Fluid, Electrolyte & Acid-Base Balance
Electrolytes serve four general functions in the body.
1. Many are essential minerals. 2. Because they are more numerous than nonelectrolytes, electrolytes control the osmosis of water between body compartments. 3. They help maintain the acid-base balance required for normal cellular activities. 4. They carry electrical current, which allows production of action potentials and graded potentials and controls secretion of some hormones and neurotransmitters. Electrical currents are also important during development.
Fluid balance (continue)
1. Osmosis is the primary way in which water moves in and out of body compartments. The concentration of solutes in the fluids is therefore a major determinant of fluid balance. 2. Most solutes in body fluids are electrolytes - compounds that dissociate into ions. 3. Fluid balance, then, means water balance, but also implies electrolyte balance; the two are inseparable.
Movement Between Interstitial and Intracellular Compartments
1. Fluid movement between interstitial and intracellular compartments depends on the concentrations of Na+ and K+ and on the secretion of aldosterone, antidiuretic hormone (ADH), and atrial natriuretic peptide (ANP). 2. Fluid imbalance may lead to overhydration, water intoxication, and circulatory shock.
Water continue / Fluid intake (gain) normally equals
fluid output (loss), so the body maintains a constant volume.
Water continue / Primary sources of fluid intake are
ingested liquids and foods (preformed water) and water produced by dehydration synthesis reactions of anabolism (metabolic water).
About 80% of the extracellular fluid (ECF) is
interstitial fluid and 20% is blood plasma
Alkalosis (or alkalemia)
is a blood pH above 7.45. Its principal effect is overexcitability of the CNS through facilitation of synaptic transmission.
Acidosis (or acidemia)
is a blood pH below 7.35. Its principal effect is depression of the central nervous system (CNS) through depression of synaptic transmission.
Hypercalcemia
is an abnormally high level of calcium in the blood.
Hypochloremia
is an abnormally low level of chloride in the blood resulting from excessive vomiting, dehydration, or therapy with certain diuretics.
carbonic acid-bicarbonate buffer system
is an important regulator of blood pH and is based on the bicarbonate ion (HCO3-).
phosphate buffer system
is an important regulator of pH, both in red blood cells and in the kidney tubular fluids.
Respiratory Alkalosis
is characterized by a decreased arterial blood pCO2 and increased pH and is caused by hyperventilation; metabolic alkalosis is characterized by increased bicarbonate concentrate and results from nonrespiratory loss of acid (e.g., excessive vomiting) or excess intake of alkaline drugs. 3. Metabolic acidosis or alkalosis is compensated by respiratory mechanisms; respiratory acidosis or alkalosis is compensated by renal mechanisms.
metabolic alkalosis
is characterized by increased bicarbonate concentrate and results from nonrespiratory loss of acid (e.g., excessive vomiting) or excess intake of alkaline drugs. 3. Metabolic acidosis or alkalosis is compensated by respiratory mechanisms; respiratory acidosis or alkalosis is compensated by renal mechanisms.
protein buffer system
system is the most abundant buffer in body cells and plasma. Inside red blood cells the protein hemoglobin is an especially good buffer for carbonic acid (H2CO3-).
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
Intracellular fluid (ICF) in, the most abundant cation is
K+, and the most abundant anions are proteins and phosphates (HPO42-).
hypomagnesemia
Magnesium deficiency, may be caused by malabsorption, diarrhea, alcoholism, malnutrition, excessive lactation, diabetes mellitus, and certain types of diuretics.
electrolytes
Most solutes in body fluids - compounds that dissociate into ions.
extracellular fluid (ECF), the most abundant cation is
Na+ and the most abundant anion is Cl-.
