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Renal > Physiology > Flashcards

Physiology Flashcards

1
Q

Osmolarity

A

Number of solute particles per litre

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2
Q

Osmolarity of body fluids

A

300mosmol/L

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3
Q

Specific gravity

A

Weight of particles

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4
Q

Total body water exists as 2 major compartments

A

ECF

ICF

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5
Q

ECF includes:

A

Plasma
IF
Lymph and transcellular fluid

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6
Q

How are fluid compartments measured?

A

Tracers

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7
Q

Useful tracers

A

TBW: water
ECF: Inulin
Plasma: albumin

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8
Q

How to calculate volume

A

V = Dose/Concentration

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9
Q

Main ions in ECF

A

Na
Cl
HCO3-

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10
Q

Main ions in ICF

A

K
Mg
Negatively charged proteins

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11
Q

Changes in ICF/ECF during gain/loss of water

A

Similar changes (both increase or decrease)

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12
Q

Changes in ICF/ECF during gain/loss of NaCl

A

Opposite changes (one increases and other decreases)

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13
Q

What happens in gain/loss of isotonic fluid?

A

No change in fluid osmolarity, change in ECF only

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14
Q

Electrolyte

A

Any substance that dissolves to form free ions

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15
Q

What ion plays a role in establishing membrane potential?

A

K

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16
Q

Effects of hypokalaemia

A

Paralysis

Cardiac arrest

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17
Q

How is salt imbalance manifested?

A

Changes in ECF volume

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18
Q

2 types of nephron

A

Juxtamedullary

Cortical

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19
Q

Juxtamedullary nephrons

A

Long loop of henle
Vasa recta
Concentrated urine

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20
Q

Cortical nephrons

A

Short loop of henle

Peritubular capillaries

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21
Q

Function of macula densa

A

Modified tubular cells

Sense NaCl content

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22
Q

Granular/juxtamedullar cells

A

Secrete renin

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23
Q

What % of plasma that enters glomerulus is filtered?

A

20%

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24
Q

Rate of filtration

A

[X]plasma x GFR

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25
Q

Rate of excretion

A

[X]urine x urine flow rate (Vu)

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26
Q

Rate of reabsorption

A

Rate of filtration - Rate of excretion

Filtration > Excretion

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27
Q

Rate of secretion

A

Rate of excretion - Rate of filtration

Filtration

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28
Q

3 layers of filtration barrier/glomerular membrane

A

Glomerular capillary endothelium
Basement membrane
Slit processes of podocytes

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29
Q

Forces comprising net filtration pressure

A

Glomerular capillary hydrostatic pressure (55) BPgc
Bowman’s capsule hydrostatic pressure (15) HPgc
Glomerular Capillary oncotic pressure (30) COPgc
Bowman’s capsule oncotic pressure (0) COPbc

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30
Q

Net filtration pressure

A

10mmHg

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31
Q

Major determinant of net filtration pressure

A

Glomerular capillary hydrostatic pressure (BPgc)

Constant along capillary (due to back pressure, smaller efferent)

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32
Q

GFR

A

Rate at which protein free plasma is filtered

Kf x net filtration pressure

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33
Q

What happens to urine if GFR increases/decreases?

A

GFR increases = more urine

GFR decreases = less urine

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34
Q

Extrinsic regulation of GFR

A

Sympathetic control - baroreceptor reflex

BPgc controlled by vasoconstriction/dilation

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35
Q

Intrinsic autoregulation of GFR

A

Myogenic mechanism

Tubuloglomerular feedback

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36
Q

Effect of vasoconstriction on GFR

A

Less blood flow = decreased BPgc = decreased GFR

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37
Q

Effect of vasodilation on GFR

A

More blood flow = increased BPgc = increased GFR

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38
Q

Autoregulation

A

Stops short term changes in BP affecting GFR

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39
Q

Myogenic mechanism of autoregulation

A

Increased BP = vascular smooth muscle stretched = vasoconstriction of afferent

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40
Q

Tubuloglomerular feedback mechanism of autoregulation

A

If GFR rises = more NaCl detected by JGA = vasoconstriction of afferent

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41
Q

Which type of control can override?

