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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
Specific functions of Angiotensin II
Constrict both A+E arterioles Increase resistance Decrease blood flow
26
Which arteriole is more sensitive to angiotensin II
EFFERENT arterioles
27
Low vs. high doses of angiotensin II
Low doses of angiotensin II will constrict EFFERENT arterioles High doses of angiotensin II will constrict both AFFERENT and EFFERENT arterioles
28
Effect of renin-angiotensin II-aldosterone system on hemorrhage example
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
29
An increase in EFFERENT arteriole resistance will result in (RBF and net ultrafiltration pressure)
Decrease RBF | Increase net ultrafiltration pressure
30
Increase in AFFERENT and EFFERENT arteriolar resistance will result in (RBF and net ultrafiltration pressure)
Decrease RBF | Decrease net ultrafiltration pressure
31
Atrial netriuretic peptide (ANP) effect
Dilation of AFFERENT arterioles | Constriction of EFFERENT arterioles
32
Effects of ANP on RBF and GFR
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
Prostaglandins types
Prostaglandin E2 | Prostaglandin I2
34
Function of prostaglandins in afferent and efferent arterioles
Vasodilation of afferent and efferent arterioles
35
What 3 mechanisms are activated together in hemorrhage
Sympathetic nervous system Renin-angiotensin II-aldosterone Prostaglandins
36
Effect of prostaglandins
Decrease the vasoconstriction of sympathetic nervous system and aldosterone II which is causing decrease in RBF (renal failure) Vasodilation
37
What inhibits prostaglandins
NSAIDs | Ibuprofen
38
Function of dopamine
It is a precursor of norepinephrine
39
In low doses, what does dopamine do
Dilates cerebral, cardiac and renal arterioles + constricts skeletal muscle and cutaneus arterioles
40
When is dopamine administered
During hemorrhage to protect critical organs through vasodilation of their vessels
41
First step into formation of urine
Glomerular filtration rate
42
Where does RBF enter in glomerular capilaries
Bowman's space
43
Name of the filtered fluid
Ultrafiltrate
44
What does the ultrafiltrate contain
H2O and small solutes | NO PROTEINS AND BLOOD CELLS
45
What does the ultrafiltration of plasma have to cross to get to Bowman's space
Fenestrated capillary endothelium Capillary basement membrane Podocytes
46
Is glomerular membrane size and charge selective
Yes, both
47
Filtration rate determined by
Net ultrafiltration pressure | Ultrafiltration coefficient
48
Driving force of the filtration rate
Through Starling's equation: the net hydrostatic and oncotic pressure gradients between glomerular plasma and filtrate in Bowman's space
49
Pgc
Glomerular capillary hydrostatic pressure
50
High Pgc will favor
A greater SNGFR | Single Nephron Glomerular Filtration Rate
51
Pbs
Bowman's space hydrostatic pressure
52
High Pbs will favor
Decrease in SNGFR
53
πbs
Bowman's space oncotic pressure
54
High ∏bs will favor
Increase in SNGFR
55
Changes in Pgc (Glomerular capillary hydrostatic pressure) come from
Changes in resistance of afferent and efferent arterioles
56
Constriction of AFFERENT arteriole on Pgc
Decreased Pgc
57
Constriction of EFFERENT arteriole on Pgc
Increase Pgc
58
Pbs (Hydrostatic pressure in Bowman's space) changes due to
Obstructing urine flow (stones) Because urine cannot go to bladder and goes back to kidney Pbs increases --> Decrease in GFR
59
∏gc (Oncotic pressure in glomerular capillaries) from
Changes in plasma protein concentration
60
Increase in plasma protein effect on πgc
Increase in πgc = decrease ultrafiltration pressure = decrease GFR
61
Decrease in plasma protein in πgc
Decrease πgc = increase ultrafiltration pressure = increase GFR
62
Why does an increase in πgc cause a decrease in ultrafiltration pressure and GFR
Because proteins cannot be filtrated
63
RBF and RPF
Renal BLOOD Flow | Renal PLASMA Flow
64
Filtration Fraction =
FF = GFR / RPF
65
Normal RPF filtered and not filtered
20% filtered and 80% not filtered
66
Increase in FF consequence
Changes in protein concentration and πgc from reabsorption
67
Renal clearance definition
Volume of plasma completely cleared of a substance / unit time
68
Highest renal clearance substances
INULIN | PAH (Para-aminohippurate)
69
Lowest renal clearances substances
Protein | Glucose
70
Why does Na+, urea, phosphate and Cl have clearances higher than 0
Because they are initially filtered and partially reabsorbed
71
Characteristics of measuring glomerular filtration rate
Freely filtered Cannot be reabsorbed / secreted It cannot alter GFR
72
Gold standard glomerular marker is
Inulin
73
Why is inulin the gold standard
Because it is NOT BOUND to plasma so it is freely filtered | Once filtered, it is not reabsorbed nor secreted
74
Amount of inulin filtered =
Excreted
75
Problem with inulin
It is an exogenous substance so it has to be administered intravenously
76
What endogenous substance is measured instead of inulin
Creatine
77
Does creatine overestimate or underrate GFR
Overestimate
78
Equation to estimate GFR with creatine
Serum + urine [Creatine] + urine V = GFR (overestimated)

RENAL (9 decks)

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