Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings PowerPoint ® Lecture prepared by Kathleen A. Ireland, Seabury Hall, Maui, Hawaii Anatomy & Physiology M A R T I N I FIRST EDITION C h a p t e r 27 Fluid, Electrolyte, and Acid–Base Balance PowerPoint® Lecture Slides prepared by Jason LaPres Lone Star College - North Harris Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Maintenance of normal fluid volume and composition is vital Extracellular fluid (ECF) Interstitial fluid, plasma, and other body fluids Intracellular fluid (ICF) The cytosol
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Fluid balance The amount of water gained each day equals the amount lost Electrolyte balance The ion gain each day equals the ion loss Acid-base balance H + gain is offset by their loss Fluid and electrolyte balance
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings The ECF and the ICF are two distinct fluid compartments ICF The cytosol of cells Makes up about two-thirds of the total body water ECF Major components include the interstitial fluid and plasma Minor components include all other extracellular fluids
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 25.1a Figure 25.1 The Composition of the Human Body
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Homeostatic mechanisms respond to changes in ECF No receptors directly monitor fluid or electrolyte balance Respond to changes in plasma volume or osmotic concentrations All water moves passively in response to osmotic gradients Body content of water or electrolytes rises if intake exceeds outflow Regulation of fluids and electrolytes
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 25.2 Cations and Anions in Body Fluids Figure 25.2
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Antidiuretic hormone (ADH) Stimulates water conservation and the thirst center Aldosterone Controls Na + absorption and K + loss along the DCT Natriuretic peptides (ANP and BNP) Reduce thirst and block the release of ADH and aldosterone Primary regulatory hormones
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Interplay between fluid balance and electrolyte balance Different mechanisms regulate fluid and electrolyte balance This distinction is vital in the clinical setting
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Fluid moves freely within ECF compartment Water losses are normally balanced by gains Eating Drinking Metabolic generation Fluid movement within the ECF
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 25.3 Fluid Exchanges Figure 25.3
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings The major routes of fluid exchange with the environment include: Water loss Temperature rise from fever Water gains Fluid exchange with the environment
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Hyponatremia Na + concentration in the ECF is reduced (overhydration) Hypernatremia Na + in the ECF is abnormally high Dehydration Develops when water loss outpaces water gains Water excess and depletion
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Water movement between ECF and ICF If ECF becomes hypertonic relative to ICF, water moves from ICF to ECF If ECF becomes hypotonic relative to ICF, water moves from ECF into cells Fluid shifts PLAY Animation: Introduction to body fluids
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Problems with Electrolyte Balance Usually result from sodium ion imbalances Potassium imbalances are less common, but more dangerous
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Rate of sodium uptake across digestive tract directly proportional to dietary intake Sodium losses occur through urine and perspiration Shifts in sodium balance result in expansion or contraction of ECF Large variations corrected by homeostatic mechanisms Too low, ADH / aldosterone secreted Too high, ANP secreted Sodium balance
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 25.4 Figure 25.4 The Homeostatic Regulation of Normal Sodium Ion Concentrations in Body Fluids
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 25.5 Figure 25.5 The Integration of Fluid Volume Regulation and Sodium Ion Concentrations in Body Fluids
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Potassium ion concentrations in ECF are low Not as closely regulated as sodium Potassium ion excretion increases as ECF concentrations rise Aldosterone secreted pH rises Potassium retention occurs when pH falls Potassium balance
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Calcium balance Bone reserves, absorption in the digestive tract, and loss at kidneys Magnesium balance Absorbed by the PCT to keep pace with urinary losses ECF Concentrations of other electrolytes
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Phosphate balance Absorbed by the PCT in response to calcitriol Chloride balance Absorbed at digestive tract to balance losses in urine and sweat ECF Concentrations of other electrolytes PLAY Animation: Electrolyte homeostasis
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings The pH of the ECF remains between 7.35 and 7.45 If plasma levels fall below 7.35 (acidemia), acidosis results If plasma levels rise above 7.45 (alkalemia), alkalosis results Alteration outside these boundaries affects all body systems Can result in coma, cardiac failure, and circulatory collapse The importance of pH control
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Volatile acid Can leave solution and enter the atmosphere (e.g. carbonic acid) Fixed acids Acids that do not leave solution (e.g. sulfuric and phosphoric acids) Organic acids Participants in or by-products of aerobic metabolism Types of acids in the body
