FINAL EXAM - Lecture 5

Question 1

Clearance is always

Answer 1

volume of substance cleared from the plasma

Question 2

If creatinine is being reduced, then

Answer 2

renal function is being reduced

Question 3

When someone has acute hypertension, how does the kidney respond pre glomerular capsule? Say the map is 200mmHg

Answer 3

• Afferent arteriole would constrict to prevent as much overperfusion as possible, but it can only constrict so much.

Question 4

Say the MAP is 200mmHg, what happens to the pressure in the GC? and what is the result of that?

Answer 4

90mmHg (normal 60mmHg), which would change our NFP, and increase our GFR. Reabsorption doesnt increase and we would produce insane amounts of urine. So, obviously, the afferent arterioles are good at maintaining blood flow.

Question 5

What is a consequence of a low MAP, such as 50mmHg?

Answer 5

GFR decreases, so kidneys arent filtering as much, will elevate things the kidneys were supposed to filter

Question 6

When we have chronic HTN or things like uncontrolled diabetes, what can happen to afferent arteriole?

Answer 6

may become stiff and calcified just like any other blood vessels, and wont be able to dilate as much to compensate for a drop in blood pressure.

Question 7

What is another consequence of chronic HTN?

Answer 7

glomerular capsular gets beaten up from all the pressure, podocytes may break, scarring in capillary bed, altered filtration, structures may not stay together.

Question 8

What is getting the MOST messed up by chronic HTN?

Answer 8

Glomerular capillary bed

Question 9

Agent that effects efferent arteriole more

Answer 9

Angiotensin II

Still affects afferent, just efferent most.

Question 10

Drugs will primarily relax which arteriole (pressors or dilators)

Answer 10

afferent arteriole MOST, but efferent arteriole will also be affected.

Question 11

If we have high pressure/high GFR, macula densa would sense increased flow and do what?

Answer 11

Decrease angiotensin II to dilate the efferent arteriole

Question 12

Where is majority of reabsorption occuring?

Answer 12

Proximal tubule, almost everything.

Question 13

is there reabsorption happening at every segment of tubular structure?

Answer 13

Yes, some segments more than others.

Question 14

what percentage of water is reabsorbed in the Proximal tubule?

Answer 14

2/3rds

Question 15

Where is creatinine most concentrated in proximal tubule?

Answer 15

At the end. Water is being reabsorbed but creatinine isnt, so the concentration is going up the further you go down the tubule.

Question 16

Where is the “sensory” area thats watching the numbers of sodiums and chloride?

Answer 16

macula densa. mostly watching for sodium.

Question 17

How does the macula densa gauge the GFR?

Answer 17

by watching Na and Cl. If there is a higher amount of NaCl, it will detect that the GFR is higher than normal.

Question 18

How does the macula densa know how much Na and Cl pass through?

Answer 18

Its counting how many molecules come through (maybe)

Question 19

If GFR is low, what will macula densa do?

Answer 19

Increase Angiotensin II which will constrict efferent arteriole and increase GFR

Question 20

What does angiotensin II do?

Answer 20

Increases salt reabsorption, and constricts efferent arteriole.

Question 21

Where is the increased salt absorption from angiotensin II?

Answer 21

proximal tubule

Question 22

What percent is normal of Na and Cl is reabsorbed in proximal tubule?

Answer 22

2/3rds

Question 23

What are the consequences of the increased reabsorption of NaCl in proximal tubule even though GFR is normal?

Answer 23

Macula densa would detect low NaCl, increase angtiotensin II, which would constrict efferent arteriole and increase NaCl reabsorption, leading to elevated blood pressures in the glomerular capillary, causing damage if its a long term problem.

Question 24

What kind of drug would you give if your NaCl reabsorption is elevated?

Answer 24

Angiotensin II blocker or ARB

Question 25

For every glucose we reabsorb, we have to reabsorb

Answer 25

one sodium along with it, cause sodium is going down its concentration gradient (140:14)

Question 26

What is the sodium concentration of initial part of proximal tubule?

Answer 26

140

Question 27

If we have elevated glucose, this would be more glucose being filtered, and more being reabsorbed. How does this affect other reabsorption?

Answer 27

Increased sodium reabsorption, less sodium reaching macula densa, so macula densa would increase GFR. This is why diabetes destroys kidneys.

Question 28

What ends up destroying kidneys in diabetes?

Answer 28

Hyperfiltration.

Increased glucose will increase sodium reabsorption, making macula densa think GFR is low, increasing angiotensin II, putting more pressure on glomerular capillaries

Question 29

How are amino acids reabsorbed?

Answer 29

uses sodium concentration gradient, just like glucose (1:1 ratio)

Question 30

What can create the same problem with diabetes hurting the kidneys?

