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Physiology 216 > Module 5: Acid-Base Balance > Flashcards

Module 5: Acid-Base Balance Flashcards

1
Q

Define an acid

A

Substances that release H+ when in solution

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2
Q

Define a base

A

Substances that bind with free H+ in solution

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3
Q

Define a strong acid

A

Substance that completely dissociates into H+ and is anion in solution

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4
Q

Define a weak acid

A

A substance that only partially dissociates into H+ and its anion in solution

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5
Q

What characterizes a strong/weak base

A

Its ability to bind H+

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6
Q

What is the difference in [H+] between solution A with a pH of 2.6 and solution B with a pH of 6.6?

A

10^4
or 10 000

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7
Q

What is the normal pH of arterial blood?

A

7.45

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8
Q

What is the normal pH of venous blood

A

7.35

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9
Q

At what blood pH does acidosis occur at?

A

Anything below 7.35

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10
Q

At what blood pH does alkalosis occur at?

A

Anything above 7.45

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11
Q

How does acidosis affect nerve and muscle cell function?

A

It suppresses the CNS

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12
Q

How dos alkalosis affect nerve and muscle cell function

A

It leads to over-excitability of both the CNS and PNS

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13
Q

Describe the effects acidosis or alkalosis could have on enzymes

A

It would either speed up or slow down enzymatic activities

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14
Q

Describe how acidotic blood will affect K+

A

More H+ than K+ will be secreted, leading to an increase in plasma K+, this will then lead to increased ability for excitable cells to become activated

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15
Q

What are 3 primary sources of H+

A

Carbonic Acid Formation
Inorganic acids produced from breakdown of nutrients
Organic acids from intermediary metabolism

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16
Q

Describe how carbonic acid is formed. What does it dissociate into?

A

CO2 and H2O byproducts from cellular respiration is converted into carbonic acid by carbonic anhydrase
It then dissociates into bicarbonate and H+

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17
Q

In tissues where CO2 is removed, which direction is the reaction directed towards

A

The backwards direction to produce less H+

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18
Q

How do vegetables counter the acidity of protein

A

Vegetables produce more basic compounds, which can help counter the H+ formed by protein metabolism of sulphuric acid and phosphoric acid

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19
Q

Give an example of an organic acid produced from intermediary metabolism

A

Lactic acid produced in the muscles
Fatty acids due to fat metabolism

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20
Q

What is a chemical buffer system

A

A mixture of two chemicals that interact in such a way to resist pH changes when something acidic/basic is added to the system

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21
Q

What are the four different buffer systems

A

The carbonic acid/bicarbonate buffer system
The protein buffer system
The haemoglobin buffer system
The phosphate buffer system

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22
Q

Describe what would happen if a base is added to a solution with the carbonic acid/bicarbonate buffer system

A

The base will bind with free H+, resulting in more carbonic acid produced

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23
Q

T/F
The phosphate buffer system is the most important in the body

A

False
The H2CO4/HCO3- is the most important in the body

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24
Q

What is the one limitation of the carbonic acid/bicarbonate system

A

It cannot buffer against changes in H2CO3 or HCO3-

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25
Q

Why is the carbonic acid/bicarbonate system highly affective (2)

A

1) Both carbonic acid and bicarbonate are present in high quantities in the ECF
2) Both carbonic acid and bicarbonate are high

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26
Q

What does the Henderson-Hasselbalch Equation do

A

Defines the relationship between H+ and a buffer system pair

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27
Q

What makes protein a good buffer system?

A

Because they are composed of amino acids, which that contain acidic and basic groups

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28
Q

Where is the protein buffer system most importantr?

A

For intracellular fluids, as they are very rich in protein

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29
Q

What is the haemoglobin buffer system most useful for?

A

H+ generated from metabolically produced CO2

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30
Q

Describe the phosphate buffer system

A

Uses an acid phosphate salt that can donate an H+ when the H+ concentration falls or accept an H+ when [H+] increases

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31
Q

What is the most important role for the phosphate buffer system?

A

Controlling the pH of the urine

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32
Q

How does the respiratory system play a role in buffering

A

By altering ventilation to increase or decrease the removal of CO2

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33
Q

T/F
Decreasing ventilation increases CO2

A

True
The decrease of exhalation of CO2 allows it to accumulate in the blood

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34
Q

A decrease of CO2 has what affect on H2CO3 and therefore bicarbonate and H+

A

It will decrease H2CO3 and therefore bicarbonate and H+

35
Q

T/F
The respiratory system is the fastest buffer system

A

False
It is slower than the chemical buffer systems, also not as efficient

36
Q

Why is the respiratory buffer system not as efficient as chemical ones?

A

It can only return the pH to 50% of the normal level

37
Q

The respiratory system is particularly important for control of H+ concentration coming from what compound?

A

H+ coming from carbonic acid

38
Q

The kidneys are important for removing H+ produced by what compounds?

A

Sulphur, phosphorus, and lactic acid

39
Q

What are three ways that the kidneys help to control the pH of the ECF?

A

Excretion of H+
Excretion/reabsorption of HCO3-
Secretion of ammonia

40
Q

What is the pH of urine?
What mainly influences this?

A

6.0
The excretion of ammonia makes it more acidic

41
Q

T/F
The rate of H+ secretion is under hormonal control

A

False
It is under neither hormonal or neural control, but it is related to the acid-base status of the ECF

42
Q

Describe the process of secretion of H+ from the kidneys

A

CO2 enters the tubular cells and with water, under the influence of intracellular carbonic anhydrase, forms H2CO3, which dissociates into H+ and HCO3- , a carrier on the luminal membrane will then transport the H+ into the tubular fluid

43
Q

If plasma CO2 concentration decreases, what happens to H+ secretion?

A

It also decreases

44
Q

T/F
The kidneys are able to adjust H+ secretion from both carbonic and non-carbonic acid sources

A

True

45
Q

Describe how HCO3- is reabsorbed in the kidneys

A

HCO3- in the tubular fluid combines with secreted H+ to form H2CO3, which breaks down into CO2 and H2O. These then cross the luminal membrane into a tubular cell, where carbonic anhydrase converts CO2 and H2O back into H2CO3, which freely dissocates back into HCO3- and H+
HCO3- then crosses the basolateral membrane and leaves the cell

46
Q

T/F
A greater amount of HCO3- is filtered than H+ is secreted

A

False
A greater amount of H+ is secreted than HCO3+ filtered

47
Q

How is “new” HCO3- created?

A

CO2 from the plasma and tubular cell metabolism, as well as hydroxyl radicals are converted to HCO3- within the tubular cells

48
Q

Describe how reabsorption of HCO3- is impacted when plasma [H+] are below normal

A

There is only a partial reabsorption of HCO3- with excess excretion in the urine.

49
Q

The tubular cells can secrete H+ until the tubular fluid is what pH?

A

4.5

50
Q

What are the two important urinary buffers?

A

Phosphate
Ammonia

51
Q

What is the primary purpose of phosphate filtration?

A

To remove excess phosphate from the body

52
Q

When does the secretion of ammonia occur?

A

When the phosphate buffer systems are overwhelmed

53
Q

Describe the ammonia buffer system

A

Ammonia is secreted into the tubular fluid from the tubular cells and then reacts with H+ to form ammonium ion
The ammonium ion is not reabsorbed, but excreted in the urine, ultimately removing H+ from the body

54
Q

T/F
When the [HCO3-]:[CO2] ratio falls below 20:1, this will cause acidosis

A

True
Bc the pH is less than 7.4

55
Q

What is respiratory acidosis?

A

The buildup of CO2 in the plasma, which causes the [HCO3-]:[CO2] ratio to fall below 20:1

56
Q

What causes respiratory acidosis?
Name 2 conditions that could cause this

A

When there is hypoventilation and less than normal amounts of CO2 are removed in the lungs

Emphysema, chronic bronchitis, asthma, severe pneumonia

57
Q

How is respiratory acidosis compensated?

A

Chemical buffers take up the extra H+
The kidneys secrete more H+ while both reabsorbing HCO3- and generating new HCO3-

58
Q

T/F
The respiratory system cannot play a role in respiratory acidosis compensation

A

True
Because the respiratory system caused the issue in the first place, it cannot help compensate for it

59
Q

What is respiratory alkalosis?

A

When there is a decrease in CO2 concentration that increases the [HCO3-]:[CO2] ratio above 20:1, leading to an increased pH

60
Q

What causes respiratory alkalosis
Provide two examples

A

When there is an increase in ventilation

Fever, anxiety, severe infections

61
Q

How is respiratory alkalosis compensated for?

