Transcript Fluid/Electrolytes/pH

Fluid,
Electrolyte,
and AcidBase
Balance
Fluid
Solvent
Fluid
• Solution is a mixture
• Most abundant component
Solute
in a solution is the solvent.
• Other components are solutes.
• Solutions are good for delivering food,
removing waste.
– Examples include blood, urine, intracellular
fluid, interstitial fluid, etc.
Water
• The most important biological solvent is water.
• Healthy males are about 60% water; healthy
females are around 50%
• Infants have low body fat, low bone mass, and
are 73% or more water
• Total water content declines throughout life
• In old age, only about 45% of body weight is
water
The solvent is always water but
that leaves three questions?
1. What solutions
are there?
– Intracellular
fluid
– Interstitial fluid
– Blood plasma
2. What solutes
are there?
– Electrolytes
– NonElectrolytes
3. How much solute
is in the solution
(concentration)?
– Moles/Liter
– mEq
Fluid Compartments in the Body
•
•
You can divide your body into two
compartments, intracellular fluid and
extracellular fluid.
Its more complete to think of your body
as divided into three solution-filled
compartments.
1. Intracellular fluid
2. Interstitial fluid
3. Blood plasma
Fluid Compartments
Intracellular fluid (ICF) – about two
thirds by volume, contained in
cells
Interstitial fluid
(IF) – fluid in
spaces
between cells
Plasma the
fluid portion
of the
blood
Edema is accumulation of fluid
in the ____________.
A. Special fluid compartments
B. Interstitial space
C. Intracellular space
D. Plasma
E. All of the above.
Extracellular and Intracellular
Fluids
• Extracellular fluids are similar (except for
the high protein content of plasma)
– Sodium is the chief cation
– Chloride is the major anion
• Intracellular fluids have low
sodium and chloride
Na+
Na+
Cl-
ClHPO4K+
K+
HPO4-
– Potassium is the chief cation
– Phosphate is the chief anion
Cl-
K+
K+
HPO4K+
HPO4Na+
Na+
Na+
Cl-
Extracellular and Intracellular
Fluids
Outside Cell
Inside Cell
Outside Cell
Inside Cell
Electrolyte Comp. of Body Fluids
The solvent is always water but
that leaves three questions?
1. What solutions
are there?
– Intracellular
fluid
– Interstitial fluid
– Blood plasma
2. What solutes
are there?
– Electrolytes
– NonElectrolytes
3. How much solute
is in the solution
(concentration)?
– Moles/Liter
– mEq
Composition of Body Fluids
• Solutes can be either electrolytes
or nonelectrolytes.
– Electrolytes = charged molecules
• inorganic salts, all acids and bases, and some
proteins
– Nonelectrolytes = uncharged molecules
• examples include glucose, lipids, creatinine, and
urea
All solutes can move water.
But, electrolytes are much
more powerful at it
Isotonic
Osmosis
Hypotonic
• The movement
of water to
follow solutes
Hypertonic
Electrolytes
• Electrolytes have greater osmotic power than
nonelectrolytes due to charge.
• Ions can use charge to sense/influence over a
large distance.
The solvent is always water but
that leaves three questions?
1. What solutions
are there?
– Intracellular
fluid
– Interstitial fluid
– Blood plasma
2. What solutes
are there?
– Electrolytes
– NonElectrolytes
3. How much solute
is in the solution
(concentration)?
– Moles/Liter
– mEq
Concentration
• Understanding concentration is important
because “the dose makes the poison.”
• The speed, and effectiveness of
hormones, drugs, poisons and other
chemicals is dependent on concentration.
– In general, if you double the concentration of
something, you double its rate of reaction.
AB  A + B
Concentration of Solutes
• Concentration may be expressed in several
ways but essentially the amount per given
volume.
