Fluid, electrolyte and acid base balance.pptx

Fluid, electrolyte and acid base balance
Noor Ullah
noor1.qau@gmail.com
2/16/2023 1
Noor Ullah KMU

Water
• Water is 99% of fluid outside cells (extracellular fluid)
• Is an essential ingredient of cytosol (intracellular fluid)
• All cellular operations rely on water
• As a diffusion medium for gases, nutrients, and waste products
• The body must maintain normal volume and composition of
• Extracellular fluid (ECF)
• Intracellular fluid (ICF)
2/16/2023 Noor Ullah KMU 2

Fluid Balance
• Fluid Balance is a daily balance between Amount of water gained and Amount
of water lost to environment
• Involves regulating content and distribution of body water in ECF and ICF
• The Digestive System is the primary source of water gains plus a small amount
from metabolic activity
• The Urinary System is the primary route of water loss

Electrolytes
• Are ions released through dissociation of inorganic compounds
• Can conduct electrical current in solution
• Electrolyte balance
• When the gains and losses of all electrolytes are equal
• Primarily involves balancing rates of absorption across digestive tract with rates
of loss at kidneys and sweat glands

Acid–Base Balance
• Precisely balances production and loss of hydrogen ions (pH)
• The body generates acids during normal metabolism
• Tends to reduce pH
• The Kidneys secrete hydrogen ions into urine
• Generate buffers that enter bloodstream in distal segments of distal convoluted
tubule (DCT) and collecting system
• The Lungs affect pH balance through elimination of carbon dioxide

Water
• 60% of male body weight
• 50% of female body weight
• Mostly in intracellular fluid
• Water Exchange: Water exchange between ICF and
ECF occurs across plasma membranes by
• Osmosis
• Diffusion
• Carrier-mediated transport

Water distribution

Major Subdivisions of ECF
• Interstitial fluid of peripheral tissues
• Plasma of circulating blood
• Minor Subdivisions of ECF:
• Lymph, perilymph, and endolymph
• Cerebrospinal fluid (CSF)
• Synovial fluid
• Serous fluids (pleural, pericardial, and peritoneal)
• Aqueous humor

Exchange among Subdivisions of ECF
• Exchange of fluid among subdivisions occurs primarily across endothelial lining
of capillaries
• From interstitial spaces to plasma
• Through lymphatic vessels that drain into the venous system

Fluid Compartments
Figure 27–1a The Composition of the Human Body.

Solute content of ECF and ICF
• Solutes are broadly classified into:
• Electrolytes – inorganic salts, all acids and bases, and some proteins
• Nonelectrolytes – examples include glucose, lipids, creatinine, and urea
• Electrolyte concentration is expressed in units of milliequivalents per liter
(mEq/L), a measure of the number of electrical charges in one liter of
solution
• Electrolytes have greater osmotic power than nonelectrolytes
• Water moves according to osmotic gradients

Solute content of ECF and ICF
• Each fluid compartment of the body has a distinctive pattern of electrolytes
• 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
• Potassium is the chief cation
• Phosphate is the chief anion

Fluid Compartments
Figure 27–2 Cations and Anions in Body Fluids.

Osmotic regulation of fluid across the compartments
• Compartmental exchange is regulated by osmotic and hydrostatic pressures
• Net leakage of fluid from the blood is picked up by lymphatic vessels and returned to
the bloodstream
• Exchanges between interstitial and intracellular fluids are complex due to the
selective permeability of the cellular membranes

Osmotic regulation of fluid across the compartments
• Ion fluxes are restricted and move selectively by active transport
• Nutrients, respiratory gases, and wastes move uni directionally
• Plasma is the only fluid that circulates throughout the body and links external and
internal environments
• Osmolalities of all body fluids are equal; changes in solute concentrations are
quickly followed by osmotic changes

Basic Concepts in the Regulation of Fluids and Electrolytes
• All homeostatic mechanisms that monitor and adjust body fluid composition
respond to changes in the ECF, not in the ICF
• No receptors directly monitor fluid or electrolyte balance
• Cells cannot move water molecules by active transport
• The body’s water or electrolyte content will rise if dietary gains exceed
environmental losses, and will fall if losses exceed gains

Primary Regulatory Hormones
• Hormones affecting fluid and electrolyte balance are:
1. Aldosterone
2. Natriuretic peptides
3. Antidiuretic hormone (ADH)

