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BIO 139- Human Anatomy & Physiology II SPRING 2013 1 Chapter 21- Water, Electrolyte, and Acid-Base Balance MARY CAT FLATH, PH.D. Copyright 2013 Dr. Mary Cat Flath Chapter 21- Water, Electrolyte, and Acid-Base Balance 2 Review of Inorganic Substances from Chap 2 Introduction Distribution of Body Fluids Water Balance Electrolyte Balance Acid-Base Balance Acid-Base Imbalances Copyright 2013 Dr. Mary Cat Flath Inorganic Substances 3 Oxygen Carbon Dioxide Water Salts Acids Bases Copyright 2013 Dr. Mary Cat Flath Inorganic Substances: OXYGEN and Carbon Dioxide 4 OXYGEN Is required for cellular respiration Animal cells use oxygen to release energy from nutrients By-product is carbon dioxide Copyright 2013 Dr. Mary Cat Flath Inorganic Substances: WATER 5 Water is a polar molecule that demonstrates hydrogen bonding and therefore it possesses very unique characteristics. a. Water is an excellent solvent b. Water participates in many chemical reactions • Dehydration (synthesis) is when water is removed from adjacent atoms (of molecules) to form a bond between them. • Hydrolysis (degradation) is when water is used to break bonds between molecules. c. Water is an excellent temperature buffer. d. Water provides an excellent cooling mechanism e. Water serves as a lubricant f. Water is the most abundant component in cells (about 5270%). Copyright 2013 Dr. Mary Cat Flath Inorganic Molecules: Acids, Bases, Salts 6 Acids, Bases, and Salts When dissolved in water, these release cations and anions. These ions are referred to as electrolytes (charged particles) Electrolytes must be maintained within a very narrow range in our blood and tissues (i.e. homeostasis); Needed for muscle contraction, nerve impulses, bone growth, et cetera; Examples include Na+, K+, Cl-, Ca+, PO4-; HCO3-, etc. Copyright 2013 Dr. Mary Cat Flath Acids 7 Acids dissociate (ionize) in water to form: a. a hydrogen cation, H+, and b. an anion. c. Example = HCl (hydrochloric acid). • H2O HCl → H+ + Cl- Copyright 2013 Dr. Mary Cat Flath Bases 8 Bases dissociate (ionize) in water to form: a b. c. a hydroxyl anion, OH-, and a cation. Example = NaOH (sodium hydroxide). H2O NaOH → Na+ + OH Copyright 2013 Dr. Mary Cat Flath Salts 9 Salts dissociate (ionize) into ions when dissolved in water. an anion is formed and a cation is formed. Example = NaCl in water. H2O ↓ NaCl → Na+ + Cl Copyright 2013 Dr. Mary Cat Flath Acid and Base Concentration 10 The relative concentrations of hydrogen ions and hydroxyl ions determine the pH in our blood, fluids, and tissues. pH in body = [H+] + [OH-] . pH = -log[H+]; pH Scale ranges from 0 to 14. 0 ---------------------------7---------------------------14 acidic [H+] > [OH-] Copyright 2013 Dr. Mary Cat Flath neutral [H+] = [OH-] basic [H+] < [OH-] Fig. 2.10 pH Scale Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Relative amounts of H+ (red) and OH– (blue) Acidic H+ pH 0 Acidic 2.0 gastric juice 1 3.0 apple juice 4.2 tomato juice 6.6 cow’s milk 5.3 cabbage Copyright 2013 Dr. Mary Cat Flath 6 8.0 egg white 7.0 distilled water 6.0 corn 2 3 4 5 + H concentration increases 8.4 7.4 sodium human bicarbonate blood 7 Neutral 11 8 OH– 10.5 milk of magnesia 9 10 11 concentration increases 11.5 household ammonia Basic OH– 12 13 14 Basic (alkaline) Physiologic pH 12 Physiologic pH = 7.4 (7.35-7.45) a. b. pH < 7.35 = acidosis; lethal below 7.0; pH > 7.45 = alkalosis; lethal above 7.8. c. Buffering Systems prevent abrupt pH changes keeping pH near 7.4 Copyright 2013 Dr. Mary Cat Flath Buffering Systems 13 Definition: Buffers prevent abrupt change in pH. usually weak acids; function by donating H+ when needed and by accepting H+ when in excess; very important in biological systems! Example = the carbonic acid (H2CO3) buffering system. H2CO3 HCO3+ H+ carbonic acid (H+ donor) bicarbonate ion (H+ acceptor) when pH is rising equation goes to the right when pH is falling equation goes to the left Copyright 2013 Dr. Mary Cat Flath hydrogen ion Chapter 21- Water, Electrolyte, and Acid-Base Balance 14 Review of Inorganic Substances from Chap 2 Introduction Distribution of Body Fluids Water Balance Electrolyte Balance Acid-Base Balance Acid-Base Imbalances Copyright 2013 Dr. Mary Cat Flath Introduction 15 • Homeostasis has been a unifying theme in BIO 137 and BIO 139. • The ability of an organism to maintain a relatively stable internal environment. • Water and electrolytes are included in this delicate balance or state of equilibrium. • Water and electrolyte input must equal their output. • Keep in mind water and electrolyte balance are interdependent Copyright 2013 Dr. Mary Cat Flath Chapter 21- Water, Electrolyte, and Acid-Base Balance 16 Review of Inorganic Substances from Chap 2 Introduction Distribution of Body Fluids Water Balance Electrolyte Balance Acid-Base Balance Acid-Base Imbalances Copyright 2013 Dr. Mary Cat Flath Distribution of Body Fluids 17 Water Content of the Body Infants = 73% of body weight Males = 63% of body weight Females = 52% of body weight Total amount of water is affected by age, body mass, and body fat. Copyright 2013 Dr. Mary Cat Flath Distribution of Body Fluids 18 Fluid Compartments in the Body Two main fluid compartments INTRACELLULAR COMPARTMENT Fluid inside cells 63% of body weight EXTRACELLULAR COMPARTMENT Includes blood plasma, interstitial fluid, and lymph 37% of body weight Copyright 2013 Dr. Mary Cat Flath Fluid Compartments 19 • An average adult female is about 52% water by weight, and an average male about 63% water by weight There are about 40 liters of water (with its dissolved electrolytes) in the body, distributed into two major compartments: • Intracellular fluid – 63% - fluid inside cells • Extracellular fluid – 37% - fluid outside cells • Interstitial fluid • Blood plasma • Lymph • Transcellular fluid – separated from other extracellular fluids by epithelial layers • Cerebrospinal fluid • Aqueous and vitreous humors • Synovial fluid • Serous fluid Copyright 2013 Dr. Mary Cat Flath Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 40 38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 Extracellular fluid (37%) Liters • Intracellular fluid (63%) 20 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Total body water Interstitial fluid Plasma Membranes of body cells Intracellular fluid (63%) Lymph Transcellular fluid Extracellular fluid (37%) Copyright 2013 Dr. Mary Cat Flath Distribution of Body Fluids 21 Electrolyte Concentration The overall concentration of electrolytes is the same in the two fluid compartments. However, there are different concentrations of specific ions in the different compartments. Copyright 2013 Dr. Mary Cat Flath Distribution of Body Fluids 22 BODY FLUID COMPOSITION BODY FLUID EXTRACELLULAR FLUID: Blood plasma, interstitial fluid, and lymph INTRACELLULAR FLUID HIGH CONCENTRATION Na+, Cl-, Ca++, HCO3-, (plasma – high proteins) K+, PO4-, Mg++, SO4Negatively charged proteins (A-) LOW CONCENTRATION K+, Mg++, PO4-, SO4- Na+, Cl-, HCO3- Copyright 2013 Dr. Mary Cat Flath Body Fluid Composition Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Relative concentrations and ratios of ions in extracellular and intracellular fluids 150 140 Extracellular fluid 130 Intracellular fluid 120 110 Ion concentration (m Eq/L) • Extracellular fluid composition: • high concentrations of sodium, calcium, chloride and bicarbonate ions • Low concentrations of potassium, magnesium, phosphate and sulfate • Blood plasma, interstitial fluid and lymph • Intracellular fluid composition • high concentrations of potassium, magnesium, phosphate, sulfate, and proteins. • Low concentration of sodium, chloride, and bicarbonate ions 100 90 80 70 60 50 40 30 20 10 0 Na+ Ratio 14:1 K+ Ca+2 Mg+2 Cl- 1:28 5:1 1:19 26:1 (Extracellular: intracellular) Copyright 2013 Dr. Mary Cat Flath HCO3- PO4-3 SO4-2 3:1 1:19 23 1:2 Distribution of Body Fluids • Movement of Fluid Between Compartments • Two major factors regulate the movement of water and electrolytes from one fluid compartment to another • Hydrostatic pressure Fluid leaves plasma at arteriolar end of • Osmotic pressure Capillary wall capillaries because Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. outward force of hydrostatic pressure predominates Plasma Interstitial fluid Transcellular fluid Serous membrane Copyright 2013 Dr. Mary Cat Flath Fluid returns to plasma at venular ends of capillaries because inward force Lymph of colloid osmotic vessel pressure predominates Hydrostatic pressure Lymph within interstitial spaces forces fluid into lymph capillaries Intracellular fluid Cell membrane Interstitial fluid is in equilibrium with transcellular and 24 intracellular fluids Chapter 21- Water, Electrolyte, and Acid-Base Balance 25 Review of Inorganic Substances from Chap 2 Introduction Distribution of Body Fluids Water Balance Electrolyte Balance Acid-Base Balance Acid-Base Imbalances Copyright 2013 Dr. Mary Cat Flath Water Intake 26 • The volume of water gained each day varies among individuals averaging about 2,500 milliliters daily for an adult: • 60% from drinking • 30% from moist foods Average daily intake of water Average daily output of water • 10% as a bi-product of Water lost in sweat (150 mL or 6%) Water of Water lost in feces oxidative metabolism of metobolism (150 mL or 6%) (250 mL or 10%) Water in Water lost through nutrients called water of moist food skin and lungs (750 mL or 30%) (700 mL or 28%) metabolism Total intake Total output Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. (2,500 mL) (2,500 mL) Water in beverages (1,500 mL or 60%) (a) Copyright 2013 Dr. Mary Cat Flath Water lost in urine (1,500 mL or 60%) (b) Regulation of Water Intake 27 The primary regulator of water intake is thirst. Copyright 2013 Dr. Mary Cat Flath Water Output 28 • Water normally enters the body only through the mouth, but it can be lost by a variety of routes including: • Urine (60% loss) • Feces (6% loss) • Sweat (sensible perspiration) (6% loss) • Evaporation from the skin (insensible perspiration) • The lungs during breathing * Evaporation from the skin and Lungs is a 28% loss) Copyright 2013 Dr. Mary Cat Flath ADH regulates water reabsorption in the nephron (DCT and CD) 29 Triggers for ADH release include: Stimulation of posterior pituitary Prolonged fever Excessive sweating, vomiting, or diarrhea concentrates blood plasma Severe blood loss Traumatic burns Increased plasma osmolality Copyright 2013 Dr. Mary Cat Flath Regulation of Water Output 30 The osmoreceptor-ADH mechanism in the hypothalamus regulates the concentration of urine produced in the kidney.. Copyright 2013 Dr. Mary Cat Flath See Clinical Application 21.1 31 Water Balance Disorders: Dehydration Water Intoxication Edema Copyright 2013 Dr. Mary Cat Flath Chapter 21- Water, Electrolyte, and Acid-Base Balance 32 Review of Inorganic Substances from Chap 2 Introduction Distribution of Body Fluids Water Balance Electrolyte Balance Acid-Base Balance Acid-Base Imbalances Copyright 2013 Dr. Mary Cat Flath Electrolyte Balance 33 • An electrolyte balance exists when the quantities of electrolytes the body gains equals those lost Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Foods Fluids Metabolic reactions Electrolyte intake Electrolyte output Perspiration Copyright 2013 Dr. Mary Cat Flath Feces