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
Acid-Base Balance (continue)
Normal pH of body fluids Arterial blood is 7.4 Venous blood and interstitial fluid is 7.35 Intracellular fluid is 7.0 Alkalosis or alkalemia - arterial blood pH rises above 7.45 Acidosis or acidemia - arterial pH drops below 7.35 (physiological acidosis)
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
Chemical Buffer Systems (continue)
One or two molecules that act to resist pH changes when strong acid or base is added Three major chemical buffer systems Bicarbonate buffer system Phosphate buffer system Protein buffer system Any drifts in pH are resisted by the entire chemical buffering system
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
Developmental Aspects
Water content of the body is greatest at birth (70-80%) and declines until adulthood, when it is about 58% At puberty, sexual differences in body water content arise as males develop greater muscle mass Homeostatic mechanisms slow down with age Elders may be unresponsive to thirst clues and are at risk of dehydration The very young and the very old are the most frequent victims of fluid, acid-base, and electrolyte imbalances
Composition of Body Fluids
Water is the universal solvent Solutes are broadly classified into: Electrolytes - inorganic salts, all acids and bases, and some proteins Nonelectrolytes - examples include glucose, lipids, creatinine, and urea Electrolytes have greater osmotic power than nonelectrolytes Water moves according to osmotic gradients
Fluid Compartments
Water occupies two main fluid compartments Intracellular fluid (ICF) - about two thirds by volume, contained in cells Extracellular fluid (ECF) - consists of two major subdivisions Plasma - the fluid portion of the blood Interstitial fluid (IF) - fluid in spaces between cells Other ECF - lymph, cerebrospinal fluid, eye humors, synovial fluid, serous fluid, and gastrointestinal secretions
Selectively permeable membranes separate
body fluids into distinct compartments. Plasma membranes of individual cells separate intracellular fluid from interstitial fluid. Blood vessel walls divide interstitial fluid from blood plasma. Although fluids are in constant motion from one compartment to another, the volume of fluid in each compartment remains fairly stable - another example of homeostasis.
Homeostasis of pH is maintained by
buffer systems, exhalation of carbon dioxide, and kidney excretion.
A change in blood pH that leads to acidosis or alkalosis can be
compensated to return pH to normal.
Water continue / The stimulus for fluid intake (gain) is
dehydration resulting in thirst sensations; one mechanism for stimulating the thirst center in the hypothalamus is the renin-angiotension II pathway, which responds to decreased blood volume (therefore decreased blood pressure).
hypocalcemia
An abnormally low level of calcium. it may be caused by increased calcium loss, reduced calcium intake, elevated levels of phosphate (as the level of phosphate increases, the level of calcium decreases), or altered regulation (as might occur in hypoparathyroidism).
hypophosphatemia
An abnormally low level of phosphate may occur through transient intracellular shifts, increased urinary losses, decreased intestinal absorption, increased utilization, and alcoholism.
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
anions
negatively charged ions
cations
positively charged ions
Metabolic acidosis or alkalosis is compensated by
respiratory mechanisms;
milliequivalents/liter, or mEq/l
The total concentration of cations and anions
milliosmotes/liter, or (mOsm/l)
The total concentration of particles in solution
Ammonium Ion Excretion
This method uses ammonium ions produced by the metabolism of glutamine in PCT cells Each glutamine metabolized produces two ammonium ions and two bicarbonate ions Bicarbonate moves to the blood and ammonium ions are excreted in urine
Renal Compensation
To correct respiratory acid-base imbalance, renal mechanisms are stepped up Acidosis has high PCO2 and high bicarbonate levels The high PCO2 is the cause of acidosis The high bicarbonate levels indicate the kidneys are retaining bicarbonate to offset the acidosis Alkalosis has Low PCO2 and high pH The kidneys eliminate bicarbonate from the body by failing to reclaim it or by actively secreting it
Generating New Bicarbonate Ions
Two mechanisms carried out by type A intercalated cells generate new bicarbonate ions Both involve renal excretion of acid via secretion and excretion of hydrogen ions or ammonium ions (NH4+)
Respiratory acidosis and respiratory alkalosis are
primary disorders of blood pCO2. On the other hand, metabolic acidosis and metabolic alkalosis are primary disorders of bicarbonate (HCO3- ) concentration
pH of body fluids may be adjusted by a change in the
rate and depth of respirations, which usually takes from 1 to 3 minutes.
pH of body fluid, in turn, affects the
rate of breathing
Movement Between Plasma and Interstitial Compartments
1. The movement of substances between plasma and interstitial fluid occurs across capillary membranes, primarily by diffusion. 2. At the arterial end of a capillary, fluid moves from plasma into interstitial fluid (filtration); at the venous end, fluid moves in the opposite direction (reabsorption). 3. Note that not all fluid filtered at one end of the capillary is reabsorbed at the other, some of the fluid instead passes into lymphatic capillaries, through the lymphatic circulation, and back into the cardiovascular system. 4. That state of near equilibrium at the arterial and venous ends of a capillary between filtered fluid, absorbed fluid, and fluid picked up by the lymphatic system is referred to as Startling's law of the capillaries.