Antidiuretic Hormone (ADH)
• Stimulates water conservation at kidneys
• Reducing urinary water loss and concentrating urine
• Stimulates thirst center and promote fluid intake
• ADH is produced by stimulation of osmoreceptors in hypothalamus and released
by posterior lobe of pituitary

Antidiuretic Hormone (ADH)
• Osmoreceptors monitor osmotic concentration of ECF
• Change in osmotic concentration alters osmoreceptor activity
• Osmoreceptor neurons secrete ADH
• Rate of release varies with osmotic concentration
• Higher osmotic concentration increases ADH release

Aldosterone
• Aldosterone is secreted by suprarenal cortex in response to rising K+ or falling
Na+ levels in blood
• Activation of renin–angiotensin system
• Determines rate of Na+ absorption and K+ loss along DCT and collecting system
• “Water Follows Salt”. High plasma aldosterone concentration causes kidneys to
conserve salt
• Conservation of Na+ by aldosterone stimulates water retention

Natriuretic Peptides
• Natriuretic Peptides- ANP and BNP are released by cardiac muscle cells in
response to abnormal stretching of heart walls
• Reduce thirst, Block release of ADH and aldosterone, causes diuresis and thus
lower blood pressure and plasma volume
• When the body loses water, plasma volume decreases, electrolyte
concentrations rise
• When the body loses electrolytes, water is lost by osmosis
• Regulatory mechanisms are different

Fluid Balance
• Water circulates freely in ECF compartment
• At capillary beds, hydrostatic pressure forces water out of plasma and into
interstitial spaces
• Water is reabsorbed along distal portion of capillary bed when it enters
lymphatic vessels
• ECF and ICF are normally in osmotic equilibrium
• No large-scale circulation between compartments

Fluid Movement within the ECF
• Net hydrostatic pressure pushes water out of plasma Into interstitial fluid
• Net colloid osmotic pressure draws water out of interstitial fluid Into plasma
• ECF fluid volume is redistributed from lymphoid system to venous system
(plasma)
• Interaction between opposing forces results in continuous filtration of fluid
• ECF volume is 80% in interstitial fluid and minor fluid compartment and is
20% in plasma

Fluid Gains and Losses
• Water losses
• Body loses about 2500 mL of water each day through urine, feces, and insensible perspiration
• Fever can also increase water loss
• Sensible perspiration (sweat) varies with activities and can cause significant water loss (4
L/hour)
• Water gains about 2500 mL/day
• Required to balance water loss
• Through eating (1000 mL), drinking (1200 mL), metabolic generation (300 mL)

Fluid Movement
Figure 27–3 Fluid Gains and Losses

Source Daily Input (ml)
Method of Elimination Daily Output (ml)
Water content of food 1000
Water consumed as liquid 1200
Metabolic water produced during catabolism 300
Total 2500
Urination 1200
Evaporation at skin 750
Evaporation at lungs 400
Loss in feces 150
Total 2500
Water balance

Regulation of water intake
• Mainly by volume of water intake
• Dehydration – when water loss is greater than gain
• Decrease in volume, increase in osmolarity of body fluids
• Stimulates thirst center in hypothalamus
• 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

The thirst mechanism

Disorders of Water Balance: Dehydration
• Water loss exceeds water intake and the body is in negative fluid balance
• Causes include: hemorrhage, severe burns, prolonged vomiting or diarrhea,
profuse sweating, water deprivation, and diuretic abuse
• Signs and symptoms: thirst, dry flushed skin, and oliguria
• Prolonged dehydration may lead to weight loss, fever, and mental confusion
• Other consequences include hypovolemic shock and loss of electrolytes

Disorders of Water Balance: Dehydration
Excessive loss of H2O from
ECF
1 2 3
ECF osmotic
pressure rises
Cells lose H2O
to ECF by
osmosis; cells
shrink
(a) Mechanism of dehydration

Disorders of Water Balance: Water toxicity
• Renal insufficiency or an extraordinary amount of water ingested quickly can lead
to cellular overhydration, or water intoxication
• ECF is diluted – sodium content is normal but excess water is present
• The resulting hyponatremia promotes net osmosis into tissue cells, causing
swelling
• These events must be quickly reversed to prevent severe metabolic disturbances,
particularly in neurons

Disorders of Water Balance: Water toxicity
Excessive H2O enters
the ECF
1 2 ECF osmotic
pressure falls
3 H2O moves into
cells by osmosis;
cells swell
(b) Mechanism of hypotonic hydration

