Download - Water, Electrolytes, And Acid-Base Balance
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Water, Electrolytes, andAcid-Base Balance
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Body Fluids
Intracellular
All fluids inside cells of body
About 40% of total body weight
Extracellular
All fluids outside cells
About 20% of total body weight
Subcompartments
Interstitial fluid and plasma; lymph, CSF, synovial
fluid
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Water Content Regulation
Content regulated sototal volume of water in
body remains constant
Kidneys primary
regulator of waterexcretion
Regulation processes Osmosis
Osmolality
Baroreceptors
Learned behavior
Sources of water Ingestion
Cellular metabolism
Routes of water loss
Urine
Evaporation
Perspiration Respiratory passages
Feces
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Extracellular Fluid Osmolality
Osmolality
Adding or removing
water from a solutionchanges this
Increased osmolality
Triggers thirst andADH secretion
Decreased osmolality
Inhibits thirst and
ADH secretion
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Hormonal Regulation of
Blood Osmolality
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Regulation of ECF Volume
Mechanisms
Neural
Renin-angiotensin-aldosterone
Atrial natriuretic
hormone (ANH)
Antidiuretic hormone(ADH)
Increased ECF results in Decreased aldosterone secretion
Increased ANH secretion
Decreased ADH secretion
Decreased sympathetic stimulation
Decreased ECF results in Increased aldosterone secretion
Decreased ANH secretion
Increased ADH secretion Increased sympathetic stimulation
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Hormonal Regulation of
Blood Volume
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Hormonal Regulation of
Blood Volume
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Regulation of ECF Volume
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Regulation of ICF and ECF
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Regulation of Electrolytes in ECF
Electrolytes
Molecules or ions with
an electrical charge
Water ingestion adds
electrolytes to body
Kidneys, liver, skin,
lungs remove from
body
Concentration changes
only when growing,
gaining or losing
weight
Na+
Ions Dominant ECF cations Responsible for 90-95% of
osmotic pressure
Regulation of Na+ ions Kidneys major route of
excretion
Small quantities lost insweat
Terms Hypernatremia
Hyponatremia
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Mechanisms Regulating Blood Sodium
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Mechanisms Regulating Blood Sodium
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Abnormal Plasma Levels of
Sodium Ions
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Regulation of Chloride,
Potassium, Magnesium Ions
Chloride ions Predominant anions in
ECF
Magnesium ions Capacity of kidney to
reabsorb is limited
Excess lost in urine
Decreased extracellular
magnesium results ingreater degree ofreabsorption
Potassium ions
Maintained in narrow
range
Affect resting membrane
potentials
Aldosterone increases
amount secreted
Terms
Hyperkalemia
Hypokalemia
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Potassium Ion Regulation in ECF
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Abnormal Concentration of Potassium
Ions
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Abnormal Plasma Levels of
Magnesium Ions
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Regulation of Blood Magnesium
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Regulation of Calcium Ions
Regulated withinnarrow range Elevated extracellular
levels prevent
membranedepolarization
Decreased levels leadto spontaneous action
potential generation
Terms Hypocalcemia
Hypercalcemia
PTH increases Ca2+ extracellular levels and
decreases extracellular
phosphate levels
Vitamin D stimulatesCa2+ uptake in intestines
Calcitonin decreases
extracellular Ca2+ levels
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Regulation of Calcium Ions
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Regulation of Phosphate Ions
Under normal conditions, reabsorption of phosphate occurs
at maximum rate in the nephron An increase in plasma phosphate increases amount of
phosphate in nephron beyond that which can be reabsorbed;
excess is lost in urine
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Regulation of Blood Phosphate
A id d B
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Acids and Bases
and Buffers
Acids
Release H+ into
solution Bases
Remove H+ from
solution
Acids and bases Grouped as strong or
weak
Buffers: Resist changes inpH When H+ added, buffer
removes When H+ removed, buffer
replaces
Types of buffer systems
Carbonic acid/bicarbonate Protein
Phosphate
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Regulation of Acid-Base Balance
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Buffer Systems
R i t R l ti f
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Respiratory Regulation of
Acid-Base Balance
Respiratory regulation of pH is achieved
through carbonic acid/bicarbonate buffer
system
As carbon dioxide levels increase, pH decreases
As carbon dioxide levels decrease, pH increases
Carbon dioxide levels and pH affect respiratory
centers
Hypoventilation increases blood carbon dioxide levels
Hyperventilation decreases blood carbon dioxide levels
R i t R l ti f
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Respiratory Regulation of
Acid-Base Balance
R l R l ti f A id B
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Renal Regulation of Acid-Base
Balance
Secretion of H+ into filtrate and reabsorption of
HCO3
- into ECF cause extracellular pH to
increase HCO
3
- in filtrate reabsorbed
Rate of H+ secretion increases as body fluid pH
decreases or as aldosterone levels increase Secretion of H+ inhibited when urine pH falls
below 4.5
Kid R l ti f
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Kidney Regulation of
Acid-Base Balance
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Hydrogen Ion Buffering
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Acidosis and Alkalosis
Acidosis: pH body fluids below 7.35Respiratory: Caused by inadequate ventilation
Metabolic: Results from all conditions other
than respiratory that decrease pH Alkalosis: pH body fluids above 7.45
Respiratory: Caused by hyperventilation
Metabolic: Results from all conditions otherthan respiratory that increase pH
Compensatory mechanisms
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Acidosis and Alkalosis