• Moles/liter
• Milliequivalents per liter (mEq/L), a measure of
the number of electrical charges in one liter of
solution
– mEq/L = (concentration of ion in [mg/L]/the atomic
weight of ion)  number of electrical charges on one
ion
Electrolyte Concentration
• Expressed in milliequivalents per liter
(mEq/L), a measure of the number of
electrical charges in one liter of solution
• mEq/L = (concentration of ion in [mg/L]/the
atomic weight of ion)  number of
electrical charges on one ion
• For single charged ions, 1 mEq = 1 mOsm
• For bivalent ions, 1 mEq = 1/2 mOsm
It takes half as many Ca++ as Na+ to make 1 mEq because Ca++ has two charges
• Transition
Fluid Movement Among
Compartments
Water Balance and ECF
Osmolality
• To remain properly hydrated, water intake
must equal water output
• Water intake sources
– Ingested fluid (60%) and solid food (30%)
– Metabolic water or water of oxidation (10%)
• Water output
– Urine (60%) and feces (4%)
– Insensible losses (28%), sweat (8%)
Fluid Movement Among
Water intake sources
Ingested fluid (60%)Compartments
and solid food (30%)
Outputs
Metabolic water or water of oxidation
(10%)
Water output
Urine (60%) and feces (4%)
Insensible losses (28%), sweat (8%)
Intake Sources
Food
660 ml
Fluids
1540 ml
Water Intake and Output
Water Disturbances
• You can have two types of water
disturbances.
– Too much or too little pure water
• Will affect ion concentrations and thus a number of
things such as excitability of neurons, muscles,
and the heart.
– Too much or too little isotonic fluid (water plus
salt).
• Mainly affects blood pressure.
Disturbances of Water
Homeostasis
water and
solute
water
Too much
Hypervolemia
Overhydration
Too little
Hypovolemia
Dehydration
Disturbances of Water
Homeostasis: Sample Causes
water and
solute
Too much
Too little
IV errors
Water retention
High salt diet
Cell damage
Blood loss
Fluid loss
water
Excessive drinking
Sweating
diarrhea
Disturbances of Water
Homeostasis: Sample Effects
water and
solute
Too much
High blood
pressure
Low blood pressure
Too little
water
Dilutes solutes
Arrythmias
CNS dysfunction
Concentrates
solutes
Arrythmias
CNS dysfunction
Disturbances of Water
Homeostasis: Sample Solutions
water and
solute
Too much
Too little
water
Inhibit aldosterone
Inhibit ADH
ANP
Inhibit ADH
ANP
Sympathetic
Aldosterone
ADH
Thirst
Sympathetic
ADH
Angiotensin
thirst
Fluid Homeostasis
•
There are basically six mechanisms to
regulate fluid homeostasis.
1.
2.
3.
4.
5.
6.
Anti-Diuretic Hormone (ADH)
Thirst
Renin-Angiotensin-Aldosterone System
Sympathetic Nervous System
Atrial Natriuretic Protein (ANP)
Increased GFR
1. Influence and
Regulation of ADH
• ADH is released by the posterior
pituitary in response to
osmoreceptors sensing
concentrated plasma.
• ADH inserts water channels in the collecting
duct
• Low ADH increase urine and decrease fluid
volume
• High ADH levels decrease urine and conserve
ADH
No ADH
ADH
Permeability of H20
is controlled by ADH
Which factor would increase the
secretion of ADH?
A.
B.
C.
D.
E.
Increased renal blood flow
Thirst
Excess salt consumption
Hypotonic ECF concentration
Ethanol consumption
All of the following statements
about ADH are true except:
A. The amount of water lost in the urine is inversely
proportional to the amount of ADH released.
B. ADH decreases the volume of urine and dilutes
urine.
C. In the absence of ADH, there is a lack of channels
to allow water to escape the collecing duct.
D. A decrease in blood pressure would cause an
increase in ADH release.