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
• Factors that accelerate fluid loss include: Capillary permeability, Incompetent
venous valves, localized blood vessel blockage, Congestive heart failure,
hypertension, high blood volume

Disorders of Water Balance: Edema
• Hypoproteinemia – low levels of plasma proteins
• Forces fluids out of capillary beds at the arterial ends
• Fluids fail to return at the venous ends
• Results from protein malnutrition, liver disease, or glomerulonephritis
• Blocked (or surgically removed) lymph vessels:
• Cause leaked proteins to accumulate in interstitial fluid
• Exert increasing colloid osmotic pressure, which draws fluid from the blood
• Interstitial fluid accumulation results in low blood pressure and severely impaired
circulation

Electrolyte balance- Sodium
• Sodium is the dominant cation in ECF
• Sodium salts provide 90% of ECF osmotic concentration
• Sodium chloride (NaCl)
• Sodium bicarbonate
• Normal Sodium Concentrations in ECF about 140 mEq/L
• In ICF is 10 mEq/L or less

Electrolyte balance- Na
• Sodium ion uptake across digestive epithelium and excretion in urine and
perspiration
• Typical Na+ gain and loss: is 48–144 mEq (1.1–3.3 g) per day
• If gains exceed losses, total ECF content rises
• If losses exceed gains, ECF content declines
• Changes in ECF Na+ content do not produce change in concentration
• Corresponding water gain or loss keeps concentration constant

Sodium Balance and ECF Volume
• Na+ regulatory mechanism changes ECF volume
• Keeps concentration stable
• When Na+ losses exceed gains, ECF volume decreases (increased water loss)
• Maintaining osmotic concentration
• Large Changes in ECF Volume are corrected by homeostatic mechanisms that
regulate blood volume and pressure
• If ECF volume rises, blood volume goes up, If ECF volume drops, blood volume
goes down

Electrolyte Balance
Figure 27–4 The Homeostatic Regulation of Normal Sodium
Ion Concentrations in Body Fluids.

Hypo and hypernatremia
• Hyponatremia: Body water content rises (overhydration)
• ECF Na+ concentration <136 mEq/L
• Hypernatremia: Body water content declines (dehydration)
• ECF Na+ concentration >145 mEq/L

ECF and plasma volume regulation
ECF Volume: If ECF volume is inadequate blood volume and blood pressure decline
Renin–angiotensin system is activated and water and Na+ losses are reduced, as a
result ECF volume increases
Plasma Volume: If plasma volume is too large, venous return increases,
stimulating release of natriuretic peptides (ANP and BNP), reducing thirst,
blocking secretion of ADH and aldosterone, Salt and water loss at kidneys
increases and finally ECF volume declines

Potassium Balance
• 98% of potassium in the human body is in ICF
• Cells expend energy to recover potassium ions diffused from cytoplasm into ECF
• Processes of Potassium Balance: Rate of gain across digestive epithelium, rate
of loss into urine
• Potassium is the dominant cation in ICF
• Normal potassium concentrations in ICF: about 160 mEq/L
• In ECF: is 3.5–5.5 mEq/L

Potassium Loss in Urine
• Potassium level is regulated by activities of ion pumps along distal portions of
nephron and collecting system
• Na+ from tubular fluid is exchanged for K+ in peritubular fluid
• Are limited to amount gained by absorption across digestive epithelium (about
50–150 mEq or 1.9–5.8 g/day)

Calcium Balance
• Calcium is most abundant mineral in the body
• A typical individual has 1–2 kg (2.2–4.4 lb) of this element
• 99% of which is deposited in skeleton
• Calcium Absorption: At digestive tract and reabsorption along DCT
• Is stimulated by PTH and calcitriol
• Calcium Ion Loss: In bile, urine, or feces, is very small (0.8–1.2 g/day)

Hormones and Calcium Homeostasis
• Parathyroid hormone (PTH) and calcitriol: Raise calcium concentrations in ECF
• Calcitonin: Opposes PTH and calcitriol

Hypercalcemia
• Exists if Ca2+ concentration in ECF is >5.5 mEq/L
• Is usually caused by hyperparathyroidism- over secretion of PTH
• Other causes: Malignant cancers (breast, lung, kidney, bone marrow)
• Excessive calcium or vitamin D supplementation

Hypocalcemia
• Exists if Ca2+ concentration in ECF is <4.5 mEq/L
• Is much less common than hypercalcemia
• Is usually caused by chronic renal failure
• May be caused by hypoparathyroidism- Under secretion of PTH
• Vitamin D deficiency