A

Extrinsic control, e.g. in haemorrhage

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42
Q

What pathology increases HPbc

A

Kidney stone

Decreased GFR

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43
Q

What pathology increases COPgc

A

Diarrhoea

Decreased GFR

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44
Q

What pathology decreases COPgc

A

Burns

Increased GFR

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45
Q

What pathology decreases Kf

A

Physical damage

Decreased GFR

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46
Q

Plasma clearance

A

Measure of how effectively plasma cleared of a substance ml/min

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47
Q

How to calculate clearance

A

Rate of excretion/Plasma concentration

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48
Q

Inulin and creatinine clearance

A

= GFR

Filtered, not reasorbed or secreted

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49
Q

Glucose clearance

A

= 0

Filtered, completely reabsorbed

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50
Q

Urea clearance

A

less than GFR, reabsorbed

51
Q

H+ clearance

A

> GFR

Filtered, secreted, not reabsorbed

52
Q

What do you use to calculate RPF

A

PAH (filtered, secreted completely, not reabsorbed, completely cleared from plasma)

53
Q

RPF

A

650ml/min

54
Q

RBF

A

1200ml/min

55
Q

Fluid reabsorbed in PCT is ________ with filtrate

A

Iso-osmotic

56
Q

What is reabsorbed in PCT?

A 
Sugars 100%
Amino acids 100%
Phosphate
Sulphate
Lactate
Na 67%
57
Q

What is secreted in PCT?

A 
H+
Hippurates
NTs
Bile pigments
Uric acid
Drugs
Toxins
58
Q

Barriers to transcellular reabsorption

A

Apical membrane, tubular cell, basolateral membrane, interstitial fluid, capillary endothelium

59
Q

Primary active transport

A

Energy directly required (hydrolysis of ATP) to move substance against concentration gradient, e.g. Na/K

60
Q

Secondary active transport

A

Carrier molecule transported coupled to ion concentration gradient (Na) e.g. Na/glucose

61
Q

Symport

A

Secondary AT in same direction

62
Q

Antiport

A

Secondary AT in opposite directions

63
Q

What is essential for Na reabsorption?

A

Na/K on basolateral membrane

64
Q

Water is reabsorbed via what route?

A

Paracellular route - follows Cl

65
Q

After glucose transporters are saturated, what happens?

A

Glucose excretion

66
Q

Transport maximum for glucose

A

2mmol/min

67
Q

Tubular fluid is ________ when it leaves PCT

A

Iso-osmotic 300mosmol/L

68
Q

Function of LOH

A

Generates concentration gradient to allow formation of concentrated urine

69
Q

Opposing flow in 2 limbs of LOH is termed:

A

Countercurrent flow

70
Q

The LOH and vasa recta establish a __________ medullary IF

A

Hyperosmotic

71
Q

NaCl reabsorption in thin ascending limb

A

Passive

72
Q

NaCl reabsorption in thick ascending limb

A

Active transport

73
Q

Fluid entering ascending LOH is:

A

Hypertonic

74
Q

Fluid leaving LOH and entering DCT is:

A

Hypotonic 100mosmol/L

75
Q

What else contributes to medullary osmolarity?

A

Urea cycle

76
Q

Where is urea recycled?

A

Between CD and ascending LOH

77
Q

2 solute hypothesis contributing to medullary gradient

A

NaCl

Urea

78
Q

Range of urine production

A

0.3-25ml/min

79
Q

What is the countercurrent exchanger?

A

Vasa recta

80
Q

ANP functions

A

Decreases Na reabsorption
Vasodilation of afferent arteriole
Decreases BP
Decreases symp activity

81
Q

PTH functions

A

Na reabsorption

Phosphate excretion

82
Q

Early DCT

A

Na/K/2Cl

83
Q

Late DCT

A

Ca reabsorption
Na reabsorption
K reabsorption
H secretion

84
Q

Where is ADH receptor?

A

Basolateral membrane of DCT and CD

85
Q

Functions of ADH

A

Increases aquaporins at apical membrane

86
Q

In presence and absence of ADH where is impermeable to water?

A

Absence: ascending LOH, DCT, CD
Presence: ascending LOH

87
Q

At what bladder volume do stretch receptors initiate micturition reflex?

