Physiology of Acid-Base Balance

Question 1

What organs are the main contributors to acid-base balance?

Answer 1

Kidney, lungs, natural/biological buffers

Question 2

come back to 1st slide

Question 3

What is acid-base balance?

Answer 3

The maintenance of the constancy of the physiologic range of acid-base status of the body

the regulation of the pH of the body fluids towards maintaining a normal range of acid-base status for a given animal species

The physiologic adjustments of the hydrogen ionh concentration of the extracellular fluids towards its physiologic limits for optimum physiological activities

Question 4

What is pH?

Answer 4

The level of hydrogen ions (H+) available in a solution

Question 5

What is the smallest ionic particle in biological systems?

Answer 5

a hydrogen ion
(single, very reactive, proton)
(shows severe effects on the physiological activities of the body even in low concentrations)

Question 6

An increase in H+ concentration means:

Answer 6

a decrease in pH and the condition is said to be acidic

Question 7

A decrease in H+ concentration means:

Answer 7

an increase in pH and the condition is said to be basic

Question 8

What are the normal pH levels in dogs?

Answer 8

7.35-7.45 (same as cat)

Question 9

What are the normal pH levels in cats?

Answer 9

7.35-7.45 (same as dog)

Question 10

What are the normal pH levels in horses?

Answer 10

7.32-7.44

Question 11

What is the normal pH of mammalian arterial blood?

Answer 11

7.36-7.44

Question 12

What is the average mammalian arterial blood pH?

Answer 12

7.4

Question 13

What does a pH lower than normal cause?

Answer 13

acidosis

Question 14

What does a pH higher than normal cause?

Answer 14

alkalosis

Question 15

What is caused by low O2 partial pressure levels?

Answer 15

hypoxemia

blood oxygen levels are lower than normal, which can leading to hypoxia

Question 16

What is caused by high O2 partial pressure levels?

Answer 16

oxygen toxicity

Question 17

What is caused by low bicarbonate (HCO3) levels?

Answer 17

metabolic acidosis

Question 18

What is caused by high bicarbonate (HCO3) levels?

Answer 18

metabolic alkalosis

Question 19

What are normal bicarbonate levels in dogs?

Answer 19

18-24 mEq/L

Question 20

What are normal bicarbonate levels in cats?

Answer 20

18-24 mEq/L

Question 21

What are normal partial pressure of CO2 levels in dogs?

Answer 21

30-40 mmHg (millimeters of mercury)

Question 22

What are normal partial pressure of CO2 levels in cats?

Answer 22

30-40 mmHg

Question 23

What are normal partial pressure of O2 levels in dogs?

Answer 23

85-110 mmHg

Question 24

What are normal partial pressure of O2 levels in cats?

Answer 24

90-110 mmHg

Question 25

The pH of body fluids is easily disturbed by an addition of small amounts of:

Answer 25

A strong acid or base

Question 26

What is caused by CO2 partial pressure levels above normal?

Answer 26

respiratory acidosis

Question 27

What is caused by CO2 partial pressure levels below normal?

Answer 27

respiratory alkalosis

Question 28

What are normal partial pressure of CO2 levels in cats and dogs?

Answer 28

30-40 mmHg

Question 29

Respiratory changes are defined by _______.

Answer 29

changes of arterial PCO2 (partial pressure of carbon dioxide)

Question 30

What are metabolic changes?

Answer 30

changes of arterial bicarbonate ions that are not attributed to a change in PCO2 (partial pressure of carbon dioxide)

Question 31

slide 7

Question 32

What are acids?

Answer 32

substances that donate hydrogen ions (protons) to a solution

Question 33

What are bases?

Answer 33

substances that accept and bind hydrogen ions (protons) from a solution

Question 34

When is acid-base balance in ECF disrupted?

Answer 34

When acids or bases are added to or removed from the body fluids

Question 35

What is acidemia?

Answer 35

A depression of blood pH to a value below the normal range

Question 36

What is alkalemia?

Answer 36

An increase in blood pH to a value above the normal range

Question 37

The addition of excess acid or removal of base from the ECF causes:

Answer 37

acidosis

Question 38

The addition of excess base or removal of acid from the ECF causes?

Answer 38

alkalosis

Question 39

What are the main sources of body acids and bases?

Answer 39

- ingestion in food (Protein diet= more acid, plant diet= more bases) - cellular metabolism - gain or loss of acids and bases during disease conditions (insufficient respiratory ventilation, vomiting, diarrhea, renal insufficiency)

Question 40

During the metabolism of feeds of plant origin, what forms in the bloodstream?

Answer 40

large amounts of base, in the form of bicarbonate

Question 41

Where is bicarbonate usually excreted?

Answer 41

in urine (this explains why the urine of herbivores is usually alkaline)

Question 42

Which type(s) of animal excrete alkaline urine?