Answer 30

Increased amino acids in blood.

but its usually not the same scale as glucose, because you arent eating while you sleep unlike uncontrolled diabetes where your blood sugar is high in your sleep.

Question 31

Where are the glucose reabsorption transporters in the kidney?

Answer 31

Only the proximal tubule.

Question 32

What is the side of the cell called that makes up the wall of the tubular lumen? rear wall of that cell that makes up interstitial side?

Answer 32

apical; basolateral

Question 33

if we want to make glucose non-existent in tubule, how do you get rid of the rest of it?

Answer 33

SGLT with Na+ cant do it, would need to use energy.

Question 34

If glucose in the tubular cells is higher than the side of the interstitium, how does glucose get across to interstitium?

Answer 34

Just uses it concentration gradient to get across and passively cross the basolateral side through glut-2 transporters. but if the concentration gradient is higher in the interstitium, it would require energy.

Question 35

Early parts of proximal tubule is called ____ and later is called________________

Answer 35

S1; S2 and S3

Question 36

Where is majority of glucose reabsorbed? what %? How much sodium is required?

Answer 36

S1 segment, SGLT transporters (90%) 1Na+:1 glucose

Question 37

What transporter gets glucose out the basolateral side of cell in S1 segment?

Answer 37

Glut-2

Question 38

What is the effiency and affinity of SGLT2 transporters?

Answer 38

highly efficient, low affinity though.

Question 39

What types of transporters are on S2 and S3 segment? what percent of glucose? How much sodium is required?

Answer 39

basal side SGLT1, 10%.
Basolateral side GLUT-1
2Na+:1 glucose

Question 40

What is the affinity of SGLT1 transporters?

Answer 40

High affinity, because its lower capacity/lower density and needs to get rid of the rest of glucose.

Question 41

why does SGLT1 require more sodium?

Answer 41

because the fluid is more diluted

Question 42

Where is there the least amount of SGLT?

Answer 42

S3

Question 43

The amount of glucose being filtered is entirely dependent on the

Answer 43

plasma glucose concentration

Question 44

If our GFR is 1.25dL/min, and normal glucose is 100mg/dL, we should have how much glucose being filtered per minute?

Answer 44

1.25 x 100 = 125mg/min

Question 45

If we have a GFR of 140mL/min, and a glucose of 80mg/dL, what is our amount of glucose being filtered per minute?

Answer 45

GFR = 1.4dL/min (convert to dL to match glucose)

1.4dL/min x 80mg/dL = 112mg/min (cross out dL)

Question 46

When you see filtered load, it means

Answer 46

stuff that has dissolved in plasma thats being filtered.

Question 47

if its freely filtered it means you can take what equation to figure out how much is being filtered out?

Answer 47

Concentration x flow = quantity of stuff filtered

Question 48

The point at which glucose is no longer being completely reabsorbed, and it should show up in urine

Answer 48

threshold.

The book says this occurs at 200mg/dL, but schmidt thinks its lower than that

Question 49

When the SGLT transport is maxxed out, the excretion of glucose ratio to excess glucose is

Answer 49

1:1. it’s maxxed out, so any excess glucose beyond that will not be reabsorbed and all of it will be excreted in urine because those pumps are saturated.

Question 50

At what glucose level will transport maximum be reached?

Answer 50

300mg/dL. Any excess glucose will be excreted in urine.

Question 51

At what point is glucose a 1:1 ratio of being filtered to being excreted in urine?

Answer 51

300mg/dL. Every molecule of glucose above 300mg/dL will not be reabsorbed. When its below 300, extra glucose is being reabsorbed but some is also excreting in urine.

Question 52

Where is the macula densa?

Answer 52

Thick ascending loop of henle, right before DCT.

Question 53

Where is the GFR speedometer located?

Answer 53

Macula densa

Question 54

What releases the renin when the macula densa thinks GFR is too low?

Answer 54

Juxtaglomerular cells above the afferent and efferent arterioles

Question 55

Renin will convert what into what?

Answer 55

Angiotensinogen to angiontensin I

Question 56

Where is angiotensinogen produced?

Answer 56

liver

Question 57

Angiotensin I is turned into what by what?

Answer 57

Angiotensin II via ACE (angiotensin converting enzyme)

Question 58

Where is ACE found?

Answer 58

large amounts in the lungs

Question 59

ANG II does what to efferent and afferent arteriole?

Answer 59

constricts efferent arteriole and dilates afferent arteriole

Question 60

How does the afferent arteriole dilate?

Answer 60

Nitric oxide.

Question 61

What is a consequence of a SGLT inhibitor?

Answer 61

everything downstream of glucose that isnt getting reabsorbed, causes excess glucose downstream in urethra and makes it a breeding ground for bacteria, causes its sticky and may cause immune to destroy them too cause they now look funny.