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Urinary System > Flow, GFR And Pharmacology > Flashcards

Flow, GFR And Pharmacology Flashcards

1
Q

What is the average renal blood flow?

A

1.1 L/min

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2
Q

What is the renal plasma flow?

A

Renal blood flow minus the haematocrit (erythrocyte volume fraction - usually 45%)
RPF = 0.55 x RBF

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3
Q

Generally, how many segmental arteries are there per kidney?

A

5

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4
Q

What are the 2 types of nephron?

A

Cortical

Juxtamedullary

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5
Q

Give some features of cortical nephrons

A

Small glomerulus
Afferent arteriole has large diameter than efferent
Sympathetic rich
High concentration of renin

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6
Q

Give some features of the juxtamedullary nephrons

A

Big glomerulus
Diameter of afferent close to diameter of efferent
Sympathetic poor
Almost no concentration of renin

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7
Q

How much of the blood from a renal artery is filtered at any one time?

A

20%

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8
Q

What are the 3 layers of the glomerular filter?

A

Capillary endothelium
Basement membrane
Podocyte layer

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9
Q

Which molecule do we think is the biggest molecule that can pass through glomerular filtration?

A

Inulin

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10
Q

Which charge is repelled more at the glomerulus?

A

Negative charges

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11
Q

What are the 3 forces acting at the filter?

A

Hydrostatic pressure in capillary
Hydrostatic pressure in Bowman’s capsule
Oncotic pressure in capillary

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12
Q

What is the myogenic response?

A

The control over GFR by changing the tone of the arteriole walls
Controls GFR through day-to-day BP changes

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13
Q

Describe the effect on the GFR of an increase in tone in the afferent arteriole

A

Increased resistance leads to reduced blood flow
Decreased hydrostatic pressure
Decreased GFR

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14
Q

Why doesn’t the flow rate change?

A

Because change is resistance is proportional to change in pressure

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15
Q

Which organs have the best autoregulation?

A

Heart
Brain
Kidneys

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16
Q

What is the role of autoregulation?

A

To keep GFR within the normal ranges

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17
Q

Describe tubular-glomerular feedback

A

Changes in tubular flow rate occur as a result of changes in GFR
This changes the amount of NaCl that reaches the DCT
Cl- ions detected in the macula densa
Stimulates juxtaglomerular apparatus to release appropriate chemicals

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18
Q

What chemicals can be released by the JGA and what are their effects?

A

Adenosine - vasodilator of the efferent arteriole - reduces GFR
Prostaglandins - vasodilator of afferent arteriole - increases GFR

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19
Q

Describe glucose cotransport in the PCT

A

Via SGLUT
2 Na+ ions plus 1 glucose molecule
Secondary active transport

20
Q

What substances do we secrete into the kidney tubules?

A

Protons (H+)
Potassium
Organic anions and cations (a lot of the drugs that we prescribe)

21
Q

Give examples of endogenous cations

A 
ACH
Dopamine
Adrenaline
Histamine
Serotonin
22
Q

Give examples of drugs that are cations

A

Sulfonamides
Morphine
Atropine

23
Q

Give examples of endogenous anions

A

Urate
Bile salts
Fatty acids

24
Q

Give examples of drugs that are anions

A

Penicillin
Salicylate
NSAIDs

25
Q

What is the normal GFR range for males and females?

A 
Males = 115 - 125 ml/min
Females = 90 - 100
26
Q

What is the formula for renal clearance?

A

RC = UV/P

U = urinary conc of substance
V = flow rate of urine formation 
P = plasma conc of same substance
27
Q

What factors does the complicated eGFR equation take into account?

A

Age
Sex
Mass
Ethnicity

28
Q

What does xenobiotic mean?

A

Not belonging in the body

29
Q

What processes contribute to pharmacokinetics?

A

Absorption
Distribution
Metabolism
Excretion

30
Q

What is drug clearance?

A

The rate of elimination by the kidney and the liver

31
Q

How do we work out the half-life of a drug?

A

(0.693 x Vd) / CL

0.693 - constant
Vd - volume of distribution
CL - clearance rate of drug

32
Q

Generally the rate of removal of a drug is proportional to…

A

The drug’s free concentration in the plasma

Linear properties

33
Q

If a drug is more lipophilic how does this affect its excretion?

A

Can diffuse more easily back out of the kidney tubule

Across the plasma membrane

34
Q

How does plasma protein binding affect drug excretion?

A

Reduces the amount of drug available for glomerular filtration
(And/or removal by the anion/cation transporters in the tubules)

35
Q

If the drug has a high volume of distribution then the drug is more likely to be …

A

Lipophilic

36
Q

Does a large volume of distribution increase or decrease the half life?

A

Increase

37
Q

Describe the 2 phases of liver metabolism

A

Phase I = reduction, oxidation, hydroxylation
Phase II = conjugation
(Both phases act to increase charge to make kidney excretion easier)

38
Q

What occurs when weak acidic anions are present in acidic urine?

A

Will be protonated
Become electrically neutral
Diffuse out of the nephron

39
Q

What happens when weak acidic anions are in more alkaline urine?

A

Less likely to be protonated

More will be excreted (as will be charged therefore less likely to be reabsorbed)

40
Q

What happens when weak bases are in acidic urine?

A

Will become protonated
Less lipophilic
More drug excreted

41
Q

What happens when weak bases are in more alkaline urine?

A

More likely to be electrically neutral
More lipophilic
Can diffuse out of nephron
Less excreted

42
Q

Define renal clearance

A

The virtual volume of plasma that would be totally cleared of a given solute per unit time.

43
Q

Describe the features of inulin that make it good for measuring GFR

A 
Inert
Only filtered (not secreted or reabsorbed)
44
Q

What molecules can be used to estimate GFR?

A

Creatinine

Inulin

45
Q

What are the downsides of using inulin?

A

Expensive

Has to be injected

Urinary System (14 decks)

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