Physiology Flashcards

1
Q

What is tonicity?

A

The effect a solution has on a cell.

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2
Q

How much fluid in the body is intracellular and extracellular?

A

Intra- 67%

Extra- 33%

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3
Q

What are the 4 compartments and percentages of extracellular body fluid?

A

Plasma- 20%
Interstitial fluid- 80%
Lymph- Negligible
Transcellular- Negligible

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4
Q

What tracer can be used to measure total body water?

A

3H2O- Ditritrium oxide/T2O

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5
Q

What tracer can be used to measure ECF?

A

Inulin

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6
Q

What tracer can be used to measure plasma?

A

Labeled albumin

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7
Q

What is the function of the kidneys?

A
Water and salt balance
Acid base balance
Excrete waste and drugs
Maintain plasma volume and osmolarity
Secrete renin and erythropoietin
Activate VD
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8
Q

What is the primary function of the kidney?

A

To regulate volume, composition and osmolarity of body fluids.

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9
Q

What is the functional unit of the kidney?

A

Nephron

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10
Q

What are the two types of nephron?

A

Juxtamedullary

Cortical

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11
Q

What are some of the important parts of the nephron?

A
Blood vessels
Glomerulus 
Proximal tubule
Loop of Henle
Distal tubule
Collecting duct
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12
Q

What are the two parts of the loop of Henle?

A

Descending and ascending limbs

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13
Q

What is the glomerulus contained within?

A

Bowman’s capsule

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14
Q

What is found next to the glomerulus between the afferent and efferent arterioles?

A

Juxtaglomerular apparatus

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15
Q

What two special cell types are found in the juxtaglomerular apparatus?

A

Granular cells

Macula densa

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16
Q

What percentage of the plasma that enters the glomerulus is filtered?

A

20%

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17
Q

What two things can occur between the tubules and peritubular capillaries?

A

Tubular secretion and reabsorption

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18
Q

How do you calculate the rate of filtration?

A

[X]plasam x GFR

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19
Q

How do you calculate the rate of excretion of a substance?

A

[X] urine x Vu (urine flow rate)

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20
Q

How do you calculate the rate of reabsorption of a substance?

A

Rate of filtration of X - rate of excretion of X

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21
Q

How do you calculate the rate of secretion of a substance?

A

Rate of filtration of X - rate of excretion of X

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22
Q

What are some barriers to filtration?

A

Endothelium
Basement membrane
Podocytes

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23
Q

How do barriers to filtration work?

A

Physical barrier

Charge barrier

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24
Q

What four forces control GFR?

A

Glomerular capillary blood pressure (BPgc)
Bowman’s capsule oncotic pressure (COPbc)
Capillary oncotic pressure (COPgc)
Bowman’s capsule hydrostatic pressure (HPbc)

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25
Q

Which two forces govern fluid leaving the capillaries into the bowman’s capsule?

A

Glomerular capillary blood pressure (BPgc)

Bowman’s capsule oncotic pressure (COPbc)

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26
Q

Which two forces govern fluid leaving the bowman’s capsule into the capillaries?

A

Capillary oncotic pressure (COPgc)

Bowman’s capsule hydrostatic pressure (HPbc)

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27
Q

Under normal conditions what are the values for the four forces governing GFR?

A

Glomerular capillary blood pressure- 55mmHg
Bowman’s capsule oncotic pressure- 0mmHg
Capillary oncotic pressure- 30mmHg
Bowman’s capsule hydrostatic pressure-15mmHg

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28
Q

What is the net filtration pressure normally?

A

10mmHg

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29
Q

What is another term for the forces governing GFR?

A

Starling forces

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30
Q

What is GFR?

A

Rate at which protein free plasma is filtered from glomerulus into bowman’s capsule per unit time

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31
Q

How do you calculate GFR?

A

Kf (how holey the membrane is) x net filtration pressure

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32
Q

What is normal GFR?

A

125ml/min

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33
Q

What is an extrinsic method of regulating GFR?

A

Alter diameter of blood vessels to glomerulus

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34
Q

What are the two intrinsic/autoregulation mechanisms of regulating GFR?

A

Myogenic

Tubuloglomerular feedback

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35
Q

What does myogenic autoregulation involve?

A

Vascular smooth muscle into kidneys increases then automatically constricts.

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36
Q

What does tubuloglomerular feedback autoregulation involve?

A

Juxtaglomerular apparatus- mechanism unknown.

Rise in GFR leads to more NaCl in tubules causing constriction.

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37
Q

What do the macula densa cells in the juxtaglomerular apparatus do?