Mechanisms
and
Consequences
of ADH
Release
2. Thirst
• The hypothalamus
controls thirst
• The hypothalamic thirst
center is stimulated:
– By a decline in plasma volume of 10%–15%
– By increases in plasma osmolality of 1–2%
– Via baroreceptor input, angiotensin II, and
other stimuli
• How could a neuron sense increased Na+
concentration?
2. Thirst
• Thirst is quenched as soon as we begin to
drink water
• Feedback signals that inhibit the thirst
centers include:
– Moistening of the mucosa of the mouth and
throat
– Activation of stomach and intestinal stretch
receptors
Regulation
of Water
Intake:
Thirst
Mechanism
3. Renin-Angiotensin Mechanism
• Is triggered when the JG cells release renin
• Renin acts on angiotensinogen (liver) to release
angiotensin I
• Angiotensin I is converted to angiotensin II by ACE
(capillaries)
• Angiotensin II goes to adrenal cortex
• Aldosterone is released
– Causes mean arterial pressure to rise
• Stimulates the adrenal cortex to release aldosterone
Increase Na+ absorption in DCT/CD
• As a result, both systemic and glomerular
hydrostatic pressure rise
Juxtaglomerular Apparatus
(JGA)
Distal Tubule
comes back up
near glomerulus
ReninAngiotensin
Mechanism
Collecting Duct
In response to increased levels of
aldosterone, the kidneys produce
A. Urine with a lower concentration of sodium
ions.
B. Urine with a lower concentration of
potassium ions.
C. A larger volume of urine.
D. Urine with a lower specific gravity.
E. Urine with less urea.
4. Sympathetic Nervous System
• Decreased blood pressure stimulates the
sympathetic nervous system.
• Sympathetic nervous system can control
the afferent arteriole and thus constricts it.
– Decrease GFR = less water loss = increase in
bp
Constricts
5. Atrial Natriuretic Peptide
(ANP)
• Reduces blood pressure and
blood volume by inhibiting:
– Events that promote vasoconstriction
– Na+ and water retention
• Is released in the heart atria as a response
to stretch (elevated blood pressure)
• Inhibits angiotensin II production
• Promotes excretion of sodium and water
Which of the following statements
about the atrial natriuretic peptide
(ANP) are incorrect?
A. It suppresses the release of renin and
aldosterone.
B. It reduces blood pressure and inhibits
vasoconstriction.
C. It is released in response to stretching
certain cells in the heart.
D. It acts as a potent diuretic but does not
affect Na+ levels in the body.
6. Glomerular filtration
• Excess fluid results in higher pressures in
the glomerulus
– Equals higher GFR and loss of fluid into urine
• Which decreases fluid volume
• Too little fluid results in lower pressures in
the glomerulus
– Equals lower GFR and retention of fluid
• Which increases fluid volume
When large amounts of pure
water are consumed
A. A fluid shift occurs and the volume of the
ICF decreases.
B. The volume of the ICF will increase due to
osmosis.
C. The volume of the ECF will decrease.
D. The ECF becomes hypertonic to the ICF.
E. Osmolarities of the two compartments will be
slightly lower.
When water is lost from the ECF
but electrolytes are retained,
A. Osmosis moves water from the ICF to the
ECF.
B. Water levels remain homeostatic.
C. The osmolarity of the ECF falls.
D. There is an increase in the volume in the
ICF.
E. Both ECF and ICF become more dilute.
Physiology adjustments of water
and electrolytes are made by
A.
B.
C.
D.
E.
Aldosterone.
Atrial natriuretic peptide.
ADH.
None of the above
All of the above.