Urine Electrolyte Intake 34 • The electrolytes of greatest importance to cellular functions are • sodium, potassium, calcium, magnesium, chloride, sulfate, phosphate, bicarbonate, and hydrogen ions. • These ions are primarily obtained from foods, but some are from water and other beverages, and some are by-products of metabolism Copyright 2013 Dr. Mary Cat Flath Regulation of Electrolyte Intake 35 • Ordinarily, a person obtains sufficient electrolytes by responding to hunger and thirst • A severe electrolyte deficiency may cause salt craving (rare) Copyright 2013 Dr. Mary Cat Flath Electrolyte Output 36 • The body loses some electrolytes by perspiring (more on warmer days and during strenuous exercise) • Some are lost in the feces • The greatest output is as a result of kidney function and urine output Copyright 2013 Dr. Mary Cat Flath Regulation of Electrolyte Output 37 The concentrations of positively charged ions, such as sodium (Na+), potassium (K+) and calcium (Ca+2) are of particular importance These ions are vital for nerve impulse conduction, muscle fiber contraction, and maintenance of cell membrane permeability Sodium ions account for nearly 90% of the positively charged ions in extracellular fluids. Regulation of Na+: Aldosterone causes reabsorption of Na+ in DCT Regulation of K+: Aldosterone causes secretion/excretion of K+ in DCT. Regulation of Ca++: Calcitonin decreases blood Ca++ and PTH increases blood Ca++ Copyright 2013 Dr. Mary Cat Flath Regulation of Electrolyte Output Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Potassium ion concentration increases Calcium ion Concentration decreases Parathyroid glands are stimulated Adrenal cortex is signaled Parathyroid hormone is secreted Aldosterone is secreted Renal tubules conserve calcium and increase secretion of phosphate Intestinal absorption of calcium increases Activity of bone-resorbing osteoclasts increases Renal tubules increase reabsorption of sodium ions and increase secretion of potassium ions Increased phosphate excretion in urine Addition of phosphate to bloodstream Sodium ions are conserved and potassium ions are excreted Copyright 2013 Dr. Mary Cat Flath Calcium ion concentration returns toward normal Normal phosphate concentration is maintained 38 Sodium and Potassium Imbalances 39 Hyponatremia (low blood sodium) caused by prolonged sweating, diarrhea, vomiting, renal disease, Addison’s disease, or excessive water intake can result in osmosis of water into cells – water intoxication. Hypernatremia (high blood sodium) caused by water loss (diabetes insipidus –ADH deficiency, osmotic diuresis- Diabetes Mellitus, increased perspiration, high fever or heat stroke) or sodium gain (hyperaldosteronism) can result in CNS disturbances – confusion, stupor, coma. Hypokalemia (low blood potassium) caused by diuretics, renal disease, or alkalosis can result in muscle weakness or paralysis, respiratory difficulty, and atrial and ventricular arrhythmias. Hyperkalemia (high blood potassium) caused by renal disease, drugs, Addisons’s disease, or acidosis can result in paralysis of skeletal muscle and cardiac arrest. Copyright 2013 Dr. Mary Cat Flath Chapter 21- Water, Electrolyte, and Acid-Base Balance 40 Review of Inorganic Substances from Chap 2 Introduction Distribution of Body Fluids Water Balance Electrolyte Balance Acid-Base Balance Acid-Base Imbalances Copyright 2013 Dr. Mary Cat Flath Acid-Base Balance 41 • pH is an indirect measure of the H+ ion concentration • Our body maintains a slightly alkaline pH of 7.35-7.45. • Metabolic and respiratory processes work together to keep H+ levels in this normal range. Copyright 2013 Dr. Mary Cat Flath Normal Metabolism produces Acids/ Hydrogen Ions 42 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Aerobic