There are several ways to express the concentration of chemicals dissolved in body fluids.
1. The total amount of solute in a solution is expressed as a percent. 2. The total concentration of cations and anions is expressed as milliequivalents/liter, or mEq/l. 3. The total concentration of particles in solution is expressed as milliosmotes/liter, or (mOsm/l).
several ways to express the concentration of chemicals dissolved in body fluids.
1. The total amount of solute in a solution is expressed as a percent. 2. The total concentration of cations and anions is expressed as milliequivalents/liter, or mEq/l. 3. The total concentration of particles in solution is expressed as milliosmotes/liter, or (mOsm/l).
extracellular fluid normal pH is.
7.35-7.45.
hyperkalemia
A higher-than-normal blood potassium level, can cause death by inducing fibrillation of the heart.
hypokalemia
A lower-than-normal blood potassium level may result from vomiting, diarrhea, high sodium intake, kidney disease, and therapy with some diuretics. (Cardiac Arrhythmia)
Bicarbonate Buffer System
A mixture of carbonic acid (H2CO3) and its salt, sodium bicarbonate (NaHCO3) (potassium or magnesium bicarbonates work as well) If strong acid is added: Hydrogen ions released combine with the bicarbonate ions and form carbonic acid (a weak acid) The pH of the solution decreases only slightly If strong base is added: It reacts with the carbonic acid to form sodium bicarbonate (a weak base) The pH of the solution rises only slightly This system is the only important ECF buffer
Fluid compartments and fluid balance
A. Body fluid B. Selectively permeable membranes separate body fluids into distinct compartments. C. Fluid balance
ACID-BASE BALANCE (continue)
A. The overall acid-base balance of the body is maintained by controlling the H+ concentration of body fluids, especially extracellular fluid. B. The normal pH of extracellular fluid is 7.35-7.45. C. Homeostasis of pH is maintained by buffer systems, exhalation of carbon dioxide, and kidney excretion. 1. Most buffer systems of the body consist of a weak acid and the salt of that acid (which functions as a weak base); together they function to prevent rapid, drastic changes in the pH of a body fluid by changing strong acids and bases into weak acids and bases. Buffers work within fractions of a second. 2. The important buffer systems include the carbonic acid-bicarbonate system, the phosphate system, and the protein system.
Acid-Base Balance
A. The overall acid-base balance of the body is maintained by controlling the H+ concentration of body fluids, especially extracellular fluid. B. The normal pH of extracellular fluid is 7.35-7.45. C. Homeostasis of pH is maintained by buffer systems, exhalation of carbon dioxide, and kidney excretion. 1. Most buffer systems of the body consist of a weak acid and the salt of that acid (which functions as a weak base); together they function to prevent rapid, drastic changes in the pH of a body fluid by changing strong acids and bases into weak acids and bases. Buffers work within fractions of a second. 2. The important buffer systems include the carbonic acid-bicarbonate system, the phosphate system, and the protein system.
