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RENAL > I: Renal Physiology > Flashcards

I: Renal Physiology Flashcards

1
Q

How is a stable milieu interior achieved

A

Filtration of circulating blood from glomerulus
Selective reabsorption
Selective secretion

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2
Q

What % of cardiac output does the kidney receive

A

25%
1.25L/min
180L/day

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3
Q

Relationship between Renal outflow (Q) and pressure gradient of renal artery and renal vein

A

Directly proportional

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4
Q

Relationship between renal flow (Q) and resistance of renal vasculature

A

Inverserly proportional

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5
Q

Major mechanism to change blood flow

A

Arteolar resistance achieved through afferent/efferent arterioles

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6
Q

Variation of arterial pressures (in regulation)

A

80-200mmHg

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7
Q

Even though pressure can be regulated, what will ALWAYS be kept CONSTANT

A

The flow

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8
Q

When is the only time where renal flow will decrease

A

When arterial pressure decreases <80mmHg

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9
Q

What arteriole resistance is controlled

A

The AFFERENT arteriole

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10
Q

What are the different theories of renal autoregulation

A
  1. Myogenic theory
  2. Tubuloglomerular feedback
  3. Metabolic theory
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11
Q

Main thought in myogenic theory

A

Afferent arterioles react to an increase in arterial pressure by resisting to flow (to control the constant flow)

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12
Q

In what LAW is based the myogenic theory

A

In LaPlace’s Law, where an increase in intravascular pressure causes CONSTRICTION of vessels to maintain pressure

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13
Q

According to LaPlace’s Law, what will a decrease in intravascular pressure cause

A

Vasodilation of afferent arterioles

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14
Q

In what situation will there be increased resistance in afferent arterioles

A 
In a case of increased intravascular pressure where afferent arterioles will react by contracting to maintain a CONSTANT RBF though GFR will:
Increase in (Afferent arterioles)
Decrease in (Efferent arterioles)
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15
Q

Changes in RBF and GFR from increased and decreased intravascular pressure

A

Increase in P = constant RBF and increased GFR

Decrease in P = constant RBF and increased GFR

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16
Q

Why does GFR increase in Efferent arterioles during low pressure

A

Because there is vasodilation of afferent vessels

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17
Q

Tubuloglomerular feedback main idea

A

Macula densa will respond by secreting a vasoactive substance to CONSTRICT afferent arterioles

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18
Q

Increase in GFR to macula densa will cause

A

Local vasoconstriction of AFFERENT arterioles, causing a reduction of RBF and GFR (efferent arterioles)

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19
Q

What component of tubular fluid is sensed at macula densa

A

Na+, Cl-

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20
Q

What vasoactive substance secreted by juxtaglomerular apparatus

A

Adenosine, ATP, thromboxane

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21
Q

Exogenous regulation RBF

A
  1. Sympathetic nervous system + circulating catecholamines
  2. Angiotensin II
  3. Atrial Natriuretic Peptide (ANP)
  4. Prostaglandin
  5. Dopamine
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22
Q

How does the sympathetic nervous system achieve vasoconstriction

A

By activation of a1 receptors

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23
Q

During hemorrhage

A

Decrease BP = Increase sympathetic outflow to heart and vessels = Vasoconstriction afferent arterioles = decrease in RBF and GFR = Increase arterial pressure

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24
Q

Angiotensin II function

A

Vasoconstrictor of afferent and efferent arterioles

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25
Q

Specific functions of Angiotensin II

A

Constrict both A+E arterioles
Increase resistance
Decrease blood flow

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26
Q

Which arteriole is more sensitive to angiotensin II

A

EFFERENT arterioles

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27
Q

Low vs. high doses of angiotensin II

A

Low doses of angiotensin II will constrict EFFERENT arterioles
High doses of angiotensin II will constrict both AFFERENT and EFFERENT arterioles

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28
Q

Effect of renin-angiotensin II-aldosterone system on hemorrhage example

A

Hemorrhage = decreased arterial pressure = activation of renin-angiotensin II-aldosterone system = activation of sympathetic nerve activity = constriction of AFFERENT and EFFERENT arterioles = decreased RBF and GFR = INCREASED BLOOD PRESSURE

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29
Q

An increase in EFFERENT arteriole resistance will result in (RBF and net ultrafiltration pressure)

A

Decrease RBF

Increase net ultrafiltration pressure

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30
Q

Increase in AFFERENT and EFFERENT arteriolar resistance will result in (RBF and net ultrafiltration pressure)

A

Decrease RBF

Decrease net ultrafiltration pressure

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31
Q

Atrial netriuretic peptide (ANP) effect

A

Dilation of AFFERENT arterioles

Constriction of EFFERENT arterioles

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32
Q

Effects of ANP on RBF and GFR

A

Increase in both RBF and GFR because afferent arterioles are DILATED (more flow into system) and efferent are CONSTRICTED (more filtration due to less outflow)

