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BMS242 CVS Phys > L5-6 Acid-Base Balance > Flashcards

L5-6 Acid-Base Balance Flashcards

1
Q

Describe the pH scale

A

Logarithmic and reciprocal

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2
Q

Fall in pH leads to ________ in H+

A

Increase

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3
Q

Rise in pH leads to ________ in H+

A

Decrease

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4
Q

What would the result of a 1 unit pH change be in H+

A

x10 change

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5
Q

Why must pH be carefully controlled

A

A small pH change will have profound phyisological effects

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6
Q

Normal pH range

A

7.35 - 7.45

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7
Q

Describe the effects fluctuations in H+ may have

A

Change the excitability of muscles/nerves
Enzyme activities changed
Change in K+ levels

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8
Q

What organ does hyperkalaemia have a hug effect on in praticular

A

Heart

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9
Q

pH of gastric secretions

A

0.7

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10
Q

pH of CSF

A

7.3

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11
Q

pH of pancreatic secretions

A

8.1

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12
Q

pH of the final urine

A

5.4

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13
Q

How many moles of CO2 metabolised per day

A

15

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14
Q

Diet is a huge source of

A

Acid

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15
Q

How many mmol net H+ due to metabolism

A

40

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16
Q

One source of alkali

A

Fruit

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17
Q

Western diet contributes to

A

Excess ingestion of acid

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18
Q

How many mmole of H+ in per day through diet

A

20

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19
Q

Net H+ gain per day

A

70 mmol

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20
Q

3 Systems involved in the control of acid-base balance

A

Blood and tissue buffers
Respiration
Renal

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21
Q

Which is the only method which directly allows the extrusion of H+/OH-

A

Renal

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22
Q

Examples of buffers

A

Hb HCO3- Pi Weak acids/bases on proteins

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23
Q

Equation for the primary ECF buffer

A

CO2 + H2O H2CO3 HCO3- + H+

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24
Q

What is the name of the primary ECF buffer

A

Carbonic acid/bicarbonate buffer

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25
Q

Describe what would happen to the Carbonic acid/bicarbonate buffer if there was an increase in CO2

A

Eqbm shift right to minimise change

More H+ produced

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26
Q

What is the equation for pH in the Carbonic acid/bicarbonate buffer system

A

Ph = pK + [HCO3/H2CO3]

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27
Q

What can be said about the concentrations of H2CO3 + CO2 at eqbm

A

Equal

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28
Q

Rewrite the equation of the Carbonic acid/bicarbonate buffer system to include CO2

A

pH = pK + [HCO3/CO2]

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29
Q

What is pK at 37 deg

A

6.1

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30
Q

Describe what would happen to the Davenport diagram if acid was added

A

Conc of HCO3- decreases
pH decreases
Metabolic acidosis

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31
Q

What is the normal [HCO3]//[CO2]

A

20:1

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32
Q

Using the normal [HCO3]/[CO2] calculate pH

A 
pH = 6.1 + log 20
pH = 7.4
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33
Q

Describe what would happen to the Davenport diagram if CO2 conc was increased

A

Increase in [hco3]
Decrease in pH
Respiratory acidosis

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34
Q

Describe what would happen to the Davenport diagram if base was added

A

Increase in [hco3]
Increase in pH
Metabolic alkalosis

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35
Q

Describe what would happen to the Davenport diagram if concentration of CO2 decreases

A

Decrease in [hco3]
Increase in pH
Respiratory alkalosis

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36
Q

Two chemoreceptors involved in the control of blood gas composition

A

Central and peripheral

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37
Q

Hypoxia is

A

Decrease in O2

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38
Q

Hypercapnia is

A

Increase in CO2

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39
Q

Peripheral chemoreceptors are found

A

Carotid and aortic bodies

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40
Q

Main stimulus for the peripheral chemoreceptors

A

Hypoxia

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41
Q

What 3 nerves are involved with the peripheral chemoreceptors

A

Sinus
Vagus
Glossopharyngeal

42
Q

Weight of the carotid bodies

A

2mg

43
Q

Supporting cells of the carotid body are called

A

Type II supporting cells

44
Q

What two stuructures of the carotid body help increase blood flow

A

Arteriole

Siusoid

45
Q

What is the receptive cell of the carotid body

A

Glomus cell

46
Q

Compare blood flow through the carotid body to the brain

A

Carotid body has over 40x per unit mass than the brain

47
Q

Describe the mechanism of activation of the glomus cell in response to
Dec PO2 Inc PCO2 Dec pH

