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Human Anatomy & Physiology Fluid, Electrolyte, and Acid-Base Balance

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Human Anatomy & Physiology Fluid, Electrolyte, and Acid-Base Balance 10/26/2014 PowerPoint® Lecture Slides Body Water Content prepared by Human Anatomy Barbara& Physiology Heard, Atlantic Cape Community • Infants: 73% or more water (low body fat, College Ninth Edition low bone mass) • Adult males: ~60% water C H A P T E R 26 • Adult females: ~50% water (higher fat content, less skeletal muscle mass) – Adipose tissue least hydrated of all Fluid, Electrolyte, • Water content declines to ~45% in old age and Acid-Base Balance © Annie Leibovitz/Contact Press Images © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. Figure 26.1 The major fluid compartments of the body. Fluid Compartments Total body water Volume = 40 L 60% of body weight Plasma • Total body water = 40 L of ECF 20% 3 L,= Volume • Two main fluid compartments – Intracellular fluid (ICF) compartment: 2/3 in Interstitial Intracellular fluid (ICF) cells Volume = 25 L fluid (IF) Volume = 12 L 40% of body weight – Extracellular fluid (ECF) compartment: 1/3 80% of ECF outside cells • Plasma: 3 L • Interstitial fluid (IF): 12 L in spaces between cells – Usually considered part of IF: lymph, CSF, humors of the eye, synovial fluid, serous fluid, and gastrointestinal Extracellular secretions fluid (ECF) Volume = 15 L 20% of body weight © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. Electrolyte Concentration Electrolyte Concentration • For single charged ions (e.g. Na+), 1 mEq = 1 mOsm • For bivalent ions (e.g. Ca2+), 1 mEq = 1/2 mOsm • 1 mEq of either provides same amount of charge © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. 1 10/26/2014 Extracellular and Intracellular Fluids Extracellular and Intracellular Fluids • Each fluid compartment has distinctive • ICF: pattern of electrolytes – Low Na+ and Cl– • ECF – Major cation: K+ 2– – All similar – Major anion HPO4 • Major cation: Na+ – More soluble proteins than in plasma • Major anion: Cl– – Except: higher protein, lower Cl– content of plasma © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. Figure 26.2 Electrolyte composition of blood plasma, interstitial fluid, and intracellular fluid. Figure 26.3 Exchange of gases, nutrients, water, and wastes between the three fluid compartments of the body. 160 Lungs Gastrointestinal Kidneys tract 140 120 Blood plasma Interstitial fluid 100 Blood O2 CO2 Nutrients H2O, H2O, Nitrogenous Intracellular fluid plasma Ions Ions wastes Na+ Sodium 80 K+ Potassium Ca2+ Calcium Mg2+ Magnesium O2 CO2 Nutrients H2O Ions Nitrogenous 60 Interstitial – Bicarbonate wastes HCO3 fluid Cl– Chloride 2– solute Total concentration (mEq/L) HPO4 Hydrogen 40 phosphate 2– SO4 Sulfate 20 Intracellular 0 fluid in tissue cells Na+ K+ Ca2+ Mg2+ HCO – Cl– HPO 2– SO 2– Protein © 2013 Pearson Education, Inc. 3 4 4 © 2013 Pearson Education, Inc. anions Water Balance and ECF Osmolality Figure 26.4 Major sources of water intake and output. • Water intake must = water output = ~ 2500 100 ml Feces 4% Metabolism 10% 250 ml Sweat 8% ml/day 200 ml Insensible loss • Water intake: beverages, food, and Foods 30% 750 ml 700 ml via skin and metabolic water lungs 28% • Water output: urine (60%), insensible 2500 ml water loss (lost through skin and lungs), Urine 60% perspiration, and feces Beverages 60% 1500 ml 1500 ml Average intake Average output © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. per day per day 2 10/26/2014 Figure 26.5 The thirst mechanism for regulating water intake. Maintenance of Body fluid Osmolality ECF osmolality Plasma volume (5 –10%) Blood pressure Osmoreceptors Saliva Granular cells • Osmolality maintained at ~ 280 – 300 in hypothalamus in kidney mOsm Renin-angiotensin- aldosterone Dry mouth mechanism • Rise in osmolality Angiotensin II – Stimulates thirst Hypothalamic – ADH release thirst center Sensation of thirst; person takes a • Decrease in osmolality drink Water moistens – Thirst inhibition mouth, throat; stretches stomach, – ADH inhibition intestine Water absorbed from GI tract Initial stimulus ECF osmolality Physiological response Plasma volume Result Increases, stimulates © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. Reduces, inhibits Regulation of Water Output: Influence of Figure 26.6 Mechanisms and consequences of ADH release. ECF osmolality Na+ concentration ADH in plasma Plasma volume Stimulates • Other factors may trigger ADH release (5–10%), BP Osmoreceptors Inhibits – Large changes in blood volume or pressure in hypothalamus Negative feedback inhibits • E.g., BP ADH release due to blood vessel Baroreceptors in atria and Stimulates baroreceptors and renin-angiotensin-aldosterone large vessels mechanism Stimulates Posterior pituitary • Factors lowering