33
Q

Prostaglandins types

A

Prostaglandin E2

Prostaglandin I2

34
Q

Function of prostaglandins in afferent and efferent arterioles

A

Vasodilation of afferent and efferent arterioles

35
Q

What 3 mechanisms are activated together in hemorrhage

A

Sympathetic nervous system
Renin-angiotensin II-aldosterone
Prostaglandins

36
Q

Effect of prostaglandins

A

Decrease the vasoconstriction of sympathetic nervous system and aldosterone II which is causing decrease in RBF (renal failure)
Vasodilation

37
Q

What inhibits prostaglandins

A

NSAIDs

Ibuprofen

38
Q

Function of dopamine

A

It is a precursor of norepinephrine

39
Q

In low doses, what does dopamine do

A

Dilates cerebral, cardiac and renal arterioles + constricts skeletal muscle and cutaneus arterioles

40
Q

When is dopamine administered

A

During hemorrhage to protect critical organs through vasodilation of their vessels

41
Q

First step into formation of urine

A

Glomerular filtration rate

42
Q

Where does RBF enter in glomerular capilaries

A

Bowman’s space

43
Q

Name of the filtered fluid

A

Ultrafiltrate

44
Q

What does the ultrafiltrate contain

A

H2O and small solutes

NO PROTEINS AND BLOOD CELLS

45
Q

What does the ultrafiltration of plasma have to cross to get to Bowman’s space

A

Fenestrated capillary endothelium
Capillary basement membrane
Podocytes

46
Q

Is glomerular membrane size and charge selective

A

Yes, both

47
Q

Filtration rate determined by

A

Net ultrafiltration pressure

Ultrafiltration coefficient

48
Q

Driving force of the filtration rate

A

Through Starling’s equation: the net hydrostatic and oncotic pressure gradients between glomerular plasma and filtrate in Bowman’s space

49
Q

Pgc

A

Glomerular capillary hydrostatic pressure

50
Q

High Pgc will favor

A

A greater SNGFR

Single Nephron Glomerular Filtration Rate

51
Q

Pbs

A

Bowman’s space hydrostatic pressure

52
Q

High Pbs will favor

A

Decrease in SNGFR

53
Q

πbs

A

Bowman’s space oncotic pressure

54
Q

High ∏bs will favor

A

Increase in SNGFR

55
Q

Changes in Pgc (Glomerular capillary hydrostatic pressure) come from

A

Changes in resistance of afferent and efferent arterioles

56
Q

Constriction of AFFERENT arteriole on Pgc

A

Decreased Pgc

57
Q

Constriction of EFFERENT arteriole on Pgc

A

Increase Pgc

58
Q

Pbs (Hydrostatic pressure in Bowman’s space) changes due to

A

Obstructing urine flow (stones) Because urine cannot go to bladder and goes back to kidney
Pbs increases –> Decrease in GFR

59
Q

∏gc (Oncotic pressure in glomerular capillaries) from

A

Changes in plasma protein concentration

60
Q

Increase in plasma protein effect on πgc

A

Increase in πgc = decrease ultrafiltration pressure = decrease GFR

61
Q

Decrease in plasma protein in πgc

A

Decrease πgc = increase ultrafiltration pressure = increase GFR

62
Q

Why does an increase in πgc cause a decrease in ultrafiltration pressure and GFR

A

Because proteins cannot be filtrated

63
Q

RBF and RPF

A

Renal BLOOD Flow

Renal PLASMA Flow

64
Q

Filtration Fraction =

A

FF = GFR / RPF

65
Q

Normal RPF filtered and not filtered

A

20% filtered and 80% not filtered

66
Q

Increase in FF consequence

A

Changes in protein concentration and πgc from reabsorption

67
Q

Renal clearance definition

A

Volume of plasma completely cleared of a substance / unit time

68
Q

Highest renal clearance substances

A

INULIN

PAH (Para-aminohippurate)

69
Q

Lowest renal clearances substances

A

Protein

Glucose

70
Q

Why does Na+, urea, phosphate and Cl have clearances higher than 0

A

Because they are initially filtered and partially reabsorbed

71
Q

Characteristics of measuring glomerular filtration rate

A

Freely filtered
Cannot be reabsorbed / secreted
It cannot alter GFR

72
Q

Gold standard glomerular marker is

A

Inulin

73
Q

Why is inulin the gold standard

A

Because it is NOT BOUND to plasma so it is freely filtered

Once filtered, it is not reabsorbed nor secreted

74
Q

Amount of inulin filtered =

A

Excreted

75
Q

Problem with inulin

A

It is an exogenous substance so it has to be administered intravenously

76
Q

What endogenous substance is measured instead of inulin

A

Creatine

77
Q

Does creatine overestimate or underrate GFR

A

Overestimate

78
Q

Equation to estimate GFR with creatine

A

Serum + urine [Creatine] + urine V = GFR (overestimated)

RENAL (9 decks)

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