1. Hole’s Essentials of Human Anatomy & Physiology David Shier Jackie Butler Ricki Lewis Power Points prepared by Melanie Waite-Altringer Biology Faculty Member of Anoka-Ramsey Community College Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display. APR Enhanced Lecture Outlines

2. 2 Chapter 18 Water, Electrolyte, and Acid-Base Balance

3. 3 Introduction A.To be in balance, the quantities of fluids and electrolytes (molecules that release ions in water) leaving the body should be equal to the amounts taken in. B.Anything that alters the concentrations of electrolytes will also alter the concentration of water, and vice versa. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

4. 4 Distribution of Body Fluids A.Fluids occur in compartments in the body, and movement of water and electrolytes between compartments is regulated. B.Fluid Compartments 1.The average adult female is 52% water by weight, while a male is 63% water, the difference due to the female’s additional adipose tissue. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

5. 5 2.The intracellular fluid compartment includes all the water and electrolytes within cells. 3.The extracellular fluid compartment includes all water and electrolytes outside of cells (interstitial fluid, plasma, and lymph). Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

6. 6 4.Transcellular fluid includes the cerebrospinal fluid of the central nervous system, fluids within the eyeball, synovial fluid of the joints, serous fluid within body cavities, and exocrine gland secretions. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

7. 7 Fig18.01 Total body water Interstitial fluid Plasma Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Lymph Transcellular fluid Extracellular fluid (37%) Intracellular fluid (63%) Membranes of body cells

8. 8 C.Body Fluid Composition 1.Extracellular fluids have high concentrations of sodium, chloride, and bicarbonate ions, and lesser amounts of potassium, calcium, magnesium, phosphate, and sulfate ions. 2.Intracellular fluid has high concentrations of potassium, phosphate, and magnesium ions, and lesser amounts of sodium, chloride, and bicarbonate ions. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

9. 9 D.Movement of Fluid between Compartments 1.Hydrostatic pressure and osmotic pressure regulate the movement of water and electrolytes from one compartment to another. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

10. 10 2.Although the composition of body fluids varies from one compartment to another, the total solute concentrations and water amounts are normally equal. 3.A net gain or loss of water will cause shifts affecting both the intracellular and extracellular fluids due to osmosis. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

11. 11 Fig18.03 Interstitial fluid Intracellular fluid Capillary wall Serous membrane Transcellular fluid Lymph Plasma Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 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

12. 12 Water Balance A.Water balance exists when water intake equals water output. B.Water Intake 1.The volume of water gained each day varies from one individual to the next. 2.About 60% of daily water is gained from drinking, another 30% comes from moist foods, and 10% from the water of metabolism. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

13. 13 3.Regulation of Water Intake a.The thirst center in the hypothalamus is the primary regulator of water intake. b.The thirst mechanism derives from the osmotic pressure of extracellular fluids and a thirst center in the hypothalamus. c.Once water is taken in, the resulting distention of the stomach will inhibit the thirst mechanism. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

14. 14 D.Water Output 1.Water is lost in urine, feces, perspiration, evaporation from skin (insensible perspiration), and from the lungs during breathing. 2.The route of water loss depends on temperature, relative humidity, and physical exercise. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

15. 15 3.Regulation of Water Output a.The distal convoluted tubules of the nephrons and collecting ducts regulate water output. b.Antidiuretic hormone from the posterior pituitary causes a reduction in the amount of water lost in the urine. c.When drinking adequate water, the ADH mechanism is inhibited, and more water is expelled in urine. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

16. 16 Fig18.04 Average daily intake of water Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Average daily intake of water Water of metabolism (250 mL or 10%) Water in moist food (750 mL or 30%) Water in beverages (1,500 mL or 60%) Total intake (2,500 mL) Total output (2,500 mL) Water lost in sweat (150 mL or 6%) 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%) (a)(b)

17. 17 Electrolyte Balance A.An electrolyte balance exists when the quantities of electrolytes gained equals the amount lost. B.Electrolyte Intake 1.The electrolytes of greatest importance to cellular metabolism are sodium, potassium, calcium, magnesium, chloride, sulfate, phosphate, bicarbonate, and hydrogen ions. 2.Electrolytes may be obtained from food or drink or produced as a by-product of metabolism. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

18. 18 3.Regulation of Electrolyte Intake a.A person ordinarily obtains sufficient electrolytes from foods eaten. b.A salt craving may indicate an electrolyte deficiency. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

