Exam 3 Lecture: Glomerular Filtration

Question 1

What is the function of fenestrated capillaries?

Answer 1

hold back red blood cells and larger plasma proteins bigger than the size of albumin

Question 2

What is albumin?

Answer 2

the most common protein found in blood

Question 3

What are the fenestrated capillaries covered in and what do they do?

Answer 3

covered in laminin and fibronectin which repel negatively charged molecules

Question 4

What is in the lamina rara and what does it do?

Answer 4

laminin, fibronectin, heparan sulphate and they repel negatively charged molecules

Question 5

What type of proteins do the lamina densa filter?

Answer 5

collagenous proteins for less than 2nm

Question 6

What is the slit diaphragm made out of?

Answer 6

protein - mostly nephrin

Question 7

What does the slit diaphragm filter based on?

Answer 7

size - they have small pores

Question 8

What do the supporting podocytes of the slit diaphragm filter based on?

Answer 8

the basis of charge as they are covered in negative charge

Question 9

How easy is it for a neutral protein to cross the filtration barrier?

Answer 9

it depends on the size, since their charge is 0, that is not a factor, but the bigger they are the harder it is for them to cross the barrier

Question 10

How easy is it for a catatonic protein to cross the filtration barrier?

Answer 10

it is still size dependent, but catatonic proteins have an easier time crossing the filtration barrier because the negative charge of the filtration barrier does not repel them very well

Question 11

How easy is it for anionic proteins to cross the filtration barrier?

Answer 11

it is also size dependent, but anionic proteins also have a difficult time crossing the barrier because the negative charge of the filtration barrier will repel them away

Question 12

If proteins get through the filtration barrier, what must happen to them?

Answer 12

they must be reabsorbed or passed in the urine

Question 13

If proteins are not filtered, what happens?

Answer 13

the kidney cannot regulate serum protein concentration

Question 14

What drives fluid movement out of the capillaries of the glomerulus??

Answer 14

hydrostatic and oncotic pressures

Question 15

What has the biggest influence on fluid movement?

Answer 15

hydrostatic pressure

Question 16

In what direction does capillary hydrostatic pressure push?

Answer 16

Pc, pushes out of the capillary

Question 17

What is Pc generated by?

Answer 17

the resistance difference of afferent/efferent arterioles

Question 18

What direction does bowman’s space hydrostastic pressure push?

Answer 18

Pbs, pushes into the capillary

Question 19

Which hydrostatic pressure is bigger?

Answer 19

the capillary hydrostatic pressure - therefore the net effect of hydrostatic pressure is to push plasma out of the glomerulus

Question 20

What is oncotic pressure?

Answer 20

osmotic pressure caused by colloids (plasma proteins)

Question 21

Where is the protein concentration in the capillaries the highest?

Answer 21

in Bowman’s space

Question 22

In what direction does oncotic capillary pressure push?

Answer 22

in

Question 23

In what direction does bowman’s space oncotic pressure push?

Answer 23

in, but it is negligible

Question 24

What are the starling’s forces?

Answer 24

the forces of hydrostatic and oncotic pressure: Capillary hydrostatic pressure, bowman’s space hydrostatic pressure, capillary oncotic pressure and bowman’s space oncotic pressure

Question 25

What determines whether a fluid moves into or out of the capillary?

Answer 25

the balance of the starlings forces

Question 26

What is the largest Starling's force?

Answer 26

Pc

Question 27

What is the biggest determinant of GFR?

Answer 27

Pc

Question 28

What s the easiest way for the kidney to modulate GFR?

Answer 28

keep a handle on Pc

Question 29

If it is easier for blood to enter the glomerulus than leave it, what will this do to the Pc and GFR?

Answer 29

increase the Pc and increase the GFR

Question 30

If it is easier for blood to leave the glomerulus than enter it, what will this do to the Pc and GFR?

Answer 30

reduce the Pc and reduce GFR

Question 31

Constriction of afferent and dilation of efferent equals...

Answer 31

decreased Pc therefore decreased GFR

Question 32

Relaxation of afferent and constriction of efferent equals...

Answer 32

increased Pc therefore increased GFR

Question 33

Usually, what does disease affect in relation to GFR?

Answer 33

it usually decreases GFR

Question 34

What does schistosomiasis do to GFR?

Answer 34

it decreases it and results in renal failure

Question 35

How does schistosomiasis reduce GFR?

Answer 35

causes antigens to collect in the filtration apparatus initiating a war at the glomerulus, shredding the filtration apparatus

Question 36

What does decreased plasma protein levels lead to?