• Transition
Disorders of Water Balance: Edema
• Atypical accumulation of fluid in the interstitial
space, leading to tissue swelling
• Caused by anything that increases flow of fluids
out of the bloodstream or hinders their return
Disorders of Water Balance: Edema
•
Four main causes of edema are
1. Increased blood pressure
1. Incompetent venous valves, localized blood
vessel blockage
2. Congestive heart failure, hypertension, high
blood volume
2. Capillary permeability due to injury
3. Decreased osmotic pressure: decreased
albumin production by diseased liver
4. Lymphatic obstruction
Capillaries
2. Capillary
permeability
due to injury:
Fluid leaks
out of
capillary
1. Increased
blood
pressure
increases
pressure
on fluid to
leave
capillary
4. Lymphatic
obstruction: if
lymph cannot
drain, fluid backs
up
3. Decreased osmotic pressure: no
proteins means fluid cannot be pulled
back into capillary via osmosis
All of the following would cause
edema except:
A.
B.
C.
D.
Hypotension
Hypoproteinemia
Liver disease
Incompetent venous valves
Electrolytes
Electrolyte balance in the body
usually refers to the balance of
_________.
A.
B.
C.
D.
Salts
Organic molecules
Acids
Bases
The most prevalent electrolyte
in the extracellular fluid is
A.
B.
C.
D.
E.
F.
Potassium.
Magnesium.
Phosphate.
Sodium.
Chloride.
Calcium.
Electrolytes act as…
• Co-factors: assist a molecule in getting in
the right shape (Fe in hemoglobin)
• Conduct electricity: Action potential
• Secretion/release of neurotransmitters
• Muscle contraction
• Acid/base balance
• Transport: (Na+ helps transport glucose,
etc.)
Cations and Anions
• Electrolytes are referred to by their charge.
• Cations are positively charged
– Na+ K+ Ca2+ Mg2+
• Anions are negatively charged.
– Cl-, Bicarbonate, Phosphate, Sulfate,
Proteins, Lactate,
Electrolytes
• Small deviations in electrolyte
concentration have serious life-threatening
consequences.
• The three most important ions are Na+, K+,
Ca2+.
Electrolytes
• The three most important ions are Na+, K+,
Ca2+.
• Four things to keep in mind with these
electrolytes.
– What are the imbalances called
– What causes the imbalances
– What are the results of the imbalances
– How does the body correct the imbalance.
Capital punishment usually employs
KCl injection. Why would this kind
of an injection cause death?
A. Increased K+ causes hyperpolarization of
membranes.
B. Hyperkalemia results in acidosis which is
lethal.
C. Hypokalemia causes dehydration.
D. Increased K+ results in disruption of the
electric potential of cardiac tissue.
+
Na
The amount of
excreted by
the kidneys should be…
A.
B.
C.
D.
Near Zero
The same as consumed in the diet
More than is consumed in the diet.
An amount always equivalent to K+ losses.
• The next 16 slides (54-70) that lead up to
pH came with the textbook and they may
clarify the electrolyte homeostasis charts.
But, your main source of info should be
the electrolyte charts.
Sodium in Fluid and Electrolyte
Balance
• Sodium holds a central position in fluid and
electrolyte balance
• Sodium salts:
– Account for 90-95% of all solutes in the ECF
– Contribute 280 mOsm of the total 300 mOsm
ECF solute concentration
• Sodium is the single most abundant cation in
the ECF
• Sodium is the only cation exerting significant
osmotic pressure
Sodium in Fluid and Electrolyte
Balance
• Changes in plasma sodium levels affect:
– Plasma volume, blood pressure
– ICF and interstitial fluid volumes
• Renal reabsorption is coupled to sodium
urine
blood
ion transport
– No sodium = diminished
renal function
H20
Na+ Na+
Other
K+
H20
H20
Na+
K+
K+
Other
Na+
Na+
Na+
Regulation of Sodium Balance:
Aldosterone
• Sodium reabsorption is controlled by
aldosterone
• When aldosterone levels are high, all
remaining Na+ is actively reabsorbed
• Water follows sodium if tubule permeability
has been increased with ADH
• Note the relationship between ADH and
aldosterone.
Regulation of Sodium Balance:
Aldosterone
• Note the relationship between ADH and
aldosterone.
– Aldosterone moves Na+
– ADH moves water
• The two usually work together but not
always.
