Anatomy Physiology SIXTH EDITION Chapter 27 part 1

Anatomy & Physiology SIXTH EDITION Chapter 27, part 1 Fluid, Electrolyte, and Acid-Base Balance Power. Point® Lecture Slide Presentation prepared by Dr. Kathleen A. Ireland, Biology Instructor, Seabury Hall, Maui, Hawaii Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Frederic H. Martini Fundamentals of

Learning Objectives • Explain what is meant by “fluid balance, ” “electrolyte balance, ” and “acid-base balance” • Compare the compositions of intracellular and extracellular fluids • Identify the hormones that play important roles in regulating fluid and electrolyte balance • Describe the movement of fluid that takes place within the ECF, between the ECF and the ICF, and between the ECF and the environment Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Learning Objectives • Discuss how sodium, potassium, calcium and chloride ions are regulated to maintain electrolyte balance • Explain the buffering systems that balance the p. H of the intracellular and extracellular fluids • Describe the compensatory mechanisms involved in acid-base balance Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

SECTION 27 -1 Fluid, Electrolyte and Acid-base Balance: An Overview Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Maintenance of normal fluid volume and composition is vital • Extracellular fluid (ECF) • Interstitial fluid, plasma, and other body fluids • Intracellular fluid (ICF) • The cytosol Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Fluid and electrolyte balance • Fluid balance • The amount of water gained each day equals the amount lost • Electrolyte balance • The ion gain each day equals the ion loss • Acid-base balance • H+ gain is offset by their loss Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

SECTION 27 -2 An Introduction to Fluid and Electrolyte Balance Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

The ECF and the ICF are two distinct fluid compartment • ICF • The cytosol of cells • Makes up about two-thirds of the total body water • ECF • Major components include the interstitial fluid and plasma • Minor components include all other extracellular fluids Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Figure 27. 1 The Composition of the Human Body Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 27. 1 a

Regulation of fluids and electrolytes • Homeostatic mechanisms respond to changes in ECF • No receptors directly monitor fluid or electrolyte balance • Respond to changes in plasma volume or osmotic concentrations • All water moves passively in response to osmotic gradients • Body content of water or electrolytes rises if intake exceeds outflow Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Figure 27. 2 Cations and Anions in Body Fluids Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 27. 2

Primary regulatory hormones • Antidiuretic hormone (ADH) • Stimulates water conservation and the thirst center • Aldosterone • Controls Na+ absorption and K+ loss along the DCT • Natriuretic peptides (ANP and BNP) • Reduce thirst and block the release of ADH and aldosterone Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Interplay between fluid balance and electrolyte balance • Different mechanisms regulate fluid and electrolyte balance • This distinction is vital in the clinical setting Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

SECTION 27 -3 Fluid Balance Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Fluid movement within the ECF • Fluid moves freely within ECF compartment • Water losses are normally balanced by gains • Eating • Drinking • Metabolic generation Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Figure 27. 3 Fluid Exchanges Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 27. 3

Fluid exchange with the environment • The major routes of fluid exchange with the environment include: • Water loss • Temperature rise from fever • Water gains Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Water excess and depletion • Hyponatremia • Na+ concentration in the ECF is reduced (overhydration) • Hypernatremia • Na+ in the ECF is abnormally high • Dehydration • Develops when water loss outpaces water gains Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Fluid shifts • Water movement between ECF and ICF • If ECF becomes hypertonic relative to ICF, water moves from ICF to ECF • If ECF becomes hypotonic relative to ICF, mater moves from ECF into cells PLAY Animation: Introduction to Body Fluids Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

SECTION 27 -4 Electrolyte Balance Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Problems with Electrolyte Balance • Usually result from sodium ion imbalances • Potassium imbalances are less common, but more dangerous Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Sodium balance • Rate of sodium uptake across digestive tract directly proportional to dietary intake • Sodium losses occur through urine and perspiration • Shifts in sodium balance result in expansion or contraction of ECF • Large variations corrected by homeostatic mechanisms • Too low, ADH / aldosterone secreted • Too high, ANP secreted Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Figure 27. 4 The Homeostatic Regulation of Normal Sodium Ion Concentrations in Body Fluids Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 27. 4

Figure 27. 5 The Integration of Fluid Volume Regulation and Sodium Ion Concentrations in Body Fluids Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 27. 5

Potassium balance • Potassium ion concentrations in ECF are low • Not as closely regulated as sodium • Potassium ion excretion increases as • ECF concentrations rise • Aldosterone secreted • p. H rises • Potassium retention occurs when p. H falls Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

ECF Concentrations of other electrolytes • Calcium balance • Bone reserves, absorption in the digestive tract, and loss at kidneys • Magnesium balance • Absorbed by the PCT to keep pace with urinary losses Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

ECF Concentrations of other electrolytes • Phosphate balance • Absorbed by the PCT in response to calcitriol • Chloride balance • Absorbed at digestive tract to balance losses in urine and sweat PLAY Animation: Electrolyte homeostasis Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings