BIO 139
Human Anatomy & Physiology II
SPRING 2014
Chapter 21- Water,
Electrolyte, and Acid-Base
Balance
MARY CAT FLATH, PH.D.
Chapter 21- Water, Electrolyte, and
Acid-Base Balance
2
 Review of Inorganic Substances from
Chapter 2
 Introduction
 Distribution of Body Fluids
 Water Balance
 Electrolyte Balance
 Acid-Base Balance and Imbalances
Copyright 2014 Dr. Mary Cat Flath
Inorganic Substances:
OXYGEN and Carbon Dioxide
Inorganic Substances
3
4
 OXYGEN
 Oxygen

Is required for cellular respiration
Animal
cells use oxygen to release
energy from nutrients
By-product is carbon dioxide
 Carbon Dioxide
 Water
 Salts
 Acids
 Bases
Copyright 2014 Dr. Mary Cat Flath
Copyright 2014 Dr. Mary Cat Flath
Inorganic Substances: WATER
Inorganic Molecules: Acids, Bases, Salts
5
6
 Water is a polar molecule that demonstrates hydrogen bonding and
therefore it possesses very unique characteristics.
Water is an excellent solvent
b.
Water participates in many chemical reactions
• Dehydration (synthesis) is when water is removed from
adjacent atoms (of molecules) to form a bond between them.
• Hydrolysis (degradation) is when water is used to break
bonds between molecules.
c.
Water is an excellent temperature buffer.
d.
Water provides an excellent cooling mechanism
e.
Water serves as a lubricant
f.
Water is the most abundant component in cells (52-70%).
 a.
 Acids, Bases, and Salts

 When dissolved in water, these release cations and




Copyright 2014 Dr. Mary Cat Flath
anions.


These ions are referred to as electrolytes (charged particles)
Electrolytes must be maintained within a very narrow range in our blood
and tissues (i.e. homeostasis);
Needed for muscle contraction, nerve impulses, bone
growth, and many more metabolic processes;
 Examples include Na+, K+, Cl-, Ca+, PO4-; HCO3-, etc.

Copyright 2014 Dr. Mary Cat Flath
1
Acids
Bases
7
8
Acids dissociate (ionize) in water to form:
 a. a hydrogen cation, H+, and
 b. an anion.
 c. Example = HCl (hydrochloric acid).
 Bases dissociate (ionize) in water to form:
a
b.
c.



a hydroxide anion, OH-, and
a cation.
Example = NaOH (sodium hydroxide).

H2O
H2O

 NaOH → Na+ + OH

 HCl → H+ + Cl-


Copyright 2014 Dr. Mary Cat Flath
Copyright 2014 Dr. Mary Cat Flath
Salts
Acid and Base Concentration
9
10
 The relative concentrations of hydrogen ions and hydroxide
 Salts dissociate (ionize) into ions when
ions determine the pH in our blood, fluids, and tissues.
dissolved in water.
an anion is formed and

a cation is formed (i.e. electrolytes)

Example = NaCl in water.
 pH in body = [H+] + [OH-] .

 pH = -log[H+];
 pH Scale ranges from 0 to 14.
 0 ---------------------------7---------------------------14
H2O

↓
 NaCl → Na+ + Cl
 acidic
[H+] > [OH-]
Copyright 2014 Dr. Mary Cat Flath
Physiologic pH
pH Scale
12
 Physiologic pH = 7.4 (7.35-7.45)
 a.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Acidic
H+
pH 0
Acidic
2.0
gastric
juice
1
3.0
apple
juice
basic
[H+] < [OH-]
Copyright 2014 Dr. Mary Cat Flath
Fig. 2.10
Relative
amounts
of H+ (red)
and OH–
(blue)
neutral
[H+] = [OH-]
4.2
tomato
juice
6.6
cow’s
milk
5.3
cabbage
Copyright 2014 Dr. Mary Cat Flath
6
8.0
egg
white
7.0
distilled
water
6.0
corn
2
3
4
5
H+ concentration increases
8.4
7.4
sodium
human bicarbonate
blood
7
Neutral
11
8
OH–
 b.
10.5
milk of
magnesia
9
10
11
concentration increases
pH < 7.35 = acidosis; lethal below 7.0;
pH > 7.45 = alkalosis; lethal above 7.8.
11.5
household
ammonia
Basic
OH–
12
13
14
Basic (alkaline)
 c. Buffering Systems prevent abrupt pH changes
keeping pH near 7.4.
Copyright 2014 Dr. Mary Cat Flath
2
Chapter 21- Water, Electrolyte, and
Acid-Base Balance
Buffering Systems
13
14
 Definition:







Buffers prevent abrupt change in pH.
usually weak acids;
function by donating H+ when needed and by accepting H+ when
in excess;
very important in biological systems!
Example = the carbonic acid (H2CO3) buffering system.
H2CO3

HCO3+
H+
carbonic acid
(H+ donor)
bicarbonate ion
(H+ acceptor)
hydrogen ion
 when pH is rising equation goes to the right
 when pH is falling equation goes to the left
Copyright 2014 Dr. Mary Cat Flath
 Review of Inorganic Substances from
Chapter 2
 Introduction
 Distribution of Body Fluids
 Water Balance
 Electrolyte Balance
 Acid-Base Balance and Imbalances
Copyright 2014 Dr. Mary Cat Flath
Chapter 21- Water, Electrolyte, and
Acid-Base Balance
Introduction to Water, Electrolyte,
and Acid-Base
Balance
15
• Homeostasis has been a unifying theme in BIO 137 and BIO
139.
• The ability of an organism to maintain a relatively stable
internal environment.
• Water and electrolytes are included in this delicate balance
or state of equilibrium.
• Water and electrolyte input must equal their output.
• Keep in mind water and electrolyte balance are
interdependent upon one another…
Copyright 2014 Dr. Mary Cat Flath
16
 Review of Inorganic Substances from
Chapter 2
 Introduction
 Distribution of Body Fluids
 Water Balance
 Electrolyte Balance
 Acid-Base Balance and Imbalances
Copyright 2014 Dr. Mary Cat Flath
Distribution of Body Fluids
Distribution of Body Fluids
17
 Water Content of the Body
 Infants = 73% of body weight
 Males = 63% of body weight
 Females = 52% of body weight
18
 Fluid Compartments in the Body
 Two main fluid compartments
 INTRACELLULAR COMPARTMENT


 Total amount of water is affected by
 age
 body mass
 body fat
Copyright 2014 Dr. Mary Cat Flath