Magnesium Balance
• Magnesium is an important structural component of bone
• The adult body contains about 29 g of magnesium
• About 60% is deposited in the skeleton
• Is a cofactor for important enzymatic reactions*
• Phosphorylation of glucose
• Is effectively reabsorbed by PCT
• Daily dietary requirement to balance urinary loss is about 24–32 mEq (0.3–0.4 g)

Magnesium Ions (Mg2+
)
• Mg2+
In body fluids are primarily present in ICF
• Mg2+ concentration in ICF is about 26 mEq/L
• ECF concentration is much lower

Phosphate Ions (PO4)
• Phosphate is required for bone mineralization
• About 740 g PO4 is bound in mineral salts of the skeleton
• Daily urinary and fecal losses: about 30–45 mEq (0.8–1.2 g)
• In ICF, PO4 is required for formation of high-energy compounds, activation of
enzymes, and synthesis of nucleic acids
• In plasma, PO4 is reabsorbed from tubular fluid along PCT
• Plasma concentration is 1.8–2.9 mEq/L

Chloride Ions (Cl-)
• Chloride Ions are the most abundant anions in ECF
• Plasma concentration is 97–107 mEq/L
• ICF concentrations are usually low
• Are absorbed across digestive tract with Na+
• Are reabsorbed with Na+ by carrier proteins along renal tubules
• Daily loss is small: 48–146 mEq (1.7–5.1 g)

Electrolyte balance

T
ABLE 27-3 A Review of Important Terms
Relating to Acid-Base Balance
pH
Neutral
Acidic
Basic, or
alkaline
Acid
Base
Salt
Buffer
The negative exponent (negative logarithm) of the
hydrogen ion concentration [H+]
A solution with a pH of 7; the solution contains
equal numbers of hydrogen ions and hydroxide ions
A solution with a pH below 7; in this solution,
hydrogen ions [H+] predominate
A solution with a pH above 7; in this
solution, hydroxide ions [OH- ] predominate
A substance that dissociates to release hydrogen
ions, decreasing pH
A substance that dissociates to release hydroxide ions
or to tie up hydrogen ions, increasing pH
An ionic compound consisting of a cation other than
hydrogen and an anion other than a hydroxide ion
A substance that tends to oppose changes in the pH
of a solution by removing or replacing hydrogen ions;
in body fluids, buffers maintain blood pH within
normal limits (7.35-7.45)
Acid- Base balance

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
• Acidosis: Physiological state resulting from abnormally low plasma pH
• Acidemia: plasma pH < 7.35
• Alkalosis: Physiological state resulting from abnormally high plasma pH
• Alkalemia: plasma pH > 7.45

Sources of Hydrogen Ions
• Most hydrogen ions originate from cellular metabolism
• Breakdown of phosphorus-containing proteins releases phosphoric acid into the
extracellular fluid
• Anaerobic respiration of glucose produces lactic acid
• Fat metabolism yields organic acids and ketone bodies
• Transporting carbon dioxide as bicarbonate releases hydrogen ions

Types of Acids in the Body
• Three types: Volatile acids, Fixed acids and Organic acids
• Volatile Acids: These can leave solution and enter the atmosphere
• Carbonic acid is an important volatile acid in body fluids
• At the lungs, carbonic acid breaks down into carbon dioxide and water and
diffuses into alveoli
• Carbon dioxide in solution in peripheral tissues interacts with water to form
carbonic acid

Carbonic Anhydrase (CA)
• Carbonic acid then catalyzed by Carbonic Anhydrase (CA) to release Hydrogen
ions and Bicarbonate ions
• Carbonic Anhydrase (CA) can be found in cytoplasm of red blood cells, Liver and
kidney cells and parietal cells of the stomach

CO2 and pH
• Most CO2 in solution converts to carbonic acid
• pCO2 is the most important factor affecting pH in body tissue
• pCO2 and pH are inversely related
• When CO2 levels rise H+ and bicarbonate ions are released and pH goes down
• At alveoli CO2 diffuses into atmosphere
• H+ and bicarbonate ions in alveolar capillaries drop and Blood pH rises

Acid–Base Balance
Figure 27–6 The Basic Relationship between pCO2and Plasma pH.