respiration of glucose Anaerobic respiration of glucose Incomplete oxidation of fatty acids Oxidation of sulfur-containing amino acids Hydrolysis of phosphoproteins and nucleic acids Carbonic acid Lactic acid Acidic ketone bodies Sulfuric acid Phosphoric acid H+ Internal environment Acids MUST be neutralized. Copyright 2013 Dr. Mary Cat Flath Regulation of Hydrogen Ion Concentration 43 • pH greater than 7.45 = alkalosis • pH less than 7.35 = acidosis • Acid-base balance is maintained (usually by elimination of acids) in one of three ways: • Chemical Buffer Systems – work immediately • Respiratory excretion of carbon dioxide – works in minutes to hours • Renal excretion of hydrogen ions – works in hours to 2-3 days and has longer maintenance Copyright 2013 Dr. Mary Cat Flath Chemical Buffer Systems 44 Chemical buffer systems are in all body fluids and are based on chemicals that combine with excess acids or bases. These act immediately. • Bicarbonate buffer system • H2CO3 ↔ H + + HCO3• When pH is rising: → • When pH is falling: ← • Phosphate buffer system • H2PO4- H+ + HPO4-2 • When pH is rising: → • When pH is falling: ← • Protein buffer system • Involve plasma proteins (i.e. albumin) and certain proteins in cells (hemoglobin in red blood cells). Copyright 2013 Dr. Mary Cat Flath Respiratory Buffer System 45 Bicarbonate Buffering System is the main buffer in ECF CA CO2 + H2O ↔ H2CO3 ↔ H + + HCO3Changes in CO2 concentration lead directly to changes in H+ and pH. CO2 concentration and H+ concentration are directly proportional H+ concentration and pH are inversely proportional Copyright 2013 Dr. Mary Cat Flath Respiratory Buffer System 46 Decreased ventilation leads to a increased CO2 in the body pushing the reaction to the right. Increased ventilation leads to a decreased CO2in the body pushing the reaction to the left. This system works within minutes to hours, but it is only temporary. Copyright 2013 Dr. Mary Cat Flath Respiratory Excretion of Carbon Dioxide: Physiologic Buffer System • The respiratory center in the brainstem helps regulate hydrogen ion concentrations in the body fluids by controlling the rate and depth of breathing (Pontine/pneumotaxic area in pons) • If body cells increase their production of CO2… Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cells increase production of CO2 CO2 reacts with H2O to produce H2CO3 H2CO3 releases H+ Respiratory center is stimulated Rate and depth of breathing increase Copyright 2013 Dr. Mary Cat Flath 47 More CO2 is eliminated through lungs Renal Regulation of Acid-Base Balance 48 The kidneys can secrete and reabsorb HCO3and H+ ions to regulate pH. The kidneys respond within hours to days. Copyright 2013 Dr. Mary Cat Flath Renal Excretion of Hydrogen Ions 49 • Nephrons help regulate the hydrogen ion concentration of body fluids by excreting hydrogen ions in the urine Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. High intake of proteins Increased metabolism of amino acids Increased concentration of H+ in urine Increased secretion of H+ into fluid of renal tubules Increased formation of sulfuric acid and phosphoric acid Copyright 2013 Dr. Mary Cat Flath Concentration of H+ in body fluids returns toward normal Increased concentration of H+ in body fluids Time Course of pH Regulation • Various regulators of hydrogen ion concentration operate at different rates • Acid-base (chemical) buffers function rapidly • Respiratory and renal (physiological buffers) mechanisms function more slowly = minutes to several days to begin to resist pH changes. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Bicarbonate buffer system First line of defense against pH shift Chemical buffer system Phosphate buffer system Protein buffer system Second line of defense against pH shift Respiratory mechanism (CO2 excretion) Physiological buffers Renal mechanism (H+ excretion) Copyright 2013 Dr. Mary Cat Flath 50 Chapter 21- Water, Electrolyte, and Acid-Base Balance 51 Review of Inorganic Substances from Chap 2 Introduction Distribution of Body Fluids Water Balance Electrolyte Balance Acid-Base Balance Acid-Base Imbalances Copyright 2013 Dr. Mary Cat Flath 21.6: Acid-Base Imbalances 52 • Chemical and physiological buffer systems ordinarily maintain the hydrogen ion concentration of body fluids within very narrow pH range of 7.35-7.45. • Abnormal conditions may disturb the acid-base balance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Alkalosis Acidosis pH scale 6.8 7.0 7.35 7.45 7.8 8.0 Normal pH range Copyright 2013 Dr. Mary Cat Flath Survival range 52 Abnormalities in Acid-Base Balance • Acidosis results from the accumulation of acids or loss of bases, both of which cause abnormal increases in the hydrogen ion concentrations of body fluids • Alkalosis results from a loss of acids or an accumulation of bases accompanied by a decrease in hydrogen ion concentrations Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Accumulation of acids Loss of bases Increased concentration of H+ Acidosis pH drops pH scale 7.4 Alkalosis pH rises Decreased concentration of H+ Copyright 2013 Dr. Mary Cat Flath Loss of acids Accumulation of bases 53 Abnormalities in Acid-Base Balance 54 Health problems may lead to imbalances in acid-base concentrations and fluid and electrolyte balance Diabetes Mellitus COPD Kidney Disease Vomiting Diarrhea Hormonal Imbalances Copyright 2013 Dr. Mary Cat Flath Abnormalities in Acid-Base Balance 55 RESPIRATORY IMBALANCES affect carbonic acid concentrations = CARBON DIOXIDE – CO2 METABOLIC IMBALANCES affect BICARBONATE ION CONCENTRATIONS – HCO3- Copyright 2013 Dr. Mary Cat Flath Abnormalities in Acid-Base Balance 56 During Abnormalities in Acid-Base Balance THE RESPIRATORY AND URINARY SYSTEMS ACT TO COMPENSATE Copyright 2013 Dr. Mary Cat Flath Abnormalities in Acid-Base Balance 57 In the kidneys, this involves the secretion and reabsorption of what ions??? If H+ is secreted, then HCO3- is reabsorbed. If HCO3- is secreted, then H+ is reabsorbed. Loss of 1 HCO3- is the same as gain of 1 H+ and vice versa Copyright 2013 Dr. Mary Cat Flath Abnormalities in Acid-Base Balance 58 Respiratory Acidosis (↑H+ = ↓pH) Respiratory Alkalosis (↓H+ = ↑pH) (increased H2CO3 )=↑CO2 (decreased H2CO3) = ↓CO2 Metabolic Acidosis (↑H+ = ↓pH) Metabolic Alkalosis (↓H+ = ↑pH) ↓HCO3- (or increase in other ↑HCO3- (or loss of acids) acids) Copyright 2013 Dr. Mary Cat Flath Respiratory Acidosis (pH< 7.35) 59 Increased H2CO3 leads to ↑CO2 causing ↑ H+ = ↓pH Causes: Hypoventilation Caused by lung disease (asthma, CF, COPD), anesthesia, drug overdose, atelectasis Stimulates Respiratory Centers (including Dorsal Respiratory Group) which leads to increased ventilation and expiration of excess CO2 Compensation: Kidneys reabsorption of HCO3- and kidneys secretion/excretion of excess H+ Copyright 2013 Dr. Mary Cat Flath Respiratory Alkalosis (pH > 7.45) 60 ↓ H2CO3 leads to ↓CO2 = ↑pH Causes: Hyperventilation possibly caused by anxiety, pulmonary embolism, fear, or mechanical ventilation causes respiratory center to decrease ventilation Compensation: Kidneys secretion/excretion of HCO3- OR kidneys reabsorption of H+ Copyright 2013 Dr. Mary Cat Flath Renal Control of Acid-Base Balance 61 Kidneys are only organ that can rid body of acids (not just H+) generated by cellular metabolism. HCO3- is key indicator of metabolic acidosis or metabolic alkalosis. Copyright 2013 Dr. Mary Cat Flath Metabolic Acidosis (pH< 7.35) 62 Decreased pH and decreased HCO3Causes: Diabetes Mellitus, severe diarrhea, renal failure, shock, Accumulation