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Physiology Renal ABS 2018 > Dynamics of Glomerular Filtration > Flashcards

Dynamics of Glomerular Filtration Flashcards

1
Q

What is the glomerular filtrate? Relation to plasma?

A

is what actually gets filtered. It is much like the plasma, only that it has very little protein.

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2
Q

Concentration in plasma=?

A

concentration in filtrate

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3
Q

What 2 substances are NOT filtered?

A
  1. Proteins

2. RBCs

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4
Q

What substances get filtered?

A
  1. H2O
  2. ALL substates
  3. ALL electrolytes
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5
Q

What does it mean for a substance to be freely filtered?

A

Substances that move from the plasma to the filtrate at the same concentration

AKA nothing gets in its way.

Goes freely from the plasma into nephron

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6
Q

Name 4 types of known freely filtered substances.

A
  • Many low-molecular-weight components of blood
    1. Ions (Na,K,Cl,HCO3)
    2. Neutral organics (glucose and urea, uric acid)
    3. ALL Amino acids
    4. ALL Peptides (insulin and ADH)
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7
Q

What is the net filtration of glomerular capillaries compared to the regular capillaries of the body per day?

A

Glomerulus= 180 L/day

Regular Capillaries= 4 L/day

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8
Q

Why can we filter so much more through the glomerular capillaries than other capillaries?

A

The glomerulus has an efferent arteriole (HIGH PRESSURE) as opposed to an efferent venule like normal capillaries. This allows for much greater filtration

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9
Q

Average total volume of plasma in humans?

A

3 L

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10
Q

How many times is all of your plasma filtered/day?

A

60 times/day (because glomerulus filters 180 L/day)

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11
Q

Normal GFR?

A

Glomerular Filtration Rate= 180 L/day

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12
Q

What’s in/ not in the glomerular filtrate?

A

In: ALL OTHER SUBSTANCES

Not in:

  1. Blood Cells
  2. ONLY has limited proteins (very few are filtered)
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13
Q

What are the 3 cell types of the glomerulus?

A
  1. Podocytes
  2. Endothelial cells
  3. Mesangial cells
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14
Q

What determine the glomerular filtration barrier?

A

AKA what determines the size of the holes

The 3 types of glomerular cells

  1. podocytes
  2. endothelial cells
  3. mesangial cells
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15
Q

Endothelial cells of the glomerulus have what?

A

Fenestrations between these cells-
They will filter out things based on SIZE.
Only things small enough will pass through

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16
Q

What are Podocytes? Their role? name?

A
  1. “podo”= foot - have foot processes
  2. Interdigitation with podocytes next to one another
  3. Filtration slits- substance must be small enough to pass through this
  4. Help keep things out based on SIZE as well.
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17
Q

What are Mesangial cells? Significance? Mechanism?

A
  1. Modified smooth muscle cells
  2. Lay down ECM proteins
  3. These cells keep things out based on CHARGE by having the same charge as cells which causes repulsion
  4. Constriction: will decrease GFR
    Dilation: will increase GFR
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18
Q

What charge do extracellular matrix proteins have?

A
  1. VERY/ MANY Negative charges

2. Fill the spaces around our cells with negative charges

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19
Q

What are the charges of proteins and cells?

A

NEGATIVE

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20
Q

What 2 glomerular cell types keep substances out based on size?

A
  1. Endothelial cells

2. Podoctyes

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21
Q

What glomerular cell type keeps substances out based on charge?

A
  1. Mesangial cells
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22
Q

What 5 substances are normally freely filtered?

A
  1. H2O
  2. Urea
  3. Glucose
  4. Sucrose
  5. Inulin
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23
Q

What substances aren’t able to be filtered?

A

LARGE PROTEINS

  1. Serum albumin
  2. Hemoglobin
  3. Egg albumin
24
Q

What substance is partially freely filtered?

A

SMALL PROTEINS

1. Myoglobin

25
Q

What is the relationship between protein size and filtration?

A

Increase in protein size= decrease in filtration (vise versa)

26
Q

What is Net Filtration Pressure? (NFP)

A

all pressures associated with the glomerulus. (SUM of hydrostatic and oncotic pressures from protein, oncotic or colloid osmotic pressure)
How does it determine what gets in?

27
Q

What are the Starling forces?

A

[HP(capillary)+ Oncotic pressure (Bowmans’s space) } - [HP (Bowman’s Space) + Oncotic pressure (capillary)]

28
Q

What is hydrostatic pressure? Where does it come from ?

A
  1. Pushes fluid OUT

2. Comes from blood pressure

29
Q

What is oncotic pressure? Where does it come from

?

A
  1. Keeps/Pulls fluid IN
  2. Comes from proteins and cells in the blood- and wants to keep fluid around those cells- will oppose the movement of water out
30
Q

NFR Equation

A

[HP(g) + oncotic (BS)] - [oncotic (g) + HP (BS)]

31
Q

Where does HP (capillary/glomerulus) push fluid?

A

Into Bowman’s capsule

32
Q

Where does the Oncotic pressure (capillary) push fluid?

A

Keeps it in the blood/ glomerulus

33
Q

Where does the Oncotic pressure (Bowman’s space) push fluid

A

Keeps it in Bowman’s space

34
Q

Fluid OUT for filtration = ?

A

+

35
Q

Fluid IN for filtration

A

-

36
Q

Do we have an oncotic pressure in Bowman’s space? Why?Why not?

A

NO

1. There are no proteins in Bowman’s space- therefore there is no oncotic pressure to keep fluid in Bowman’s space.

37
Q

How many forces favor filtration?What are they?

A
  1. Hydrostatic Pressure of glomerulus
38
Q

How many forces oppose filtration? What are they?

A
  1. Oncotic Pressure of the glomerulus

2. Hydrostatic Pressure of Bowman’s space

39
Q

NEW NFP equation?

A

[HP (g) ]+ [Oncotic (g) + HP (BS])

40
Q

Rate of Filtration equation? Define each component.

A

GFR= kf (constant) x NFP
kf= amount of surface area
NEW NFP= P (G)- P(BS)- Oncotic (G)

41
Q

Rate of Filtration equation? Define each component.

A

GFR= kf (constant) x NFP
kf= amount of surface area
NEW NFP= HP (G)- HP(BS)- Oncotic (G)

42
Q

What 4 forces that play a role in GFR?

A
  1. Kf= surface area
  2. HP (G)
  3. HP(BS)
  4. Oncotic (G)
43
Q

When will Kf change? 5 Scenarios?

A

1.Only when surface area changes– the number of nephrons change
2. In the case of renal disease- where nephrons are killed
A. end stage renal disease
B. diabetes
C. hypertension
D. Donating of kidney- decreases by half
E. Drugs causing mesangial cells to constrict

44
Q

HP (BS) constant or not? Exceptions?

A
  1. VERY CONSTANT.
  2. Obstruction of flow through the nephron- caused maybe by kidney stones
    - will cause fluid to come back and BS fills with fluid
45
Q

When will we see a change in oncotic pressure?

A

a change in the amount of proteins

46
Q

What happens when we increase or decrease oncotic (G), respectively?

A

a decrease in GFR, Increase GFR respectively

47
Q

HP (G) comes from where? Can it be regulated? How?

A

Blood Pressure

48
Q

Constriction of efferent arterioles does what to GFR?

A

Increase

49
Q

Constriction of afferent arterioles does what to GFR?

A

Decrease

50
Q

Dilation of afferent arterioles does what to GFR?

A

Increases

51
Q

Dilation of efferent arterioles does what to GFR?

A

Decrease

52
Q

What is Filtered Load? Equation?

A

The amount of substance that gets filtered /unit time

FL= GFRx [Plasma concentration of substrate]

53
Q

Filtered load works for which types of substances?

A

Freely Filtered substance (b/c it moves in at the same concentration as the plasma)

54
Q

What is the normal level of Na in the body?

A

140 mEq/L

55
Q

What is autoregulation?

A

Helps keep GFR constant with changes in BP

56
Q

What are 2 autoregulatory mechanisms? Functions

A
  1. Myogenic response= smooth muscle contraction/ dilation of blood vessels (short term effect)
  2. Tubuloglomerular Feedback= long term effect- RAS system
    - macula densa cells detect low flow–> communicate with juxtaglomerular cells (glomerulus) –> increase RENIN–> converts angiotensin I to angiotension II–> 5 effects to increase BV/ BP

Physiology Renal ABS 2018 (7 decks)

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