– Dehydration stimulates _______
– Hypovolemia stimulates _______
Regulation of Sodium Balance:
Aldosterone
• Note the relationship between ADH and
aldosterone.
– Aldosterone moves Na+
– ADH moves water
• The two usually work together but not
always.
– Dehydration stimulates __Aldosterone__
– Hypovolemia stimulates _Both___
Regulation of
Sodium
Balance:
Aldosterone
Cardiovascular System
Baroreceptors
• Baroreceptors alert the brain of increases
in blood volume (hence increased blood
pressure)
– Sympathetic nervous system impulses to the
kidneys decline
– Afferent arterioles dilate
– Glomerular filtration rate rises
– Sodium and water output increase
Cardiovascular System
Baroreceptors
• This phenomenon, called pressure
diuresis, decreases blood pressure
• Drops in systemic blood pressure lead to
opposite actions and systemic blood
pressure increases
• Since sodium ion concentration
determines fluid volume, baroreceptors
can be viewed as “sodium receptors”
Maintenance of Blood Pressure
Homeostasis
Atrial Natriuretic Peptide (ANP)
• Reduces blood pressure and blood
volume by inhibiting:
– Events that promote vasoconstriction
– Na+ and water retention
• Is released in the heart atria as a response
to stretch (elevated blood pressure)
• Promotes excretion of sodium and water
• Inhibits angiotensin II production
Mechanisms
and
Consequences
of ANP
Release
Influence of Other Hormones on
Sodium Balance
• Estrogens:
– Enhance NaCl reabsorption by renal tubules
– May cause water retention during menstrual
cycles
– Are responsible for edema during pregnancy
Regulation of Potassium
Balance
• Relative ICF-ECF potassium ion
concentration affects a cell’s resting
membrane potential
– Excessive ECF potassium decreases
membrane potential
– Too little K+ causes hyperpolarization and
nonresponsiveness
Regulation of Potassium
Balance
• Hyperkalemia and hypokalemia can:
– Disrupt electrical conduction in the heart
– Lead to sudden death
• Hydrogen ions shift in and out of cells
– Leads to corresponding shifts in potassium in
the opposite direction
– Interferes with activity of excitable cells
Regulatory Site: Cortical
Collecting Ducts
• K+ balance is controlled in the cortical collecting
ducts by changing the amount of potassium
secreted into filtrate
Regulation of Calcium
• Ionic calcium in ECF is important for:
– Blood clotting
– Cell membrane permeability
– Secretory behavior
• Hypocalcemia:
– Increases excitability
– Causes muscle tetany
Regulation of Calcium
• Hypercalcemia:
– Inhibits neurons and muscle cells
– May cause heart arrhythmias
• Calcium balance is controlled by
parathyroid hormone (PTH) and calcitonin
Acid-Base Balance
Acids and Bases
• Acid/Base is essentially the quantity of H+
(protons) and OH– (hydroxy) floating in the
solution.
• We care about H+ and OH– because
– they bind to proteins and change their shape,
usually diminishing their function.
– They affect K+ homeostasis
– They affect Ca2+ homeostasis
Acids and Bases
An H+ could bind to this H and
O and create water. This
would change the shape of
this protein
•So many things in your body will react with H and OH.
•When they react, their shape is changed.
•These change in shapes can change how things work
K+ and H+ Flow in Opposite
Directions Across the PM
• Another reason to
be concerned about
H+ is that it
exchanges with K+
across the plasma
membrane.
– High H+ causes K+
to leave the cell
– Low H+ causes K+ to
enter the cell
H+
H+
H+
K+
K+
H+
K+
K+
K+
K+
H+
K+
K+
H+
H+
Terri Schiavo
K+ and H+ Flow in Opposite
Directions Across the PM
• Another reason to
be concerned about
H+ is that it
exchanges with K+
across the plasma
membrane.
– So disorders of acid
become disorders of
K+.