Answer 42

Ruminants, equids, and other herbivores

Question 43

Which type(s) of animal excrete acidic urine?

Answer 43

Dogs, cats, and other carnivores

Question 44

What are the 3 main mechanisms the body uses for the regulation of acid-base status?

Answer 44

- Acid-base buffer system (compounds) - Respiratory mechanism (Lungs) - renal mechanism (Kidney)

Question 45

What is a buffer?

Answer 45

A compound that has the capacity to regulate the availability of reactive hydrogen in a system (can react with hydrogen or release hydrogen)

Question 46

What is an acid-base buffer system?

Answer 46

The combination of a weak acid (protonated compound) and a weak base- the salt (unprotonated compound)

Question 47

When a strong acid is added, it reacts with the ______.

Answer 47

weak base

Question 48

When a strong base is added, it reacts with the _____.

Answer 48

weak acid

Question 49

In an acid-base buffer system, either the weak acid or base helps prevent pH changes by reacting when either a _______ or _____ is present.

Answer 49

strong acid; strong base

Question 50

What are the 3 important types of buffer systems?

Answer 50

- Bicarbonate buffer system (main buffering system in ECF) - Phosphate buffer system (intracellular) - Protein buffer system (plasma and Hemoglobin)

Question 51

What is the weak acid component in the bicarbonate buffer system?

Answer 51

(Carbonic acid) H2CO3

Question 52

What is the weak base component in the bicarbonate buffer system?

Answer 52

(bicarbonate) HCO3-

Question 53

What is the weak acid component in the phosphate buffer system?

Answer 53

dihydrogen phosphate (H2PO4), in the form of sodium dihydrogen phosphate (NaH2PO4)

Question 54

What is the weak base component in the phosphate buffer system?

Answer 54

hydrogen phosphate (HPO4), in the form of disodium hydrogen phosphate (Na2HPO4)

Question 55

The weak acid component of a buffer easily ___ hydrogen, while the weak base component easily ___ hydrogen.

Answer 55

releases; accepts

Question 56

If the pH is low, HCO3 can ____ H+.

Answer 56

Pick up -> H2CO3

Question 57

If the pH is high, HCO3 can ____ H+.

Answer 57

Release -> H+ + HCO3

Question 58

What are the elements of proteins that form the 3 weak (amino) acids in plasma?

Answer 58

- C-terminal carboxyl group, N-terminal amino group, and side chain amino group of glutamic acid - Side chain amino group of lysine - Imidazole group of histidine

Question 59

What is the second most important blood buffer and most important and effective protein buffer?

Answer 59

Hemoglobin

Question 60

Why does hemoglobin have about 6x more buffering capacity than the plasma proteins?

Answer 60

It is in higher concentration than plasma proteins (?)

Question 61

How is excess CO2 removed from the body?

Answer 61

hyperventilation

Question 62

What makes a buffer poor?

Answer 62

The pKa of the buffer is far away from the desired pH to establish. The pKa of the buffer should be very close to the intended pH to restore

Question 63

The bicarbonate buffer system plays the most important role in maintaining the pH of ________. Why?

Answer 63

body fluids - all the components of the system (HCO3 and H2CO3) are well separately regulated by the renal and respiratory systems respectively.

Question 64

How do the lungs contribute to the buffer mechanism?

Answer 64

CO2 builds up hypoventilation- respiratory acidosis the extent to which ventilation maintains normal CO2 partial pressure

Question 65

The kidney manages the concentrations of ____ & _____ in the blood.

Answer 65

H+ and HCO3

Question 66

How does the kidney maintain the acid-base balance of the body?

Answer 66

By the secretion of H+ ions and the retention of HCO3. This is accompanied by sodium reabsorption

Question 67

Acidemia and hypercapnia (high CO2) result in what in the kidney?

Answer 67

increased H+ secretion

Question 68

Alkalemia and hypocapnia (low CO2) result in what in the kidney?

Answer 68

decresead H+ secretion

Question 69

What does a high pH (alkalosis) do in the kidney?

Answer 69

It depresses hydrogen ion secretion into the tubular lumen.

Question 70

What does a low pH (acidosis) do in the kidney?

Answer 70

It increases the rate of hydrogen ion secretion into the tubular lumen.

Question 71

comeback to slide 27 with table

Question 72

How does Acidosis affect potassium?

Answer 72

H+ secretion is increased and goes into the urine while K is moved out of the cells (potassium is retained in plasma) | potassium shifts from inside the cell to outside ## Footnote can lead to hyperkalemia

Question 73

How does Alkalosis affect potassium?

Answer 73

H+ secretion is decreased in cells and retained, leading to lower K levels (hypokalemia) | increased potassium excretion