Answer 36

a decrease in capillary oncotic pressure, and increase the GFR; happens during liver impairment

Question 37

What do uroliths or plugs lead to?

Answer 37

increased hydrostatic pressure in bowman's space which inhibits GFR

Question 38

What signifies 'good' renal clearance?

Answer 38

if a substance is freely filtered, not reabsorbed or secreted by the tubules and passed in the urine

Question 39

What signifies 'bad' renal clearance?

Answer 39

if the substance gets caught in the filtration apparatus, or is reabsorbed in the tubules and returned to the blood

Question 40

How is clinical evaluation of renal function measured?

Answer 40

by monitoring creatinine or BUN

Question 41

What does high levels of creatinine signify?

Answer 41

Low GFR, less is getting cleared through filtration

Question 42

What is the purpose of autoregulation?

Answer 42

To offset the consequences that a change in BP can do to the kidney and keep it functioning properly

Question 43

What can a spike in BP cause in the absence of autoregulation?

Answer 43

increase the amount of blood flowing down the afferent arteriole and slamming into the glomeruli causing damage

Question 44

What does autoregulation control?

Answer 44

blood flow into the glomeruli to prevent changes to the GFR despite the changes in systemic blood pressure

Question 45

What is the range of BP that the kidney can autoregulate for?

Answer 45

80-180 mmHg

Question 46

What are the two mechanisms of autoregulation?

Answer 46

the myogenic mechanism and tubulohlomerular feedback

Question 47

Where does the myogenic mechanism occur?

Answer 47

in the afferent arteriole

Question 48

When blood pressure has increased, what does the myogenic mechanism do in order to fix the problem?

Answer 48

vasoconstriction of the afferent arteriole and decreased blood flow

Question 49

When blood pressure has decreased, what does the myogenic mechanism do in order to fix the problem?

Answer 49

vasodilation of the afferent arteriole and increased blood flow

Question 50

Which mechanism of autoregulation is the fastest?

Answer 50

the myogenic mechanism

Question 51

What is the only thing that the myogenic mechanism senses?

Answer 51

changes in BP

Question 52

What is the sensor for tubuloglomerular feedback?

Answer 52

the fluid in the distal tubule

Question 53

What is the trigger for tubuloglomerular feedback?

Answer 53

Fluctuations in BP change GFR meaning distal tubule fluid composition is altered; ion concentration is the trigger

Question 54

What would the ion levels resemble in the distal tubule if GFR were high?

Answer 54

they would also be high

Question 55

What would the ion levels resemble in the distal tubule if GFR were low?

Answer 55

they would be low

Question 56

What are ion levels in the distal tubule fluid sensed by?

Answer 56

the macula densa

Question 57

What component of autoregulation is tubuloglomerular feedback considered?

Answer 57

the regulatory component

Question 58

Explain the Renin-Angiotensin system.

Answer 58

1. Angiotensionogen is made in the liver, then meets Renin in the afferent arterioles 2. Renin converts Angiotensionogen into Angiotensin I 3. Angiotensin I is converted into Angiotensin II via a converting enzyme in the lungs

Question 59

What are the functions of angiotensin II?

Answer 59

- systemic arteriolar vasoconstriction to increase blood pressure - Increase aldosterone secretion - promotes ADH secretion - Increases tubular NaCl uptake

Question 60

How does the tubuloglonerular feedback mechanism work in response to high blood pressure?

Answer 60

1. High ion levels are sensed by NKCC2 on the apical surface of the macula densa 2. ATP and/or adenosine is relased by the macula densa 3. ATP/adenosine activate receptors on extraglomerular mesangial cells 3. Increased intracellular Ca causes the afferent tubule to contract, and the juxtaglomerular cells do not release renin

Question 61

How does the tubuloglomerular feedback mechanism work in response to low blood pressure?

Answer 61

1. Low ion levels are sensed 2. Macula densa releases PGE2 3. PGE2 causes arteriole vasodilation and JG releases renin 4. Angiotensin II increases causing systemic vasoconstriction (prefers to contract the efferent arteriole) PGE2 production increases

Question 62

What do NSAID's do to tubuloglomerular feedback?

Answer 62

they inhibit prostaglandin production, there is no vasodilation and GFR is not normalized

Question 63

What is the most important autoregulation mechanism?

Answer 63

the myogenic mechanism because it protects against injury where as tubuloglomerular feedback just focuses on GFR and homeostasis