Fluid inside cells
63% of body weight
EXTRACELLULAR COMPARTMENT


Includes blood plasma, interstitial fluid, and lymph
37% of body weight
Copyright 2014 Dr. Mary Cat Flath
3
Fluid Compartments
19
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Total body water
40
38
36
34
32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
Interstitial fluid
Extracellular
fluid
(37%)
Plasma
Lymph
Intracellular fluid
(63%)
Membranes of
body cells
Transcellular fluid
Liters
•
20
An average adult female is about 52% water by weight,
and an average male about 63% water by weight
There are about 40 liters of water (with its dissolved
electrolytes) in the body, distributed into two major
compartments:
• Intracellular fluid – 63% - fluid inside cells
• Extracellular fluid – 37% - fluid outside cells
• Interstitial fluid
• Blood plasma
• Lymph
• Transcellular fluid – separated from other
extracellular fluids by epithelial layers
• Cerebrospinal fluid
• Aqueous and vitreous humors
• Synovial fluid
• Serous fluid
Extracellular fluid
(37%)
Intracellular
fluid
(63%)
Copyright 2014 Dr. Mary Cat Flath
Copyright 2014 Dr. Mary Cat Flath
Distribution of Body Fluids
Distribution of Body Fluids
21
22
BODY FLUID COMPOSITION
Electrolyte Concentration
The overall concentration of electrolytes is the same
in the two fluid compartments.
BODY FLUID
EXTRACELLULAR
FLUID: Blood
plasma, interstitial
fluid, and lymph
INTRACELLULAR
FLUID
HIGH
CONCENTRATION
Na+, Cl-, Ca++, HCO3-,
(plasma – high
proteins)
K+, PO4-, Mg++, SO4Negatively charged
proteins (A-)
LOW
CONCENTRATION
K+, Mg++, PO4-, SO4-
Na+, Cl-, HCO3-
However, there are different concentrations of
specific ions in the different compartments.
Copyright 2014 Dr. Mary Cat Flath
Copyright 2014 Dr. Mary Cat Flath
Distribution of Body Fluids
Body Fluid Composition
• Extracellular fluid composition:
• high concentrations of sodium,
calcium, chloride and
bicarbonate ions
• Low concentrations of
potassium, magnesium,
phosphate and sulfate
• Blood plasma, interstitial fluid
and lymph
• Intracellular fluid composition
• high concentrations of
potassium, magnesium,
phosphate, sulfate, and
proteins.
• Low concentration of sodium,
chloride, and bicarbonate ions
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Relative concentrations and ratios of ions in extracellular and intracellular fluids
150
140
Extracellular fluid
130
Intracellular fluid
110
100
outward force of
hydrostatic pressure
predominates
Plasma
90
80
70
60
Interstitial fluid
50
40
30
20
Transcellular
fluid
10
0
Na+
Ratio 14:1
K+
Ca+2
Mg+2
Cl-
1:28
5:1
1:19
26:1
(Extracellular: intracellular)
Copyright 2014 Dr. Mary Cat Flath
• Movement of Fluid Between Compartments
• Two major factors regulate the movement of water and electrolytes
from one fluid compartment to another
• Hydrostatic pressure
Fluid leaves plasma
at arteriolar end of
• Osmotic pressure
Capillary wall
capillaries because
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120
Ion concentration (m Eq/L)
•
HCO3- PO4-3
3:1
SO4-2
1:19
23
1:2
Serous
membrane
Copyright 2014 Dr. Mary Cat Flath
Fluid returns to
plasma at venular
ends of capillaries
because inward force
Lymph of colloid osmotic
vessel pressure predominates
Hydrostatic pressure
Lymph within interstitial
spaces forces fluid
into lymph capillaries
Intracellular
fluid
Cell
membrane
Interstitial fluid is
in equilibrium with
transcellular and
24
intracellular fluids
4
Chapter 21- Water, Electrolyte, and
Acid-Base Balance
Water Intake
25
 Review of Inorganic Substances from
Chapter 2
 Introduction
 Distribution of Body Fluids
 Water Balance
 Electrolyte Balance
 Acid-Base Balance and Imbalances
Copyright 2014 Dr. Mary Cat Flath
26
• The volume of water gained each day varies among individuals
averaging about 2,500 milliliters daily for an adult:
• 60% from drinking
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Average daily intake of water
