Glomerular Filtration

Question 1

what types of molecules are excluded from the glomerular filtration barrier?

Answer 1

large, negatively charged things

Question 2

what does “perm selectivity” mean?

Answer 2

size and charge selective

Question 3

what are characteristics of the glomerular capillaries?

Answer 3

• high hydrostatic pressure
• constant hydrostatic pressure
• large surface area for filtration

Question 4

what is the charge of the basement membrane?

Answer 4

negative- repels large negative things, attracts positive things

Question 5

what are the proteins in the filtration slit?

Answer 5

nephrin

podocin

Question 6

what does nephrin do?

Answer 6

filtration slit protein

extracellular, linked to podocin inside foot process

Question 7

what does podocin do?

Answer 7

filtration slit protein

inside foot processes, connects to nephrin and signals EC events

Question 8

what does damage to the filtration slit do?

Answer 8

changes permeability

Question 9

what is the clearance ratio formula?

Answer 9

Cx/Cinulin

Question 10

why is inulin special?

Answer 10

inulin is freely filtered

anything larger than inulin is not filtered

Question 11

what properties of a molecule will change its clearance ratio and how?

Answer 11

increased size –> decreases clearance ratio
increased positive charge–> increases clearance ratio
increased negative charge–>decreases clearance ratio a lot

Question 12

what is serum nephritis?

Answer 12

increased anion filtration due to loss of negative charge at filtration barrier

Question 13

what is the starling formula for glomerular filtration?

Answer 13

GFR = Kf [(Pc-Pbs) - COPx]
Kf- glomerular filtration constant (surface area and permeability)
Pc-Pbs- transmural hydrostatic pressure
COP- colloidal protein osmotic pressure

Question 14

what is the ultrafiltration pressure equation?

Answer 14

Puf = (Pc - Pbs) - COPx

always positive or 0

Question 15

how does COP change along the glomerular capillary?

Answer 15

increases (afferent < efferent)

water is removed, which concentrates the remaining solutes

Question 16

how does the ultrafiltration pressure change along the length of the capillary?

Answer 16

decreases because COP increases

Question 17

when is the glomerular filtration in equilibrium?

Answer 17

COP = hydrostatic pressure

Question 18

what is normal GFR?

Answer 18

100-120ml/min (180L/day)

Question 19

what happens at filtration equilibrium?

Answer 19

no reabsorption

Question 20

what does glomerular filtration depend on?

Answer 20

blood flow and pressure gradient

Question 21

how does filtration fraction vary with renal plasma flow?

Answer 21

normal 15-20%
low- 20%
high <15%

Question 22

what is the effect of decreasing arteriolar resistance?

Answer 22

increases renal plasma flow, glomerular pressure, and GFR

Question 23

what is the effect of increasing arteriolar resistance?

Answer 23

decreases RPF, glomerular pressure, and GFR

Question 24

what controls renal blood flow?

Answer 24

sum of afferent and efferent resistances

Question 25

what controls glomerular capillary pressure?

Answer 25

relative resistances of the afferent and efferent arterioles

Question 26

what is the most important regulator of RPF and GFR?

Answer 26

afferent arteriole resistance

Question 27

what is the effect of decreasing efferent arteriole resistance?

Answer 27

increases RPF

decreases glomerular capillary pressure and GFR

Question 28

what is the effect of increasing efferent arteriole resistance?

Answer 28

decreases RPF
increases glomerular capillary pressure
decreases GFR with large change, increase with small

Question 29

where does angiotension II preferentially act? what does it do?

Answer 29

constricts the efferent arterioles

Question 30

what do changes in GFR affect?

Answer 30

Na excretion

- water excretion is affected by tubular water reabsorption

Question 31

what are extrinsic controllers that result in decreased GFR?

Answer 31

sympathetic nerves- adrenergic and catacholamines
antiotension II
vasopressin (ADH)
endothelin, thromboxane
dehydration, hemorrhage

Question 32

what are extrinsic controllers that result in increased GFR?

Answer 32

ANP, dopaminergic nerves, NO
prostaglandins
high dietary proteins, pregnancy