when only the AFFERENT arteriole is constricted?

Answer 8

All 3 decrease. Less blood is perfusing the glomerulus (RBF), so GFR goes down, and therefore PGC is reduced.

Question 9

What happens to PGC, RBF and GFR if only the EFFERENT arteriole is constricted?

Answer 9

PGC increases because of buildup of blood in the glomerulus. RBF decreases because less blood can leave the efferent arteriole. GFR increases initially with PGC, but then goes down as RBF dominates.

Question 10

As compared to the brain on a per-gram basis, how much O2 do the kidneys use? How much blood flow?

Answer 10

Consume O2 at 2x the rate.

7x the amount of BF.

Question 11

O2 consumption is related to:

Answer 11

The high rate of Na reabsorption in the tubules.

Question 12

What sympathetic receptor is on renal vasculature? How is it distributed between afferent and efferent arterioles?

Answer 12

a1

More a1 on the afferent than the efferent arteriole.

Question 13

Common vasoconstrictors (3):

Answer 13

Sympathetic nerves (catecholamines)
Angiotensin II
Endothelin

Question 14

Common vasodilators (6):

Answer 14

PGE2, PGI 1, NO, Bradykinin, DA, ANP

Question 15

Glomerular balance

Answer 15

Adjusts reabsorption rate within the renal tubules when GFR changes.
GFR inc, RR inc.

Question 16

Link between filtered load and GFR

Answer 16

Direct relationship. The higher the GFR, the more normally filtered substances (Glc, AA, etc) are filtered (filtered load).

Question 17

Autoregulation goal

Answer 17

Maintain RBF and GFR within narrow limits across wide ranges of BPs.

Question 18

What 2 forces can increase resistance in renal vasculature?

Answer 18

Myogenic reflex (local reflex)
Juxtaglomerular apparatus (tubuloglomerular feedback) as a physiological feedback.

Question 19

What is the autoregulatory range?

Answer 19

80-170 mmhg

Question 20

Local myogenic feedback reflex mechanism

Answer 20

BVs resist stretch during times of increased BP (increases resistance).
SM contraction and Ca signaling)
Afferent arteriolar constriction, efferent arteriole dilation.

Question 21

Juxtaglomerular apparatus contains (3)

Answer 21

Macula densa cells
JG cells
Extraglomerular mesangial cells

Question 22

Tubuloglomerular feedback mechanism (5)

Answer 22

Senses tubular NaCl conc.
Feeds back signal to adjust arteriolar resistance as needed.
Signals between macula densa cells and JG cells.
Maintains constant Na+ delivery to the DCT and constant GFR.
Releases renin.

Question 23

Macula densa signaling during increased renal perfusion (4)

Answer 23

Increased delivery of NaCl to JG apparatus.
Increased ATP/adenosine
Vasoconstriction of the afferent arteriole (Ca signaling)
Decreased GFR

Question 24

Macula densa signaling during decreased renal perfusion (3)

Answer 24

Macula densa signals to JG cells to secrete renin.

Results in efferent arteriolar vasoconstriction AND afferent arteriolar dilation, via NO.

Question 25

Vasodilation of the afferent arteriole's effect on: RBF, GFR, peritubular capillary hydrostatic pressure
PGs
Bradykinin
NO
DA
ANP

Answer 25

Increase
Increase
Increase

Question 26

Vasoconstriction of the afferent arteriole’s effect on: RBF, GFR, peritubular capillary hydrostatic pressure
ACE inhibitors

Answer 26

Decrease
Decrease
Decrease

Question 27

Vasodilation of the efferent arteriole’s effect on: RBF, GFR, peritubular capillary hydrostatic pressure
Sympathetics

Answer 27

Increase
Decrease
Increase

Question 28

Vasodilation of the efferent arteriole’s effect on: RBF, GFR, peritubular capillary hydrostatic pressure
Angiotensin II

Answer 28

Decrease
Increase/no change
Decrease