1
Q
What does acid-base balance refer to in the body?
A
The regulation of hydrogen ions (H⁺) in body fluids.
2
Q
How are acids defined in terms of H⁺?
A
Substances that release H⁺ when in solution.
3
Q
How are bases defined in terms of H⁺?
A
Substances that bind free H⁺ in solution.
4
Q
What is a key characteristic of acids at the molecular level?
A
They are hydrogen-containing substances that dissociate into H⁺ and an anion in solution.
5
Q
Do all hydrogen-containing substances qualify as acids? Why or why not?
A
No, only those whose hydrogen can dissociate; if hydrogen is tightly bound, the substance is not classified as an acid.
6
Q
What is an anion?
A
A negatively charged ion.
7
Q
What happens when hydrochloric acid (HCl) is placed in solution?
A
It dissociates almost completely into H⁺ and Cl⁻.
8
Q
What happens when carbonic acid (H₂CO₃) is placed in solution?
A
It partially dissociates into H⁺ and HCO₃⁻.
9
Q
What does “dissociation” mean in the context of acids?
A
The separation of a compound into H⁺ and its corresponding anion in solution.
10
Q
What determines whether an acid is strong or weak?
A
The degree to which it dissociates into H⁺ in solution.
11
Q
How is a strong acid defined?
A
An acid that completely dissociates into H⁺ and anions in solution.
12
Q
How is a weak acid defined?
A
An acid that only partially dissociates into H⁺ and anions in solution.
13
Q
Which is stronger: HCl or H₂CO₃, and why?
A
HCl, because it dissociates completely, releasing more H⁺.
14
Q
If equal amounts of HCl and H₂CO₃ are added to solutions, which produces more H⁺?
A
HCl produces more H⁺ because it is a strong acid.
15
Q
What is the defining function of bases in solution?
A
To bind free H⁺ and remove it from solution.
16
Q
How do strong and weak bases differ?
A
Strong bases bind H⁺ more easily than weak bases.
17
Q
What happens when sodium hydroxide (NaOH) is added to water?
A
It dissociates into Na⁺ and OH⁻.
18
Q
How does OH⁻ from a base affect H⁺ concentration?
A
OH⁻ binds to free H⁺ to form water, decreasing H⁺ concentration.
19
Q
What is the overall effect of adding a strong base on pH?
A
It decreases H⁺ concentration, making the solution more basic (increasing pH).
20
Q
How are solutions classified as acidic or basic?
A
Based on their hydrogen ion (H⁺) concentration relative to pure water.
21
Q
Why was the term pH developed?
A
To express the concentration of H⁺ in a solution in a more convenient way.
22
Q
What is the typical hydrogen ion concentration in extracellular fluid (ECF)?
A
4 × 10⁻⁸ moles/L (M).
23
Q
Why are small changes in [H⁺] physiologically important?
A
Because [H⁺] is extremely low, so even small changes can have significant effects.
24
Q
What does a base-10 logarithm (log₁₀) represent?
A
How many times 10 must be multiplied by itself to produce a given number.
25
What is log₁₀(10)?
1
26
What is log₁₀(100)?
2
27
What is the formula used to calculate pH?
pH = log₁₀(1 / [H⁺]).
28
What is the relationship between [H⁺] and pH?
They are inversely related: as [H⁺] increases, pH decreases.
29
What does a lower pH indicate about a solution?
It is more acidic and has a higher [H⁺].
30
What does a higher pH indicate about a solution?
It is more basic (alkaline) and has a lower [H⁺].
31
Why does each pH unit represent a 10-fold change in [H⁺]?
Because the pH scale is logarithmic (base 10).
32
How does [H⁺] compare between pH 7 and pH 6?
A solution at pH 7 has 10 times less H⁺ than a solution at pH 6.
33
What is the pH of pure water?
7.0
34
Why is pure water considered neutral?
Because very little H₂O dissociates into H⁺ and OH⁻, so it is neither acidic nor basic.
35
What defines an acidic solution in terms of pH?
A pH less than 7.0 (higher [H⁺] than pure water).
36
What defines a basic (alkaline) solution in terms of pH?
A pH greater than 7.0 (lower [H⁺] than pure water).
37
What is the pH of lemons?
2.0
38
What is the pH of vinegar?
2.4
39
What is the pH of bananas?
4.7
40
What is the pH of milk?
6.6
41
What is the pH of sodium bicarbonate?
8.9
42
What is the typical pH of most soaps?
Around 10
43
What is the pH of drain cleaner and what does this indicate?
pH 14; it is a very strong base.
44
What is the pH of a 0.0025 M HCl solution?
2.6
45
The log (1/H+) = pH equation can be reorgnized as?
[H+] = 10^-pH
46
Suppose another substance has a pH of 6.6. Find the hydrogen ion concentration of this substance.
2.51 x 10^-7 M
47
What is the approximate difference in hydrogen ion concentration between the first substance (solution A) with a pH of 2.6, and the second substance (solution B) with a pH of 6.6?
Solution A has a [H+] 10,000 times higher than Solution B
48
How is pH in body fluids regulated?
It is highly regulated to maintain normal physiological function.
49
What is the normal pH of arterial blood?
7.45
50
What is the normal pH of venous blood?
7.35
51
What value is typically used as the average normal blood pH?
7.4
52
What is acidosis?
A condition where blood pH falls below 7.35.
53
What is alkalosis?
A condition where blood pH rises above 7.45.
54
What pH range is incompatible with life?
Below 6.8 or above 8.0.
55
How quickly can extreme pH changes (below 6.8 or above 8.0) cause death?
Within a few seconds
56
What are the three main effects of large changes in pH?
Effects on nerve/muscle function, enzyme activity, and potassium (K⁺) balance.
57
How does acidosis affect the central nervous system?
It suppresses CNS activity.
58
What are early symptoms of acidosis on the CNS?
Disorientation
59
What can severe acidosis lead to?
Coma and death
60
How does alkalosis affect the nervous system?
It causes over-excitability of both the central and peripheral nervous systems.
61
What can extreme alkalosis cause?
Death due to respiratory muscle spasms or convulsions.
62
What is the optimal pH for most enzyme activity in the body?
Around 7.4.
63
How do pH changes affect enzyme activity?
They can either speed up or slow down enzymatic reactions.
64
Why are changes in enzyme activity due to pH harmful?
Because both increased and decreased activity can have deleterious effects.
65
How can changes in [H⁺] affect potassium (K⁺) levels?
H⁺ can substitute for K⁺ in secretion, altering plasma K⁺ levels.
66
What happens to plasma K⁺ levels during acidosis?
Plasma K⁺ increases.
67
Why does plasma K⁺ increase during acidosis?
More H⁺ is secreted instead of K⁺, leading to K⁺ retention in the plasma.
68
How does increased plasma K⁺ affect excitable cells?
It causes them to depolarize and become more excitable.
69
Is H⁺ constantly produced in the body under normal conditions?
Yes, there is an almost constant production or release of H⁺ into body fluids.
70
What is the main source of H⁺ production in the body?
Metabolic activities.
71
What are the three primary sources of H⁺ in the body?
Carbonic acid formation, inorganic acids from nutrient breakdown, and organic acids from intermediary metabolism.
72
What are the metabolic by-products of cellular respiration?
CO₂ and H₂O.
73
What enzyme facilitates the formation of carbonic acid from CO₂ and H₂O?
Carbonic anhydrase
74
What is the chemical reaction for carbonic acid formation and dissociation?
CO₂ + H₂O ↔ H₂CO₃ ↔ HCO₃⁻ + H⁺
75
In which direction is the carbonic acid reaction driven in tissues, and why?
Forward, because CO₂ is produced, leading to increased H⁺ formation.
76
In which direction is the carbonic acid reaction driven in the lungs, and why?
Backward, because CO₂ is removed, reducing H⁺.
77
What condition ensures no net change in H⁺ from carbonic acid reactions?
When respiration balances metabolic activity.
78
What type of nutrients contribute to inorganic acid production?
Dietary proteins.
79
What acids are formed from the breakdown of proteins?
Sulphuric acid and phosphoric acid.
80
Which elements in proteins lead to acid formation?
Sulphur and phosphorus.
