Glomerular Filtration and Renal Clearance

Question 1

What is the selectively of the filtration barrier determined by?

Answer 1

Molecular size of intravascular components
Electrical charge of filtration barrier components (all negative)

Question 2

What is the capillary endothelium filled with?

Answer 2

Negatively charged glycoprotein

Question 3

What is the basement membrane made up of?

Answer 3

Collagen, proteoglycans
Physical barrier, electrostatic repulsion

Question 4

What is the key selective barrier in filtration?

Answer 4

Filtration silts

Question 5

What is the composition of the ultra-filtrate?

Answer 5

Most ions and low molecular weight components
Exclusion of larger plasma proteins
Positively charged marcomolecules

Question 6

What is typical renal blood flow?

Answer 6

20% of total CO

Question 7

What is typical renal plasma flow?

Answer 7

605ml/min

Question 8

What is typical GFR?

Answer 8

125ml/min

Question 9

What is the average excretion rate?

Answer 9

1ml/min

Question 10

What does GFR equal to?

Answer 10

Kf x NFP

Question 11

What is the filtered load?

Answer 11

Total amount of any substance freely filtered from renal glomerular capillaries into Bowman’s space
calculated by GFR x [X] in plasma

Question 12

How can GFR be altered?

Answer 12

Constriction and dilation of AA and EA

Question 13

What does a rise in blood pressure cause in relation to GFR?

Answer 13

Increased excretion of salt and water

Question 14

How do kidneys regulate their blood flow?

Answer 14

Adjusting vascular resistance in response to changes in arterial pressure

Question 15

What is normal blood pressure?

Answer 15

90mmHg

Question 16

What are 2 mechanisms responsible for regulation of RBF and GFR?

Answer 16

Myogenic mechanism
Tubuloglomerular feedback
Regulate tone of AA

Question 17

Describe the myogenic mechanism.

Answer 17

Vascular smooth muscle contracts when stretched
Fast acting - protects from short-term fluctuations in blood pressure

Question 18

Describe the tubuloglomerular feedback.

Answer 18

Macula densa cells act as salt sensors
High levels of Na+ -> decrease in GFR by AA constriction

Question 19

What uptakes NaCl across macula densa cells?

Answer 19

NKCC2 channel -> increased ATP and adenosine

Question 20

What does ATP and adenosine bind to on AA?

Answer 20

ATP - P2X receptors
ADO - adensoine A1 receptors

Question 21

What does receptor binding lead to?

Answer 21

Increase in Ca2+ -> vasoconstriction of AA -> GFR decreases

Question 22

What 2 neurotransmitters causes vasoconstriction?

Answer 22

Norepinephrine and epinephrine bind to alpha 1 adrenoreceptors

Question 23

What 2 vasoactive factors cause vasoconstriction?

Answer 23

Angiotensin 2
Endothelin

Question 24

What 2 vasoactive factors cause vasodilation?

Answer 24

Nitric Oxide
Prostaglandins

Question 25

What is renal clearance?

Answer 25

Volume of plasma from which that substance is completely removed by kidneys per unit time

Question 26

What is the equation for clearance (mL/min)?

Answer 26

(urine conc. of X)(mg/mL) x (urine volume per unit time)(mL/min) / Plasma conc. of X mg?mL

Question 27

How is PAH cleared?

Answer 27

Freely filtered, not reabsorbed, fully secreted
Clearance = renal plasma flow (605ml/min)

Question 28

How is Inulin cleared?

Answer 28

Freely filtered, not reabsorbed, secreted, synthesized or metabolized
Clearance = GFR (125ml/min)

Question 29

How are glucose and AA cleared?

Answer 29

Freely filtered, fully reabsorbed, not scereted
Clearance = 0ml/min

Question 30

Which substance’s clearance is used for routine GFR assessment?

Answer 30

Creatinine

Question 31

How is creatinine cleared?

Answer 31

Freely filtered, not reabsorbed but small amount secreted by proximal tubule

Question 32

What measurement is more common to use as an indicator of GFR?

Answer 32

Plasma creatinine

Question 33

What is a strong indicator of renal disease?

Answer 33

Rising plasma creatinine