RBF and GFR

Question 1

3 layers of glomerular capillary filtration barrier

Answer 1

Podocytes
Basement membrane
Endothelium

Question 2

______ is associated with endothelial surface layer of glomerular cap filtration barrier and is negatively charged, so it has ability to regulate filtration based on size AND charge

Answer 2

Glycocalyx

Question 3

Origin of Tamm-Horsfall proteins

Answer 3

Produced by thick ascending limb of LOH

[presence in urine is normal]

Question 4

How is ultrafiltration coefficient (Kf) calculated?

Answer 4

Kf = hydraulic conductivity L(p) x surface area S(f)

[L(p) = permeability]

Question 5

What forces favor vs. oppose filtration at the glomerulus?

Answer 5

Favoring filtration:
Glomerular hydrostatic pressure P(GC)
Bowman’s capsule oncotic pressure pi(BC) = normally 0

Opposing filtration:
Bowman’s capsule hydrostatic pressure P(BC)
Glomerular capillary oncotic pressure pi(GC)

Question 6

Difference between glomerulotubular balance vs. tubuloglomerular feedback

Answer 6

Balance = changing reabsorption rate in tubular environment based on fluctuations in GFR

Feedback = maintaining RBF and GFR in the face of changing tubular contents

Question 7

What are the 3 components of the JG apparatus

Answer 7

Macula densa cells

JG granular cells

Extraglomerular mesangial cells

Question 8

Tubuloglomerular feedback mechanism

Answer 8

Macula dense senses tubular [NaCl]

Feeds back signal to adjust arteriolar resistance as needed via mesangial cells

Goal is to maintain constant Na+ delivery to distal tubule and constant GFR

Renin release

Question 9

Macula densa signaling in response to increased NaCl as in tubuloglomerular feedback mechanism

Answer 9

Increased delivery of NaCl to macula densa

Increased ATP/adenosine

Vasoconstricts afferent arteriole (Ca signaling)

Decreased GFR

Question 10

How would macula densa respond to increased renal perfusion pressure

Answer 10

Signals generated by macula densa result in VASOCONSTRICTION of AFFERENT arteriole to decrease GFR (mediated by adenosine and ATP)

Question 11

How would macula densa respond to decreased renal perfusion pressure

Answer 11

With decreased perfusion pressure, GFR decreases thus decreased NaCl delivery

Macula densa signals JG granular cells to secrete renin

Renin –> angiotensin II (potent vasoconstrictor) to restore BP –> results in EFFERENT arteriolar VASOCONSTRICTION as well as afferent arteriolar dilation mediated by NO

Question 12

Which of the following would increase sensitivity to tubuloglomerular feedback?

A. Volume expansion
B. ANP
C. High-protein diet
D. PGE2
E. Nitric oxide

Answer 12

D. PGE2

The rest would decrease sensitivity to TGF

Question 13

Constriction of afferent arterioles effects on P(uf), GFR, RBF, and peritubular capillary hydrostatic pressure

Answer 13

P(uf) decreases

GFR decreases

RBF decreases

Pc decreases

Question 14

Dilation of afferent arterioles effects on P(uf), GFR, RBF, and peritubular capillary hydrostatic pressure

Answer 14

P(uf) increases

GFR increases

RBF increases

Pc increases

Question 15

Constriction of efferent arterioles effects on GFR, RBF, and peritubular capillary hydrostatic pressure

Answer 15

GFR increases or stays same

RBF decreases

Pc decreases

Question 16

Dilation of efferent arterioles effects on GFR, RBF, and peritubular capillary hydrostatic pressure

Answer 16

GFR decreases

RBF increases

Pc increases

Question 17

Chronic effects of sympathetic stim on kidneys

Answer 17

Decreased urinary output

Decreased urinary Na+ excretion

Increased water intake

Question 18

Effect of low levels of angiotensin II on GFR and RBF

Answer 18

GFR increases

RBF decreases

Question 19

Effect of high levels of angiotensin II on GFR and RBF

Answer 19

GFR decreases

RBF decreases

Question 20

Effect of increased ANP on RBF and GFR

Answer 20

GFR increases

RBF increases (d/t vasodilation)

Question 21

Effect of decreased prostaglandin formation on GFR

Answer 21

Significant reduction in GFR due to loss of vasoconstriction buffering normally provided in afferent arteriole

Question 22

A patient with uncontrolled DM and associated large increases in blood glucose would exhibit what changes in RBF and GFR

Answer 22

RBF increases

GFR increases