81
How do strong acids like sulphuric and phosphoric acid affect H⁺ levels?
They freely dissociate, increasing H⁺ in body fluids.
82
Are sulphuric acid and phosphoric acid strong or weak acids?
Strong acids.
83
How do fruits and vegetables affect acid-base balance?
They produce more bases than acids, helping counteract H⁺.
84
What happens to H⁺ levels in a protein-rich diet?
Excess H⁺ is produced.
85
What are organic acids from intermediary metabolism?
Acids produced during normal metabolic processes, such as fat and muscle metabolism.
86
What are examples of organic acids in the body?
Fatty acids and lactic acid.
87
Are organic acids strong or weak acids?
Weak acids.
88
Do weak organic acids still contribute to H⁺ levels?
Yes, they dissociate and add to the free H⁺ pool.
89
What is a chemical buffer?
A mixture of two chemicals that resist pH changes when an acid or base is added.
90
Why are buffer systems important in the human body?
Because pH must be maintained within a very narrow range.
91
What is a buffer system?
A system of two chemicals that undergo a reversible reaction to either remove or add H⁺ to stabilize pH.
92
How many buffer systems are in the human body?
4
93
What are the four buffer systems in the body?
Carbonic acid–bicarbonate, protein, haemoglobin, and phosphate buffer systems.
94
What is the chemical equation for the carbonic acid–bicarbonate buffer system?
H₂CO₃ ↔ HCO₃⁻ + H⁺
95
What happens in the buffer system when a base is added?
The base binds free H⁺, causing the reaction to shift forward and release more H⁺.
96
What happens in the buffer system when an acid is added?
The reaction shifts backward, reducing the amount of free H⁺.
97
What happens when a strong acid is added to an unbuffered solution?
All added H⁺ remains free, increasing acidity.
98
What happens when a strong acid is added to a buffered solution?
Buffer components (e.g., HCO₃⁻) bind some of the H⁺, reducing the increase in acidity.
99
What role does bicarbonate (HCO₃⁻) play in buffering?
It binds free H⁺ to remove it from solution.
100
Why is the carbonic acid–bicarbonate buffer system the most important?
It buffers most pH changes in the body (except those caused by CO₂-generated H₂CO₃).
101
Why can’t the carbonic acid–bicarbonate system buffer changes in H₂CO₃ or HCO₃⁻ themselves?
Because a buffer system cannot buffer its own components.
102
What is one reason the carbonic acid–bicarbonate buffer system is highly effective?
Both H₂CO₃ and HCO₃⁻ are present in high concentrations in the ECF.
103
How does high concentration of buffer components improve buffering?
It increases the system’s capacity to resist pH changes.
104
What is the second reason the carbonic acid–bicarbonate buffer system is effective?
Its components are tightly regulated in the body.
105
How do the kidneys contribute to buffer regulation?
They regulate HCO₃⁻ (bicarbonate) levels.
106
How does the respiratory system contribute to buffer regulation?
It regulates H₂CO₃ by controlling CO₂ levels.
107
Describe how the H2CO3:HCO3- buffer pair operates to minimize changes in pH during Intense exercise and vomiting.
Intense exercise results in the formation of lactic acid. This lactic acid means a higher concentration of H+ in the body, which will bind to HCO3- and drive the reaction to the left. This effectively removes the H+ so that it cannot increase the acidity of the ECF.
The opposite also happens when there is a decrease of H+, which occurs following vomiting, in which the H2C O3 dissociates to release a H+ and prevent the ECF from becoming too basic.
108
What does the Henderson-Hasselbalch equation describe?
The relationship between H⁺ and a buffer system pair, allowing calculation of the pH around which the buffer operates.
109
What is the Henderson-Hasselbalch equation for the bicarbonate buffer system?
pH = pKa + log [HCO₃⁻ / H₂CO₃]
110
How is the Henderson-Hasselbalch equation adapted for the human body?
Since [H₂CO₃] ≈ [CO₂], the equation is rewritten as: pH = pKa + log [HCO₃⁻ / CO₂]
111
What does pKa represent in the Henderson-Hasselbalch equation?
The acid dissociation constant for a given acid; it is constant for that acid.
