Blood Flow/GFR (lec 9)

Question 1

Renal blood flow (RBF) = how much of CO?

Why?

Answer 1

1/4

Filters plasma (20%)

Question 2

RBF: Filtration Fraction eqn?

Answer 2

GFR/RPF

GFR = Glomerular Filtration Rate
RPF = Renal Plasma Flow

Question 3

RBF normal value?

Answer 3

1.1 L/min

Question 4

RPF eqn?

Answer 4

Renal Plasma Flow

= (1-Hct)RBF

e.g. (1-.45)1.1L/min = 605 ml/min

Question 5

Regulation of RBF: Vasoconstrictors

Affect which type of nerve?

Results in?

Answer 5

SNS: α1 receptors

↓ RBF, GFR

Question 6

Regulation of RBF: Vasoconstrictors

Which hormones/chemicals?

Answer 6

Ang II, ADH, ATP, endothelin

Question 7

Ang II constricts which arterioles?

Answer 7

BOTH eff and aff

eff > aff

Question 8

Regulation of RBF: Vasodilators

Result in?

Answer 8

↑ RBF, GFR

Question 9

Regulation of RBF: Vasodilators

Which hormones/chemicals?

Answer 9

Atrial Natriuretic Peptide (ANP)
Glucocorticoids
NO
Prostaglandins (PGE2, PGI2)

Question 10

Autoregulation keeps RBF/GFR within what range?

Can be overridden by what?

Answer 10

80-180 mmHg (keeps BF constant w/i this range of pressure Δs)

large ↑ in symp tone

Question 11

Severe blood loss affects RBF/GFR how?

Answer 11

↓

Question 12

Mechanisms of autoregulation?

Answer 12

1) Myogenic: contracts in response to stretch

2) Tubuloglomerular feedback:flow-dependent

Question 13

Tubuloglomerular feedback mechanism?

Answer 13

↑ GFR -> ↑ NaCl to LOH ->
macula densa responds ->
↑ aff arteriole resistance ->
↓ RBF/GFR

Question 14

Glomerular Filtration: components of filtrate?

Answer 14

non-protein-bound, small MW molecules

same [ ] as in plasma

Question 15

Substances in filtrate separated by?

Answer 15

size, electrical charge

Question 16

Route of filtration?

Answer 16

fenestrae ->
basal lamina (- charge) ->
filtration slits (- charge)

Question 17

Neg charge of basal lamina and slits do what?

Answer 17

repel proteins

Question 18

GFR eqn?

Answer 18

Kf [(Pgc - Pbc) - (πgc - πbc)]

or

Kf x NFP

NFP = net filtration pressure

Question 19

Kf is?

Range?

Answer 19

filtration coeff

7-15

Question 20

Kf ↓ by what?

Answer 20

mesangial cells

Question 21

Pgc is?

Answer 21

BP in glomerular capillary (glom-capillary hydrostatic pressure)

Driving force for GFR

Question 22

Pbc is?

Answer 22

Back pressure in Bowman’s Capsule

↓ GFR

Question 23

πgc is?

Answer 23

oncotic pressure of glom capillary blood

caused by protein in plasm vs no protein in filtrate

Question 24

πgc affects GFR how?

Answer 24

↓ GFR

Question 25

What happens to πgc as plasma enters BC?

Answer 25

↑

Question 26

πbc is?

Answer 26

oncotic pressure in BC

(U) zero

Question 27

Net Filtration Pressure (NFP) eqn?

Answer 27

(Pgc + πbc) - (Pbc + πgc)

Question 28

Pbc calculated how?

Answer 28

Aff Pgc - Aff πgc
or
Eff Pgc - Eff πgc

Question 29

Typical average pressure of:

Pgc?

πgc?

Pbc?

πbc?

Kf?

Answer 29

Pgc = 45

πgc = 26

Pbc = 10

πbc = 0

Kf = 14

Question 30

Typical value of:

NFP?

GFR?

Answer 30

NFP = 9

GFR = 126

Question 31

↑ aff and ↑ eff resistance affects Pgc and RFB how?

Answer 31

φ Pgc

↓↓ RBF

Question 32

↑ aff resistance affects Pgc and RFB how?

Answer 32

↓ Pgc

↓ RBF

Question 33

↑ eff resistance affects Pgc and RFB how?

Answer 33

↑ Pgc

↓ RBF