A 
Inhibition of the BK K channels 
Depolarisation
Action potential firing 
VGCC open 
Ca influx 
NT release 
Afferent nerve fibre stimulation
48
Q

What NTs are released from the glomus cell

A

Ach, dopamin, NA, 5-HT, Substance P, ANP

49
Q

What is different in SIDs babies and normal babies in terms of the peripheral chemoreceptors

A

Increase [] of dopamine and NA in SIDs babies glomus cell

50
Q

Describe how the sensitivity to PO2 of the peripheral chemoreceptor changes with acid-base status

A

At lower pH they are more sens. to pO2

51
Q

Describe how sensitivity to pCO2 of the peripheral chemoreceptor changes with pH

A

At the higher pH they are less sensitive to changes in pCO2

52
Q

Central chemoreceptors are the primary source for the

A

Tonic drive for breathing

53
Q

What is the main activator for the central chemoreceptors

A

Hypercapnia

54
Q

A change in CO2 P from 40-45 mmHg will have what affect on the central chemoreceptors, how does this compare to what would be seen in response to pO2

A

double the ventilation rate

this would only be seen with a 50% decrease in PO2

55
Q

What is the experiemental evidence for the central chemoreceptors

A

Perfusion of the cerebral ventricles with an acidic solution and hyperventilation was observed

56
Q

Descrive the location of the central chemoreceptors

A

Within the brain parenchyma
Bathed in BECF
Separated from the arterial blood by the BBB

57
Q

Describe the effect an increase in arterial pCO2 would have on the BECF, what long term compensation may be involved

A

Inc Arterial pCO2
Inc BECF pCO2
Dec BECF pH
Less bicarbonate buffering power (fewer proteins) so a larger pH fall
LONG TERM - Bicarbonate may be transported out of the blood

58
Q

Describe what effect the poor ionic perm of the BBB has on metabolic disorders compared with respiratory disorders

A

Metabolic - no change in Co2 - only change in H+ - these can’t cross the BBB
Respiratory - CO2 can cross the BBB and affect pH
METABOLIC DISORDERS CHANGE THE BECF BY 10-35% OF THAT OBSERVED WITH RESPIRATORY DISORDERS FOR THE SAME PH CHANGE IN THE BLOOD

59
Q

Can H+ cross BBB

A

No

60
Q

Can HCO3- cross BBB

A

No

61
Q

Can CO2 cross BBB

A

Yes

62
Q

Where do the central chemoreceptors project to

A

The ventrolateral medulla and other brainstem nuclei

63
Q

How many neuronal populations of the central chemoR, what are they called

A

2

Acid activating + inhibiting

64
Q

Acid inhibiting release

A

GABA

65
Q

Acid activating release

A

Serotonin

66
Q

What is seen in SIDS babies in terms of the central chemoreceptors

A

Lack the serotonergic neurones

67
Q

Response of both ChemoR to respiratory acidosis

A

Both central and peripheral
Normoxic central 65-80%
Peripheral faster
As PO2 falls the response to PCO2 is enhanced

68
Q

Response of both ChemoR to metabolic acidosis

A 
Severe - hyperventilation 
- --- Kussmaul breathing 
Descrease in PCO2
Peripheral acute response 
Central longer term role
69
Q

Effect of breathing faster or CO2 and pH

A

Dec CO2, Dec H+, Inc pH

70
Q

Effect of breathing slower on CO2 and pH

A

Inc CO2, Inc H+, Dec pH

71
Q

Effect of dec pH on resp rate

A

Inc rate to increase loss of CO2

72
Q

Effect of inc pH on resp rate

A

Dec rate to decrease loss of CO2

73
Q

Three renal mechanisms

A

HCO3- handling
Urine acidification
Ammonia synthesis

74
Q

90% of HCO3- handling takes place in the

A

Proximal tubule

75
Q

10% of HCO3- handling takes place in the

A

Distal tubule

76
Q

Describe how HCO3- handling takes place in the proximal cell

A

Na/K ATPase sets up low IC Na
NHE (1 Na in, 1 H+ out)
H+ out combines with filtered HCO3-
Forms H2CO3
Carbonic anhydrase catalyses the breakdown of H2C03 –> CO2 + H20
Both move into the cell when in the cell an intracellualr form of carbonic anhydrase reforms the H2CO3
H+ out through the NHE
HCO3- out through a basolateral HCO3/Na co transporter

77
Q

What is different in HCO3- handling in the proximal and distal tubule

A

Proton pump instead of NHE in the distal tubule

78
Q

Acidification of the urine accounts for what percentage of base conservation

A

25%

79
Q

Is NAH2PO4 an acid phosphate or alkaline

A

Acid

80
Q

Is NAHPO4 an acid phosphate or alkaline

A

Alkaline

81
Q

Describe how NaH2PO4/NaHPO4 is used in the acidifcaiton of the urine

A

Na/K ATP establishes a low IC Na
CO2 and H2O enter cell, combine under influence of carbonic anhydrase to H2CO3 this disociates to HCO3- and H+, H+ out through apical NHE, HcO3- out through basolateral channel
Na in H+ out through NHE
Filtered NaHPO4- combines with the H+ forms the acid salt

82
Q

What other two substances can be used in acidification of the urine

A

Uric acid and creatinine

83
Q

Is ammonia permeable to the membrane

A

Yes

84
Q

Is ammonium permemable, why?

A

No, charged

85
Q

What chemical can ammonia form from

A

Glutamine

86
Q

Describe how ammonia can be formed from glutamine

A

Glutamine to a-ketoglutarate

With loss of two ammonia and 2 H+ released

87
Q

Describe how ammonia production can be used for base conservation

A

Glutamine to a-keto in the cell (produces 2NH3 and 2H+)
NH3 diffuses out
H+ out through NHE
Combine out of the cell to form ammonium
Cant diffuse back into the cell

88
Q

Ammonia production base conservation is an example of

A

Diffusion trapping

89
Q 
What is the renal response for acidosis for :
H+ excretion
HCO3- excretion
pH of urine 
Change in plasma pH
A

Increase
Zero no change
Decrease
Increase

90
Q 
What is the renal response for alkalosis for :
H+ excretion
HCO3- excretion
pH of urine 
Change in plasma pH
A

Decrease
Increase
Increase
Decrease

91
Q

Describe respiratory acidosis and the renal compensations

A

CO2 elimination decreases
Due to lung disease (emphysema, chronic bronchitus)

Inc secretion of H+, inc reab of HCO3- rise in blood pH but the further rise in HCO3-

92
Q

Describe respiratory alkalosis and the renal compensations

A

CO2 eliminaition increases
Hyperventilation as cause due to fear/stress/pain

Dec secretion of H+, Dec reab of HCO3- fall in pH but the further drop in HCO3-

93
Q

Describe metabolic acidosis, the respiratory compensation and then subsequent renal correction

A

Due to ingestion of acid/ loss of alkaline fluid
e.g. diahorrea, diabetic ketoacidosis

Inc resp rate to dec arterial pCO2, increase pH and drop in PCO2

Increased secretion of H+ and increased reabsorption of HCO3-

94
Q

Describe metabolic alkalosis, the respiratory compensation and subsequent renal correction

A

Due to ingestion of alkaline fluid, loss of acid (may be from vomitting)

Dec resp rate, to increase arterial PCO2, decrease in pH

NO RENAL CORRECTION IN THIS INSTANCE IT IS UNABLE TO HELP

95
Q

What is a mixed dissorder

A

More than one primary alkalosis/acidosis

96
Q

If they are both the same type of dissorder the pH will be

A

Additive

97
Q

If the disorders are opposite then the pH will be

A

Subtractive

98
Q

How do alcoholic patients have a mixed disorder

A

Metbolic acidosis from the breakdown of the alcohol

Metabolic alkalosis from vomitting

99
Q

How is asthma a mixed dissorder

A 
Respiratory acidosis 
Lactic acidosis (form of metabolic acidosis)
100
Q

How are COPD an example of a mixed dissorder

A

Respiratory acidosis

Metabolic alkalosis

101
Q

What is the treatment for COPD

A

Diuretics

102
Q

How is salicylate poisoning an example of a mixed dissorder

A 
Respiratory alkalosis (aspirin stimulates the respiratory centre)
Metabolic acidosis (Increases the ammount of acid)

BMS242 CVS Phys (12 decks)

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