1. Chapter 21 *Lecture Outline with Anatomy & Physiology Revealed Images Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. *See separate Image PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes.

2. 2 Type Course Number Here: Type Course Name Here Chapter 21 Type Professor Name Here Type Academic Rank Here Type Department Name Here Type Institution Name Here

3. 3 21.1: Introduction The term balance suggests a state of constancy For water and electrolytes that means equal amounts enter and leave the body Mechanisms that replace lost water and electrolytes and excrete excesses maintain this balance This results in stability of the body at all times Keep in mind water and electrolyte balance are interdependent

4. 4 21.2: Distribution of Body Fluids Body fluids are not uniformly distributed They occupy compartments of different volumes that contain varying compositions Water and electrolyte movement between these compartments is regulated to stabilize their distribution and the composition of body fluids

5. 5 Fluid Compartments 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 Extracellular fluid (37%) Intracellular fluid (63%) 40 38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 Liters Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

6. Total Body Water 40 liters (10.6 gallons) 6 63% Intracellular Fluidd37% Extracellular Fluid Interstitial Fluid Plasma Lymph Transcellular Fluid Female – 52% Male – 63%

7. 7 Total body water Interstitial fluid Plasma Lymph Transcellular fluid Extracellular fluid (37%) Membranes of body cells Intracellular fluid (63%) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

8. 8 Body Fluid Composition Extracellular fluids are generally similar in composition including high concentrations of sodium, calcium, chloride and bicarbonate ions Blood plasma has more proteins than interstitial fluid or lymph Intracellular fluids have high concentrations of potassium, magnesium, phosphate, and sulfate ions Ion concentration (m Eq/L) 20 30 50 60 70 80 90 100 1 10 120 130 140 Relative concentrations and ratios of ions in extracellular and intracellular fluids 150 40 10 0 14:1Ratio (Extracellular: intracellular) Na + 1:28 K+K+ 5:1 Ca +2 1:19 Mg +2 26:1 Cl  3:1 HCO 3  1:19 PO 4  3 1:2 SO 4  2 Extracellular fluid Intracellular fluid Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

9. 9 Movement of Fluid Between Compartments Two major factors regulate the movement of water and electrolytes from one fluid compartment to another Hydrostatic pressure Osmotic pressure Interstitial fluid Capillary wall Transcellular fluid Lymph Plasma Serous membrane Intracellular fluid Cell membrane Lymph vessel Fluid leaves plasma at arteriolar end of capillaries because outward force of hydrostatic pressure predominates Fluid returns to plasma at venular ends of capillaries because inward force of colloid osmotic pressure predominates Hydrostatic pressure within interstitial spaces forces fluid into lymph capillaries Interstitial fluid is in equilibrium with transcellular and intracellular fluids Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

10. 10 21.3: Water Balance Water balance exists when water intake equals water output Homeostasis requires control of both water intake and water output

11. 11 Water Intake 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 10% as a bi-product of oxidative metabolism of nutrients called water of metabolism Water in beverages (1,500 mL or 60%) Average daily intake of water Water lost in sweat (150 mL or 6%) Total output (2,500 mL) Average daily output of water (a)(b) Total intake (2,500 mL) Water in moist food (750 mL or 30%) Water of metobolism (250 mL or 10%) Water lost in feces (150 mL or 6%) Water lost through skin and lungs (700 mL or 28%) Water lost in urine (1,500 mL or 60%) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

12. 12 Regulation of Water Intake The primary regulator of water intake is thirst.

13. 13 Water Output 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 the lungs is a 28% loss)

14. 14 Regulation of Water Output The osmoreceptor-ADH mechanism in the hypothalamus regulates the concentration of urine produced in the kidney.

15. 15 21.1 Clinical Application Water Balance Disorders

16. 16 21.4: Electrolyte Balance An electrolyte balance exists when the quantities of electrolytes the body gains equals those lost FoodsFluids Metabolic reactions Electrolyte intake Electrolyte output UrinePerspirationFeces Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

17. 17 Electrolyte Intake The electrolytes of greatest importance to cellular functions release 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

18. 18 Regulation of Electrolyte Intake Ordinarily, a person obtains sufficient electrolytes by responding to hunger and thirst A severe electrolyte deficiency may cause salt craving

19. 19 Electrolyte Output 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

20. Regulation of Electrolyte Output 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 20

21. Regulation of Electrolyte Output 21 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Potassium ion concentration increases Adrenal cortex is signaled Aldosterone is secreted Renal tubules increase reabsorption of sodium ions and increase secretion of potassium ions Sodium ions are conserved and potassium ions are excreted Calcium ion Concentration decreases Parathyroid glands are stimulated Parathyroid hormone is secreted Intestinal absorption of calcium increases Renal tubules conserve calcium and increase secretion of phosphate Calcium ion concentration returns toward normal Normal phosphate concentration is maintained Activity of bone-resorbing osteoclasts increases Increased phosphate excretion in urine Addition of phosphate to bloodstream

22. 22 21.2 Clinical Application Sodium and Potassium Imbalances

23. 23 21.5: Acid-Base Balance Acids are electrolytes that ionize in water and release hydrogen ions Bases are substances that combine with hydrogen ions Acid-base balance entails regulation of the hydrogen ion concentrations of body fluids This is important because slight changes in hydrogen ion concentrations can alter the rates of enzyme-controlled metabolic reactions, shift the distribution of other ions, or modify hormone actions pH number indicates the degree to which a solution is acidic or basic (alkaline). The more acid the solution, the lower its pH The more alkaline the solution, the higher its pH