• 30% from moist foods
• 10% as a bi-product of
oxidative metabolism of
nutrients called water of
metabolism
Water of
metobolism
(250 mL or 10%)
Water in
moist food
(750 mL or 30%)
Total intake
(2,500 mL)
Average daily output of water
Water lost in sweat
(150 mL or 6%)
Water lost in feces
(150 mL or 6%)
Water lost through
skin and lungs
(700 mL or 28%)
Total output
(2,500 mL)
Water in
beverages
(1,500 mL or 60%)
(a)
Water lost in urine
(1,500 mL or 60%)
(b)
Copyright 2014 Dr. Mary Cat Flath
Regulation of Water Intake
27
The primary regulator of water intake is thirst.
Water Output
•Water normally enters the body only
•
through
the mouth, but it can be lost
by a variety of routes including:
28
• Urine (60% loss)
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Average daily intake of water
• Evaporation from the skin
and lungs during breathing
(28% loss)
• Feces (6% loss)
Water of
metobolism
(250 mL or 10%)
Water in
moist food
(750 mL or 30%)
Total intake
(2,500 mL)
Water in
beverages
(1,500 mL or 60%)
• Sweat (6% loss)
(a)
Copyright 2014 Dr. Mary Cat Flath
Average daily output of water
Water lost in sweat
(150 mL or 6%)
Water lost in feces
(150 mL or 6%)
Water lost through
skin and lungs
(700 mL or 28%)
Total output
(2,500 mL)
Water lost in urine
(1,500 mL or 60%)
(b)
Copyright 2014 Dr. Mary Cat Flath
Antidiuretic Hormone (ADH) regulates
water reabsorption in nephron (DCT & CD)
Regulation of Water Output
29
Conditions that trigger release of ADH include:
30
The osmoreceptor-ADH mechanism in the hypothalamus regulates
the concentration of urine produced in the kidney through GFR.
- Stimulation of posterior pituitary (by
hormone?)
- Prolonged fever
- Excessive sweating, vomiting, or diarrhea
which concentrates blood plasma
- Severe blood loss
- Traumatic burns
- Increased plasma osmolality
Copyright 2014 Dr. Mary Cat Flath
Copyright 2014 Dr. Mary Cat Flath
5
See Clinical Application 21.1
Chapter 21- Water, Electrolyte, and
Acid-Base Balance
32
31
 Review of Inorganic Substances from
Water Balance Disorders:
Dehydration
Water Intoxication
Edema
Copyright 2014 Dr. Mary Cat Flath
Chapter 2
 Introduction
 Distribution of Body Fluids
 Water Balance
 Electrolyte Balance
 Acid-Base Balance and Imbalances
Copyright 2014 Dr. Mary Cat Flath
Electrolyte Balance
Electrolyte Intake
33
34
An electrolyte balance exists when the quantities of electrolytes
the body gains equals those lost
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Foods
Fluids
Metabolic
reactions
Electrolyte intake
• Ordinarily, a person obtains sufficient electrolytes by
responding to hunger and thirst
Electrolyte output
Perspiration
Feces
• The electrolytes of greatest importance to cellular functions are
• sodium, potassium, calcium, magnesium, chloride, sulfate,
phosphate, bicarbonate, and hydrogen ions.
• These ions are primarily obtained from foods, but some are
from water and other beverages, and some are by-products of
metabolism
• A severe electrolyte deficiency may cause salt craving (rare)
Urine
Copyright 2014 Dr. Mary Cat Flath
Copyright 2014 Dr. Mary Cat Flath
Electrolyte Output
Regulation of Electrolyte Output
36
35
 The concentrations of positively charged ions, such as sodium (Na+),
• The body loses some electrolytes by
potassium (K+) and calcium (Ca+2) are of particular importance
 These ions are vital for nerve impulse conduction, muscle fiber
contraction, and maintenance of cell membrane permeability
•perspiring (more on
warmer days and during strenuous exercise)
• Some are lost in the feces
• The greatest output is as a result of
kidney function and urine output
Copyright 2014 Dr. Mary Cat Flath
 Sodium ions account for nearly 90% of the positively charged
ions in extracellular fluids.
 Regulation of Na+: Aldosterone causes reabsorption
of Na+ in DCT
 Regulation of K+: Aldosterone causes secretion/
excretion of K+ in DCT
 Regulation of Ca++: Calcitonin decreases blood Ca++ and
PTH increases blood Ca++
Copyright 2014 Dr. Mary Cat Flath
6
Regulation of Electrolyte Output
Sodium and Potassium Imbalances
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Hyponatremia (low blood sodium) caused by prolonged sweating, diarrhea,
38
Potassium ion
concentration increases
vomiting, renal disease, Addison’s disease, or excessive water intake can result
in osmosis of water into cells – water intoxication.
Calcium ion
Concentration decreases
Parathyroid glands
are stimulated
Hypernatremia (high blood sodium) caused by water loss (diabetes
Adrenal cortex is signaled
insipidus –ADH deficiency, osmotic diuresis- Diabetes Mellitus, increased
perspiration, high fever or heat stroke) or sodium gain (hyperaldosteronism)
can result in CNS disturbances – confusion, stupor, coma.
Parathyroid hormone
is secreted
Aldosterone is secreted
Renal tubules conserve
calcium and increase
secretion of phosphate
Intestinal absorption
of calcium increases
Hypokalemia (low blood potassium) caused by diuretics, renal disease, or
Activity of bone-resorbing
osteoclasts increases
Renal tubules
increase reabsorption of
sodium ions and increase
secretion of potassium ions
alkalosis can result in muscle weakness or paralysis, respiratory difficulty, and
atrial and ventricular arrhythmias.
Increased phosphate
excretion in urine
Hyperkalemia (high blood potassium) caused by renal disease, drugs,
Addition of phosphate
to bloodstream
Sodium ions are
conserved and potassium
ions are excreted
Calcium ion concentration
returns toward normal
37
Copyright 2014 Dr. Mary Cat Flath
WATER BALANCE
Addisons’s disease, or acidosis can result in paralysis of skeletal muscle and
cardiac arrest.
Normal phosphate
concentration is maintained
Copyright 2014 Dr. Mary Cat Flath
ELECTROLYTE BALANCE
Most abundant molecule in animals:
Infants 73%; Males: 63%; Females: 52%
Electrolyte Intake is primarily through food, some
fluids, and some through metabolism.
Average is 40L: depends of age, body mass, body fat
Electrolyte Output is primarily through kidney
function= urine, some perspiration, some feces.
Body Fluid is in two compartments:
Intracellular Fluid = 63%
Extracellular Fluid = 37%
Most important are: K+, Na+, Cl-, Ca++, HCO3- , H+
Electrolyte Concentration varies between
compartments:
High Inside: K+
High Outside: Na+, Cl-, Ca++, HCO3-
Na+ ions account for 90% of cations in ECF.
Movements between compartments due to:
Hydrostatic Pressure or
Osmotic Pressure
Na+ regulation = Aldosterone ↑ reabsorption through
DCT;
K+ regulation = Aldosterone ↑ secretion through DCT
Water Intake: 2500mL Average
60% drinking, 30% moist foods, 10% water of
metabolism
THIRST is primary regulator of water intake when as
much as 1% water is lost (through hypothalamus)
Ca++ regulation = calcitonin causes secretion in DCT;
PTH causes reabsorption through DCT
Water Output: 60% urine, 28% evaporation from skin
& breathing, 6% feces, 6% sweat
ADH regulates water output through reabsorption in
DCT and CD
Chapter 21- Water, Electrolyte, and
Acid-Base Balance
40
 Review of Inorganic Substances from
Chapter 2
 Introduction
 Distribution of Body Fluids
 Water Balance
 Electrolyte Balance
 Acid-Base Balance and Imbalances
Copyright 2014 Dr. Mary Cat Flath
Acid-Base Imbalances
Acid-Base Balance
41
• pH is an indirect measure of the H+ ion concentration
• Our body maintains a slightly alkaline pH of 7.35-7.45.
42
• Chemical and physiological buffer systems ordinarily
maintain the hydrogen ion concentration of body fluids
within very narrow pH range of 7.35-7.45.
• Abnormal conditions may disturb the acid-base balance
• Chemical, respiratory, and metabolic processes work
together to keep H+ levels in this normal range.
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Alkalosis
Acidosis
pH scale
6.8
7.0
7.35 7.45
7.8
8.0
Normal pH range
Copyright 2014 Dr. Mary Cat Flath
Copyright 2014 Dr. Mary Cat Flath
Survival range
42
7
Normal Metabolism produces Acids/
Hydrogen Ions
Regulation of Hydrogen Ion
Concentration
43
44
• pH greater than 7.45 = alkalosis
• pH less than 7.35 = acidosis
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Aerobic
respiration
of glucose
Anaerobic
respiration
of glucose
Incomplete
oxidation of
fatty acids
Oxidation of
sulfur-containing
amino acids
Hydrolysis of
phosphoproteins
and nucleic acids
Carbonic
acid
Lactic
acid
Acidic ketone
bodies
Sulfuric
acid
Phosphoric
acid
• Acid-base balance is maintained (usually by elimination of
acids) in one of three ways:
• Chemical Buffer Systems – work immediately
• Respiratory Mechanisms – work in minutes to hours
• Renal/Metabolic Mechanisms– work in hours to 2-3 days
and have longer maintenance
H+
Internal environment
Acids MUST be neutralized.
Copyright 2014 Dr. Mary Cat Flath
Copyright 2014 Dr. Mary Cat Flath
Lines of Defense Against pH Shift
Chemical Buffer Systems
46
•
Chemical buffer systems are in all body fluids and are based on chemicals that
combine with excess acids or bases. These act immediately.
• Bicarbonate buffer system
• H2CO3 ↔ H + + HCO3• When pH is rising: →
• When pH is falling: ←
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Bicarbonate
buffer system
First line of defense
against pH shift
Chemical
buffer system
Phosphate
buffer system
• Phosphate buffer system
• H2PO4-  H+ + HPO4-2
• When pH is rising: →
• When pH is falling: ←
Protein
buffer system
Second line of
defense against
pH shift
Respiratory
mechanism
(CO2 excretion)
• Protein buffer system
• Involve plasma proteins (i.e. albumin) and certain proteins in cells
(hemoglobin in red blood cells).
Physiological
buffers
Renal
mechanism
(H+ excretion)
Copyright 2014 Dr. Mary Cat Flath
Copyright 2014 Dr. Mary Cat Flath
45
Lines of Defense Against pH Shift
Abnormalities in Acid-Base Balance
• Acidosis results from the
accumulation of acids or loss of
bases, both of which cause abnormal
increases in the hydrogen ion
concentrations of body fluids
• Alkalosis results from a loss of
acids or an accumulation of bases
accompanied by a decrease in
hydrogen ion concentrations
•
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Accumulation
of acids
Loss of
bases
Bicarbonate
buffer system
Increased concentration of H+
Acidosis
First line of defense
against pH shift
Phosphate
buffer system
pH drops
Protein
buffer system
pH scale
7.4
Loss of
acids
Respiratory
mechanism
(CO2 excretion)
Alkalosis
pH rises
Second line of
defense against
pH shift
Decreased concentration of H+
Copyright 2014 Dr. Mary Cat Flath
Chemical
buffer system
Accumulation
of bases
47
Physiological
buffers
Renal
mechanism
(H+ excretion)
Copyright 2014 Dr. Mary Cat Flath
48
8
Abnormalities in Acid-Base Balance
Abnormalities in Acid-Base Balance
49
50
Health problems may lead to imbalances in acid-base
concentrations and fluid and electrolyte balance.
The “biggies” include:
Diabetes Mellitus
COPD
Kidney Disease
Vomiting
Diarrhea
Hormonal Imbalances
Copyright 2014 Dr. Mary Cat Flath
RESPIRATORY IMBALANCES affect carbonic acid
concentrations = CARBON DIOXIDE – CO2
METABOLIC (RENAL) IMBALANCES affect
BICARBONATE ION CONCENTRATIONS – HCO3-
Copyright 2014 Dr. Mary Cat Flath
Abnormalities in Acid-Base Balance
Respiratory Buffer System
51
52
During Abnormalities in Acid-Base Balance
THE RESPIRATORY AND
URINARY SYSTEMS ACT
TO COMPENSATE
Bicarbonate Buffering System is the main buffer in ECF
CA
CO2 + H2O ↔ H2CO3 ↔ H + + HCO3Changes in CO2 concentration lead directly to changes in
H+ and pH.
CO2 concentration and H+ concentration are directly
proportional
H+ concentration and pH are inversely proportional
Copyright 2014 Dr. Mary Cat Flath
Copyright 2014 Dr. Mary Cat Flath
Respiratory Buffer System
Respiratory Excretion of Carbon
Dioxide: Physiologic Buffer System
53
Decreased ventilation leads to increased CO2 in the body
pushing the reaction to the right.
Increased ventilation leads to a decreased CO2 in the body
pushing the reaction to the left.
• The respiratory center in the
brainstem helps regulate
hydrogen ion concentrations in
the body fluids by controlling
the rate and depth of breathing
(Pontine/pneumotaxic area in
pons)
• If body cells increase their
production of CO2…
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Cells increase production of CO2
CO2 reacts with H2O to produce H2CO3
H2CO3 releases H+
Respiratory center is stimulated
This system works within minutes to hours, but it is only
temporary.
Rate and depth of breathing increase
Copyright 2014 Dr. Mary Cat Flath
Copyright 2014 Dr. Mary Cat Flath
54
More CO2 is eliminated through lungs
9
Lines of Defense Against pH Shift
Renal Regulation of Acid-Base Balance
56
•
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Bicarbonate
buffer system
First line of defense
against pH shift
Chemical
buffer system
The kidneys can secrete and reabsorb
HCO3-
Phosphate
buffer system
Protein
buffer system
Second line of
defense against
pH shift
and H+ ions to regulate pH.
Respiratory
mechanism
(CO2 excretion)
The kidneys respond within hours to days.
Physiological
buffers
Renal
mechanism
(H+ excretion)
Copyright 2014 Dr. Mary Cat Flath
Copyright 2014 Dr. Mary Cat Flath
55
Abnormalities in Acid-Base Balance
Abnormalities in Acid-Base Balance
57
In the kidneys,
this involves the secretion and reabsorption of what ions???
If H+ is secreted,
then HCO3- is reabsorbed.
If HCO3- is secreted,
then H+ is reabsorbed.
58
Respiratory Acidosis
Respiratory Alkalosis
(↑H+ = ↓pH)
(increased H2CO3 )=↑CO2
(↓H+ = ↑pH)
(decreased H2CO3) = ↓CO2
Summarize as:
↓pH=↑CO2
Summarize as:
↑pH=↓CO2
Metabolic Acidosis
(↑H+ = ↓pH)
Metabolic Alkalosis
(↓H+ = ↑pH)
↓pH = ↓HCO3-
↑pH = ↑HCO3-
Loss of 1 HCO3- is the same as gain of 1 H+ and vice versa
Copyright 2014 Dr. Mary Cat Flath
Copyright 2014 Dr. Mary Cat Flath
Respiratory Acidosis (pH< 7.35)
Respiratory Alkalosis (pH > 7.45)
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Increased H2CO3 leads to ↑CO2 causing ↑ H+ = ↓pH
Causes:
Hypoventilation
caused by lung disease (asthma, CF, COPD),
anesthesia, drug overdose, atelectasis
Stimulates Respiratory Centers (including Dorsal Respiratory
Group) which leads to
increased ventilation and expiration of excess CO2
↓ H2CO3 leads to ↓CO2 = ↑pH
Causes:
Hyperventilation possibly caused by anxiety, pulmonary
embolism, fear, or mechanical ventilation
causes respiratory center to decrease ventilation
Compensation:
Kidneys secretion/excretion of HCO3- OR
kidneys reabsorption of H+
Compensation: Kidneys reabsorption of HCO3- and
kidneys secretion/excretion of excess H+
Copyright 2014 Dr. Mary Cat Flath
Copyright 2014 Dr. Mary Cat Flath
10
Metabolic/Renal Control of Acid-Base
Balance
Metabolic Acidosis (pH< 7.35)
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Decreased pH and decreased HCO3Kidneys are only organ that can rid body of acids
(not just H+) generated by cellular metabolism.
HCO3- is key indicator of metabolic acidosis or
metabolic alkalosis.
Causes:
Diabetes Mellitus, severe diarrhea, renal failure, shock,
Accumulation of non-respiratory acids or excessive loss
of HCO3Ingestion of excessive alcohol
Starvation
Compensation:
kidneys secretion/excretion of H+ AND
reabsorption of HCO3- AND
increased CO2 release by lungs
Copyright 2014 Dr. Mary Cat Flath
Copyright 2014 Dr. Mary Cat Flath
Metabolic Alkalosis (pH > 7.45)
Maintaining Metabolic Acid-Base Balance in Kidney
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Increased pH and increased HCO3Causes:
Severe vomiting, diuretics, excessive base intake
Compensation:
kidneys secretion of HCO3- and
decreased respiration
Copyright 2014 Dr. Mary Cat Flath
OR
Secretion/excretion of HCO3- (by nephron)
Copyright 2014 Dr. Mary Cat Flath
Abnormalities in Acid-Base Balance
Respiratory Acidosis
↓pH and↑CO2
Reabsorption of HCO3- (by nephron)
Abnormalities in Acid-Base Balance
Respiratory Alkalosis
↑pH and↓CO2
Respiratory Acidosis
Metabolic Acidosis
Metabolic Alkalosis
Metabolic Acidosis
↓pH and ↓HCO3-
↑pH and ↑HCO3-
Causes: Hypoventilation (lung
disease, anesthesia, drug
overdose, atelectasis)
Respiratory Centers (Dorsal)
↑ ventilation and expiration of
excess CO2
Causes: diabetes mellitus,
severe diarrhea, renal failure,
shock
Kidneys reabsorb HCO3- and
secrete H+ and respiration rate
is increased
Copyright 2014 Dr. Mary Cat Flath
65
Respiratory Alkalosis
↑
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Causes: Hyperventilation
(anxiety, PE, fear, poisoning, high
altitudes, mechanical ventilation)
Respiratory Centers ↓ventilation
Metabolic Alkalosis
Causes: Severe vomiting,
diuretics, excessive base intake
Kidneys secrete HCO3- and
reabsorb H+ and respiration rate
is decreased
Copyright 2014 Dr. Mary Cat Flath
11
Abnormalities in Acid-Base Balance
Respiratory Acidosis
↓pH and↑CO2
Causes: Hypoventilation (lung
disease, anesthesia, drug
overdose, atelectasis)
Respiratory Centers (Dorsal)
↑ ventilation and expiration of
excess CO2
67Respiratory Alkalosis
↑pH and↓CO2
Causes: Hyperventilation
(anxiety, PE, fear, poisoning, high
altitudes, mechanical ventilation)
Respiratory Centers ↓ventilation
Metabolic Acidosis
Metabolic Alkalosis
↓pH and ↓HCO3-
↑pH and ↑HCO3-
Causes: diabetes mellitus,
severe diarrhea, renal failure,
shock
Kidneys reabsorb HCO3- and
secrete H+ and respiration rate
is increased
Causes: Severe vomiting,
diuretics, excessive base intake
Kidneys secrete HCO3- and
reabsorb H+ and respiration rate
is decreased
Copyright 2014 Dr. Mary Cat Flath
ACID-BASE BALANCE
Physiologic pH = 7.35-7.45
Acidosis <7.35; Alkalosis >7.45
Buffers prevent pH change: Three lines of defense against pH shift are:
1. Chemical Buffers - immediate
2. Respiratory Mechanisms – minutes to hours
3. Renal/Metabolic – hours to days
First Line of Defense - Chemical Buffers
work immediately
a. Carbonic Acid Buffer System
b. Phosphate Buffer System
c. Protein Buffer System
Second Line of Defense – Respiratory
Mechanisms work in minutes to hours
pH is inversely proportional to CO2
Respiratory Acidosis
↓pH and↑CO2
Causes: Hypoventilation (lung
disease, anesthesia, drug
overdose, atelectasis)
Respiratory Centers (Dorsal)
↑ ventilation and expiration of
excess CO2
Respiratory Alkalosis
↑pH and↓CO2
Causes: Hyperventilation
(anxiety, PE, fear, poisoning,
high altitudes)
Respiratory
Centers↓ventilation increasing
blood CO2
Metabolic Acidosis
↓pH and ↓HCO3Causes: diabetes mellitus, severe
diarrhea, renal failure, shock
Kidneys reabsorb HCO3- and
secrete H+ and Respiratory
Centers ↑ ventilation and
expiration of excess CO2
Metabolic Alkalosis
↑pH and ↑HCO3Causes: Severe vomiting,
diuretics, excessive base intake
Kidneys secrete HCO3- and
reabsorb H+ and Respiratory
Centers ↓ventilation increasing
blood CO2
CO2 + H2O ↔ H2CO3 ↔ H + + HCO3An increase in CO2 pushes reaction to right (↓pH)
A decrease in CO2 pushes reaction to left (↑pH)
Third Line of Defense – Metabolic/Renal
Mechanisms work in hours to days
pH is directly proportional to HCO3CO2 + H2O ↔ H2CO3 ↔ H + + HCO3An increase in HCO3 pushes reaction to left (↑pH)
A decrease in HCO3-pushes reaction to right(↓pH)
Chapter 21- Water, Electrolyte, and
Acid-Base Balance
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 Review of Inorganic Substances from
Chapter 2
 Introduction
 Distribution of Body Fluids
 Water Balance
 Electrolyte Balance
 Acid-Base Balance and Imbalances
Copyright 2014 Dr. Mary Cat Flath
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