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Physiology > Acid-Base Balance and Temperature Regulation > Flashcards

Acid-Base Balance and Temperature Regulation Flashcards

1
Q

What does acid-base balance refer to?

A

Precise regulation of unbound hydrogen ions (H+)

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2
Q

What are acids?

A

Substances that dissociate from H+ when in solution

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3
Q

Do all substances containing hydrogen dissociate into H+?

A

No. Many substances (like carbs) contain hydrogen but do not dissociate

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4
Q

What determines the strength of an acid?

A

Its tendency to dissociate. A stronger acid has a greater tendency to dissociate

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5
Q

How is the strength of an acid expressed?

A

By its dissociation constant

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6
Q

What is a base?

A

A substance that can combine with free H+, removing it from solution

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7
Q

How do strong and weak bases differ?

A

A strong base binds H+ more readily than a weak base

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8
Q

How does the concentration of H+ in the extracellular fluid (ECF) compare to that of Na+?

A

The concentration of H+ in normal ECF is 3 million times lower than Na+

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9
Q

Why is H+ concentration expressed logarithmically as pH?

A

Due to its low values in the ECF

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10
Q

What is the relationship between acidity and pH?

A

Higher acidity (higher H+) = lower pH

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11
Q

What does each unit change in pH represent?

A

A 10-fold change in H+ concentration. For example, a pH of 7 has ten times fewer H+ than a pH of 6.

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12
Q

What is the pH of water and what is it considered?

A

7.0, considered neutral

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13
Q

What does a pH lower than 7.0 indicate?

A

More H+, acidic

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14
Q

What does a pH higher than 7.0 indicate?

A

Less H+, alkaline/basic

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15
Q

What is the normal pH of blood?

A

Around 7.4 (slightly basic)

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16
Q

What are the typical pH values for arterial and venous blood?

A

Arterial: 7.45, Venous: 7.35 (due to carbonic acid/CO2)

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17
Q

What is acidosis?

A

Blood pH below 7.35

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18
Q

What is the lethal pH level for blood?

A

6.8 is lethal in seconds

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19
Q

What is alkalosis?

A

Blood pH above 7.45

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20
Q

At what pH does alkalosis become lethal?

A

8.0 is lethal in seconds

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21
Q

What can small changes in H+ concentration lead to?

A

Dramatic consequences

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22
Q

What is the effect of increased H+ on the central nervous system (CNS)?

A

Depresses the CN

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23
Q

How does decreased H+ affect the CNS?

A

Increases CNS excitability, leading to twitches, spasms, convulsions, and potentially death

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24
Q

How can H+ deviations impact proteins?

A

Affect protein shape, disturbing metabolic activity of enzymes

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25
Q

How is K+ balance related to H+ regulation?

A

Renal tubular cells can secrete either K+ or H+ to reabsorb Na+. In acidosis, the body compensates by secreting H+ instead of K+, and the opposite occurs in alkalosis.

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26
Q

What cardiac abnormalities can result from H+ deviations?

A

H+ deviations can affect K+ concentrations, leading to cardiac abnormalities

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27
Q

How is H+ input balanced with output in the body?

A

Input is minimally affected by ingestion. The main input is from metabolic activity

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28
Q

What is the main source of H+ input in the body?

A

Carbonic acid formation. Metabolically produced CO2 combines with water to form carbonic acid (H2CO3), which dissociates into H+ and bicarbonate (HCO3)

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29
Q

What are other sources of H+ input besides carbonic acid formation?

A

Inorganic acids during nutrient breakdown and organic acids (fatty acids, lactic acid) produced during metabolic activities

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30
Q

What are the three lines of defense against changes in H+?

A

Chemical buffers, respiratory pH control, and renal pH control

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31
Q

What are chemical buffers?

A

Dissolved compounds that minimize pH changes in either direction

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32
Q

How do chemical buffers work?

A

They act as a pair of substances in a reversible reaction, where one substance can bind to H+ and the other can yield it

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33
Q

Give an example of a chemical buffer system.

A

H2CO3 (carbonic acid) with H+/HCO3 (bicarbonate)

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34
Q

How many chemical buffer systems does the body have?

A

Four: H2CO3/HCO3, protein buffer system, Hgb buffer system, and phosphate buffer system

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35
Q

Describe the importance of the H2CO3/HCO3 buffer system.

A

t’s the most important pH buffer in the ECF. It is abundant in the ECF and readily available to resist pH changes. Each component (H2CO3 and HCO3) is closely regulated, with the kidneys regulating HCO3 and the lungs regulating CO2

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36
Q

Where is the protein buffer system primarily important?