intracellular fluid (ICF)
About two-thirds of the body's fluid is located in cells (Fluid within cells; 2/3 of all body fluid is within cells)
Respiratory and Renal Compensations
Acid-base imbalance due to inadequacy of a physiological buffer system is compensated for by the other system The respiratory system will attempt to correct metabolic acid-base imbalances The kidneys will work to correct imbalances caused by respiratory disease
Reabsorption of Bicarbonate
Carbon dioxide combines with water in tubule cells, forming carbonic acid Carbonic acid splits into hydrogen ions and bicarbonate ions For each hydrogen ion secreted, a sodium ion and a bicarbonate ion are reabsorbed by the PCT cells Secreted hydrogen ions form carbonic acid; thus, bicarbonate disappears from filtrate at the same rate that it enters the peritubular capillary blood Carbonic acid formed in filtrate dissociates to release carbon dioxide and water Carbon dioxide then diffuses into tubule cells, where it acts to trigger further hydrogen ion secretion
Renal Mechanisms of Acid-Base 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 The most important renal mechanisms for regulating acid-base balance are: Conserving (reabsorbing) or generating new bicarbonate ions Excreting bicarbonate ions Losing a bicarbonate ion is the same as gaining a hydrogen ion; reabsorbing a bicarbonate ion is the same as losing a hydrogen ion Hydrogen ion secretion occurs in the PCT and in type A intercalated cells Hydrogen ions come from the dissociation of carbonic acid
Fluid Movement Among 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 Two-way water flow is substantial
Hydrogen Ion Regulation
Concentration of hydrogen ions is regulated sequentially by: Chemical buffer systems - act within seconds The respiratory center in the brain stem - acts within 1-3 minutes Renal mechanisms - require hours to days to effect pH changes
Hydrogen Ion Excretion
Dietary hydrogen ions must be counteracted by generating new bicarbonate The excreted hydrogen ions must bind to buffers in the urine (phosphate buffer system) Intercalated cells actively secrete hydrogen ions into urine, which is buffered and excreted Bicarbonate generated is: Moved into the interstitial space via a cotransport system Passively moved into the peritubular capillary blood 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
Extracellular and Intracellular Fluids
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 Sodium and potassium concentrations in extra- and intracellular fluids are nearly opposites This reflects the activity of cellular ATP-dependent sodium-potassium pumps Electrolytes determine the chemical and physical reactions of fluids Proteins, phospholipids, cholesterol, and neutral fats account for: 90% of the mass of solutes in plasma 60% of the mass of solutes in interstitial fluid 97% of the mass of solutes in the intracellular compartment
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
aldosterone
In Chloride (Cl-) regulates sodium reabsorption; the negatively charged chloride follows the positively charged sodium.
Respiratory Compensation
In metabolic acidosis: The rate and depth of breathing are elevated Blood pH is below 7.35 and bicarbonate level is low As carbon dioxide is eliminated by the respiratory system, PCO2 falls below normal In respiratory acidosis, the respiratory rate is often depressed and is the immediate cause of the acidosis In metabolic alkalosis: Compensation exhibits slow, shallow breathing, allowing carbon dioxide to accumulate in the blood Correction is revealed by: High pH (over 7.45) and elevated bicarbonate ion levels Rising PCO2
Body Water Content
Infants have low body fat, low bone mass, and are 73% or more water Total water content declines throughout life Healthy males are about 60% water; healthy females are around 50% This difference reflects females': Higher body fat Smaller amount of skeletal muscle In old age, only about 45% of body weight is water
preformed water
Primary sources of fluid intake are ingested liquids and foods
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 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
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
Chemical Buffer Systems
Strong acids - all their H+ is dissociated completely in water Weak acids - dissociate partially in water and are efficient at preventing pH changes Strong bases - dissociate easily in water and quickly tie up H+ Weak bases - accept H+ more slowly (e.g., HCO3¯ and NH3)
Startling's law of the capillaries.
That state of near equilibrium at the arterial and venous ends of a capillary between filtered fluid, absorbed fluid, and fluid picked up by the lymphatic system is referred to as
extracellular fluid (ECF)
The other third of the body's fluid (The fluid outside the body's cells) a. About 80% of the ECF is interstitial fluid and 20% is blood plasma. b. Some of the interstitial fluid is localized in specific places, such as lymph; cerebrospinal fluid; gastrointestinal tract fluids; synovial fluid; fluids of the eyes (aqueous humor and vitreous body) and ears (endolymph and perilymph); pleural, pericardial, and peritoneal fluids between serous membranes; and glomerular filtrate in the kidneys.
Physiological Buffer Systems
The respiratory system regulation of acid-base balance is a physiological buffering 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¯ During carbon dioxide unloading, hydrogen ions are incorporated into water When hypercapnia or rising plasma H+ occurs: Deeper and more rapid breathing expels more carbon dioxide Hydrogen ion concentration is reduced Alkalosis causes slower, more shallow breathing, causing H+ to increase Respiratory system impairment causes acid-base imbalance (respiratory acidosis or respiratory alkalosis)
dehydration
The stimulus for fluid intake (gain), resulting in thirst sensations; one mechanism for stimulating the thirst center in the hypothalamus is the renin-angiotension II pathway, which responds to decreased blood volume (therefore decreased blood pressure).
percent
The total amount of solute in a solution
Bicarbonate Ion Secretion
When the body is in alkalosis, type B intercalated cells: Exhibit bicarbonate ion secretion Reclaim hydrogen ions and acidify the blood The mechanism is the opposite of type A intercalated cells and the bicarbonate ion reabsorption process Even during alkalosis, the nephrons and collecting ducts excrete fewer bicarbonate ions than they conserve
Hypernatremia
a higher-than-normal blood sodium level, can result from water loss, water deprivation, or sodium gain.
