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Physiology > Acids & Bases > Flashcards

Acids & Bases Flashcards

1
Q

What is an acid?

A

Any molecule that will release H+ when put into solution.

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2
Q

What is a base?

A

Any molecule that will accept H+.

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3
Q

The more free H+ there are in solution, the more _____ the solution and the ______ the pH.

A

acidic, lower.

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4
Q

Below 7…

A

Acidic

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5
Q

Above 7…

A

Basic

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6
Q

Equal to 7…

A

Neutral

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7
Q

What is the pH of body fluids?

A

7.35-7.45

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8
Q

Arterial blood pH?

A

7.45

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9
Q

Venous blood pH?

A

7.35

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10
Q

Define acidosis.

A

Term used to describe body fluids when pH is below 7.4

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11
Q

Define alkalosis.

A

Occurs when pH is above 7.4

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12
Q

Describe the source of acid in the body.

A
  1. When cells in the body make energy, they produce CO2 as a byproduct, which can (with the help of carbonic anhydrase) combine with water is RBC’s to produce carbonic acid.
  2. Carbonic acid will dissociate into free H+ and bicarbonate ions.
  3. As a result, there is generally no net increase in free H+ in the plasma.
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13
Q

Why is carbonic acid known as a volatile acid?

A

Because the carbonic acid reforms into CO2, which is then removed at the lungs.

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14
Q

What are examples of non-volatile acids?

A

Hydrochloric, sulphuric and lactic acid.

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15
Q

True or false; non-volatile acids can be removed by the lungs.

A

FALSE: Non-volatile acids are a significant source of free H+ and are constantly produced throughout the body.

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16
Q

Define buffer.

A

Any molecule that can reversibly bind/release free H+. Buffers bind to free H+, thereby reducing the amount of free H+ in solution.

17
Q

True of false; buffers prevent the pH from changing.

A

FALSE: Buffers cannot prevent the pH from changing, they only help to minimize any pH change until the free H+ can be removes via the kidneys or lungs.

18
Q

List the intracellular buffers.

A

Phosphates and intracellular proteins (hemoglobin).

19
Q

Can free H+ bind to intra or extracellular fluid?

A

Both

20
Q

What is the most powerful extracellular buffer?

A

Bicarbonate ion

21
Q

What can hemoglobin bind with?

A

Hb inside RBC’s can reversibly bind with free H+ to help stabilize the acidity. Hb can also bind with CO2 to reduce potential acidity should CO2 combine with H2O to form carbonic acid.

22
Q

What detects CO2 gas?

A

Central and peripheral chemoreceptors.

23
Q

What happens when CO2 levels increase?

A

Central and peripheral receptors detect change and cause an increase in ventilation. Increased ventilation causes more CO2 to be removed from the lungs, which will then return blood CO2 back to normal.

24
Q

How do the kidneys maintain a constant pH?

A
  1. Excrete H+ that comes from non-volatile acids.
  2. Attempt to reabsorb all bicarbonate ions that are filtered at the glomerulus.
  3. Create new bicarbonate ions which then get absorbed into circulation.
25
Q

What % of bicarbonate that is filtered in the glomerulus is absorbed and where in the nephron is it absorbed?

A

90%, in the proximal tubule.

26
Q

Where is H+ excreted in the nephron and by what mechanism?

A

Proximal tubule by the Na+/H+ exchanger

Late distal tubule by the H+/ATP pump

27
Q

Explain the reabsorption of bicarbonate ions/secretion of H+.

A
  1. Bicarbonate ions (filtered freely at the glomerulus into the filtrate) cannot directly be reabsorbed by tubule cells.
  2. Bicarbonate ions must be converted into CO2, which is then reabsorbed.
  3. Once in the tubule cells, CO2 combines with H2O, and with the help of carbonic anhydrase, will produce bicarbonate and H+.
  4. Bicarbonate ions leave tubule cells by simple diffusion and reabsorbed back into circulation.
  5. Remaining H+ in the cell are secreted into the lumen by Na+/H+ exchanger.
  6. For every bicarbonate ion reabsorbed, there must be one H+ secreted.
28
Q

When can acidosis occur?

A

When there is too much H+ (acid) OR too little bicarbonate ion (most common base in the body).

29
Q

When can alkalosis occur?

A

When there is too much bicarbonate and too little H+.

30
Q

What is respiratory acidosis caused by and when can it occur?

A

Caused by decreased ventilation and increased partial pressure of CO2. This can occur if the respiratory centre in the brain stem is damaged r from lung damage resulting in decreased ability to remove CO2 from the blood.

31
Q

How can respiratory acidosis be counteracted?

A

By buffers in the blood and excretion of excess H+ by the kidneys.

32
Q

What is respiratory alkalosis caused by and when can it occur?

A

Caused by an increase in ventilation and decreased partial pressure of CO2. Although infrequent, can be caused by stress or emotionally induces hyperventilation. Hyperventilation will increase removal of CO2 from the blood, causing the decrease in PCO2. High altitudes can also result in respiratory alkalosis when low O2 levels cause low PO2 levels in the blood that stimulates hyperventilation.

33
Q

How can respiratory alkalosis be counteracted?

A

The excretion of bicarbonate ions from the kidneys.

34
Q

What is metabolic acidosis caused by and when can it occur?

A

Caused by a number of factors that result in a decrease in extracellular bicarbonate ions. Metabolic acidosis DOES NOT involve increased CO2 in the blood. Causes include…

  1. Kidney failure resulting in the inability to excrete acids in urine/inability to reabsorb bicarbonate from the filtrate.
  2. Formation of excess metabolic acids in the body.
  3. Ingestion of acids (most common = aspirin/methyl alcohol).
  4. Loss of bicarbonate in diarrhea
35
Q

What is metabolic alkalosis caused by and when can it occur?

A

Caused by either buildup of bicarbonate ions or the loss of H+ from the body. Most common cause is the loss of HCl from the stomach from vomiting, or the ingestion of alkaline drugs (sodium bicarbonate for treating ulcers).

36
Q

What are the three ways the body deals with the accumulation of acids?

A
  1. Buffers
  2. Kidneys
  3. Respiratory System
37
Q

How do buffers deal with the accumulation of acids?

A

Reversibly bind with free H+ until they can be removed, don’t dramatically affect the pH of blood.

38
Q

How does the respiratory system deal with the accumulation of acids?

A

Can detect levels of CO2 (a potential source of acid) and remove it from the body.

39
Q

How do they kidneys deal with the accumulation of acids?

A

Remove free H+ from nonvolatile acids.

Physiology (3 decks)

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