112
What is the pKa of H₂CO₃?
6.1
113
How do you calculate the pH of the extracellular fluid (ECF) using the Henderson-Hasselbalch equation?
pH = pKa + log [HCO₃⁻ / CO₂]; for normal ECF: pH = 6.1 + log[20/1] = 7.4
114
What is the normal ratio of HCO₃⁻ to CO₂ in the body?
20:1
115
What is the normal pH of the extracellular fluid (ECF)?
7.4
116
Why is the Henderson-Hasselbalch equation useful clinically?
It allows prediction of pH changes based on changes in bicarbonate or CO₂, helping assess acid-base balance.
117
Calculate the pH of a solution if the p Ka = 2.1, [HCO 3-] = 0.57 M, and [C
O2] = 0.23 M.
2.5
118
Why are proteins excellent buffers?
Because amino acids in proteins contain acidic and basic groups that can donate or accept H⁺.
119
Where is the protein buffer system most important?
Intracellular fluids, as cells are rich in protein.
120
Do plasma proteins significantly buffer pH?
No, compared to the H₂CO₃:HCO₃⁻ system, plasma proteins play a minor role.
121
What happens if intracellular pH rises?
Amino acids act as acids and release H⁺.
122
What happens if intracellular pH falls?
Amino acids act as bases and absorb H⁺.
123
What is the role of haemoglobin in acid-base balance?
It buffers H⁺ generated from metabolically produced CO₂, preventing venous blood from becoming too acidic.
124
What happens to the haemoglobin buffer system in the lungs?
The reaction reverses to release CO₂ for exhalation.
125
How is CO₂ in plasma buffered?
Most CO₂ entering RBCs forms H₂CO₃ with the help of carbonic anhydrase
126
How does haemoglobin help with CO₂ buffering?
H⁺ generated from H₂CO₃ binds to haemoglobin, preventing acidification of body fluids and freeing O₂ for tissues.
127
What happens to H₂CO₃ in plasma?
It dissociates into HCO₃⁻ and H⁺.
128
What is the chemical equation for the phosphate buffer system?
Na₂HPO₄ + H⁺ ↔ NaH₂PO₄ + Na⁺
129
How does the phosphate buffer system work when [H⁺] falls?
It donates H⁺ to maintain pH.
130
How does the phosphate buffer system work when [H⁺] rises?
It accepts H⁺ to reduce acidity.
131
Why is the phosphate buffer system less significant in ECF?
Its concentration in ECF is low.
132
Where is the phosphate buffer system most effective?
Inside cells and in the urine.
133
What is the main role of the phosphate buffer system in urine?
To buffer excreted H⁺ in the tubular fluid.
134
Why is the phosphate buffer system the only buffer in urine?
Excess dietary phosphate is filtered by the kidneys and accumulates in the tubular fluid, where it can buffer H⁺.
135
How does the phosphate buffer system contribute to intracellular pH regulation?
Higher phosphate concentrations inside cells allow it to effectively accept or donate H⁺.
136
Carbonic Acid: Bicarbonate Buffer System
Primary ECF buffer against non-carbonic acids changes
137
Protein Buffer System
Primary ICF buffer, also buffers ECF
138
Haemoglobin Buffer System
Primary buffer against carbonic acid changes
139
Phosphate Buffer System
Important urinary buffer; also buffers ICF
140
What is the main function of chemical buffers?
To quickly add or remove H⁺ from body fluids to resist pH changes.
141
Why are chemical buffers considered the first line of defense against pH changes?
Because they act almost instantaneously to neutralize H⁺.
142
Do chemical buffers have unlimited capacity to absorb H⁺?
No, they have a limited capacity and can eventually become overwhelmed.
143
Why can chemical buffers only remain effective long-term?
Because H⁺ is eventually removed by the respiratory and renal systems.
144
How do the respiratory and renal systems contribute to pH control?
By eliminating H⁺ from the body, not by buffering it.
145
What happens if chemical buffers were relied upon alone without the respiratory or renal systems?
They would eventually be overwhelmed due to constant H⁺ addition from metabolism.
146
Why is the respiratory system important in acid-base balance?