Hyponatremia
a lower-than-normal blood sodium level, may be caused by excessive perspiration, vomiting or diarrhea, therapy with certain diuretics, and burns.
Respiratory acidosis
acidosis is characterized by an elevated pCO2 and decreased pH and is caused by hypoventilation or other causes of reduced gas exchange in the lungs; metabolic acidosis is characterized by a decreased bicarbonate level and decreased pH, and results from an abnormal increase in acid metabolic products (other than CO2), loss of bicarbonate, or failure of the kidneys to excrete H+ ions derived from metabolism of dietary proteins.
Water continue / Under normal conditions, fluid output (loss) is
adjusted by antidiuretic hormone (ADH), atrial natriuretic peptide (ANP), and aldosterone, all of which regulate urine production.
Regulation of Cl- balance in body fluids is indirectly controlled by
aldosterone. regulates sodium reabsorption; the negatively charged chloride follows the positively charged sodium.
Electrolytes (ions)
are chemicals that dissolve in body fluids and dissociate into cations (positively charged ions) and anions (negatively charged ions). Electrically charged ions in solution, (sodium, chloride, potassium, magnesium, calcium), maintain balance of water outside the cell
Electrolytes (ions)
are chemicals that dissolve in body fluids and dissociate into cations (positively charged ions) and anions (negatively charged ions). inorganic salts, all acids and bases, and some proteins. They have greater osmotic power than nonelectrolytes Water moves according to osmotic gradients (Electrolytes have a greater effect on osmosis than nonelectrolytes) Electrolytes determine the chemical and physical reactions of fluids
Nonelectrolytes
are compounds with covalent bonds; these include most organic compounds, such as glucose, urea, and creatinine. (examples include glucose, lipids, creatinine, and urea)
Phosphates (HPO42-, HPO42-, and PO43-)
are important intracellular anions. 1. They are structural components of bone and teeth. They are also required for the synthesis of nucleic acids and high-energy compounds such as ATP, and for buffering reactions (e.g., the phosphate buffer system). 2. The level of phosphate in blood plasma is also regulated by PTH and CT. 3. An abnormally low level of phosphate, called hypophosphatemia, may occur through transient intracellular shifts, increased urinary losses, decreased intestinal absorption, increased utilization, and alcoholism. 4. Hyperphosphatemia occurs most often when the kidneys fail to excrete excess phosphate, as may occur in renal insufficiency. It can also result from increased intake of phosphates or destruction of cells, which releases phosphate into the blood.
Fluid balance
balance means that the various body compartments contain the required amount of water, proportioned according to their needs.
Body fluid
refers to body water and its dissolved substances; it averages 60% of total body weight, but may fluctuate widely.
Compensation
refers to the physiological response to an acid-base imbalance.
Magnesium (Mg2+)
is primarily an intracellular cation. 1. It activates several enzyme systems involved in the metabolism of carbohydrates and proteins and is needed for operation of the sodium pump (Na+/K+ ATPase). It is also important in neuromuscular activity, neural transmission with the central nervous system (CNS0, and myocardial functioning. 2. Magnesium level is regulated by aldosterone. 3. Magnesium deficiency, called hypomagnesemia, may be caused by malabsorption, diarrhea, alcoholism, malnutrition, excessive lactation, diabetes mellitus, and certain types of diuretics. 4. Hypermagnesemia, or magnesium excess, occurs mainly in persons with renal failure who have an increased intake of magnesium, such as magnesium-containing antacids. Other causes include Addison's disease, acute diabetic acidosis, severe dehydration, and hypothermia.
Water
is the largest single constituent in the body, varying from 45% to 75% of body weight, depending on age and the amount of fat present.