24. 24 Sources of Hydrogen Ions Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. H+H+ Hydrolysis of phosphoproteins and nucleic acids Internal environment Oxidation of sulfur-containing amino acids Incomplete oxidation of fatty acids Anaerobic respiration of glucose Aerobic respiration of glucose Phosphoric acid Sulfuric acid Acidic ketone bodies Carbonic acid Lactic acid

25. 25 Strengths of Acids and Bases Acids: Strong acids ionize more completely and release more H + Ex: HCl Weak acids ionize less completely and release fewer H + Ex: H 2 CO 3 Bases: Strong bases ionize more completely and release more OH - or other negative ions Weak bases ionize less completely and release fewer OH - or other negative ions

26. 26 Regulation of Hydrogen Ion Concentration Either an acid shift or an alkaline (basic) shift in the body fluids could threaten the internal environment Normal metabolic reactions generally produce more acid than base The reactions include cellular metabolism of glucose, fatty acids, and amino acids Maintenance of acid-base balance usually eliminates acids in one of three ways: Acid-base buffer systems Respiratory excretion of carbon dioxide Renal excretion of hydrogen ions

27. 27 Chemical buffer systems are in all body fluids and are based on chemicals that combine with excess acids or bases. Bicarbonate buffer system The bicarbonate ion converts a strong acid to a weak acid Carbonic acid converts a strong base to a weak base H + + HCO 3 -  H 2 CO 3  H + + HCO 3 - Phosphate buffer system The monohydrogen phosphate ion converts a strong acid to a weak acid The dihydrogen phosphate ion converts a strong base to a weak base H + + HPO 4 -2  H 2 PO 4 -  H + + HPO 4 -2 Protein buffer system NH 3 + group releases a hydrogen ion in the presence of excess base COO - group accepts a hydrogen ion in the presence of excess acid Chemical Buffer Systems

28. 28

29. 29 The respiratory center in the brainstem helps regulate hydrogen ion concentrations in the body fluids by controlling the rate and depth of breathing If body cells increase their production of CO 2 … Respiratory Excretion of Carbon Dioxide Cells increase production of CO 2 CO 2 reacts with H 2 O to produce H 2 CO 3 H 2 CO 3 releases H + Respiratory center is stimulated Rate and depth of breathing increase More CO 2 is eliminated through lungs Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

30. Respiratory System 30

31. 31 Nephrons help regulate the hydrogen ion concentration of body fluids by excreting hydrogen ions in the urine Renal Excretion of Hydrogen Ions Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. High intake of proteins Increased metabolism of amino acids Increased formation of sulfuric acid and phosphoric acid Increased concentration of H + in body fluids Increased secretion of H + into fluid of renal tubules Concentration of H + in body fluids returns toward normal Increased concentration of H + in urine

32. Urinary System 32

33. 33 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 Phosphate buffer system Protein buffer system First line of defense against pH shift Second line of defense against pH shift Chemical buffer system Physiological buffers Bicarbonate buffer system Respiratory mechanism (CO 2 excretion) Renal mechanism (H + excretion) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Time Course of pH Regulation

34. 34 21.6: Acid-Base Imbalances Chemical and physiological buffer systems ordinarily maintain the hydrogen ion concentration of body fluids within very narrow pH ranges Abnormal conditions may disturb the acid-base balance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Acidosis Alkalosis pH scale 6.8 7.0 8.07.8 7.35 7.45 Normal pH range Survival range

35. 35 Acidosis 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. Loss of bases Accumulation of acids Acidosis Increased concentration of H + pH scale pH drops pH rises Alkalosis Decreased concentration of H + Accumulation of bases Loss of acids 7.4

36. 36 Two major types of acidosis are respiratory acidosis and metabolic acidosis Acidosis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Decreased gas exchange Decreased rate and depth of breathing Obstruction of air passages Accumulation of CO 2 Respiratory acidosis Excessive production of acidic ketones as in diabetes mellitus Kidney failure to excrete acids Accumulation of nonrespiratory acids Metabolic acidosis Excessive loss of bases Prolonged diarrhea with loss of alkaline intestinal secretions Prolonged vomiting with loss of intestinal secretions Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

37. 37 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 Hyperventilation Excessive loss of CO 2 Decrease in concentration of H 2 CO 3 Decrease in concentration of H + Respiratory alkalosis Gastric drainage Vomiting with loss of gastric secretions Loss of acids Net increase in alkaline substances Metabolic alkalosis

38. 38 Important Points in Chapter 21: Outcomes to be Assessed 21.1: Introduction Explain the balance concept. Explain the importance of water and electrolyte balance. 21.2: Distribution of Body Fluids Describe how body fluids are distributed in compartments. Explain how fluid composition varies among compartments and how fluids move from one compartment to another. 21.3: Water Balance List the routes by which water enters and leaves the body. Explain the regulation of water input and water output.

39. 39 Important Points in Chapter 21: Outcomes to be Assessed 21.4: Electrolyte Balance List the routes by which electrolytes enter and leave the body. Explain the regulation of the input and the output of electrolytes. 21.5: Acid-Base Balance Explain acid-base balance. Identify how pH number describes the acidity and alkalinity of a body fluid. List the major sources of hydrogen ions in the body. Distinguish between strong acids and weak acids. Explain how chemical buffer systems, the respiratory center, and the kidneys keep the pH of body fluids relatively constant.

40. 40 Important Points in Chapter 21: Outcomes to be Assessed 21.6: Acid-Base Imbalances Describe the causes and consequences of increase or decrease in body fluid pH.

41. 41 Quiz 21 Complete Quiz 21 now! Read Chapter 22.