PowerPoint Lecture Outlines to accompany Hole’s Human Anatomy and Physiology Tenth Edition Shier  Butler  Lewis Chapter 21 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 21-1

Chapter 21 Water, Electrolyte, and Acid-Base Balance Of the 40 liters of water in the body of an average adult male, about two-thirds is intracellular, and one-third is extracellular 21-2

Fluid Compartments 21-3

Body Fluid Composition 21-4

Movement of Fluids Between Compartments Net movements of fluids between compartments result from differences in hydrostatic and osmotic pressures 21-5

Water Balance urine production is most important in the regulation of water balance 21-6

Regulation of Water Intake increase in osmotic pressure of extracellular fluid stimulates osmoreceptors in thirst center person feels thirsty drinking and distension of the stomach by water stimulate nerve impulses that inhibit thirst center water is absorbed osmotic pressure of extracellular fluid returns to normal 21-7

Regulation of Water Output Dehydration osmotic pressure increases in extracellular fluids osmoreceptors in hypothalamus stimulated hypothalamus signals posterior pituitary to release ADH urine output decreases Excess Water Intake osmotic pressure decreases in extracellular fluids osmoreceptors stimulated in hypothalamus hypothalamus signals posterior pituitary to decrease ADH output urine output increases 21-8

Electrolyte Balance 21-9

Potassium and Sodium Balance 21-10

Calcium Balance 21-11

Sources of Hydrogen Ions aerobic respiration of glucose produces carbonic acid anaerobic respiration of glucose produces lactic acid incomplete oxidation of fatty acids produces acidic ketone bodies oxidation of amino acids containing sulfur produces sulfuric acid breakdown of phosphoproteins and nucleic acids produces phosphoric acid some hydrogen ions are absorbed through digestive tract 21-12

Strengths of Acids and Bases Weak bases ionize less completely and release fewer OH - Strong bases ionize more completely and release more OH - Weak acids ionize less completely and release fewer H + Strong acids ionize more completely and release more H

Regulation of Hydrogen Ion Concentration acid-base buffer systems respiratory excretion of carbon dioxide renal excretion of hydrogen ions 21-14

Acid-Base Buffer Systems Bicarbonate 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 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

Acid-Base Buffer Systems Protein Buffer System NH3+ group releases hydrogen ions in the presence of excess base COO- group accepts hydrogen ions in the presence of excess acid 21-16

Respiratory Excretion of Carbon Dioxide 21-17

Renal Excretion of Hydrogen Ions 21-18

Summary of Acid-Base Balance 21-19

Clinical Application Acid-Base Imbalances If the pH of arterial blood drops to 6.8 or rises to 8.0 for more than a few hours, the person usually cannot survive factors that lead to respiratory acidosis acidosis versus alkalosis 21-20

Clinical Application Metabolic acidosis Respiratory alkalosisMetabolic alkalosis 21-21