Presentation is loading. Please wait.

Presentation is loading. Please wait.

Chapter 27 Lecture Outline*

Similar presentations

Presentation on theme: "Chapter 27 Lecture Outline*"— Presentation transcript:

1 Chapter 27 Lecture Outline*
Rod R. Seeley Idaho State University Trent D. Stephens Idaho State University Philip Tate Phoenix College *See PowerPoint Image Slides for all figures and tables pre-inserted into PowerPoint without notes. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2 Water, Electrolytes, and
Chapter 27 Water, Electrolytes, and Acid-Base Balance

3 Body Fluids Intracellular fluid compartment
All fluids inside cells of body About 40% of total body weight Extracellular fluid compartment All fluids outside cells About 20% of total body weight Subcompartments Interstitial fluid and plasma; lymph, CSF, synovial fluid Primary intracellular ions, interstitial fluid ions, and plasma ions Intracellular cation = K+ Interstitial fluid cation = Na+ Plasma cation = Na+ Intracellular anion = Phosphate Interstitial fluid = Cl- Plasma anion = Cl-

4 Body Fluid Compartments

5 Regulation of Water Content
Sources of water Ingestion Cellular metabolism Routes of water loss Urine Evaporation Perspiration Respiratory passages Feces Content regulated so total volume of water in body remains constant Kidneys are primary regulators of water excretion Regulation processes Osmosis Osmolality Baroreceptors Learned behavior

6 Extracellular Fluid Osmolality
Measure of water vs. solute concentration; the higher the solute concentration, the higher the osmolality Adding or removing water from a solution changes osmolality Increased osmolality: triggers thirst and ADH secretion Decreased osmolality: inhibits thirst and ADH secretion

7 Hormonal Regulation of Blood Osmolality

8 Regulation of ECF Volume
ECF can increase or decrease even if osmolality of extracellular fluid is maintained Carotid sinus and aortic arch baroreceptors monitor blood pressure, juxtaglomerular apparatuses monitor pressure changes, receptors in walls of atria and large vessels respond to small changes in BP These receptors activate these mechanisms Neural: increase in BP recognized by baroreceptors. Decreased sympathetic stimulation of afferent arteriole leads to increased pressure in glomerulus leading to increased filtration and increased urine output. Renin-angiotensin-aldosterone Atrial natriuretic hormone (ANH) Antidiuretic hormone (ADH)

9 Increase in Blood Volume

10 Decrease in Blood Volume

11 Regulation of ECF Volume

12 Regulation of Electrolytes in ECF
Regulation of Na+ ions Kidneys major route of excretion Small quantities lost in sweat {sweat = (in decreasing amounts) water, Na+, urea, Cl-K+, NH3}. Insensible perspiration is water evaporating from skin. Sensible perspiration is secreted by the sweat glands. Contains solutes Terms Hypernatremia: elevated plasma Na+ Hyponatremia: decreased Na+ Electrolytes Molecules or ions with an electrical charge Ingestion adds electrolytes to body Kidneys, liver, skin, lungs remove from body Concentration changes only when growing, gaining or losing weight Na+ Ions Dominant ECF cations Responsible for 90-95% of osmotic pressure

13 Regulation of ICF and ECF




17 Regulation of Chloride, Potassium, Magnesium Ions
Potassium ions Maintained in narrow range Affect resting membrane potentials Aldosterone increases amount secreted Terms Hyperkalemia: abnormally high levels of potassium in extracellular fluid Hypokalemia: abnormally low levels of potassium in extracellular fluid. Chloride ions Predominant anions in ECF Magnesium ions Capacity of kidney to reabsorb is limited Excess lost in urine Decreased extracellular magnesium results in greater degree of reabsorption

18 Potassium Ion Regulation in ECF


20 Regulation of Calcium Ions
PTH increases Ca2+ extracellular levels and decreases extracellular phosphate levels Vitamin D stimulates Ca2+ uptake in intestines Calcitonin decreases extracellular Ca2+ levels Regulated within narrow range Elevated extracellular levels prevent membrane depolarization Decreased levels lead to spontaneous action potential generation Terms Hypocalcemia Hypercalcemia

21 Regulation of Calcium Ions


23 Regulation of Blood Magnesium


25 Regulation of Phosphate Ions
Under normal conditions, reabsorption of phosphate occurs at maximum rate in the nephron An increase in plasma phosphate increases amount of phosphate in nephron beyond that which can be reabsorbed; excess is lost in urine Hypophosphatemia: reduced absorption from intestine due to vitamin D deficiency or alcohol abuse. Hyperphosphatemia: renal failure, chemotherapy, hyperparathyroidism (secondary to elevated plasma calcium levels)

26 Regulation of Blood Phosphate


28 Acids and Bases and Buffers
Buffers: Resist changes in pH When H+ added, buffer removes it When H+ removed, buffer replaces it Types of buffer systems Carbonic acid/bicarbonate Protein Phosphate Acids Release H+ into solution Bases Remove H+ from solution Acids and bases Grouped as strong or weak

29 Comparison of Strong and Weak Acids

30 Regulation of Acid/Base Balance
Buffers: if pH rises, buffers bind H+; if pH falls, buffers release H+ Protein buffer: Intracellular and plasma proteins absorb H+. Provide ¾ of buffering in body. E.g., hemoglobin. Bicarbonate buffering system: Important in plasma Phosphate buffer system: important as an intracellular buffer Respiratory center: if pH rises, respiratory rate decreases; if pH falls, respiratory rate increases Kidneys: if pH rises, distal tubule decreases H+ secretion into the urine and decreases HCO3- absorption into the blood (more H2CO3 will dissociate into H+ and HCO3-); if pH falls, distal tubule increases H+ secretion into the urine and increases HCO3- absorption into the blood


32 Increase in Blood pH

33 Decrease in Blood pH

34 Respiratory Regulation of Acid-Base Balance
Achieved through carbonic acid/bicarbonate buffer system As carbon dioxide levels increase, pH decreases As carbon dioxide levels decrease, pH increases Carbon dioxide levels and pH affect respiratory centers Hypoventilation increases blood carbon dioxide levels Hyperventilation decreases blood carbon dioxide levels

35 Respiratory Regulation of Acid-Base Balance

36 Renal Regulation of Acid-Base Balance
Secretion of H+ into filtrate and reabsorption of HCO3- into ECF cause extracellular pH to increase HCO3- in filtrate reabsorbed Rate of H+ secretion increases as body fluid pH decreases or as aldosterone levels increase Secretion of H+ inhibited when urine pH falls below 4.5

37 Kidney Regulation of Acid-Base Balance

38 Hydrogen Ion Buffering

39 Acidosis and Alkalosis
Acidosis: pH body fluids below 7.35 Respiratory: Caused by inadequate ventilation- reduced elimination of CO2, asthma, damage to respiratory center in brain, emphysema. Metabolic: Results from all conditions other than respiratory that decrease pH- diarrhea, vomiting, ingesting overdose of aspirin, untreated diabetes mellitus, anaerobic respiration Alkalosis: pH body fluids above 7.45 Respiratory: Caused by hyperventilation, high altitude (reduced partial pressure of O2 Metabolic: Results from all conditions other than respiratory that increase pH- severe vomiting, too much aldosterone, ingestion of substances like bicarbonate of soda. Compensatory mechanisms


Download ppt "Chapter 27 Lecture Outline*"

Similar presentations

Ads by Google