Fixed Acids
• Once produced they remain in body fluids until eliminated by kidneys
• Sulfuric acid and phosphoric acid are most important fixed acids in the body
• These are generated during catabolism of:
• amino acids
• phospholipids
• nucleic acids

Organic Acids
• When produced by aerobic metabolism, they are metabolized rapidly hence do
not accumulate
• When produced by anaerobic metabolism (e.g., lactic acid), they build up rapidly

Body buffers
• A buffer is a solution of a weak acid and its conjugate base that resists changes
in pH in both directions—either up or down.
• A buffer works best in the middle of its range, where the amount of un
dissociated acid is about equal to the amount of the conjugate base.
• One can soak up excess protons (acid), the other can soak up excess hydroxide
(base).

Blood Buffer Systems
• Why necessary?
• If the acids produced in the body from the catabolism of food and other cellular
processes are not removed or buffered, the body’s pH would drop
• Significant drops in pH interferes with cell enzyme systems.
• pH control is important, as many enzymes have a narrow range in which they
function optimally.
• Buffering capability is essential for the well-being of organisms, to protect them
from unwelcome changes in pH

Regulation of body pH (H+)
• Concentration of hydrogen ions(changes in blood pH) is regulated sequentially by:
1. Chemical buffer systems – act within seconds
2. Physiological buffer systems
• The respiratory mechanisms – hyperventilation or hypoventilation- acts
within 1-3 minutes
• Renal mechanisms – secretion of H+ and reabsorption of HCO3
- - require
hours to days to affect pH changes

Acid–Base Balance
Buffer Systems in Body Fluids

Carbonic Acid–Bicarbonate Buffer System
• Most body cells constantly generate carbon dioxide which is converted to
carbonic acid, which then dissociates into H+ and bicarbonate ion
• Is formed by carbonic acid and its dissociation products
• Prevents changes in pH caused by organic acids and fixed acids in ECF
• Consists of a mixture of carbonic acid (H2CO3) and its salt, sodium bicarbonate
(NaHCO3) (potassium or magnesium bicarbonates work as well)

Carbonic Acid–Bicarbonate Buffer System
• Cannot protect ECF from changes in pH that result from elevated or depressed
levels of CO2
• Functions only when respiratory system and respiratory control centers are
working normally
• Ability to buffer acids is limited by availability of bicarbonate ions

Acid–Base Balance
The Carbonic Acid–Bicarbonate Buffer System

Phosphate Buffer System
• It is a mixture of Sodium salts of dihydrogen phosphate (H2PO4¯) a weak acid
and Monohydrogen phosphate (HPO4
2¯), a weak base
• Works like the carbonic acid–bicarbonate buffer system
• This system is an effective buffer in urine and intracellular fluid

Protein Buffer Systems
• Carboxyl and amino groups in peptide bonds cannot function as buffers
• Depends on amino acids
• Respond to pH changes by accepting or releasing H+
• If pH rises
• Carboxyl group of amino acid dissociates acting as weak acid, releasing a hydrogen ion
• Carboxyl group becomes carboxylate ion
• If pH drops
• Carboxylate ion and amino group act as weak bases- Accept H+
• Form carboxyl group and amino ion

Protein Buffer Systems
• At normal pH (7.35–7.45)- Carboxyl groups of most amino acids have already
given up their H+
• Other proteins contribute to buffering capabilities are:
• Plasma proteins
• Proteins in interstitial fluid
• Proteins in ICF

Acid–Base Balance
The Role of Amino Acids in Protein Buffer Systems

The Hemoglobin Buffer System
• CO2 diffuses across RBC membrane and form carbonic acid
• As carbonic acid dissociates- Bicarbonate ions diffuse into plasma in exchange
for chloride ions (chloride shift)
• Hydrogen ions are buffered by hemoglobin molecules
• Hemoglobin Buffer is the only intracellular buffer system with an immediate
effect on ECF pH
• Helps prevent major changes in pH when plasma pCO2 is rising or falling

• Hemoglobin can accept H+ as it has histidine, which is a basic amino acid
• Moreover, deoxygenated hemoglobin has higher tendency to accept H+ (it's a
better base as compared to oxygenated hemoglobin)
• At the level of tissues, where CO2 is more, hemoglobin accepts H+
• This is due to the fact that most of the CO2 is present as H2CO3 in the body, and
H2CO3 remains in an ionized state as H+ and bicarbonate ion- thus hemoglobin
accepts H+

• At the level of the lungs, where O2 is more hemoglobin releases H+ and combines
with O2 (oxyhemoglobin is a stronger acid)
• The released H+ can combine with bicarbonate ion to form H2CO3 again which can
break down into H2O and CO2 (catalyzed by carbonic anhydrase enzyme)
• This CO2 formed is removed by lungs