Because CO₂ leads to H⁺ generation, and the respiratory system regulates CO₂ removal through ventilation.
147
What is the primary determinant of respiratory activity?
Arterial [H⁺].
148
What happens when arterial [H⁺] increases from metabolic (non-respiratory) sources?
The respiratory centre increases pulmonary ventilation to remove excess CO₂.
149
How does increased ventilation affect CO₂ and H⁺ levels?
It increases CO₂ exhalation, reducing H₂CO₃ and helping lower H⁺.
150
What happens when arterial [H⁺] decreases?
Pulmonary ventilation decreases (slower, shallower breathing).
151
How does decreased ventilation affect CO₂ and H⁺ levels?
CO₂ accumulates, increasing H₂CO₃ and H⁺.
152
How significant is the respiratory system in removing H⁺ compared to the kidneys?
It removes 100 times more H⁺ derived from carbonic acid than the kidneys.
153
Why is the respiratory system considered the second line of defense?
It is slower than chemical buffers.
154
What is a limitation of the respiratory system in correcting pH?
Alone, it can only restore pH about 50% toward normal.
155
Why are the kidneys essential for acid-base balance?
They remove excess H⁺ that buffers and the respiratory system cannot fully eliminate.
156
Which acids are primarily handled by the kidneys?
Sulphuric, phosphoric, lactic acids, and some carbonic acid.
157
What are the three main ways kidneys regulate pH?
H⁺ excretion, HCO₃⁻ excretion/reabsorption, and ammonia secretion.
158
Where does most urinary H⁺ come from?
Tubular secretion in the proximal, distal, and collecting tubules.
159
Why is little H⁺ filtered at normal pH?
Because plasma [H⁺] is very low at pH 7.4.
160
What is the typical pH of urine and why?
About 6.0, due to H⁺ secretion into tubular fluid.
161
What is the first step in H⁺ secretion by the kidneys?
CO₂ enters tubular cells (from plasma, tubular fluid, or metabolism).
162
What happens to CO₂ inside tubular cells?
It combines with H₂O (via carbonic anhydrase) to form H₂CO₃.
163
What happens to H₂CO₃ in tubular cells?
It dissociates into H⁺ and HCO₃⁻.
164
How is H⁺ secreted into tubular fluid?
Via an energy-dependent carrier on the luminal membrane.
165
Is H⁺ secretion by the kidneys hormonally or neurally controlled?
No, it is directly regulated by acid-base status.
166
How does increased plasma [H⁺] affect kidney function?
Tubular cells increase H⁺ secretion.
167
How does decreased plasma [H⁺] affect kidney function?
Tubular cells decrease H⁺ secretion.
168
How does increased plasma CO₂ affect H⁺ secretion?
It increases H⁺ secretion.
169
How does decreased plasma CO₂ affect H⁺ secretion?
It decreases H⁺ secretion.
170
Why can the kidneys regulate both carbonic and non-carbonic acids?
Because H⁺ secretion responds to both plasma [H⁺] and CO₂ levels.
171
Why is renal regulation of HCO₃⁻ important?
It is a key component of maintaining acid-base balance in the body.
172
How do the kidneys regulate plasma HCO₃⁻?
Through reabsorption of filtered HCO₃⁻ and addition of “new” HCO₃⁻ to the plasma.
173
Is HCO₃⁻ freely filterable at the glomerulus?
Yes
174
Why can’t HCO₃⁻ be directly reabsorbed in the tubules?
Because the luminal membrane is impermeable to HCO₃⁻.
175
How is HCO₃⁻ reabsorbed if it cannot cross the luminal membrane?
Indirectly, through conversion to CO₂ and H₂O.
176
What is the first step in HCO₃⁻ reabsorption?
HCO₃⁻ in tubular fluid combines with secreted H⁺ to form H₂CO₃.
177
What happens to H₂CO₃ in the tubular fluid?
It breaks down into CO₂ and H₂O.
178
Why can CO₂ and H₂O be reabsorbed into tubular cells?
Because they can cross the luminal membrane.
179
What happens to CO₂ and H₂O inside tubular cells?
Carbonic anhydrase converts them back into H₂CO₃.