blood volume: intense sweating, Releases ADH Antidiuretic vomiting, or diarrhea; severe blood loss; traumatic hormone (ADH) burns; and prolonged fever Targets Collecting ducts of kidneys Effects Water reabsorption Results in ECF osmolality Scant urine Plasma volume © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. Disorders of Water Balance Disorders of Water Balance: Hypotonic Hydration • Principal abnormalities of water balance • Cellular overhydration, or water – Dehydration intoxication – Hypotonic hydration • Occurs with renal insufficiency or rapid – Edema excess water ingestion • ECF osmolality hyponatremia net osmosis into tissue cells swelling of cells severe metabolic disturbances (nausea, vomiting, muscular cramping, cerebral edema) possible death • Treated with hypertonic saline © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. 3 10/26/2014 Figure 26.7b Disturbances in water balance. Slide 1 Disorders of Water Balance: Edema • Atypical accumulation of IF tissue swelling Excessive 1 2 ECF osmotic 3 H2O moves (not cell swelling) H2O enters pressure falls into cells by the ECF osmosis; cells swell • Result of fluid out of blood or fluid into blood • fluid out of blood caused by – Increased capillary hydrostatic pressure or permeability • Capillary hydrostatic pressure increased by incompetent venous valves, localized blood vessel blockage, congestive heart failure, blood volume • Capillary permeability increased by ongoing inflammatory Consequences of hypotonic hydration (water gain). If more water than solutes is gained, cells swell. response © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. Edema Electrolyte Balance • fluid returning to blood result of • Electrolytes are salts, acids, bases, some – Imbalance in colloid osmotic pressures, e.g., proteins hypoproteinemia ( plasma protein levels • Electrolyte balance usually refers only to low colloid osmotic pressure) salt balance • Fluids fail to return at venous ends of capillary beds • Salts control fluid movements; provide • Results from protein malnutrition, liver disease, or minerals for excitability, secretory activity, glomerulonephritis membrane permeability • Salts enter body by ingestion and metabolism; lost via perspiration, feces, urine, vomit © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. Central Role of Sodium Table 26.2 Sodium Concentration and Sodium Content • Most abundant cation in ECF – Sodium salts in ECF contribute 280 mOsm of total 300 mOsm ECF solute concentration • Only cation exerting significant osmotic pressure – Controls ECF volume and water distribution – Changes in Na+ levels affects plasma volume, blood pressure, and ECF and IF volumes © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. 4 10/26/2014 Regulation of Sodium Balance: Aldosterone Aldosterone • Regardless of aldosterone presence • Aldosterone decreased urinary output; – 65% Na+ reabsorbed in proximal tubules; 25% increased blood volume reclaimed in nephron loops – By active reabsorption of remaining Na+ in – Na + never secreted into filtrate distal convoluted tubule and collecting duct • Water in filtrate follows Na+ if ADH is • Also causes increased K+ secretion present – Na+ in urine water loss © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. Regulation of Sodium Balance: Aldosterone Regulation of Sodium Balance: Aldosterone • Renin-angiotensin-aldosterone • Renin catalyzes production of mechanism main trigger for aldosterone angiotensin II release – Prompts aldosterone release from adrenal – Granular cells of JGC secrete renin in cortex response to – Na+ reabsorption by kidney tubules • Sympathetic nervous system stimulation • Aldosterone release also triggered by • filtrate NaCl concentration elevated K+ levels in ECF • stretch (due to blood pressure) of granular cells • Aldosterone brings about its effects slowly (hours to days) © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. Figure 26.8 Mechanisms and consequences of aldosterone release. Figure 26.9 Mechanisms and consequences of ANP release. + K+ concentration Body Na content Stretch of atria in the ECF triggers renin release, of heart due to BP increasing angiotensin II Releases Negative Atrial natriuretic peptide feedback (ANP) Stimulates Targets Adrenal cortex Releases JG complex Hypothalamus and Adrenal cortex of the kidney posterior pituitary Aldosterone Effects Effects Targets Renin release* ADH release Aldosterone release Kidney tubules Angiotensin II Inhibits Inhibits Collecting ducts Effects of kidneys Vasodilation Effects + + Na reabsorption K secretion Na+ and H2O reabsorption Results in Restores Blood volume Results in Homeostatic plasma levels of Na+ and K+ Blood pressure © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. 5 10/26/2014 Figure 26.10 Mechanisms regulating sodium and water
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