Tubular Transport Flashcards

1
Q

Glomerular filtration rate (GFR) is the sum of ______ and driven by ______

A
  • filtration rates of all functioning nephrons per unit of time
  • driven by Starling forces
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2
Q

What is creatine used to measure?

A

GFR because it’s not reabsorbed or secreted

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3
Q

GFR is used to determine…

A

health of kidney function

- decrease in GFR = increase in kidney disease progression

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4
Q

Hydrostatic pressure of glomerular capillaries (Pgc) is usually at what mmHg?

A

58 mmHg

- outward force that moves fluid from glomerular capillaries to Bowman’s capsule

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5
Q

Hydrostatic pressure of glomerular capillaries (Pgc) is maintained high by…

A
  • large diameter of afferent arterioles

- small diameter of efferent arterioles

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6
Q

What is the main force that affects GFR?

A

Hydrostatic pressure of glomerular capillaries (Pgc)

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7
Q

What happens if there is an increase in hydrostatic pressure of glomerular capillaries (Pgc)?

A
  • decrease in afferent arteriole resistance

- increase in efferent arteriole resistance and renal arteriolar pressure

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8
Q

Hydrostatic pressure of fluids in Bowman’s capsule (Pb) is usually at what mmHg?

A

15 mmHg

- inward force that opposes filtration

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9
Q

Hydrostatic pressure of fluids in Bowman’s capsule (Pb) increases when…

A

nephron is obstructed

- makes sense since it opposes filtration

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10
Q

Colloid osmotic pressure of glomerular capillary proteins (PIgc) is usually at what mmHg?

A

30 mmHg

- inward force that opposes filtration

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11
Q

Colloid osmotic pressure of Bowman’s capsule is usually at…

A

zero

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12
Q

How do disease states affect intrinsic permeability and glomerular SA available (k)?

A

decrease K because there is a decreased SA

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13
Q

What can increase intrinsic permeability and glomerular SA available (k)?

A

drugs that dilate afferent arteriole

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14
Q

GFR is a function of…

A

filtration pressure and filtration coefficient of the filtration membrane over time

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15
Q

How can you measure GFR indirectly?

A

by measuring renal clearance, which is the volume of plasma cleared of a given substance by kidney over time

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16
Q

What are the four possible scenarios for a filtered substance during renal clearance?

A
  • filtered only (Csolute = GFR)
  • filtered and partly reabsorbed (Csolute < GFR)
  • filtered and all reabsorbed (Csolute = 0)
  • filtered and some secreted (Csolute > GFR)
17
Q

What gives us a direct indication of GFR?

A

substances that are only filtered

  • has to freely filter across glomerulus into Bowman’s capsule
  • not be reabsorbed or secreted by nephron
  • not metabolized or produced by kidney
18
Q

What is the most accurate way to determine GFR?

A

by measuring inulin clearance

  • not made or metabolized by cells
  • filtered only
  • administered via IV
19
Q

What is the average GFR for males and women?

A
  • average: 125 mL/min
  • males: 90-140 mL/min
  • females: 80-125 mL/min
20
Q

What is the most widely used method for clinical estimate of GFR and what are the advantages and disadvantages?

A

creatinine, which occurs during skeletal muscle metabolism

  • advantage: relatively constant concentration so no IV needed
  • disadvantage: some is secreted by PCT
21
Q

T/F: all plasma entering the kidneys is filtered

A

F, not all of it is filtered

- portion that is filtered contributes to filtration fraction (Ff)

22
Q

Filtration fraction is normally what percent of plasma volume?

A

15-20%

23
Q

How does renal plasma flow (RPF) affect filtration fraction?

A
  • decrease in RPF = increase in filtration fraction (occurs via hemorrhage, vasoconstriction)
  • increase in RPF = decrease in filtration fraction (occurs b/c of diruetics)
24
Q

RPF is usually what mL/min?

A

625mL/min

25
Q

How do you find renal blood flow (RBF)?

A

aortic pressure - renal venous pressure

26
Q

T/F: GFR and RBF are held within narrow limits

A

T via autoregulation

- holds it constant between a MAP range of 80-180 mmHg

27
Q

What are some local mechanisms responsible for autoregulation?

A
  • tubuloglomerular feedback through juxtaglomerular apparatus (JGA)
  • myogenic mechanism
  • endothelium derived products
  • inflammatory mediators
  • mesangial cells