180
What happens to H₂CO₃ inside tubular cells?
It dissociates into HCO₃⁻ and H⁺.
181
What happens to HCO₃⁻ inside tubular cells after formation?
It crosses the basolateral membrane into the plasma.
182
What happens to H⁺ inside tubular cells after formation?
It is secreted back into the tubular lumen.
183
Why is all filtered HCO₃⁻ normally reabsorbed?
Because sufficient H⁺ is secreted to convert it into CO₂ for reabsorption.
184
What does it mean to produce “new” HCO₃⁻?
HCO₃⁻ added to plasma that was not originally filtered.
185
How does “new” HCO₃⁻ production differ from reabsorption?
In reabsorption, H⁺ is recycled; in new production, H⁺ is excreted.
186
What is the first step in generating “new” HCO₃⁻?
CO₂ (from plasma or metabolism) combines with components from H₂O to form HCO₃⁻ in tubular cells.
187
What happens to newly formed HCO₃⁻ in tubular cells?
It is transported across the basolateral membrane into the plasma.
188
What happens to H⁺ generated during “new” HCO₃⁻ formation?
It is secreted into the tubular lumen.
189
How is secreted H⁺ excreted during “new” HCO₃⁻ formation?
It binds to urinary buffers (e.g., phosphate) and is excreted.
190
What is the relationship between H⁺ excretion and “new” HCO₃⁻ addition?
Each H⁺ excreted corresponds to one new HCO₃⁻ added to the plasma.
191
How changes in plasma [H+] would alter the secretion of H+ and [HCO3-]?
When plasma [H+] increases above normal, there is an increased secretion of H+ along with complete reabsorption of HCO3- and the formation of new HCO3-. This results in a decreased plasma [H+] and an increased plasma [HCO3-].
When plasma [H+] decreases below normal, there is a decreased secretion of H+ and a partial reabsorption of
HCO3- with excess excretion in the urine. This results in increased plasma [H+] and decreased plasma [HCO3-].
192
Why must large amounts of H⁺ be excreted in the urine?
Because the body produces an excess of H⁺ from metabolic processes.
193
What limits the amount of H⁺ that can be secreted into tubular fluid?
Tubular cells can only secrete H⁺ until the tubular fluid reaches a pH of about 4.5.
194
What happens when tubular fluid reaches pH 4.5?
Active H⁺ secretion can no longer continue.
195
Without urinary buffers, how much daily H⁺ could be excreted?
Only about 1% of total daily H⁺ production.
196
How do urinary buffers assist in H⁺ excretion?
They bind free H⁺, preventing it from increasing tubular acidity and allowing continued secretion.
197
What are the two main urinary buffer systems?
Phosphate and ammonia.
198
How does phosphate act as a urinary buffer?
Filtered phosphate binds H⁺ in the tubular fluid and is excreted.
199
What happens to H⁺ bound to phosphate in the tubular fluid?
It is excreted in the urine.
200
What is the primary purpose of phosphate filtration?
To remove excess phosphate from the body, not specifically to regulate pH.
201
Why is the phosphate buffer system limited?
There is no mechanism to increase phosphate secretion into the tubular fluid.
202
When does the ammonia buffer system become important?
Under acidic conditions when the phosphate buffer system is overwhelmed.
203
What is ammonia (NH₃)’s role in buffering?
It binds H⁺ to form ammonium (NH₄⁺).
204
What happens to ammonium (NH₄⁺) in the kidneys?
It is not reabsorbed and is excreted in the urine.
205
What is the significance of NH₄⁺ excretion?
It removes H⁺ from the body.
206
How is ammonia (NH₃) produced in the kidneys?
It is actively synthesized and secreted by tubular cells.
207
How does NH₃ production relate to acid levels?
It increases proportionally with excess H⁺.
208
Why is the ammonia buffer system more adaptable than phosphate?
Because NH₃ production can increase in response to higher H⁺ levels.