of non-respiratory acids or excessive loss of HCO3Ingestion of excessive alcohol Starvation Compensation: kidneys secretion/excretion of H+ AND reabsorption of HCO3- AND increased CO2 release by lungs Copyright 2013 Dr. Mary Cat Flath Metabolic Alkalosis (pH > 7.45) 63 Increased pH and increased HCO3Causes: Severe vomiting, diuretics, excessive base intake Compensation: kidneys secretion of HCO3- and decreased respiration Copyright 2013 Dr. Mary Cat Flath Maintaining Metabolic Acid-Base Balance in Kidney 64 Reabsorption of HCO3- (by nephron) OR Secretion/excretion of HCO3- (by nephron) Copyright 2013 Dr. Mary Cat Flath Acidosis • Two major types of acidosis are respiratory acidosis and metabolic acidosis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Kidney failure to excrete acids Excessive production of acidic ketones as in diabetes mellitus Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Decreased rate and depth of breathing Obstruction of air passages Decreased gas exchange Accumulation of nonrespiratory acids Metabolic acidosis Accumulation of CO2 Excessive loss of bases Respiratory acidosis Copyright 2013 Dr. Mary Cat Flath Prolonged diarrhea with loss of alkaline intestinal secretions Prolonged vomiting with loss of intestinal secretions 65 Alkalosis • Respiratory alkalosis develops as a result of hyperventilation • Metabolic alkalosis results from a great loss of hydrogen ions or from a gain in bases, both accompanied by a rise in the pH of blood Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. • Anxiety • Fever • Poisoning • High altitude Gastric drainage Vomiting with loss of gastric secretions Hyperventilation Loss of acids Excessive loss of CO2 Decrease in concentration of H2CO3 Net increase in alkaline substances Decrease in concentration of H+ Copyright 2013 Dr. Mary Catalkalosis Flath Respiratory Metabolic alkalosis 66 Abnormalities in Acid-Base Balance Respiratory Acidosis ↓pH and↑CO2 Causes: Hypoventilation (lung disease, anesthesia, drug overdose, atelectasis) Respiratory Centers (Dorsal) ↑ ventilation and expiration of excess CO2 Respiratory Alkalosis ↑pH and↓CO2 67 Causes: Hyperventilation (anxiety, PE, fear, poisoning, high altitudes, mechanical ventilation) Respiratory Centers ↓ventilation Metabolic Acidosis Metabolic Alkalosis ↓pH and ↓HCO3- ↑pH and ↑HCO3- Causes: diabetes mellitus, severe diarrhea, renal failure, shock Kidneys reabsorb HCO3- and secrete H+ and respiration rate is increased Copyright 2013 Dr. Mary Cat Flath Causes: Severe vomiting, diuretics, excessive base intake Kidneys secrete HCO3- and reabsorb H+ and respiration rate is decreased Abnormalities in Acid-Base Balance Respiratory Acidosis Metabolic Acidosis Copyright 2013 Dr. Mary Cat Flath Respiratory Alkalosis ↑ 68 Metabolic Alkalosis Abnormalities in Acid-Base Balance Respiratory Acidosis ↓pH and↑CO2 Causes: Hypoventilation (lung disease, anesthesia, drug overdose, atelectasis) Respiratory Centers (Dorsal) ↑ ventilation and expiration of excess CO2 Respiratory Alkalosis ↑pH and↓CO2 69 Causes: Hyperventilation (anxiety, PE, fear, poisoning, high altitudes, mechanical ventilation) Respiratory Centers ↓ventilation Metabolic Acidosis Metabolic Alkalosis ↓pH and ↓HCO3- ↑pH and ↑HCO3- Causes: diabetes mellitus, severe diarrhea, renal failure, shock Kidneys reabsorb HCO3- and secrete H+ and respiration rate is increased Copyright 2013 Dr. Mary Cat Flath Causes: Severe vomiting, diuretics, excessive base intake Kidneys secrete HCO3- and reabsorb H+ and respiration rate is decreased Chapter 21- Water, Electrolyte, and Acid-Base Balance 70 Review of Inorganic Substances from Chap 2 Introduction Distribution of Body Fluids Water Balance Electrolyte Balance Acid-Base Balance Acid-Base Imbalances Copyright 2013 Dr. Mary Cat Flath