Amino acids responsible for buffering action of Hb
• The ionizable groups of those amino acids that contain R-groups with additional
acid or base groups are responsible
• These amino acids include arginine, aspartic acid, cysteine, glutamic
acid, histidine, lysine, and tyrosine

Limitations of Buffer Systems
• Provide only temporary solution to acid–base imbalance
• Do not eliminate H+ ions
• Supply of buffer molecules is limited

Maintenance of Acid–Base Balance
• It requires balancing H+ gains and losses
• Coordinates actions of buffer systems with respiratory and renal mechanisms
• For homeostasis to be preserved, captured H+ must be permanently tied up in
water molecules through CO2 removal at lungs
• Be removed from body fluids through secretion at kidney

Respiratory Compensation
• Respiratory Compensation- Hyperventilation that helps stabilize pH of ECF
• Occurs whenever body pH moves outside normal limits
• Directly affects carbonic acid–bicarbonate buffer system
• Increasing or decreasing the rate of respiration alters pH by lowering or raising
the pCO2
• When pCO2 rises pH falls
• When pCO2 falls pH rises

Renal Compensation
• It is change in rates of H+ and HCO3- secretion or reabsorption by kidneys in
response to changes in plasma pH
• The body normally generates enough organic and fixed acids each day to add 100
mEq of H+ to ECF
• One way to eliminate this huge load is to excrete H+ in urine
• In the proximal convoluted tubule, Na+/H+ antiporters secrete H+ as they reabsorb
Na+

Buffers in Urine
• The ability to eliminate large numbers of H+ in a normal volume of urine depends
on the presence of buffers in urine:
1. Carbonic acid–bicarbonate buffer system
2. Phosphate buffer system
3. Ammonia buffer system

Acid–Base Balance
Kidney Tubules and pH Regulation.

Acid–Base Balance
Kidney Tubules and pH Regulation: The Production of
Ammonium Ions and Ammonia by the Breakdown of Glutamine

Renal Responses to Acidosis
1. Secretion of H+
2. Activity of buffers in tubular fluid
3. Removal of CO2
4. Reabsorption of NaHCO3

Renal Responses to Alkalosis
1. Rate of excretion at kidneys declines
2. Tubule cells do not regain bicarbonates in tubular fluid
3. Collecting system transports HCO3- into tubular fluid while releasing strong acid
(HCl) into peritubular fluid

Acid- base disorders
1. Disorders: Circulating buffers, Respiratory performance, Renal function
2. Cardiovascular conditions: Heart failure, Hypotension
3. Conditions affecting the CNS: Neural damage or disease that affects respiratory
and cardiovascular reflexes

Acid- base disorders
• Respiratory Acid–Base Disorders: Result from imbalance between CO2
generation in peripheral tissues and excretion at lungs
• Cause abnormal CO2 levels in ECF
• Metabolic Acid–Base Disorders: Result from generation of organic or fixed acids
• Conditions affecting HCO3 concentration in ECF

Acid–Base Balance Disturbances
Interactions among the Carbonic Acid–Bicarbonate Buffer System and
Compensatory Mechanisms in the Regulation of Plasma pH.

Interactions among the Carbonic Acid–Bicarbonate Buffer System and
Compensatory Mechanisms in the Regulation of Plasma pH.

Respiratory Acidosis
• Develops when the respiratory system cannot eliminate all CO2 generated by
peripheral tissues
• Primary cause- Hypoventilation
• Primary sign- Low plasma pH due to hypercapnia and high HCO-
3 , CO2 and pCO2

Respiratory Alkalosis
• Primary sign: High plasma pH due to hypocapnia and HCO-
3 and decreased CO2
and pCO2
• Primary cause- Hyperventilation

Metabolic Acidosis
1. Production of large numbers of fixed or organic acids: H+ overloads buffer
system
2. Impaired H+ excretion at kidneys
3. Severe bicarbonate loss
• Two types: Lactic acidosis: Produced by anaerobic cellular respiration
• Ketoacidosis: Produced by excess ketone bodies
• Decreased pH, HCO-
3 , CO2 and pCO2

Responses to Metabolic
Acidosis

Metabolic Alkalosis
• Is caused by elevated HCO-
3 concentrations
• Bicarbonate ions interact with H+ in solution forming H2CO3
• Reduced H+ causes alkalosis
• High pH, HCO-
3 , CO2 and pCO2

Metabolic Alkalosis.

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