A

In the intracellular fluid (ICF)

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37
Q

How does the protein buffer system work?

A

Proteins contain both acidic and basic groups that can donate or accept H+

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38
Q

Why are proteins the most important buffer in the ICF?

A

Their sheer abundance

39
Q

What is the role of the Hgb buffer system?

A

Hemoglobin buffers H+ generated from metabolically produced CO2 between tissues and lungs. Most H+ generated from CO2 at the tissue level binds to Hgb, preventing the blood at the tissues from becoming too acidic

40
Q

How does the Hgb buffer system affect venous blood pH?

A

It makes venous blood only slightly more acidic than arterial blood

41
Q

How does the phosphate buffer system work?

A

Acid phosphate salt (NaH2PO4) can donate H+, and basic phosphate salt (Na2HPO4) can accept H+ in a reversible reaction

42
Q

Is the phosphate buffer system as effective as other buffer systems?

A

No. Its concentration in the ECF is low, and it is not as abundant as proteins in the ICF

43
Q

Where does the phosphate buffer system excel?

A

As a urinary buffer. Humans consume more phosphate than needed, and this excess phosphate buffers urine during formation

44
Q

How does respiratory pH control work?

A

Altering pulmonary ventilation changes the excretion of CO2, which is a precursor to H+ generation

45
Q

Explain the relationship between CO2 and H+ generation.

A

CO2 itself is not an acid, but it combines with H2O to form carbonic acid, which then dissociates into H+ and bicarbonate

46
Q

How does the body respond to increased arterial H+ from metabolically generated CO2?

A

It triggers a respiratory reflex in the brainstem to increase pulmonary ventilation and CO2 exchange

47
Q

What happens to ventilation when metabolically generated CO2 is low?

A

Ventilation reduces

48
Q

How does pulmonary ventilation change in response to metabolic acidosis and alkalosis?

A

Metabolic acidosis increases pulmonary ventilation, while metabolic alkalosis decreases it

49
Q

How do the kidneys regulate pH?

A

By adjusting H+ excretion, bicarbonate (HCO3) excretion, and ammonia (NH3) excretion

50
Q

What is the kidneys’ role in H+ removal beyond CO2 elimination by the lungs?

A

The lungs only eliminate CO2. The generated H+ must be removed by the kidneys, along with other acids like lactic and phosphoric acid

51
Q

Are CO2 and HCO3 interchangeable in terms of their effects on pH?

A

No. While CO2 combines with H2O to form HCO3 and H+, the concentration of HCO3 is much higher than that of H+. An increase in CO2 significantly impacts H+ but not necessarily HCO3. They are separate entities

52
Q

What is respiratory acidosis?

A

Abnormally increased CO2 levels in the blood due to hypoventilation

53
Q

What can cause respiratory acidosis?

A

Lung disease, neuromuscular disease, drugs, and holding breath (transient)

54
Q

What are the compensatory mechanisms for respiratory acidosis?

A

Chemical buffers take up additional H+, and the kidneys (most importantly) retain HCO3- and add it to plasma, also increasing H+ secretion

55
Q

What is respiratory alkalosis?

A

Abnormally decreased CO2 levels in the blood due to hyperventilation

56
Q

What can cause respiratory alkalosis?

A

Fever, anxiety, aspirin poisoning, high altitude

57
Q

What are the compensatory mechanisms for respiratory alkalosis?

A

Chemical buffers liberate H+ to diminish alkalosis. Kidneys conserve H+ excretion and increase HCO3- secretion

58
Q

What is metabolic acidosis

A

Abnormally decreased HCO3- levels in the blood

59
Q

What can cause metabolic acidosis?

A

Severe diarrhea, diabetes, strenuous exercise, and severe renal failure (in which case renal mechanisms cannot compensate)

60
Q

What are the compensatory mechanisms for metabolic acidosis?

A

Buffers take up extra H+, pulmonary ventilation increases (blowing off additional CO2), and kidneys excrete more H+ and conserve HCO3-

61
Q

What is metabolic alkalosis?

A

Abnormally increased HCO3- levels in the blood

62
Q

What can cause metabolic alkalosis?

A

Vomiting, alkaline drugs

63
Q

What are the compensatory mechanisms for metabolic alkalosis?

A

Buffers liberate H+, ventilation decreases (less CO2 blown off), and kidneys conserve H+ and increase HCO3- excretion

64
Q

How do temperature extremes injure tissues?

A

Heat denatures proteins, while cold causes ice crystals to form

65
Q

Why are some temperature increases necessary?