Chloride (Cl-)
is the major extracellular anion. (outside cell negative ion) 1. It plays a role in regulating osmotic pressure between compartments and forming HCl in the stomach. 2. Regulation of Cl- balance in body fluids is indirectly controlled by aldosterone. Aldosterone regulates sodium reabsorption; the negatively charged chloride follows the positively charged sodium passively by electrical attraction. 3. Hypochloremia is an abnormally low level of chloride in the blood resulting from excessive vomiting, dehydration, or therapy with certain diuretics.
Potassium (K+)
is the most abundant cation in intracellular fluid. (in cell) 1. It is involved in maintaining fluid volume, impulse conduction, muscle contraction, and regulating pH. 2. The plasma level of K+ is under control of mineralocorticoids, mainly aldosterone. 3. A lower-than-normal blood potassium level, called hypokalemia, may result from vomiting, diarrhea, high sodium intake, kidney disease, and therapy with some diuretics. 4. A higher-than-normal blood potassium level, called hyperkalemia, can cause death by inducing fibrillation of the heart.
Sodium (Na+)
is the most abundant extracellular ion. Outside the cell positive charge) 1. It is involved in impulse transmission, muscle contraction, and participates in fluid and electrolyte balance by creating most of the osmotic pressure (the most mOsm/l) of extracellular fluid. 2. The average daily intake of sodium far exceeds the body's normal daily requirements. The kidneys excrete excess sodium and conserve it during periods of sodium restriction. 3. Its level in the blood is controlled by aldosterone, antidiuretic hormone (ADH), and atrial natriuretic peptide (ANP). 4. Hyponatremia, a lower-than-normal blood sodium level, may be caused by excessive perspiration, vomiting or diarrhea, therapy with certain diuretics, and burns. 5. Hypernatremia, a higher-than-normal blood sodium level, can result from water loss, water deprivation, or sodium gain.
Water continue / Avenues of fluid output are the
kidneys, skin, lungs, and gastrointestinal tract.
decrease in respiration rate and depth means that
less carbon dioxide is exhaled, causing the blood pH to fall.
Some of the interstitial fluid is localized in specific places, such as
lymph; cerebrospinal fluid; gastrointestinal tract fluids; synovial fluid; fluids of the eyes (aqueous humor and vitreous body) and ears (endolymph and perilymph); pleural, pericardial, and peritoneal fluids between serous membranes; and glomerular filtrate in the kidneys.
increase in the rate and depth of breaking causes
more carbon dioxide to be exhaled, thereby increasing pH.
Hypermagnesemia or magnesium excess
occurs mainly in persons with renal failure who have an increased intake of magnesium, such as magnesium-containing antacids. Other causes include Addison's disease, acute diabetic acidosis, severe dehydration, and hypothermia.
Hyperphosphatemia
occurs most often when the kidneys fail to excrete excess phosphate, as may occur in renal insufficiency. It can also result from increased intake of phosphates or destruction of cells, which releases phosphate into the blood.
calcium in plasma is regulated principally by
parathyroid hormone (PTH) and calcitonin (CT).
respiratory acidosis or alkalosis is compensated by
renal mechanisms.
Calcium (Ca2+)
the most abundant ion in the body, is principally an extracellular ion. (Positive cell) 1. It is a structural component of bones and teeth. It also functions in blood coagulation, neurotransmitter release, maintenance of muscle tone, and excitability of nervous and muscle tissue. 2. The level of calcium in plasma is regulated principally by parathyroid hormone (PTH) and calcitonin (CT). 3. An abnormally low level of calcium is called hypocalcemia. It may be caused by increased calcium loss, reduced calcium intake, elevated levels of phosphate (as the level of phosphate increases, the level of calcium decreases), or altered regulation (as might occur in hypoparathyroidism).
Osmosis
the primary way in which water moves in and out of body compartments. The concentration of solutes in the fluids is therefore a major determinant of fluid balance.
metabolic water
water produced by dehydration synthesis reactions of anabolism
buffer systems of the body consist of a
weak acid and the salt of that acid (which functions as a weak base); together they function to prevent rapid, drastic changes in the pH of a body fluid by changing strong acids and bases into weak acids and bases. Buffers work within fractions of a second. 2. The important buffer systems include the carbonic acid-bicarbonate system, the phosphate system, and the protein system.
