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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
Bicarbonate Buffer System
mixture of H2CO3 (weak acid) and salts of HCO3- (weak base) maintain ECP buffer; also operates in ICF
26
Phosphate Buffer System
salts of H2PO4- (weak acid) and HPO4 2- (weak base) important buffer in urine and ICF
27
Protein Buffer System
some amino acid side chains act as weak acids (-COOH) or weak bases (-NH2) most important buffer in ICF; also in blood plasma
28
CARBONIC ACID-BICARBONATE BUFFER SYSTEM
most important buffer of the ECF
29
Bicarbonate buffer system:
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
Bicarbonate ions enter the plasma and form the _____ which will help buffer acids entering the blood.
alkaline reserve
31
______ ⇌ ____ ⇌ ______
CO2 + H2O (carbon dioxide plus water) H2CO3 (carbonic acid) HCO3- + H+ (bicarbonate ion plus hydrogen ion)
32
Plasma HCO3- concentration averages ____ which is hundreds of thousands of times as concentrated as ____
~24 mEq/L plasma H+
33
Although H+ and HCO3- are both created from CO2 and H2O, the majority of H+ is buffered by _____
hemoglobin
34
The HCO3- in plasma is then available to buffer H+ from ___ sources, such as metabolism.
nonrespiratory
35
Weak acid = Weak base =
carbonic acid (H2CO3) sodium bicarbonate (NaHCO3)
36
Buffers strong acids ______ → ______ + ______
HCl + NaHCO3 → H2CO3 + NaCl (strong acid) + (weak base) → (weak acid) + (salt)
37
When a strong acid is added to buffering system =
the sodium bicarbonate acts as a weak base to tie up the H+ released by the strong acid
38
The net effect is that ______
the strong acid is converted to a weak acid so that arterial pH goes down very little.
39
Buffering capacity is dependent on the concentration of _____ This is closely regulated by the ____.
bicarbonate ions (alkaline reserve) kidneys
40
Buffers strong bases ______ → ______ + ______
NaOH + H2CO3 → NaHCO3 + H2O (strong base) + (weak acid) → (weak base) + (water)
41
When a strong base such as NaOH is added to buffering system =
the carbonic acid dissociates further, donating a H+ to tie up the OH- released by the strong base (and forming water)
42
The net effect is that _____
the strong base is converted to a weak base so that arterial pH goes up very little
43
buffering capacity is dependent on the concentration of ______
carbonic acid (essentially limitless)
44
Phosphate BUFFER SYSTEM
most important buffer of the ICF and urine
45
Phosphate buffer system Weak acid = Weak base =
dihydrogen phosphate (H2PO4-) monohydrogen phosphate (HPO42-)
46
In the presence of a strong acid, like hydrogen chloride (HCl):
HCl + Na2HPO4 → NaH2PO4 + Nacl (strong acid) + (weak base) → (weak acid) + (salt)
47
In the presence of a strong base, like sodium chloride (NaOH):
NaOH + Na2HPO4 → NaH2PO4 + H2O (strong base) + (weak acid) → (weak base) + (water)
48
PROTEIN BUFFER SYSTEM
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
PROTEIN BUFFER SYSTEM When the pH begins to rise:
R-COOH → R-COO- + H+ (carboxyl group)
50
PROTEIN BUFFER SYSTEM In the presence of an acid (pH drops):
R-NH2 + H+ → R-NH3+ (amine group)
51
A large percentage of the body’s total buffering capacity is through the protein buffer system inside :
cells (ex. Hemoglobin in RBC) but this also works with the proteins in plasma.
52
Respiratory and Renal systems comprise the _____
Physiological Buffering System slower than chemical buffer systems, but more powerful
53
Respiratory System :
lungs work to control pH by controlling CO2 levels (works in minutes)
54
Kidneys :
control the levels of H+ and HCO3- levels in the body (long term)
55
The respiratory system helps maintain pH by:
eliminating CO2 from the lungs
56
How respiratory system makes adjustments to pH:
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
Acid-base imbalances may be due to respiratory system dysfunction: respiratory acidosis respiratory alkalosis
Hypoventilation → CO2 retention → build up of H+ → respiratory acidosis Hyperventilation → CO2 elimination → reduce H+ → respiratory alkalosis
58
____ is a long-term mechanism for controlling acid-base balance
Renal regulation
59
Kidneys regulate acid-base balance by adjusting the amount of H+ or bicarbonate in the blood:
Directly by excreting or reabsorbing H+ Indirectly by controlling the concentration of bicarbonate ions
60
Since acidity is usually a bigger problem than alkalinity, the kidney mostly eliminates H+ by secretion and retains HCO3- by ____________
reabsorption at the nephron
61
Renal regulation of pH
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
Acidosis and Alkalosis can be classified as :
Respiratory or Metabolic
63
Acid-base imbalances classified according to cause:
Respiratory system ventilation issues: Metabolic imbalances:
64
Respiratory system ventilation issues:
(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
Metabolic imbalances:
(anything NOT caused by abnormal PCO2 levels, not respiratory problem) (normal bicarbonate levels ~24 mEq/L)
66
Metabolic acidosis:
arterial pH < 7.35 (low) HCO3- levels < 22 mEq/L (low) can be caused by diarrhea, lactic acid buildup, ketosis, excessive alcohol
67
Metabolic alkalosis:
arterial pH > 7.45 (high) HCO3- levels > 26 mEq/L (high) can be caused by vomiting, loss of stomach acid, excessive antacids
68
If a pH imbalance is caused by a respiratory disorder, it is a respiratory pH imbalance:
respiratory acidosis or respiratory alkalosis kidney will try to compensate
69
If the pH imbalance is not due to hyperventilation or hypoventilation, it is considered a metabolic pH imbalance:
metabolic acidosis or metabolic alkalosis lungs will try to compensate

Anatomy Exam 3 (11 decks)

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