H+
H+
H+
K+
K+
H+
K+
K+
K+
K+
H+
K+
K+
H+
H+
Acid and Calcium
• H+ and Ca2+
exchange on
albumin.
– High H+ means High
Ca2+
– Low H+ means Low
Ca2+
Acids and Bases
• Acids release H+ and are therefore proton
donors
HCl  H+ + Cl –
• Bases release OH– and are proton
acceptors
NaOH  Na+ + OH–
Acid-Base Balance
• Normal pH of body fluids
– Arterial blood is 7.4
– Venous blood and interstitial fluid is 7.35
– Intracellular fluid is 7.0
• Alkalosis– arterial blood pH rises above
7.45
• Acidosis arterial pH drops below 7.35
(physiological acidosis)
Acid-Base
Concentration
(pH)
• Acidic: pH 0–6.99
• Basic: pH 7.01–14
• Neutral: pH 7.00
• *note this is a log
scale
Sources of Hydrogen Ions
• Most hydrogen ions originate from cellular
metabolism
– Breakdown of phosphorus-containing proteins
releases phosphoric acid into the ECF
– Anaerobic respiration of glucose produces
lactic acid
– Fat metabolism yields organic acids and
ketone bodies
– Transporting carbon dioxide as bicarbonate
releases hydrogen ions
Hydrogen Ion Regulation
•
Concentration of hydrogen ion is
regulated sequentially by:
1. Chemical buffer systems – act within
seconds
2. The respiratory center in the brain stem –
acts within 1-3 minutes
3. Renal mechanisms – require hours to days
to effect pH changes
Chemical Buffer Systems
•
Three major chemical buffer systems
1. Bicarbonate buffer system
1. The most important as it feeds into both
respiratory and renal acid regulatory systems.
2. Phosphate buffer system
3. Protein buffer system
Bicarbonate Buffer System
High base = high pH
Carbonic acid
H2CO3  H+ + HCO3¯
Bicarbonate
High AcidOH
= low pH
• When blood pH rises, carbonic acid dissociates
to form bicarbonate and H+
• When blood pH drops, bicarbonate binds H+ to
form carbonic acid
Phosphate Buffer System
• Nearly identical to the bicarbonate system
• Its components are:
– Sodium salts of dihydrogen phosphate
(H2PO4¯), a weak acid
– Monohydrogen phosphate (HPO42¯), a weak
base
• This system is an effective buffer in urine
and intracellular fluid
Protein Buffer System
• Plasma and intracellular proteins are the
body’s most plentiful and powerful buffers
• Some amino acids of proteins have:
– Free organic acid groups (weak acids)
– Groups that act as weak bases (e.g., amino
groups)
• Amphoteric molecules are protein
molecules that can function as both a
weak acid and a weak base
Physiological Buffer Systems
• The respiratory system regulation of acidbase balance buffers acid by influencing
the carbonic acid-bicarbonate system.
• There is a reversible equilibrium between:
– Dissolved carbon dioxide and water
– Carbonic acid and the hydrogen and
bicarbonate ions
CO2 + H2O  H2CO3  H+ + HCO3¯
Respiratory Mechanisms of AcidBase Balance
CO2 + H2O  H2CO3  H+ + HCO3¯
• Heavy breathing decreases CO2 which
moves the reaction to the left
– Thus, H+ is reduced
• Shallow breathing increases CO2 which
pushes the reaction to the right.
– Thus, H+ is increased
Transport and Exchange of
Carbon Dioxide
Increased acid pushes
the reaction the the left
= more Carbonic Acid
CO2
Carbon
dioxide
+
H2O
Water

H2CO3
Carbonic
acid
H+

H+
Hydrogen
ion
+
HCO3–
Bicarbonate
ion
Transport and Exchange of
Carbon Dioxide
CO2
Carbon
dioxide
+
H2O
Water

H2CO3
Carbonic
acid
Increased OH- pulls the
reaction to the right= water
+ Bicarbonate

H+
Hydrogen
ion
OH-
HCO3–
+
Bicarbonate
ion
H20
Which condition would cause a
drop in pH?
