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Physiology- Renal > Renal 3: Filtration and Blood Flow > Flashcards

Renal 3: Filtration and Blood Flow Flashcards

1
Q

What can get through the glomerular filtration barrier?

A

Neutral molecules smaller than 20A are freely filtered
Molecules between 20-42 A are filtered to a varying degree
Cationic molecules
Anionic molecules are hindered due to negatively charged glycoproteins on surface of glomerular filtration barrier

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2
Q

The glomerular capillaries have high/low resistance and a net positive/negative charge.

A

low, negative

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3
Q

Glomerular capillaries have a large/small filtration coefficient. How do we calculate it?

A

large. Kf = PERMEABILITYgc x AREAgc

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4
Q

How are filtration and molecular radius related?

A

higher radius means lower filterability

lower radius means higher filterability

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5
Q

How are filtration and ionic charges related?

A

Anionic: shifts curve down and left. filterability lower at same radius.
Cationic: shifts curve up and right. filterability higher at the same radius.

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6
Q

Why aren’t immunoglobulins filtered?

A

Their molecular radii are greater than 42 angstroms.

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7
Q

Why isn’t albumin filtered?

A

It is a polyanionic protein with a molecular radius of 35 angstroms.

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8
Q

How do we calculate net filtration pressure?

A

Net Ultrafiltration Pressure: Pgc - Pbs - πgc + πbs

Pgc is glomerular capillary hydrostaic pressure
Pbs is Bowman’s space hydrostatic pressure
πgc is glomerular oncotic pressure
πbs is Bowman’s space oncotic pressure

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9
Q 
As blood moves through the glomerular capillaries what happens to the following?
Pgc
πgc
Pbs
net ultrafiltration pressure
A

Pgc: small decrease (low resistance capillaries)
πgc: large increase (conc of proteins that do not filter)
Pbs: no change
Net ultrafiltration pressure: decrease

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10
Q

How do we calculate glomerular flow?

A

hydraulic conductance times net pressure gradient.

GFR = Kf * (Pgc - Pbs - πgc + πbs)

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11
Q

How does a change in afferent arteriolar resistance affect (glomerular capillary hydrostatic pressure)

A

Decreased resistance increases Pgc

Increased resistance decreases Pgc

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12
Q

How does a change in the efferent arteriolar resistance affect Pgc (glomerular capillary hydrostatic pressure)

A

Decreased resistance decreases Pgc

Increased resistance increases Pgc

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13
Q

How does a chagne in the renal arteriolar pressure affect Pgc(glomerular capillary hydrostatic pressure)?

A

Increase in BP transietly increases Pgc -> inc GFR

Decrease in BP transiently decreases Pgf -> dec GFR

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14
Q

What happens to the following in early stage glomerulonephritis?
πgc
GFR
Pbs

A

decrease
increase
nothing

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15
Q

What happens to the following in late stage glomerulonephritis?
Pbs
GFR

A

increase

decrease

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16
Q

How do kidney stones affect Pbs and GFR?

A

increases Pbs

decreases GFR

17
Q

What does nephritic syndome do?

A

increases hydraulic conductance (Kf) and causes proteinuria

18
Q

What is the equation for total renal blood flow (RBF)

A

RBF = (P renal artery - P renal vein)/R renal vasculature

19
Q

Rank the following from most to least vascularization:
inner medulla
renal cortex
outer medulla

A

renal cortex&raquo_space; outer medulla&raquo_space; inner medulla

20
Q

What is the ratio of cortical nephrons to juxtamedullary nephrons

A

7 to 1

21
Q

What types of capillaries does the renal cortex contain?

A

glomerular and peritublar capillaries

22
Q

What types of capillaries does the renal medulla contain?

A

vasa recta capillaries only

23
Q

What is the sequence of vessels from the renal artery to the renal vein?

A

Renal Artery&raquo_space; Afferent Arterioles&raquo_space; Glomerular Capillaries&raquo_space; Efferent Arteriole&raquo_space; Peritubular Capillary&raquo_space; Intrarenal Vein&raquo_space; Renal Vein

24
Q

How does hydrostatic pressure change between the renal artery and vein?

A

It decreases with largest pressure decrease in afferent and efferent arterioles and smallest pressure decrease in the glomerular and peritubular capillaries

25
Q

Where does oncotic pressure increase?

A

glomerular Capillaries (concentration of plasma proteins during filtration)

26
Q

Where does oncotic pressure decrease?

A

Peritubular Capillaries (dilution of plasma proteins during reabsorption)

27
Q

Why do changes in the afferent arteriole and efferent arteriole affect Pgc and GFR?

A

Constriction of either causes an increase in resistance ->. decrease flow (RBF)
Dilation of either increases flow (RBF)
Afferent constriction means less of arterial pressure is transmitted to glomerulus -> dec Pgc -> dec GFR
Efferent constriction elevates Pgc -> inc GFR

Vice versa

28
Q 
Do the following intrinsic factors vasoconstrict or vasodilate?
endothelin
nitric oxide
adenosine
prostaglandins
dopamine
A 
vasoconstrict
vasodilate
vasoconstrict
vasodilate
vasodilate
29
Q

What are the intrinsic autoregulation components

A

smooth muscle myogenic
tubuloglomerular feedback
intrinsic factors

30
Q

What is the autoregulatory range for arterial pressure and what happens to GFR?

A

100-180 mm Hg
GFR and RBF increases at arterial pressure >180 mmHg
GFR and RBF decreases at arterial pressure <100mmHg

31
Q

What happens with renal shutdown?

A

Occurs when arterial pressure <70 mm Hg

GFR = 0ml/min but kidney is still perfused, just no urine formed

32
Q

What happens with renal death?

A

Occurs when arterial pressure = 0 mm Hg

RBF =0ml/min; Kidney no longer perfused with blood

33
Q

Describe tubuloglomerular feedback

A
  1. increased GFR
  2. increased NaCl concentration in tubule fluid in Henle’s loop
  3. signal generated by macula densa of JGA
  4. increased arterial resistance
  5. GFR decreases
34
Q

How does a hemorrhage eventually lead to decreased renal excretion? List entire pathway.

A

hemorrhage -> dec arterial blood pressure -> inc renin secretion -> inc ANG II -> inc sodium and water reabsorption -> dec less renal excretion.

ANG II also constricts renal arterioles -> dec RBF and GFR -> dec renal excretion

dec arterial BP also inc sympathetic innervation to renal nerves -> inc renin secretion further and inc constriction of renal arteries

35
Q

How does severe hypoxia affect RBF and GFR

A

decreases RBF and GFR (seen with high altitudes)

Physiology- Renal (8 decks)

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