A

The chemical buffer systems release H+ and the respiratory system decreases ventilation
If the alkalosis persists for a few days, the kidneys compensate by decreasing H+ secretion, and increasing HCO3- secretion

62
Q

T/F
The respiratory can play a role in respiratory acidosis, but not respiratory alkalosis

A

False
It CANNOT play a role in resp. acidosis, but can play a role in resp. alkalosis

63
Q

What is metabolic acidosis?

A

Acidosis caused by anything other than respiratory acidosis
Is characterized by a decrease of [HCO3-] concentration and a NORMAL [CO2]

64
Q

How do you determine the cause of metabolic acidosis?

A

Measurement of the anion gap

65
Q

What is the anion gap?

A

The difference between cations and anions in the plasma

66
Q

What cations/anions are considered when calculating this

A

[Na+] [K+]
[Cl-] [HCO3-]

67
Q

What determines a low anion gap
What can cause this?

A

< 8 mEq/L
Loss of plasma albumin, such as during haemorrhage

68
Q

What determines a normal anion gap
What can cause it?

A

8-16 mEq/L
Means there is a loss of HCO3-, maybe due to diarrhoea or renal diseases

69
Q

What determines a high anion gap?

A

> 16 mEq/L
There is a decrease in [HCO3-]

70
Q

What are the four common causes of metabolic acidosis

A

Severe diarrhea
Diabetes Mellitus
Strenuous Excersice
Uraemic Acidosis

71
Q

How would severe diarrhea cause metabolic acidosis?

A

As the digestive juices are rich in bicarbonate, in diarrhea, they may be eliminated before they can be reabsorbed, causing a decrease in their concentration
This imbalances the bicarbonate/carbonic acid buffer system, leading to a greater release of H+ from bicarbonate dissociating

72
Q

How would diabetes cause metabolic acidosis?

A

Without insulin, glucose cannot enter cells so they revert to fast metabolism to generate ATP
This causes an increase in keto acids, which raise the anion gap

73
Q

How would strenuous exercise cause metabolic acidosis?

A

When muscles resort to anaerobic metabolism, lactic acid is produced, ultimately raising the anion gap

74
Q

How would decreased renal function cause metabolic acidosis?

A

If the kidneys could not excrete the excess H+ produced from metabolism, there will be an increase in its concentration, leading to an increased anion gap

75
Q

How is metabolic acidosis compensated?

A

Buffers can take up the extra H+, and the lungs can blow off extra H+, and the kidneys can secrete more H+ or conserve HCO3-

76
Q

Describe metabolic alkalosis

A

A reduced [H+] caused by a decrease in non-carbonic acids

77
Q

What are two causes of metabolic alkalosis

A

Vomiting
Ingestion of alkaline drugs

78
Q

Describe how vomiting could lead to metabolic alkalosis?

A

The stomach contains HCl, which if vomiting occurs, the H+ leads the stomach, and therefore cannot be reabsorbed so plasma pH increases

79
Q

How does the body compensate for metabolic alkalosis?

A

The chemical buffer systems liberate H+
Ventilation reduces to raise plasma CO2
If the alkalosis persists, the kidneys will decrease H+ secretion and increase HCO3-

80
Q

Identify the pH, [CO2], [HCO3-] and [HCO3-]:[CO2] in a normal acid-base status

A

pH: Normal
[CO2]: Normal
[HCO3-]: Normal
[HCO3-]:[CO2]: 20/1

81
Q

Identify the pH, [CO2], [HCO3-] and [HCO3-]:[CO2] in compensated respiratory acidosis

A

pH: Normal
[CO2]: Increased
[HCO3-]: Increased
[HCO3-]:[CO2]: 40/2

82
Q

Identify the pH, [CO2], [HCO3-] and [HCO3-]:[CO2] in uncompensated respiratory alkalosis

A

pH: Increased
[CO2]: Decreased
[HCO3-]: Normal
[HCO3-]:[CO2]: 40/1

83
Q

Identify the pH, [CO2], [HCO3-] and [HCO3-]:[CO2] in uncompensated metabolic acidosis

A

pH: Decreased
[CO2]: Normal
[HCO3-]: Decreased
[HCO3-]:[CO2]: 10/1

Physiology 216 (5 decks)

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