A

They are needed for specialized functions to increase reaction rate

66
Q

What is the Q10 ratio?

A

The ratio between the rate of a reaction at one temperature and the rate of the same reaction at a temperature 10°C higher

67
Q

What are the common sites for monitoring body temperature?

A

Oral and axillary temperatures, typically 98.6°F

68
Q

How does rectal temperature compare to oral and axillary temperatures?

A

Rectal temperature is typically 1°F warmer

69
Q

What is the role of the hypothalamus in temperature regulation?

A

The hypothalamus acts as the body’s thermostat and thermoregulatory integration center

70
Q

What are the two categories of energy output?

A

External work and internal work

71
Q

What is an example of external work?

A

Energy used when skeletal muscles contract to move the body or objects. This could include activities like walking, running, lifting weights, or playing sports.

72
Q

What are the two types of Internal work?

A

Skeletal muscle non-movement work: shivering, posture, etc.

Everything else: pumping blood, breathing, cell transport, metabolism, repair

73
Q

What is metabolic rate?

A

The rate at which energy is expended by external and internal work

74
Q

What is the formula for metabolic rate?

A

Metabolic rate = energy expenditure / time

75
Q

What is a calorie?

A

The amount of energy required to raise the temperature of 1g of H2O by 1°C.

76
Q

What is a kilocalorie (Calorie)?

A

1000 calories. In the U.S., “calories” on food labels actually refer to kilocalories.

77
Q

What is basal metabolic rate (BMR)?

A

The metabolic activity necessary to maintain basic body functions. It represents the minimal waking rate of internal energy expenditure

78
Q

What is the primary determinant of BMR?

A

Thyroid hormone

79
Q

What is neutral energy balance?

A

A state where the amount of energy input equals energy output. This means that the energy from food intake matches the energy expended by the body for internal and external work

80
Q

What is positive energy balance?

A

When energy intake from food exceeds energy expenditure. In this state, the body stores the excess energy, often as fat.

81
Q

What is negative energy balance?

A

When energy expenditure exceeds energy intake from food. In this situation, the body taps into stored energy reserves, often resulting in weight loss

82
Q

What part of the brain primarily regulates food intake?

A

the hypothalamus

83
Q

What are the two opposing subsets of neurons in the arcuate nucleus of the hypothalamus?

A

One subset releases neuropeptide Y (NPY), a potent appetite stimulator that promotes weight gain.

The other subset releases melanocortins, which suppress appetite.

84
Q

What role does leptin play in energy balance?

A

Leptin is a hormone that:

is essential for normal body weight regulation

suppresses appetite

acts on the arcuate nucleus to inhibit NPY and stimulate melanocortins

85
Q

What is dynamic exercise?

A

Skeletal muscle contractions at changing lengths with rhythmic episodes of relaxation

Examples include: walking, running, swimming.

86
Q

What is isometric exercise?

A

Force generated at constant muscle length without rhythmic episodes of relaxation. Examples include: holding a plank, wall sit, or carrying heavy objects

87
Q

What is aerobic exercise

A

Exercise that involves oxygen usage to work output. It primarily utilizes oxygen for energy production. Examples include: jogging, cycling, swimming

88
Q

What are HDL and LDL?

A

They are types of cholesterol. HDL is considered “good” cholesterol because it helps remove cholesterol from the arteries, while LDL is considered “bad” cholesterol because high levels can contribute to plaque buildup in the arteries

89
Q

What is the major cause of muscle fatigue?

A

ADP accumulation (aka Reduced ATP). This leads to slower cross-bridge cycling in muscle fibers, making them less efficient at contracting

90
Q

How does endurance training affect muscles?

A

It enhances muscle oxidative capacity, improving their ability to use oxygen for energy production. This leads to improved endurance and reduced fatigue during sustained exercise.

91
Q

What is the effect of isometric contraction on muscles?

A

It stimulates muscle hypertrophy, leading to an increase in muscle size and strength

92
Q

What role does exercise play in calcium homeostasis?

A

Exercise helps maintain bone density and prevents osteoporosis. It also improves calcium absorption and utilization in the body.

93
Q

What are some benefits of exercise for individuals with arthritis?

A

Exercise can increase muscle strength and reduce pain and disability associated with osteoarthritis.

For those with rheumatoid arthritis (RA), exercise helps maintain joint mobility and function.

94
Q

List five benefits of exercise

A

Can help with weight loss

Helps with energy balance

Regulates blood glucose in diabetic patients

Improves quality of life

Improves immunity

Physiology (3 decks)

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