A

250-400ml

88
Q

Stimuli for ADH release?

A

Hypothalamic osmoreceptors
Left atrial stretch receptors
Upper GIT = feedforward inhibition
Nicotine stimulates ADH, alcohol inhibits ADH

89
Q

Stimuli for aldosterone release?

A

Increase in plasma K directly stimulates adrenal cortex

Decrease in plasma Na = JGA = RAAS

90
Q

Stimuli for renin release?

A

Reduced pressure in afferent arteriole
Reduced Na detected by macula densa
Reduced BP = increased symp activity = granular cells stimulated

91
Q

Treatment for HF

A

Low Na diet
Loop diuretic
ACEI

92
Q

Where is ANP produced?

A

Heart

93
Q

Stimuli for ANP release

A

Stretch receptors in heart due to increased BP

94
Q

Acidosis can lead to:

A

Depression of CNS

95
Q

Alkalosis can lead to:

A

Overexcitability of PNS then CNS

96
Q

Strong acids dissociate __________ in solution

A

Completely

97
Q

The most important physiolgical buffer is:

A

CO2/HCO3-

98
Q

What drives bicarbonate reabsorption?

A

H+ secretion

99
Q

What drives H+ secretion?

A

CO2 retention

100
Q

What happens when bicarbonate in tubular fluid is low?

A

Secreted H+ combines with phosphate = acid phosphate excreted (H2PO4)

101
Q

Amount of H+ secreted as acid phosphate can be measured as:

A

titratable acid

102
Q

What rids the body of buffer stores?

A

TA and ammonia

103
Q

Compensation

A

Restoration of pH irrespective of what happens to bicarb and CO2

104
Q

Correction

A

Resoration of pH and bicarb and CO2

105
Q

Examples of respiratory acidosis

A

COPD - chronic bronchitis, chronic epmhysema, asthma, tumour

106
Q

Respiratory acidosis on Davenport diagram

A

Left and up of normal

107
Q

How is respiratory acidosis compensated?

A

Bicarb reabsorbed, H+ secreted as TA and ammonia

New bicarb added to blood

108
Q

Why does bicarb rise in respiratory acidosis?

A

As a result of the disease (equation to right)

As a result of renal compensation (excreting acid, adding new bicarb)

109
Q

How do you correct resiratory acidosis?

A

Restoring normal ventilation

110
Q

Causes of respiratory alkalosis

A

Hyperventilation, fever, altitude

111
Q

Respiratory alkalosis on Davenport diagram

A

Right and down of normal

112
Q

Compensation in respiratory alkalosis

A

Excess removal of CO2 = decreased H+ secretion = can’t reabsorb bicarb = bicarb excreted in urine
No TA or ammonia formed = no new bicarb
Renal compensation further lowers bicarb

113
Q

How do you correct respiratory alkalosis?

A

Restore normal ventilation

114
Q

Causes of metabolic acidosis

A

Excess H+ from sources other than CO2
Ingestion of acids, DKA, lactic acidosis during exercise
Excess loss of base (diarrhoea)

115
Q

Why is bicarb depleted in metabolic acidosis?

A

Buffers excess H+

Loss of bicarb (diarrhoea)

116
Q

Respiratory compensation in metabolic acidosis

A

Decrease pH stimulates peripheral chemoreceptors = ventilation increases = CO2 blown off
H+ and bicarb lowered

117
Q

Metabolic acidosis on Davenport diagram

A

Left and down of normal

118
Q

Correction for metabolic acidosis

A

H+ secretion = TA and ammonia formed to generate more bicarb

Acid load excreted

119
Q

Metabolic alkalosis

A

Excess loss of H+ from the body

120
Q

Causes of metabolic alkalosis

A

Vomiting, ingestion of alkali, aldosterone hypersecretion

121
Q

Metabolic alkalosis on Davenport diagram

A

Right and up from normal

122
Q

Respiratory compensation for metabolic alkalosis

A

Increased pH slows ventilation (peripheral chemoreceptors)

CO2 retained = H+ rises, bicarb rises

123
Q

Correction for metabolic alkalosis

A

Not all filtered bicarb reabsorbed

No TA or ammonia = bicarb excreted

Renal (19 decks)

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