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Carbonic acid is most important factor affecting pH of ECF CO 2 reacts with water to form carbonic acid Inverse relationship between pH and concentration of CO 2 Sulfuric acid and phosphoric acid Generated during catabolism of amino acids Organic acids Metabolic byproducts such as lactic acid, ketone bodies Common Acids
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Buffer system consists of a weak acid and its anion Three major buffering systems: Protein buffer system Amino acid Hemoglobin buffer system H + are buffered by hemoglobin Carbonic acid-bicarbonate Buffers changes caused by organic and fixed acids Mechanisms of pH control
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Three major buffering systems (continued): Minor buffering system Phosphate Buffer pH in the ICF Mechanisms of pH control
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 25.6 Figure 25.6 The Basic Relationship between P CO2 and Plasma pH Animation: Relationship between P CO2 and plasma pH PLAY
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 25.7 Buffer Systems in Body Fluids Figure 25.7
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings If pH climbs, the carboxyl group of amino acid acts as a weak acid If the pH drops, the amino group acts as a weak base Hemoglobin buffer system Prevents pH changes when P CO2 is rising or falling Protein buffer system
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 25.8 Amino Acid Buffers Figure 25.8
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Carbonic acid-bicarbonate buffer system CO 2 + H 2 O H 2 CO 3 H + + CO 3 – Has the following limitations: Cannot protect the ECF from pH changes due to increased or depressed CO 2 levels Only functions when respiratory system and control centers are working normally It is limited by availability of bicarbonate ions (bicarbonate reserve) Carbonic Acid-Bicarbonate Buffering System
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 25.9a, b Figure 25.9 The Carbonic Acid-Bicarbonate Buffer System
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Lungs help regulate pH through carbonic acid - bicarbonate buffer system Changing respiratory rates changes P CO2 Respiratory compensation Kidneys help regulate pH through renal compensation Maintenance of acid-base balance
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Kidney tubules and pH Regulation Figure 25.10a, b
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Kidney tubules and pH Regulation Figure 25.10c
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Buffer systems Respiration Renal function Maintain tight control within range 7.35 – 7.45 Acid-base balance maintained by
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 25.11a Figure The Central Role of the Carbonic Acid-Bicarbonate Buffer System in the Regulation of Plasma pH
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 25.11b Figure The Central Role of the Carbonic Acid-Bicarbonate Buffer System in the Regulation of Plasma pH
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Respiratory acid base disorders Result when abnormal respiratory function causes rise or fall in CO 2 in ECF Metabolic acid-base disorders Generation of organic or fixed acids Anything affecting concentration of bicarbonate ions in ECF Acid-Base Disorders
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Results from excessive levels of CO 2 in body fluids Respiratory acidosis
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Respiratory Acid-Base Regulation Figure 25.12a
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Respiratory Acid-Base Regulation Figure 25.12b
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Relatively rare condition Associated with hyperventilation Respiratory alkalosis
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Major causes are: Depletion of bicarbonate reserve Inability to excrete hydrogen ions at kidneys Production of large numbers of fixed / organic acids Bicarbonate loss due to chronic diarrhea Metabolic acidosis
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Figure The Response to Metabolic Acidosis
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Occurs when HCO 3 – concentrations become elevated Caused by repeated vomiting Metabolic alkalosis
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Figure Metabolic Alkalosis
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Diagnostic blood tests Blood pH P CO2 Bicarbonate levels Distinguish between respiratory and metabolic Detection of acidosis and alkalosis PLAY Animation: Acid-base homeostasis
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Figure A Diagnostic Chart for Acid-Base Disorders
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings What is meant by fluid balance, electrolyte balance, and acid-base balance The compositions of intracellular and extracellular fluids The hormones that play important roles in regulating fluid and electrolyte balance The movement of fluid that takes place within the ECF, between the ECF and the ICF, and between the ECF and the environment You should now be familiar with:
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings How sodium, potassium, calcium and chloride ions are regulated to maintain electrolyte balance The buffering systems that balance the pH of the intracellular and extracellular fluids The compensatory mechanisms involved in acid-base balance You should now be familiar with: