1. PowerPoint Presentation to accompany Hole’s Human Anatomy and Physiology, 9/e by Shier, Butler, and Lewis

2. Chapter 21 Water, Electrolyte, and Acid-Base Balance

3. Fluid Compartments Women’s bodies contain about 52% water. Men’s bodies contain about 63% Intracellular fluid compartment –water and electrolytes inside cells Extracellular fluid compartment –interstitial fluid: fluid within tissue spaces –transcellular fluid: cerebrospinal fluid, serous fluid, synovial fluid, aqueous and vitreous humors

4. Figure 21.1

5. Figure 21.2

6. Body Fluid Composition Extracellular fluids –high: sodium, chloride, bicarbonate ions –low: potassium, calcium, magnesium, phosphate, sulfate ions –blood plasma contains proteins Intracellular fluids –high: potassium, phosphate, magnesium and sulfate ions –low: sodium, chloride, and bicarbonate ions –greater concentration of protein than plasma

7. Figure 21.4

8. Movement of Fluids Fluid leaves plasma due to hydrostatic pressure and returns due to osmotic pressure. Hydrostatic pressure pushes lymph into lymphatic vessels, returning interstitial fluid to the plasma. Osmotic pressure regulates fluid movement in and out of cells. Sodium concentrations are important in fluid movement.

9. Figure 21.3

10. Water Intake Food and water intake Water of metabolism (nutrient oxidation) Regulation –thirst comes from osmotic pressure sensed by osmoreceptors in the thirst center in the hypothalamus –drinking and stomach distension inhibits thirst center

11. Figure 21.5

12. Water Output Loss of water –urine, feces, sweat, skin evaporation, loss from lungs during breathing Regulation –water loss can be reduced to maintain balance –Antidiuretic hormone increases the permeability of distal tubules and collecting ducts to conserve water –ADH is inhibited during excess water intake

13. Figure 21.6

14. Electrolyte Intake Electrolytes are obtained from food and beverages. Some are released during metabolic reactions. Regulation of intake usually accompanies responding to hunger and thirst. Electrolyte imbalances may result in salt craving.

15. Figure 21.7

16. Electrolyte Output Electrolyte loss –perspiration, urine, feces –quantities vary with temperature and exercise Regulation –concentrations of sodium, potassium, and calcium are important –aldosterone regulates sodium and potassium –calcitonin and parathyroid hormone regulates calcium

17. Figure 21.8

18. Figure 21.9

19. Acid-Base Balance Electrolytes that ionize and release hydrogen ions are acids Electrolytes that combine with hydrogen ions are bases Sources of hydrogen ions –anaerobic and aerobic respiration of glucose –incomplete oxidation of fatty acids –oxidation of sulfur-containing amino acids –hydrolysis of phosphoproteins and nucleic acids

20. Figure 21.10

21. Strengths of Acids and Bases Strong acids and bases ionize nearly completely. Weak acids and bases ionize less completely. Changes in body fluid pH can threaten the internal environment. Body fluid pH is regulated.

22. Acid-Base Buffer Systems Buffer systems are composed of two or more chemicals Stronger acids and bases are converted into weaker acids and bases Buffer systems minimize pH changes –bicarbonate buffer system –phosphate buffer system –protein buffer system

23. Figure 21.13

24. Bicarbonate Buffer System Present in intra- and extracellular fluid Bicarbonate ion acts as weak base, carbonic acid acts as a weak acid Bicarbonate ions combine with excess hydrogen ions to form carbonic acid Carbonic acid dissociates to release bicarbonate ions and hydrogen ions

25. Phosphate Buffer System Important in intracellular fluid and urine pH regulation Consists of two phosphate ions Monohydrogen phosphate ions act as a weak base and combine with hydrogen ions to form dihydrogen phosphate Dihydrogen phosphate dissociates to release hydrogen ions

26. Protein Buffer System Carboxyl and amine groups present on plasma and cellular proteins can ionize to release or combine with hydrogen ions and hydroxyl ions. Proteins include albumin, hemoglobin, and others. Hemoglobin buffering works with the bicarbonate buffer system.

27. Carbon Dioxide Excretion Increase in carbon dioxide or hydrogen ion concentration stimulates the respiratory center in the brain and increases rate and depth of breathing. Lung excrete carbon dioxide. Carbon dioxide and hydrogen ion concentrations decrease.

28. Figure 21.12

29. Renal Hydrogen Ion Excretion Nephrons secrete hydrogen ions into tubular fluid. Phosphates buffer hydrogen ions in urine. Ammonia produced by renal cells is a weak base that combines hydrogen ions to form ammonium ions. Ammonium ions transport hydrogen ions out of the body.