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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
Why is the carbonic acid/bicarbonate system highly affective (2)
1) Both carbonic acid and bicarbonate are present in high quantities in the ECF 2) Both carbonic acid and bicarbonate are high
26
What does the Henderson-Hasselbalch Equation do
Defines the relationship between H+ and a buffer system pair
27
What makes protein a good buffer system?
Because they are composed of amino acids, which that contain acidic and basic groups
28
Where is the protein buffer system most importantr?
For intracellular fluids, as they are very rich in protein
29
What is the haemoglobin buffer system most useful for?
H+ generated from metabolically produced CO2
30
Describe the phosphate buffer system
Uses an acid phosphate salt that can donate an H+ when the H+ concentration falls or accept an H+ when [H+] increases
31
What is the most important role for the phosphate buffer system?
Controlling the pH of the urine
32
How does the respiratory system play a role in buffering
By altering ventilation to increase or decrease the removal of CO2
33
T/F Decreasing ventilation increases CO2
True The decrease of exhalation of CO2 allows it to accumulate in the blood
34
A decrease of CO2 has what affect on H2CO3 and therefore bicarbonate and H+
It will decrease H2CO3 and therefore bicarbonate and H+
35
T/F The respiratory system is the fastest buffer system
False It is slower than the chemical buffer systems, also not as efficient
36
Why is the respiratory buffer system not as efficient as chemical ones?
It can only return the pH to 50% of the normal level
37
The respiratory system is particularly important for control of H+ concentration coming from what compound?
H+ coming from carbonic acid
38
The kidneys are important for removing H+ produced by what compounds?
Sulphur, phosphorus, and lactic acid
39
What are three ways that the kidneys help to control the pH of the ECF?
Excretion of H+ Excretion/reabsorption of HCO3- Secretion of ammonia
40
What is the pH of urine? What mainly influences this?
6.0 The excretion of ammonia makes it more acidic
41
T/F The rate of H+ secretion is under hormonal control
False It is under neither hormonal or neural control, but it is related to the acid-base status of the ECF
42
Describe the process of secretion of H+ from the kidneys
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
If plasma CO2 concentration decreases, what happens to H+ secretion?
It also decreases
44
T/F The kidneys are able to adjust H+ secretion from both carbonic and non-carbonic acid sources
True
45
Describe how HCO3- is reabsorbed in the kidneys
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
T/F A greater amount of HCO3- is filtered than H+ is secreted
False A greater amount of H+ is secreted than HCO3+ filtered
47
How is "new" HCO3- created?
CO2 from the plasma and tubular cell metabolism, as well as hydroxyl radicals are converted to HCO3- within the tubular cells
48
Describe how reabsorption of HCO3- is impacted when plasma [H+] are below normal
There is only a partial reabsorption of HCO3- with excess excretion in the urine.
49
The tubular cells can secrete H+ until the tubular fluid is what pH?
4.5
50
What are the two important urinary buffers?
Phosphate Ammonia
51
What is the primary purpose of phosphate filtration?
To remove excess phosphate from the body
52
When does the secretion of ammonia occur?
When the phosphate buffer systems are overwhelmed
53
Describe the ammonia buffer system
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
T/F When the [HCO3-]:[CO2] ratio falls below 20:1, this will cause acidosis
True Bc the pH is less than 7.4
55
What is respiratory acidosis?
The buildup of CO2 in the plasma, which causes the [HCO3-]:[CO2] ratio to fall below 20:1
56
What causes respiratory acidosis? Name 2 conditions that could cause this
When there is hypoventilation and less than normal amounts of CO2 are removed in the lungs Emphysema, chronic bronchitis, asthma, severe pneumonia
57
How is respiratory acidosis compensated?
Chemical buffers take up the extra H+ The kidneys secrete more H+ while both reabsorbing HCO3- and generating new HCO3-
58
T/F The respiratory system cannot play a role in respiratory acidosis compensation
True Because the respiratory system caused the issue in the first place, it cannot help compensate for it
59
What is respiratory alkalosis?
When there is a decrease in CO2 concentration that increases the [HCO3-]:[CO2] ratio above 20:1, leading to an increased pH
60
What causes respiratory alkalosis Provide two examples
When there is an increase in ventilation Fever, anxiety, severe infections
61
How is respiratory alkalosis compensated for?
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
T/F The respiratory can play a role in respiratory acidosis, but not respiratory alkalosis
False It CANNOT play a role in resp. acidosis, but can play a role in resp. alkalosis
63
What is metabolic acidosis?
Acidosis caused by anything other than respiratory acidosis Is characterized by a decrease of [HCO3-] concentration and a NORMAL [CO2]
64
How do you determine the cause of metabolic acidosis?
Measurement of the anion gap
65
What is the anion gap?
The difference between cations and anions in the plasma
66
What cations/anions are considered when calculating this
[Na+] [K+] [Cl-] [HCO3-]
67
What determines a low anion gap What can cause this?
< 8 mEq/L Loss of plasma albumin, such as during haemorrhage
68
What determines a normal anion gap What can cause it?
8-16 mEq/L Means there is a loss of HCO3-, maybe due to diarrhoea or renal diseases
69
What determines a high anion gap?
>16 mEq/L There is a decrease in [HCO3-]
70
What are the four common causes of metabolic acidosis
Severe diarrhea Diabetes Mellitus Strenuous Excersice Uraemic Acidosis
71
How would severe diarrhea cause metabolic acidosis?
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
How would diabetes cause metabolic acidosis?
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
How would strenuous exercise cause metabolic acidosis?
When muscles resort to anaerobic metabolism, lactic acid is produced, ultimately raising the anion gap
74
How would decreased renal function cause metabolic acidosis?
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
How is metabolic acidosis compensated?
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
Describe metabolic alkalosis
A reduced [H+] caused by a decrease in non-carbonic acids
77
What are two causes of metabolic alkalosis
Vomiting Ingestion of alkaline drugs
78
Describe how vomiting could lead to metabolic alkalosis?
The stomach contains HCl, which if vomiting occurs, the H+ leads the stomach, and therefore cannot be reabsorbed so plasma pH increases
79
How does the body compensate for metabolic alkalosis?
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
Identify the pH, [CO2], [HCO3-] and [HCO3-]:[CO2] in a normal acid-base status
pH: Normal [CO2]: Normal [HCO3-]: Normal [HCO3-]:[CO2]: 20/1
81
Identify the pH, [CO2], [HCO3-] and [HCO3-]:[CO2] in compensated respiratory acidosis
pH: Normal [CO2]: Increased [HCO3-]: Increased [HCO3-]:[CO2]: 40/2
82
Identify the pH, [CO2], [HCO3-] and [HCO3-]:[CO2] in uncompensated respiratory alkalosis
pH: Increased [CO2]: Decreased [HCO3-]: Normal [HCO3-]:[CO2]: 40/1
83
Identify the pH, [CO2], [HCO3-] and [HCO3-]:[CO2] in uncompensated metabolic acidosis
pH: Decreased [CO2]: Normal [HCO3-]: Decreased [HCO3-]:[CO2]: 10/1

Physiology 216 (5 decks)

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