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Anatomy Exam 3 > Lecture 6 : Acid-Base Balance > Flashcards

Lecture 6 : Acid-Base Balance Flashcards

1
Q

___ is a problem for the body

A

Acidity

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2
Q

Our bodies are challenged by intake and production of ___

A

acids (more than bases)

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3
Q

How we get acid:

A

Diet - fatty acids and amino acids

Metabolism - CO2 (+H2O), lactic acid, ketoacids

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4
Q

How we get rid of acid:

A

Ventilation - CO2 (+H2O)

Renal - H+

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5
Q

pH is a measure of ____

A

free H+

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6
Q

Normal arterial blood pH is

A

~7.4 (range 7.35-7.45)

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7
Q

Alkalosis =

A

arterial blood pH > 7.45

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8
Q

Acidosis =

A

arterial blood pH < 7.35

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9
Q

If pH falls below 6.8:

A

CNS depression, coma, death

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10
Q

If pH rises above 7.8:

A

Overexcitation of nervous system, muscle tetany, convulsions, respiratory arrest

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11
Q

3 Systems Regulate Acid-Base Balance

A

Chemical buffers

Respiratory mechanisms

Renal mechanisms

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12
Q

Chemical buffers

A

1st line of defense – very fast, act in fraction of second

resist pH changes by binding H+ ions when pH drops and releasing them when pH rises

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13
Q

Respiratory mechanisms

A

Brainstem respiratory centers change respiratory rate and depth to compensate for pH changes in 1-3 min (control CO2 levels)

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14
Q

Renal mechanisms

A

Body’s most powerful acid-base regulatory system, but may require hours to days to correct blood pH (control H+/bicarbonate levels)

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15
Q

Respiratory and renal systems form -

A

“physiological buffering systems”

control pH by changing the amount of acid or base in the body

slower than chemical buffering systems, they are most powerful

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16
Q

Only____ contribute to the acidity of a solution

A

free H+

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17
Q

Strong acids/bases can produce ____ changes in pH

A

large -
because they dissociate completely

Ex: Strong base completely dissociates: Na+ and OH-

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18
Q

Weak acids/bases dissociate ___, so produce ___ change in pH; these help prevent pH changes by binding H+ or releasing H+

A

only partially

little

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19
Q

Acids are proton ____
Bases are proton ____

A

donors
acceptors

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20
Q

Chemical Buffers

A

a system of 1 or more compounds that resist pH change in the presence of a strong acid or base

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21
Q

Chemical buffer systems –

A

first line of defense to control pH of ICF and ECF

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22
Q

3 chemical buffer systems

A

Carbonic acid-Bicarbonate buffer system – extracellular fluid compartment (ECF)

Phosphate buffer system – intracellular fluid compartment (ICF) and urine

Protein buffers – both ICF and ECF

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23
Q

Chemical buffer systems have a ___ acid and a ___ base

A

weak
weak

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24
Q

The buffering system resists changes in pH by :

A

binding H+ ions when pH drops (the weak base does this)

releasing H+ ions when pH rises (the weak acid does this)

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25
Q

Bicarbonate Buffer System

A

mixture of H2CO3 (weak acid) and salts of HCO3- (weak base)

maintain ECP buffer; also operates in ICF

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26
Q

Phosphate Buffer System

A

salts of H2PO4- (weak acid) and HPO4 2- (weak base)

important buffer in urine and ICF

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27
Q

Protein Buffer System

A

some amino acid side chains act as weak acids (-COOH) or weak bases (-NH2)

most important buffer in ICF; also in blood plasma

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28
Q

CARBONIC ACID-BICARBONATE BUFFER SYSTEM

A

most important buffer of the ECF

29
Q

Bicarbonate buffer system:

A

Mixture of carbonic acid (H2CO3) and the salt sodium bicarbonate (NaHCO3)

Large amounts of plasma bicarbonate (HCO3-) produced from metabolic CO2 create the most important extracellular buffer system of the body.

30
Q

Bicarbonate ions enter the plasma and form the _____ which will help buffer acids entering the blood.

A

alkaline reserve

31
Q

______ ⇌ ____ ⇌ ______

A

CO2 + H2O
(carbon dioxide plus water)

H2CO3
(carbonic acid)

HCO3- + H+
(bicarbonate ion plus hydrogen ion)

32
Q

Plasma HCO3- concentration averages ____ which is hundreds of thousands of times as concentrated as ____

A

~24 mEq/L

plasma H+

33
Q

Although H+ and HCO3- are both created from CO2 and H2O, the majority of H+ is buffered by _____

A

hemoglobin

34
Q

The HCO3- in plasma is then available to buffer H+ from ___ sources, such as metabolism.

A

nonrespiratory

35
Q

Weak acid =

Weak base =

A

carbonic acid (H2CO3)

sodium bicarbonate (NaHCO3)

36
Q

Buffers strong acids

______ → ______ + ______

A

HCl + NaHCO3 → H2CO3 + NaCl

(strong acid) + (weak base) → (weak acid) + (salt)

37
Q

When a strong acid is added to buffering system =

A

the sodium bicarbonate acts as a weak base to tie up the H+ released by the strong acid

38
Q

The net effect is that ______

A

the strong acid is converted to a weak acid so that arterial pH goes down very little.

39
Q

Buffering capacity is dependent on the concentration of _____ This is closely regulated by the ____.

A

bicarbonate ions (alkaline reserve)

kidneys

40
Q

Buffers strong bases

______ → ______ + ______

A

NaOH + H2CO3 → NaHCO3 + H2O

(strong base) + (weak acid) → (weak base) + (water)

41
Q

When a strong base such as NaOH is added to buffering system =

A

the carbonic acid dissociates further, donating a H+ to tie up the OH- released by the strong base (and forming water)

42
Q

The net effect is that _____

A

the strong base is converted to a weak base so that arterial pH goes up very little

43
Q

buffering capacity is dependent on the concentration of ______

A

carbonic acid (essentially limitless)

44
Q

Phosphate BUFFER SYSTEM

A

most important buffer of the ICF and urine

45
Q

Phosphate buffer system
Weak acid =
Weak base =

A

dihydrogen phosphate (H2PO4-)

monohydrogen phosphate (HPO42-)

46
Q

In the presence of a strong acid, like hydrogen chloride (HCl):

A

HCl + Na2HPO4 → NaH2PO4 + Nacl

(strong acid) + (weak base) → (weak acid) + (salt)

47
Q

In the presence of a strong base, like sodium chloride (NaOH):

A

NaOH + Na2HPO4 → NaH2PO4 + H2O

(strong base) + (weak acid) → (weak base) + (water)

48
Q

PROTEIN BUFFER SYSTEM

A

buffers ICF and plasma

Individual amino acids on a protein can donate or accept H+ allowing it to function as a weak acid or base as needed

49
Q

PROTEIN BUFFER SYSTEM

When the pH begins to rise:

A

R-COOH → R-COO- + H+
(carboxyl group)

50
Q

PROTEIN BUFFER SYSTEM

In the presence of an acid (pH drops):

A

R-NH2 + H+ → R-NH3+
(amine group)

51
Q

A large percentage of the body’s total buffering capacity is through the protein buffer system inside :

A

cells
(ex. Hemoglobin in RBC)

but this also works with the proteins in plasma.

52
Q

Respiratory and Renal systems comprise the _____

A

Physiological Buffering System

slower than chemical buffer systems, but more powerful

53
Q

Respiratory System :

A

lungs work to control pH by controlling CO2 levels

(works in minutes)

54
Q

Kidneys :

A

control the levels of H+ and HCO3- levels in the body

(long term)

55
Q

The respiratory system helps maintain pH by:

A

eliminating CO2 from the lungs

56
Q

How respiratory system makes adjustments to pH:

A

Central respiratory centers are most sensitive to CO2 levels

Buildup of CO2 or H+ in blood activates respiratory centers to increase respiratory rate and depth: CO2 is “blown off” so H+ concentration is reduced

If blood pH rises, respiratory rate slowed: CO2 accumulates, pushing equation to right so H+ concentration increases and blood pH is restored to normal

57
Q

Acid-base imbalances may be due to respiratory system dysfunction:

respiratory acidosis
respiratory alkalosis

A

Hypoventilation → CO2 retention → build up of H+ → respiratory acidosis

Hyperventilation → CO2 elimination → reduce H+ → respiratory alkalosis

58
Q

____ is a long-term mechanism for controlling acid-base balance

A

Renal regulation

59
Q

Kidneys regulate acid-base balance by adjusting the amount of H+ or bicarbonate in the blood:

A

Directly by excreting or reabsorbing H+

Indirectly by controlling the concentration of bicarbonate ions

60
Q

Since acidity is usually a bigger problem than alkalinity, the kidney mostly eliminates H+ by secretion and retains HCO3- by ____________

A

reabsorption at the nephron

61
Q

Renal regulation of pH

A

H+ is secreted while HCO3- is reabsorbed (maintains bicarbonate reserve)

Phosphate buffer in filtrate ensures excretion of H+ (“trapping” H+ in filtrate)

Glutamine metabolism and NH4+ (ammonium) secretion and excretion

62
Q

Acidosis and Alkalosis can be classified as :

A

Respiratory or Metabolic

63
Q

Acid-base imbalances classified according to cause:

A

Respiratory system ventilation issues:

Metabolic imbalances:

64
Q

Respiratory system ventilation issues:

A

(normal PCO2 ~40 mm Hg)

Respiratory acidosis: Hypoventilation → PCO2 > 45 mm Hg → H+ rises; pH < 7.35

can be caused by shallow breathing, diseases that affect gas exchange such as pneumonia, cystic fibrosis, emphysema

Respiratory alkalosis:
Hyperventilation → PCO2 < 35 mm Hg → H+ falls; pH > 7.45

can be caused by stress, anxiety, pain

65
Q

Metabolic imbalances:

A

(anything NOT caused by abnormal PCO2 levels, not respiratory problem) (normal bicarbonate levels ~24 mEq/L)

66
Q

Metabolic acidosis:

A

arterial pH < 7.35 (low)
HCO3- levels < 22 mEq/L (low)

can be caused by diarrhea, lactic acid buildup, ketosis, excessive alcohol

67
Q

Metabolic alkalosis:

A

arterial pH > 7.45 (high)
HCO3- levels > 26 mEq/L (high)

can be caused by vomiting, loss of stomach acid, excessive antacids

68
Q

If a pH imbalance is caused by a respiratory disorder, it is a respiratory pH imbalance:

A

respiratory acidosis or respiratory alkalosis

kidney will try to compensate

69
Q

If the pH imbalance is not due to hyperventilation or hypoventilation, it is considered a metabolic pH imbalance:

A

metabolic acidosis or metabolic alkalosis

lungs will try to compensate

Anatomy Exam 3 (11 decks)

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