Lecture 6 - Glomerular filtration 6

Question 1

How many forces oppose ultrafiltration and how many filter out? Also what are they?

Answer 1

2 and 2

oppose - glomerular capillary hydrostatic pressure and bowman’s space oncotic pressure

filter out - glomerular capillary oncotic pressure and bowman’s space hydrostatic pressure

Question 2

How is the net filtration pressure calculated and what number is it?

Answer 2

Net filtration pressure = Glomerular capillary pressure - (colloid oncotic pressure + bowman’s space pressure)

55 - (30+15) = 10

Question 3

GFR is related to what?

Answer 3

KF and NFP

Question 4

What controls PGC?

Answer 4

relative resistances of AA and EA

Question 5

what controls resistances of AA and EA?

Answer 5

Controlled day neuronal (sympathetic) and hormonal inputs

Question 6

What effect does altering the resistances of the AA and EA have on the PGC?

Answer 6

1. ) Constricting AA will decrease the GFR because both the glomerular capillary pressure and renal plasma will fall.
2. ) Constricting EA will increase GFR because rising capillary dominates. However later on, GFR decreases because RPF dominates. Fluid is coming in fast but not going out as quick. Paradoxical effect.

Question 7

If PGC (glomerular capillary pressure) is constant then what is also constant ?

Answer 7

Net filtration

Question 8

When would we want an increase in GFR and what effect does it have?

Answer 8

Increasing GFR will decrease Na which will get rid of volume and decrease blood pressure.

Question 9

Between the range of 80-200 there is…… in GFR

Answer 9

no change because of tight regulation

Question 10

What mechanisms regulate GFR?

Answer 10

1. ) Renin - angiotensin system
2. ) autoregulation
3. ) sympathetic nerves

Question 11

What is the renin angio tensin system?

Answer 11

• located in the AA which stores and secrete renin
• this results in the formation of angiotensin II
• this directly increases the total PR and systemic BP
• this indirectly increases Na+ reabsorption, K+ secretion, and ECF volume

All in all it tends to increase the BP in response to a decreased BP at the AA.

Question 12

What is the autoregulation of the GFR?

Answer 12

Maintaining GFR in response to changing in the MAP, Venous pressure and obstruction

Question 13

What is the myogenic mechanism?

Answer 13

1. ) Increase stretch in AA
2. ) AA contracts
3. ) decreases pressure
4. ) No change in GFR

Question 14

What is the macula densa response?

Answer 14

1. ) increase fluid delivery is sensed by macula densa
2. ) AA contraction
3. ) Decrease pressure
4. ) Decrease GFR
5. ) Decrease fluid flow
6. ) GFR returns to normal

Question 15

What do the sympathetic nerves do to regulate GFR?

Answer 15

In fight or flight the response is mild with little change in GFR.

In cardiovascular shock there is a very pronounced and can even result in renal failure. GFR goes to 0.

1. ) Sympathetic Activity
2. ) Vasoconstriction
3. ) AA and EA constricts
4. ) Decrease in RPF
5. ) Decrease in GFR