Glomerular Filtration Rate

Question 1

Which two factors account for the high rate of filtration in glomerular capillaries

Answer 1

high glomerular hydrostatic pressure and large filtration coefficient

Question 2

Relationship between filtration fraction and renal plasma flow

Answer 2

The two are inversely proportional

Question 3

Equation for calculating filtration fraction

Answer 3

Filtration fraction = GFR/RPF

Question 4

What are the three components of the filtration barrier

Answer 4

endothelium of glomerular capillaries, basement membrane and epithelium of podocytes

Question 5

Heparan sulfate in the basement membrane of the filtration barrier as well as podocytes prevent passage of proteins
- Why?

Answer 5

heparan sulphate and podocytes both have negative charges, which repel the negatively charged proteins and prevent them from passing through the membrane

Question 6

Proteinemia

-what is the biological basis for this condition?

Answer 6

The basement membrane in the filtration barrier has lost its negativity which allows protein to filter through and enter urine

Question 7

Kidney stones

• increases or decreases GFR?
• how?

Answer 7

Decreases GFR

When stones lodge in the ureter, they increase the hydrostatic pressure in the Bowman’s capsule which will decrease glomerular filtration

Question 8

Increased Bowman’s capsule hydrostatic pressure _____GFR

Answer 8

decreases

Question 9

Decreased Bowman’s capsule hydrostatic pressure _____GFR

Answer 9

increases

Question 10

Increased arterial plasma colloid osmotic pressure

• increases or decreases GFR?
• how?

Answer 10

• Decreases GFR
• Increased arterial plasma colloid osmotic pressure means there is now increased protein in the glomerulus which would pull fluid into the capillary thus reducing filtration

Question 11

Increased filtration fraction

• increases or decreases GFR?
• how?

Answer 11

• decreases GFR (but initially increase)
• an increase in filtration fraction would initially cause an increase in GFR but would eventually lead to an increased protein concentration in the glomerulus then would then lead to a decrease in the GFR

Question 12

Increased renal plasma flow

• increases or decreases GFR?
• how?

Answer 12

• increases GFR
• increased renal plasma flow would cause a decrease in plasma protein concentration because of an increase in the volume of the blood, this would result in an increased GFR

Question 13

Increased Glomerular hydrostatic pressure _____ GFR

Answer 13

Increases

Question 14

Decreased Glomerular hydrostatic pressure _____ GFR

Answer 14

Decreases

Question 15

Three main factors that affect Glomerular hydrostatic pressure

Answer 15

Arterial pressure, afferent arteriolar resistance, efferent arteriolar resistance

Question 16

Increased arterial pressure

• increases or decreases GFR?
• how?

Answer 16

• increases GFR
• increased arterial pressure would increase the hydrostatic pressure in the glomerulus which would lead to an increase in GFR

Question 17

Increased afferent arteriole resistance

• increases or decreases GFR?
• how?

Answer 17

• decreases GFR
• when the afferent arteriolar resistance is increased, it reduced the blood flow into the glomerulus which would decrease pressure in the glomerulus and thus decrease GFR

Question 18

increased efferent arteriolar resistance produces a biphasic GFR response
- describe it

Answer 18

Initially, the increased efferent arteriolar resistance causes an increase in glomerular pressure which would increase GFR, however with continues resistance, it would decrease renal blood flow, which ultimately would decrease glomerular pressure and thus decrease GFR

Question 19

Why is sodium transport reduced when renal blood flow decreases

Answer 19

Blood flow to the kidneys provide oxygen for the cells. this oxygen is needed for the active transport (using ATP) of Na+

Question 20

Which renal vessels have the most resistance (in decreasing order)

Answer 20

efferent arteriole > afferent arteriole > interlobar arteries

Question 21

How does sympathetics affect GFR

-what is the mechanism?

Answer 21

Decreases GFR by causing vasoconstriction

Question 22

How does Norepinephrine, Epinephrine and Endothelin affect GFR
-what is the mechanism?

Answer 22

Decreases GFR by causing vasoconstriction

Question 23

How does prostaglandins and bradyinin affect GFR

-what is the mechanism?

Answer 23

Increases GFR by decreasing constricting effects

Question 24

How does Angiotensin II affect GFR

-what is the mechanism?

Answer 24

Increases GFR by causing vasoconstricting efferent arterioles

Question 25

How does nitric oxide affect GFR | -what is the mechanism?

Answer 25

Increases GFR by causing vasodilation

Question 26

Decreased flow rate causes _____ absorption of NaCl

Answer 26

increased absorption in NaCl

Question 27

How does the macula densa help in autoregulation?

Answer 27

When the macula densa cells sense a decrease in NaCl, it results in a decreased resistance to blood flow in the afferent arteriole which increases glomerular pressure. It also causes renin release from the juxtaglomerular cells which will ultimately make angiotensin II and constrict efferent arterioles to increase GFR

Question 28

Define filtration

Answer 28

movement of molecules from the glomerulus into the Bowman’s capsule.

Question 29

Define reabsorption

Answer 29

movement of molecules from the lumen of the renal tubule into the peritubular capillaries.

Question 30

Define secretion

Answer 30

movement of molecules from the peritubular capillaries into the lumen of renal tubule.

Question 31

Excretion

Answer 31

removal of substances in the urine.

Question 32

What does the "portal system" in the renal system consist of

Answer 32

The glomerulus and the peritubular capillaries

Question 33

By which two methods does the kidney do autoregulation?

Answer 33

Myogenic response and tubuloglomerular feedback

Question 34

In the tubuloglomerular feedback mechanism, macula densa cells send signals to ______ which causes the ______ arteriole to constrict

Answer 34

- Granular cells | - afferent

Question 35

Which cells are responsible for detecting increased/decreased flow to initiate the tubuloglomerular feedback

Answer 35

Macula densa cells

Question 36

What effects does Atrial Natriuretic Peptide have on the glomerular arterioles

Answer 36

Dilates afferent arteriole and constricts efferent arteriole

Question 37

What is the equation for excretion?

Answer 37

E= F - R +S

Question 38

Define renal clearance

Answer 38

volume of blood plasma cleared of a solute per unit of time | ml plasma/min

Question 39

Equation for renal clearance

Answer 39

Clearance of X= excretion rate of X/ plasma concentration of X