A.
B.
C.
D.
E.
Hyperventilation
Hypoventilation
Hypovolumemia
Hypernatremia
Hypokalemia
Renal Mechanisms of AcidBase Balance
• Chemical buffers can tie up excess acids or
bases, but they cannot eliminate them from the
body
• The lungs can eliminate carbonic acid by
eliminating carbon dioxide
• Only the kidneys can rid the body of metabolic
acids (phosphoric, uric, and lactic acids and
ketones) and prevent metabolic acidosis
• The ultimate acid-base regulatory organs are the
kidneys
Renal Mechanisms of AcidBase Balance
Excrete
Low pH
Absorb in PCT
Make more in
PCT
CO2 + H2O  H2CO3  H+ + HCO3¯
High pH
Excrete in DCT
Hydrogen Ion Excretion
• In response to
acidosis:
– Kidneys
generate
bicarbonate
ions and add
them to the
blood
– An equal
amount of
hydrogen ions
are added to
the urine
Respiratory Acidosis and
Alkalosis
• Result from failure of the respiratory system to
balance pH
• PCO2 is the single most important indicator of
respiratory inadequacy
• PCO2 levels
– Normal PCO2 fluctuates between 35 and 45
mm Hg
– Values above 45 mm Hg signal respiratory
acidosis
– Values below 35 mm Hg indicate respiratory
alkalosis
Respiratory Acidosis and
Alkalosis
• Respiratory acidosis is the most common
cause of acid-base imbalance
– Occurs when a person breathes shallowly, or
gas exchange is hampered by diseases such
as pneumonia, cystic fibrosis, or emphysema
• Respiratory alkalosis is a common result
of hyperventilation
Respiratory Acidosis
Occurs when a person breathes
shallowly, or gas exchange is hampered
by diseases such as pneumonia, cystic
fibrosis, or emphysema. Thus CO2
builds up.
CO2
Carbon
dioxide
CO2 builds
up which
means H+
builds up
+
H2O
Water

H2CO3
Carbonic
acid
H+

H+
Hydrogen
ion
+
HCO3–
Bicarbonate
ion
Respiratory Alkalosis
Hyperventilation decreases
CO2 levels.
H+
CO2
Carbon
dioxide
CO2
decreases
which
means H+
decreases
+
H2O
Water

H2CO3
Carbonic
acid

H+
Hydrogen
ion
+
HCO3–
Bicarbonate
ion
Metabolic Acidosis
• All pH imbalances except those caused by
abnormal blood carbon dioxide levels
• Metabolic acid-base imbalance –
bicarbonate ion levels above or below
normal (22-26 mEq/L)
• Metabolic acidosis is the second most
common cause of acid-base imbalance
– Typical causes are ingestion of too much
alcohol and excessive loss of bicarbonate
ions
– Other causes include accumulation of lactic
acid, shock, ketosis in diabetic crisis,
starvation, and kidney failure
Metabolic Alkalosis
• Rising blood pH and bicarbonate levels
indicate metabolic alkalosis
• Typical causes are:
– Vomiting of the acid contents of the stomach
– Intake of excess base (e.g., from antacids)
– Constipation, in which excessive bicarbonate
is reabsorbed
Acidosis/Alkalosis
• If the respiratory system is doing what is
expected to be doing during acidosis or
alkalosis, the cause is likely to be
metabolic.
• If the respiratory system is doing the
opposite of what is expected during
acidosis, the cause is likely to be
respiratory.
• Work this reasoning out on your own a
little.
Acidosis/Alkalosis
Acidosis/Alkalosis
Acidosis/Alkalosis
Acidosis/Alkalosis
• Or, MORE if
you want to
talk H+
instead of pH.
• Remember it
one way or
the other but
don’t get
them mixed
up.