A

Sense NaCl

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38
Q

What can raise the Bowman’s capsule hydrostatic pressure (HPbc) and what effect does this have of GFR?

A

Renal stones. Decrease GFR.

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39
Q

What can raise the Capillary oncotic pressure (COPgc) and what effect does this have on GFR?

A

Diarrhoea. Decrease GFR.

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40
Q

What can drop the Capillary oncotic pressure (COPgc) and what effect does this have on GFR?

A

Severe burns. Increase GFR

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41
Q

What is plasma clearance?

A

How effectively the kidneys can clear the blood of a substance.

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42
Q

How do you calculate plasma clearance?

A

[X]urine x Vurine/[X]plasma

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43
Q

What are the units for plasma clearance?

A

ml/min

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44
Q

Clearance of what substance is GFR based on?

A

Inulin

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45
Q

Why is inulin good for calculating GFR?

A
Freely filtered
Not reabsorbed or secreted
Not metabolised my kidney
Not toxic
Easy to measure
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46
Q

What is normal clearance of inulin?

A

125ml/min

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47
Q

is glucose filtered?

A

Yes

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48
Q

If it is filtered why is glucose not normally seen in the urine?

A

Completely reabsorbed.

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49
Q

Why does urea have a clearance lower then GFR?

A

Freely filtered and partly reabsorbed

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50
Q

Why does H+ have a clearance higher than GFR?

A

Filtered and secreted

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51
Q

What is renal plasma flow?

A

Amount of blood flowing through the kidneys

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52
Q

What can be used to calculate renal plasma flow?

A

PAH

53
Q

How can PAH be used to calculate renal plasma flow?

A

Because it is freely filtered and the molecules that don’t get filtered get secreted out.

54
Q

What is normal renal plasma flow?

A

650ml/min

55
Q

What is the filtration fraction?

A

Fraction of plasma passing through kidneys that is filtered.

56
Q

What is the normal filtration fraction?

A

20%

57
Q

How much of the GFR is normally reabsorbed in the proximal tubule?

A

80ml/min

58
Q

How much fluid normally enters the loop of Henle?

A

45ml/min

59
Q

How does the fluid reabsorbed from the proximal tubule compare to the osmolarity of the filtrate?

A

Iso-osmotic

60
Q

What is reabsorbed in the proximal tubule?

A
Sugars
AA
Phosphate
Sulphate
Lactate
61
Q

What is secreted in the proximal tubule?

A
H+
PAH
NTs
Bile pigments
Uric acid
Drugs/toxins
62
Q

What are the two forms of reabsorption?

A

Transcellular

Paracellular

63
Q

How does Na cross the luminal membrane of the proximal tubule?

A

Passive diffusion through channels

64
Q

How does Na cross the basolateral membrane of the proximal tubule?

A

NaKATPase

65
Q

Is NaKATPase a primary or secondary active transporter?

A

Primary

66
Q

What two substances can Na conc gradient be used to reabsorb in the proximal tubule?

A

Glucose

AA

67
Q

What substance can Ns conc gradient be used to secrete in the proximal tubule?

A

H+

68
Q

How does H2O and Cl get reabsorbed?

A

Paracellular following Na

69
Q

How does glucose cross the luminal membrane?

A

NaGlucose transporter

70
Q

How does glucose cross the basolateral membrane?

A

Facilitate transport down conc gradient

71
Q

At what conc does glucose reabsorption get saturated?

A

2mmol/min

72
Q

What is the point of the loop of Henle?

A

To generate a conc gradient to form hypertonic urine

73
Q

What is flow in the loop of Henle called?

A

Countercurrent

74
Q

What is absorbed in the ascending loop of Henle?

A

Na and Cl but no water

75
Q

What is absorbed in the descending loop of Henle?

A

Water

76
Q

How does the countercurrent system in the loop of Henle work?

A

NaCl absorbed in the ascending loop increases osmolarity of blood in vessels between ascending and descending thus drawing water out of descending.

77
Q

What allows for Na and Cl reabsorption at the luminal membrane of the ascending loop of Henle?

A

NaKCl triple transporter

78
Q

What drug blocks the NaKCl tripler transporter?

A

Loop diuretics

79
Q

What is the point of the countercurrent mechanism?

A

To allow for the production of different conc and volume of urine depending on ADH levels

80
Q

What is the normal urine flow rate?

A

1ml/min

81
Q

What runs alongside the loop of Henle in juxtamedullary nephrons?

A

Vasa recta

82
Q

What does vasa recta mean?

A

Straight vessels

83
Q

What do the vasa recta do?

A

Form the blood component of countercurrent mechanism.