19. C.Electrolyte Output 1.Losses of electrolytes occur through sweating, in the feces, and in urine. 2.Regulation of Electrolyte Output a.The concentrations of sodium, potassium, and calcium, are very important. b.Sodium ions account for 90% of the positively charged ions in extracellular fluids; the action of aldosterone on the kidneys regulates sodium reabsorption. 19

20. 20 c.Aldosterone also regulates potassium ions; potassium ions are excreted when sodium ions are conserved. d.Calcium concentration is regulated by parathyroid hormone, which increases the concentrations of calcium and phosphate ions in extracellular fluids and by calcitonin which does basically the reverse. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

21. 21 e.Generally, the regulatory mechanisms that control positively charged ions (cations) secondarily control the concentrations of negatively charged ions (anions). Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

22. 22 Acid-Base Balance A.Electrolytes that ionize in water and release hydrogen ions are acids; those that combine with hydrogen ions are bases. B.Maintenance of homeostasis depends on the control of acids and bases in body fluids. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

23. 23 C.Sources of Hydrogen Ions 1.Most hydrogen ions originate as by- products of metabolic processes, including: the aerobic and anaerobic respiration of glucose, incomplete oxidation of fatty acids, oxidation of amino acids containing sulfur, and the breakdown of phosphoproteins and nucleic acids. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

24. 24 Fig18.06 H+H+ Internal environment 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 Phosphoric acid Sulfuric acid Acidic ketone bodies Lactic acid Carbonic acid

25. 25 D.Strengths of Acids and Bases 1.Acids that ionize more completely are strong acids; those that ionize less completely are weak acids. 2.Bases release hydroxyl and other ions, which can combine with hydrogen ions, thereby lowering their concentration. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

26. 26 E.Regulation of Hydrogen Ion Concentration 1.Acid-base buffer systems, the respiratory center in the brain stem, and the kidneys regulate pH of body fluids. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

27. 27 2.Acid-Base Buffer Systems a.The chemical components of a buffer system can combine with a strong acid and convert it to a weaker one. b.The chemical buffer systems in body fluids include the bicarbonate buffer system, the phosphate buffer system, and the protein buffer system. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

28. 28 3.Respiratory Excretion of Carbon Dioxide a.The respiratory center in the brain stem helps to regulate hydrogen ion concentration by controlling the rate and depth of breathing. b.During exercise, the carbon dioxide, and thus the carbonic acid, levels in the blood increase. c.In response, the respiratory center increases the rate and depth of breathing, so the lungs excrete more carbon dioxide. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

29. 29 Fig18.07 Rate and depth of breathing increase Respiratory center is stimulated Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 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 + More CO 2 is eliminated through lungs

30. 30 4.Renal Excretion of Hydrogen Ions a.Nephrons secrete excess hydrogen ions in the urine. 5.Time Course of Hydrogen Ion Regulation a.Chemical buffers are considered the body’s first line of defense against shifts in pH; physiological buffer systems (respiratory and renal mechanisms) function more slowly and constitute secondary defenses. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

31. 31 Acid-Base Imbalances A.Chemical and physiological buffer systems usually keep body fluids within very narrow pH ranges but abnormal conditions may prevent this. 1.A pH below 7.35 produces acidosis while a pH above 7.45 is called alkalosis. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

32. 32 B. Acidosis 1.Two major types of acidosis are respiratory and metabolic acidosis. a. Respiratory acidosis results from an increase of carbonic acid caused by respiratory center injury, air passage obstructions, or disease processes that decrease gas exchange. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

33. 33 b. Metabolic acidosis is due to either an accumulation of acids or a loss of bases, and has many causes including kidney disease, vomiting, diarrhea, and diabetes mellitus. c. Increasing respiratory rate or the amount of hydrogen ions released by the kidney can help compensate for acidosis. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

34. 34 Fig18.12 Accumulation of nonrespiratory acids Metabolic acidosis Excessive loss of bases 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 Prolonged diarrhea with loss of alkaline intestinal secretions Prolonged vomiting with loss of intestinal secretions

35. 35 C. Alkalosis 1.Alkalosis also has respiratory and metabolic causes. a.Respiratory alkalosis results from hyperventilation causing an excessive loss of carbon dioxide. b.Metabolic alkalosis is caused by a great loss of hydrogen ions or from a gain in bases perhaps from vomiting or use of drugs. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

36. 36 Fig18.13 Hyperventilation Respiratory alkalosis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Anxiety Fever Poisoning High altitude Excessive loss of CO 2 Decrease in concentration of H 2 CO 3 Decrease in concentration of H +