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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
Describe what would happen to the Carbonic acid/bicarbonate buffer if there was an increase in CO2
Eqbm shift right to minimise change | More H+ produced
26
What is the equation for pH in the Carbonic acid/bicarbonate buffer system
Ph = pK + [HCO3/H2CO3]
27
What can be said about the concentrations of H2CO3 + CO2 at eqbm
Equal
28
Rewrite the equation of the Carbonic acid/bicarbonate buffer system to include CO2
pH = pK + [HCO3/CO2]
29
What is pK at 37 deg
6.1
30
Describe what would happen to the Davenport diagram if acid was added
Conc of HCO3- decreases pH decreases Metabolic acidosis
31
What is the normal [HCO3]//[CO2]
20:1
32
Using the normal [HCO3]/[CO2] calculate pH
``` pH = 6.1 + log 20 pH = 7.4 ```
33
Describe what would happen to the Davenport diagram if CO2 conc was increased
Increase in [hco3] Decrease in pH Respiratory acidosis
34
Describe what would happen to the Davenport diagram if base was added
Increase in [hco3] Increase in pH Metabolic alkalosis
35
Describe what would happen to the Davenport diagram if concentration of CO2 decreases
Decrease in [hco3] Increase in pH Respiratory alkalosis
36
Two chemoreceptors involved in the control of blood gas composition
Central and peripheral
37
Hypoxia is
Decrease in O2
38
Hypercapnia is
Increase in CO2
39
Peripheral chemoreceptors are found
Carotid and aortic bodies
40
Main stimulus for the peripheral chemoreceptors
Hypoxia
41
What 3 nerves are involved with the peripheral chemoreceptors
Sinus Vagus Glossopharyngeal
42
Weight of the carotid bodies
2mg
43
Supporting cells of the carotid body are called
Type II supporting cells
44
What two stuructures of the carotid body help increase blood flow
Arteriole | Siusoid
45
What is the receptive cell of the carotid body
Glomus cell
46
Compare blood flow through the carotid body to the brain
Carotid body has over 40x per unit mass than the brain
47
Describe the mechanism of activation of the glomus cell in response to Dec PO2 Inc PCO2 Dec pH
``` Inhibition of the BK K channels Depolarisation Action potential firing VGCC open Ca influx NT release Afferent nerve fibre stimulation ```
48
What NTs are released from the glomus cell
Ach, dopamin, NA, 5-HT, Substance P, ANP
49
What is different in SIDs babies and normal babies in terms of the peripheral chemoreceptors
Increase [] of dopamine and NA in SIDs babies glomus cell
50
Describe how the sensitivity to PO2 of the peripheral chemoreceptor changes with acid-base status
At lower pH they are more sens. to pO2
51
Describe how sensitivity to pCO2 of the peripheral chemoreceptor changes with pH
At the higher pH they are less sensitive to changes in pCO2
52
Central chemoreceptors are the primary source for the
Tonic drive for breathing
53
What is the main activator for the central chemoreceptors
Hypercapnia
54
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
double the ventilation rate | this would only be seen with a 50% decrease in PO2
55
What is the experiemental evidence for the central chemoreceptors
Perfusion of the cerebral ventricles with an acidic solution and hyperventilation was observed
56
Descrive the location of the central chemoreceptors
Within the brain parenchyma Bathed in BECF Separated from the arterial blood by the BBB
57
Describe the effect an increase in arterial pCO2 would have on the BECF, what long term compensation may be involved
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
Describe what effect the poor ionic perm of the BBB has on metabolic disorders compared with respiratory disorders
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
Can H+ cross BBB
No
60
Can HCO3- cross BBB
No
61
Can CO2 cross BBB
Yes
62
Where do the central chemoreceptors project to
The ventrolateral medulla and other brainstem nuclei
63
How many neuronal populations of the central chemoR, what are they called
2 | Acid activating + inhibiting
64
Acid inhibiting release
GABA
65
Acid activating release
Serotonin
66
What is seen in SIDS babies in terms of the central chemoreceptors
Lack the serotonergic neurones
67
Response of both ChemoR to respiratory acidosis
Both central and peripheral Normoxic central 65-80% Peripheral faster As PO2 falls the response to PCO2 is enhanced
68
Response of both ChemoR to metabolic acidosis
``` Severe - hyperventilation - --- Kussmaul breathing Descrease in PCO2 Peripheral acute response Central longer term role ```
69
Effect of breathing faster or CO2 and pH
Dec CO2, Dec H+, Inc pH
70
Effect of breathing slower on CO2 and pH
Inc CO2, Inc H+, Dec pH
71
Effect of dec pH on resp rate
Inc rate to increase loss of CO2
72
Effect of inc pH on resp rate
Dec rate to decrease loss of CO2
73
Three renal mechanisms
HCO3- handling Urine acidification Ammonia synthesis
74
90% of HCO3- handling takes place in the
Proximal tubule
75
10% of HCO3- handling takes place in the
Distal tubule
76
Describe how HCO3- handling takes place in the proximal cell
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
What is different in HCO3- handling in the proximal and distal tubule
Proton pump instead of NHE in the distal tubule
78
Acidification of the urine accounts for what percentage of base conservation
25%
79
Is NAH2PO4 an acid phosphate or alkaline
Acid
80
Is NAHPO4 an acid phosphate or alkaline
Alkaline
81
Describe how NaH2PO4/NaHPO4 is used in the acidifcaiton of the urine
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
What other two substances can be used in acidification of the urine
Uric acid and creatinine
83
Is ammonia permeable to the membrane
Yes
84
Is ammonium permemable, why?
No, charged
85
What chemical can ammonia form from
Glutamine
86
Describe how ammonia can be formed from glutamine
Glutamine to a-ketoglutarate | With loss of two ammonia and 2 H+ released
87
Describe how ammonia production can be used for base conservation
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
Ammonia production base conservation is an example of
Diffusion trapping
89
``` What is the renal response for acidosis for : H+ excretion HCO3- excretion pH of urine Change in plasma pH ```
Increase Zero no change Decrease Increase
90
``` What is the renal response for alkalosis for : H+ excretion HCO3- excretion pH of urine Change in plasma pH ```
Decrease Increase Increase Decrease
91
Describe respiratory acidosis and the renal compensations
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
Describe respiratory alkalosis and the renal compensations
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
Describe metabolic acidosis, the respiratory compensation and then subsequent renal correction
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
Describe metabolic alkalosis, the respiratory compensation and subsequent renal correction
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
What is a mixed dissorder
More than one primary alkalosis/acidosis
96
If they are both the same type of dissorder the pH will be
Additive
97
If the disorders are opposite then the pH will be
Subtractive
98
How do alcoholic patients have a mixed disorder
Metbolic acidosis from the breakdown of the alcohol | Metabolic alkalosis from vomitting
99
How is asthma a mixed dissorder
``` Respiratory acidosis Lactic acidosis (form of metabolic acidosis) ```
100
How are COPD an example of a mixed dissorder
Respiratory acidosis | Metabolic alkalosis
101
What is the treatment for COPD
Diuretics
102
How is salicylate poisoning an example of a mixed dissorder
``` Respiratory alkalosis (aspirin stimulates the respiratory centre) Metabolic acidosis (Increases the ammount of acid) ```

BMS242 CVS Phys (12 decks)

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