84
Q

How does the osmolarity of the fluid in the distal tubule compare to that of plasma?

A

Hypo-osmotic

85
Q

What is reabsorbed in the distal tubule?

A

NaCl and water

86
Q

What controls reabsorption in the distal tubule?

A

Hormones

87
Q

What hormones act on the distal tubule?

A

ADH
Aldosterone
ANH
Parathyroid hormone

88
Q

What effect does ADH have on the distal tubule?

A

Increase H2O reabsorption by increasing aquaporins

89
Q

What effect does aldosterone have on the distal tubule?

A

Increase Na reabsorption

Increase K and H+ secretion

90
Q

What effect does ANH have on the distal tubule?

A

Decrease Na reabsorption

91
Q

What effect does parathyroid hormone have of the distal tubule?

A

Increase Ca reabsorption

Decrease PO reabsorption

92
Q

Is the distal tubule permeable to urea?

A

Not really

93
Q

What happens to urea in the distal tubule?

A

Concentrated

94
Q

What happens in the early distal tubule?

A

NaCl reabsorption through NaKCl triple transporter

95
Q

What happens in the late distal tubule?

A

Ca, Na, Cl and H2O reabsorption

K and H+ secretion

96
Q

What happens in the early collecting duct?

A

Ca, Na, Cl and H2O reabsorption

K and H+ secretion

97
Q

What happens in the late collecting duct?

A

Low ion permeability

Permeability to urea and H2O through ADH/aquaporins

98
Q

What is the HL of ADH?

A

15 minutes

99
Q

Where is ADH released from?

A

Posterior pit

100
Q

How does ADH work?

A

Increases aquaporin numbers

101
Q

What do high levels of ADH do?

A

Increase reabsorption of H2O leading to conc urine

102
Q

What do low levels of ADH do?

A

Decrease reabsorption of H2O leading to dilute urine

103
Q

What disease is caused by a lack of ADH?

A

Diabetes insipidus

104
Q

What stimulates ADH release?

A

Decreased atrial pressure and nicotine

105
Q

What inhibits ADH release?

A

Feeding and alcohol

106
Q

Where is aldosterone released from?

A

Adrenal cortex

107
Q

What stimulate aldosterone secretion?

A

Rising K (directly) or falling Na (vis juxtaglomerular apparatus)

108
Q

How does aldosterone increase Na reabsorption?

A

Na reduction sensed by macula densa.
Macula dense stim renin release from granular cells
RAAS activated

109
Q

Where does aldosterone act?

A

Distal tubule and collecting duct

110
Q

How can aldosterone cause hypertension?

A

Failing heart decreases output leading to a perceived low BP which stims RAAS and increased Na levels

111
Q

Where is ANP made?

A

Atrial cells

112
Q

What causes ANP release?

A

Stretching of atria cells due to increased volume

113
Q

What does ANP do?

A

Increases secretion of Na

114
Q

What are three potential markers of GFR?

A

Inulin
Urea
Creatinine

115
Q

Give some advantages of inulin for measuring GFR?

A

Appears at constant rate
Freely filtered
Not reabsorbed or secreted
No extra-renal elemination

116
Q

Give some disadvantages of inulin for measuring GFR?

A

Not endogenous

Not easy to measure

117
Q

Give some advantages of urea for measuring GFR?

A

Endogenous
Easy to measure
Freely filtered
Not secreted

118
Q

Give some disadvantages of urea for measuring GFR?

A

Does not appear at constant rate
Reabsorbed
Extra-renal elimination

119
Q

Give some advantages of creatinine for measuring GFR?

A
Endogenous
Easy to measure
Freely filtered
Constant rate
Nor reabsorbed
No extra-renal met
120
Q

Give some disadvantages of creatinine for measuring GFR?

A

Secreted

121
Q

What can confuse creatinine readings?

A

Age
Sex
Muscle mass
Diet

122
Q

Are plasma proteins normally filtered out?

A

No

123
Q

How do you estimate protein in the urine?

A

Dipstick then 24h urine collection

124
Q

What level of protein in the urine indicates significant glomerular damage?

A

> 150mg/day

125
Q

How does nephrotic syndrome work?

A

Loss of albumin results in fluid leaking out of vessels to cause oedema.

126
Q

What are the 4 categories of protein in the urine?

A

Normal
Microalbuminuria
Clinical proteinuria
Nephrotic

127
Q

What is microalbuminuria?

A

Abnormal quantities of albumin being secreted but not enough to give a dipstick reading.

128
Q

Is microalbuminuria seen in diabetes?

A

Yes, earliest sign of diabetic nephropathy.