209
Which system does it correspond to: Limited capacity to resist acid/base imbalances
Buffer system
210
Which system does it correspond to: Prevent free H+ from contributing to fluid pH
Buffer system
211
Which system does it correspond to: Remove excess H+ from metabolic sources
Renal system
212
Which system does it correspond to: Remove H+ derived from carbonic acid
Respiratory system
213
Which system does it correspond to: Second line of defense
Respiratory system
214
Which system does it correspond to: Involves regulating plasma [HCO 3-]
Renal system
215
What determines changes in [H⁺] in the body?
The ratio of [HCO₃⁻] to [CO₂].
216
What is the normal [HCO₃⁻] : [CO₂] ratio?
20:1
217
What pH corresponds to the normal 20:1 ratio?
7.4
218
Why is assessing [HCO₃⁻] and [CO₂] more useful than [H⁺] alone?
It helps identify the source of the acid-base imbalance.
219
When analyzing acid-base imbalances, when do the “rules of thumb” apply?
Before compensation occurs.
220
What causes a pH change due to the respiratory system?
Abnormal [CO₂], affecting carbonic acid and H⁺ levels.
221
What causes a pH change due to metabolic factors?
Abnormal [HCO₃⁻], due to imbalance between bicarbonate and non-carbonic acid H⁺.
222
What type of acids are involved in respiratory pH changes?
Carbonic acid-derived H⁺.
223
What type of acids are involved in metabolic pH changes?
Non-carbonic acids (e.g., sulphuric, phosphoric, lactic acids).
224
What happens when the [HCO₃⁻] : [CO₂] ratio falls below 20:1?
Acidosis (pH < 7.4).
225
What happens when the [HCO₃⁻] : [CO₂] ratio rises above 20:1?
Alkalosis (pH > 7.4).
226
What is the Henderson-Hasselbalch equation?
pH = pKa + log [HCO₃⁻ / H₂CO₃].
227
How does the Henderson-Hasselbalch equation relate to acid-base balance?
It shows that pH depends on the ratio of bicarbonate to carbonic acid (or CO₂).
228
What is respiratory acidosis?
A condition where CO₂ builds up in plasma, causing the [HCO₃⁻]:[CO₂] ratio to fall below 20:1, leading to acidosis.
229
What causes respiratory acidosis?
Hypoventilation, which reduces CO₂ removal from the lungs. Conditions include emphysema, chronic bronchitis, asthma, severe pneumonia, and sometimes metabolic acidosis.
230
What happens in uncompensated respiratory acidosis?
CO₂ increases, forming more H⁺ and HCO₃⁻. H⁺ causes acidosis, but the rise in HCO₃⁻ is negligible because its plasma concentration is very high compared to H⁺.
231
How does the body compensate for respiratory acidosis?
- Chemical buffers immediately bind excess H⁺.
- Kidneys secrete more H⁺.
- Kidneys reabsorb existing HCO₃⁻ and generate new HCO₃⁻.
- Compensation continues until the [HCO₃⁻]:[CO₂] ratio is restored to 20:1 and pH returns to 7.4.
- The respiratory system cannot compensate because the problem is respiratory in origin.
232
What is respiratory alkalosis?
A condition where plasma CO₂ decreases due to hyperventilation, increasing the [HCO₃⁻]:[CO₂] ratio and raising pH.
233
What causes respiratory alkalosis?
Hyperventilation from fever, anxiety, severe infections, or other conditions that increase ventilation.
234
What happens in uncompensated respiratory alkalosis?
CO₂ decreases, [HCO₃⁻] stays mostly unchanged, leading to a higher [HCO₃⁻]:[CO₂] ratio and elevated pH.
235
How does the body compensate for respiratory alkalosis?
- Chemical buffers release H⁺ to lower pH.
- Respiratory system reduces ventilation to retain CO₂.
- If prolonged, kidneys decrease H⁺ secretion and increase HCO₃⁻ excretion.
- Compensation restores the [HCO₃⁻]:[CO₂] ratio to 20:1.
236
Why can the respiratory system decrease ventilation during respiratory alkalosis?
Because decreased [CO₂] and [H⁺] reduce the drive for ventilation, signaling the respiratory center to slow breathing.
237
It can be caused by hyperventilation.
Alkalosis
238
It is caused by an increase in the concentration of CO2 in the blood.
Acidosis
239
It increases the pH of the blood
Alkalosis
240
It is seen when the [HCO3-]:[CO2] ratio is below 20:1
Acidosis
241
It can occur with conditions such as emphysema, chronic bronchitis, asthma, severe pneumonia.
Acidosis
242
What is metabolic acidosis?
A type of non-respiratory acidosis caused by a decrease in [HCO₃⁻] with normal [CO₂]. It results from either loss of HCO₃⁻ or accumulation of non-carbonic acids.
243
How is the cause of metabolic acidosis determined?
By measuring the anion gap, which estimates unmeasured anions in plasma: ([Na+] + [K+]) - ([Cl-] + [HCO3-]) (often simplified to [Na+] - [Cl-] + [HCO3-])
244
What does a low anion gap indicate?
< 8 mEq/L, usually due to loss of plasma albumin, e.g., during hemorrhage.
245
What does a normal anion gap indicate?
8–16 mEq/L, typically caused by loss of HCO₃⁻, such as diarrhea or some renal diseases, with compensatory increase in [Cl⁻].
246
What does a high anion gap indicate?
> 16 mEq/L, caused by accumulation of unmeasured acids (e.g., lactate, keto acids, phosphate), which lowers [HCO₃⁻] through buffering.
247
What are common causes of metabolic acidosis?
- Severe diarrhea → loss of HCO₃⁻.
- Diabetes mellitus → keto acid accumulation.
- Strenuous exercise → lactate buildup.
- Uraemic acidosis → kidney failure reduces H⁺ excretion and HCO₃⁻ reabsorption.
248
How does the body compensate for metabolic acidosis?
- Chemical buffers bind excess H⁺.
- Lungs blow off CO₂ to reduce carbonic acid.
- Kidneys secrete more H⁺ and conserve HCO₃⁻.
- Full compensation may not occur in uraemic acidosis due to kidney failure.
249
What is metabolic alkalosis?
An acid-base imbalance caused by reduced [H⁺] due to a decrease in non-carbonic acids, usually associated with elevated [HCO₃⁻] and normal [CO₂], raising the [HCO₃⁻]:[CO₂] ratio above 20:1.
250
What causes metabolic alkalosis?
Vomiting → loss of stomach H⁺ increases plasma HCO₃⁻.
Ingestion of alkaline drugs → excess HCO₃⁻ absorbed from digestive tract.
251
How does the body compensate for metabolic alkalosis?
- Chemical buffers release H⁺.
- Ventilation decreases to retain CO₂.
- If persistent, kidneys decrease H⁺ secretion and increase HCO₃⁻ excretion.
- Full compensation restores [HCO₃⁻]:[CO₂] ratio to 20:1, even if both [HCO₃⁻] and [CO₂] remain elevated.
252
What happens in uncompensated metabolic alkalosis?
[HCO₃⁻]:[CO₂] ratio is elevated due to excess HCO₃⁻; no compensatory mechanisms have yet acted.
253
What happens in uncompensated metabolic acidosis?
- Decrease in [HCO3-] and a normal [CO2]
- This decrease can be caused by excessive loss of HCO3- or from the buildup of non-carbonic acids, which also decreases [HCO3-] due to buffering.
254
Under normal condition: pH, [CO2], [HCO3-], and [HCO3-]:[CO2]
pH: Normal
[CO2]: Normal
[HCO3-]: Normal
[HCO3-]:[CO2] = 20:1
255
Compensated respiratory acidosis: pH, [CO2], [HCO3-], and [HCO3-]:[CO2]
pH: Normal
[CO2]: Increased
[HCO3-]: Increased
[HCO3-]:[CO2] = 40:2 (20:1)
256
Uncompensated respiratory alkalosis: pH, [CO2], [HCO3-], and [HCO3-]:[CO2]
pH: Increased
[CO2]: Decreased
[HCO3-]: Normal
[HCO3-]:[CO2] = 20:0.5 (40:1)
257
Uncompensated metabolic acidosis: pH, [CO2], [HCO3-], and [HCO3-]:[CO2]
pH: Decreased
[CO2]: Normal
[HCO3-]: Decreased
[HCO3-]:[CO2] = 10:1
PHGY 216
flashcards
Decks in class (6)
# Cards