Acidosis/Alkalosis
Kidneys can compensate for
chronic changes by
making/excreting HCO3. This
brings pH closer to 7.4
Acidosis/Alkalosis
Acidosis
A. May reflect metabolic production of acid.
B. Is only caused by abnormal respiratory
conditions.
C. Results when blood pH exceeds 7.45
D. Is always corrected by chemical buffer
systems.
E. Is compensated for by intestinal secretion of
H+.
The only organ of the body that
can remove excess fixed acids
is the
A.
B.
C.
D.
E.
Spleen.
Liver.
Kidney.
Lungs.
Sweat glands.
A patient with alkalosis would
experience
A.
B.
C.
D.
E.
Higher blood pressures.
Increased sodium retention.
Hypoventilation.
Increased acid secretion at kidney.
Hyperventilation.
Acidosis/Alkalosis
• If a person with acidosis is breathing
rapidly, this would be what type of
acidosis?
A.
B.
C.
D.
Metabolic Acidosis
Respiratory Acidosis
Metabolic Alkalosis
Respiratory Alkalosis
Acidosis/Alkalosis
• If a person with acidosis is breathing
slowly this would be what type of acidosis.
A.
B.
C.
D.
Metabolic Acidosis
Respiratory Acidosis
Metabolic Alkalosis
Respiratory Alkalosis
Acidosis/Alkalosis
• If a person with alkalosis is breathing
slowly, this would be what type of
alkalosis?
A.
B.
C.
D.
Metabolic Acidosis
Respiratory Acidosis
Metabolic Alkalosis
Respiratory Alkalosis
Acidosis/Alkalosis
• If a person with alkalosis is breathing
rapidly, this would be what type of
alkalosis?
A.
B.
C.
D.
Metabolic Acidosis
Respiratory Acidosis
Metabolic Alkalosis
Respiratory Alkalosis
Problems with Fluid, Electrolyte,
and Acid-Base Balance
• Occur in the young, reflecting:
– Low residual lung volume
– High rate of fluid intake and output
– High metabolic rate yielding more metabolic
wastes
– High rate of insensible water loss
– Inefficiency of kidneys in infants
Case Study: Water
Intoxication
• Jennifer Strange, 28, died
after drinking more than six
and a half litres of bottled
water at KDND 107.9
January 13, 2007, in a bid
to win a Nintendo Wii for
her three children.
Case Study: Water
Intoxication
• This is true, if you drink too
much water, normally you
will throw up.
A. True
B. False
Put A or B (not T or F)
Case Study: Water Intoxication
• Your body has several methods to cope with dehydration. Choose
the following that are correct:
A. Thirst
B. Dilate the efferent arteriole
C. JG and MD cells sense low GFR and promote Na absorption
and thus water absorption.
D. ADH
E. All of these are correct
Case Study: Water Intoxication
• Your body also has several methods to cope with
overhydration hydration. Which is correct:
A. Salt appetite
B. The hypothalamus senses decreased osmolarity
and stimulates micturition.
C. Throwing up
D. That isn’t true, there are some mechanisms but
there isn’t a quick fix for overhydration.
Case Study: Water Intoxication
• What would you expect your body to do
when it is overhydrated. What are the
slow fixes?
Case Study: Water Intoxication
• Eva was reported to be a nurse. Why
would you expect water intoxication to be
dangerous. What symptoms would you
expect?
Case Study: Water Intoxication:
Head hurts and light headed
• Indicate which of the following is correct:
A.
B.
C.
D.
E.
Increased fluid equals increased blood pressure and edema. She
has excess fluid in her brain.
Na and other ions are diluted, resulted in altered neuronal function.
Cells will swell, taking up more space causing pain.
Normal chemical reactions will be slowed because the cells are
bigger and reactants are further apart.
All of these sound good to me.
Case Study: Water Intoxication:
Head hurts and light headed
• How would using Gatorade, instead of
water, changed the situation?