RP3: Glomerular Filtration, Renal Blood Flow and Their Control

Question 1

What is the filtration fraction?

Answer 1

Filtration Fraction = GFR/RPF

RPF - renal plasma flow

Question 2

Blood in Glomerular Capillaries separated from Bowman’s Space by a…

Answer 2

Filtration Barrier

Question 3

What are the three layers of the filtration barrier?

Answer 3

1. Capillary endothelium (Fenestrated)
2. Basal Lamina (Basement Membrane)
3. Podocytes (Visceral Layer of Bowman’s Capsule)
   - Foot processes that cover outside of basal lamina
   - Creates Filtration Slits

Question 4

What determines the ability of a solute to penetrate the golmerular membrane?

Answer 4

• size (smaller filter better)
• charge (cations filter better)

Question 5

What is GFR usually high?

Answer 5

high hydrostatic pressure
high Kf

Question 6

What is the equation for GFR?

Answer 6

GFR = Kf x NFP (Net Filtration Pressure)

Question 7

What is the usual values for starlings forces in the glomerular membrane?

Answer 7

glomerular hydrostatic pressure (Pg) = 60 mmHg

bowman’s capsule pressure (Pb) = 18 mmHg

glomerular oncontic pressure (Ng) = 32

Question 8

What is the usual net filtration pressure (NFP)?

Answer 8

10 mmHg
125 mL/min
180 L/day

Question 9

What is Kf?

Answer 9

the glomerular capillary filtration coefficient (Kf)

Kf = hydraulic conductivity x surface area

Question 10

What is the primary control point for GFR?

Answer 10

glomerular hydrostatic pressure (Pg)

Question 11

What are factors that influence glomerular hydrostatic pressure (Pg)?

Answer 11

• arterial pressure (effect is buffered by autoregulation)
• afferent arteriolar resistance
• efferent arteriolar resistance

Question 12

What are diseases that can affect GFR via bowman’s capsule pressure (Pb)?

Answer 12

• Tubular Obstruction
  (kidney stones, tubular necrosis)
• Urinary tract obstruction
  (prostate hypertrophy/cancer)

Question 13

GFR _________ along length of capillary.

Answer 13

decreases

Question 14

Glomerular Capillary Colloid Osmotic Pressure (πG) ________ along length of glomerular capillary

Answer 14

Increases

Question 15

Hydrostatic Pressure in Glomerular capillaries (Pg) can be altered by
altering the resistance of the…

Answer 15

afferent and efferent arterioles

Question 16

Constricting the afferent arteriole ______ GFR via Pg

Answer 16

decreases

Question 17

Constricting the efferent arteriole ______ GFR via Pg

Answer 17

increases

Question 18

Dilating the efferent arteriole ______ GFR via Pg

Answer 18

decreases

Question 19

Dilating the afferent arteriole ______ GFR via Pg

Answer 19

increases

Question 20

What diseases causes a decrease in Kf?

Answer 20

Renal disease
diabetes mellitus
hypertension

all have decreased GFR

Question 21

What diseases cause increased Pb?

Answer 21

urinary tract obstruction

decreased GFR

Question 22

What diseases cause increased πG?

Answer 22

increased plasma proteins
dehydration

decreased GFR

Question 23

What is the function of myogenic autoregulation?

Answer 23

Keeps RBF and GFR relatively constant in spite of changes in MAP

Question 24

What is the reflex associated with myogenic autoregulation?

Answer 24

vessel constriction in response to increased MAP

Question 25

What is the function of tubuloglomerular feedback (TGF)?

Answer 25

Helps ensure a nearly constant delivery of Na+ and Cl- to the distal nephron – Keeps GFR constant

Question 26

What regulatory method is the juxtaglomerular apparatus associated with?

Answer 26

Tubuloglomerular Feedback (TGF)

Question 27

What are the two cells of the juxtaglomerular apparatus?

Answer 27

Juxtaglomerular cells
Macula densa cells

Question 28

What do the juxtaglomerular cells do?

Answer 28

• Primarily in walls of afferent
  arterioles
• Secrete Renin

Question 29

What cells secrete renin?

Answer 29

juxtaglomerular cells

Question 30

What do the macula densa cells do?

Answer 30

➢ In close contact with JG cells
➢ Sense [Na+] and [Cl-] in filtrate

Question 31

What are the stimuli for renin release?

Answer 31

• decreased blood pressure
• decreased renal blood flow
• decreased NaCl delivery to macula densa

Question 32

What can increase proximal NaCl reabsorption?

Answer 32

• macula densa
• increased amino acids
• increased glucose

Question 33

What paracrines/autocrines are vasoconstrictors at the local control level?

Answer 33

endothelin
dopamine (kinda)

Question 34

What paracrines/autocrines are vasodilators at the local control level?

Answer 34

prostaglandins
NO
bradykinin
dopamine (kinda)

Question 35

What are vasoconstrictors at the systemic level?

Answer 35

sympathetic nervous system
epinephrine
Renin-angiotensin system
ANP for efferent

Question 36

What are vasodilators at the systemic level?

Answer 36

ANP for afferent

Question 37

What is Epi/NE effect on renal blood flow and GFR?

Answer 37

decrease both

Question 38

What is endothelins effect on renal blood flow and GFR?

Answer 38

decrease both

Question 39

What is angiotensin IIs effect on renal blood flow and GFR?

Answer 39

decrease renal blood flow
increase GFR

Question 40

What is ANP, PGE, bradykinin, and NO’s effect on renal blood flow and GFR?

Answer 40

increase both for all of them

Question 41

What are some other factors that increase GFR and RBF?

Answer 41

• high protein diet
• high blood glucose levels

Both of these increase GFR and result in reduced NaCl delivery to macula densa.

Question 42

What is the filtered load equation?

Answer 42

Fx = (GFR) ([X]plasma)

Question 43

What is the excretion rate equation?

Answer 43

Ex = (Uv)([X]urine)

Question 44

What is the clearance rate equation?

Answer 44

Clx = Ex/[X]plasma

➢ Clinulin and Clcreatinine used as index of GFR
➢ ClPAH used as index of RBF (Renal Blood Flow)