Chapter 21 Bio 202 Anatomy & Physiology Part 2 Tim Pimperl A & P Instructor Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction

Chapter 21

Bio 202

Anatomy & Physiology Part 2

Tim Pimperl

A & P Instructor

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2

Important Points in Chapter 21:Outcomes to be Assessed

21.1: Introduction

Explain the balance concept.

Explain the importance of water and electrolyte balance.

21.2: Distribution of Body Fluids

Describe how body fluids are distributed in compartments.

Explain how fluid composition varies among compartments and how fluids move from one compartment to another.

21.3: Water Balance

List the routes by which water enters and leaves the body.

Explain the regulation of water input and water output.

3


21.4: Electrolyte Balance

List the routes by which electrolytes enter and leave the body.

Explain the regulation of the input and the output of electrolytes.

21.5: Acid-Base Balance

Explain acid-base balance.

Identify how pH number describes the acidity and alkalinity of a body fluid.

List the major sources of hydrogen ions in the body.

Distinguish between strong acids and weak acids.

Explain how chemical buffer systems, the respiratory center, and the kidneys keep the pH of body fluids relatively constant.

4


21.6: Acid-Base Imbalances

Describe the causes and consequences of increase or decrease in body fluid pH.

5

21.1: Introduction

• The term balance suggests a state of constancy• For water and electrolytes that means equal amounts enter and leave the body• Mechanisms that replace lost water and electrolytes and excrete excesses maintain this balance• This results in stability of the body at all times• Keep in mind water and electrolyte balance are interdependent.

6

21.2: Distribution of Body Fluids

• Body fluids are not uniformly distributed• They occupy compartments of different volumes that contain varying compositions• Water and electrolyte movement between these compartments is regulated to stabilize their distribution and the composition of body fluids

7

Fluid Compartments• An average adult female is about 52% water by

weight, and an average male about 63% water by weight

• There are about 40 liters of water (with its dissolved electrolytes) in the body, distributed into two major compartments:• Intracellular fluid – 63% - fluid inside cells• Extracellular fluid – 37% - fluid outside

cells• Interstitial fluid• Blood plasma• Lymph• Transcellular fluid – separated from

other extracellular fluids by epithelial layers

• Cerebrospinal fluid• Aqueous and vitreous humors• Synovial fluid• Serous fluid

Extracellularfluid(37%)

Intracellularfluid(63%)

40

3836

34

323028262422

201816

14121086420

Lit

ers


Total Body Water40 liters (10.6 gallons)

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63% Intracellular Fluid d37% Extracellular FluidInterstitial Fluid

PlasmaLymph

Transcellular Fluid

Female – 52%Male – 63%

9

Total body water

Interstitial fluidPlasma

Lymph

Transcellular fluid

Extracellular fluid(37%)

Membranes ofbody cells

Intracellular fluid(63%)


Transcellular:CSF, aqueous & vitreoushumors, joints, body cavitiesexocrine gland secretions etc.

10

Body Fluid Composition

• Extracellular fluids are generally similar in composition including high concentrations of sodium, calcium, chloride and bicarbonate ions

• Blood plasma has more proteins than interstitial fluid or lymph

• Intracellular fluids have high concentrations of potassium, magnesium, phosphate, and sulfate ions

Ion

co

nce

ntr

ati

on

(m

Eq

/L)

20

30

50

60

70

80

90

100

110

120

130

140

Relative concentrations and ratios of ions in extracellular and intracellular fluids

150

40

10

0

14:1Ratio(Extracellular: intracellular)

Na+

1:28K+

5:1Ca+2

1:19Mg+2

26:1Cl

3:1HCO3

1:19PO4

3

1:2SO4

2

Extracellular fluid

Intracellular fluid


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Movement of Fluid Between Compartments

• Two major factors regulate the movement of water and electrolytes from one fluid compartment to another

• Hydrostatic pressure• Osmotic pressure

Interstitial fluid

Capillary wall

Transcellularfluid

Lymph

Plasma

Serousmembrane

Intracellularfluid

Cellmembrane

Lymphvessel

Fluid leaves plasmaat arteriolar end ofcapillaries becauseoutward force ofhydrostatic pressurepredominates

Fluid returns toplasma at venularends of capillariesbecause inward forceof colloid osmoticpressure predominates

Hydrostatic pressurewithin interstitialspaces forces fluidinto lymph capillaries

Interstitial fluid isin equilibrium withtranscellular andintracellular fluids


12

21.3: Water Balance

• Water balance exists when water intake equals water output• Homeostasis requires control of both water intake and water output

13

Water Intake• The volume of water gained each day varies among individuals averaging about 2,500 milliliters daily for an adult:

• 60% from drinking• 30% from moist foods• 10% as a bi-product ofoxidative metabolism ofnutrients called water ofmetabolism

Water inbeverages(1,500 mL or 60%)

Average daily intake of waterWater lost in sweat(150 mL or 6%)

Total output(2,500 mL)

Average daily output of water

(a) (b)

Total intake(2,500 mL)

Water inmoist food(750 mL or 30%)

Water ofmetobolism(250 mL or 10%)

Water lost in feces(150 mL or 6%)Water lost throughskin and lungs(700 mL or 28%)

Water lost in urine(1,500 mL or 60%)


14

Regulation of Water Intake

The primary regulator of water intake is thirst.

15

Water Output

• Water normally enters the body only through the mouth, but it can be lost by a variety of routes including:

• Urine (60% loss)• Feces (6% loss)• Sweat (sensible perspiration) (6% loss)• Evaporation from the skin (insensible perspiration)• The lungs during breathing(Evaporation from the skin and the lungs is a 28% loss)

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Regulation of Water Output

The osmoreceptor-ADH mechanism in the hypothalamus regulates the concentration of urine produced in the kidney.

17

21.1 Clinical Application

Water Balance Disorders

(Read all of this Clin. App. Carefully pg. 816 12e & 808-809 13e)

Water intox./hyponatremia Dehydrationheadacheweakness dry mouth & mucous membranesdizziness confusionnausea profuse sweating progressingmuscle cramps to no sweatingslurred speech increased temperatureconfusion loss of consciousness seizures in severe cases

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21.4: Electrolyte Balance• An electrolyte balance exists when the quantities of electrolytes the body gains equals those lost

Foods Fluids Metabolicreactions

Electrolyte intake

Electrolyte output

UrinePerspiration Feces


19

Electrolyte Intake• The electrolytes of greatest importance to cellular functions release sodium, potassium, calcium, magnesium, chloride, sulfate, phosphate, bicarbonate, and hydrogen ions• These ions are primarily obtained from foods, but some are from water and other beverages, and some are by-products of metabolism

20

Regulation of Electrolyte Intake

• Ordinarily, a person obtains sufficient electrolytes by responding to hunger and thirst• A severe electrolyte deficiency may cause salt craving

21

Electrolyte Output

• The body loses some electrolytes by perspiring (more on warmer days and during strenuous exercise)• Some are lost in the feces• The greatest output is as a result of kidney function and urine output

Regulation of Electrolyte Output

• The concentrations of positively charged ions, such as sodium (Na+), potassium (K+) and calcium (Ca+2) are of particular importance

• These ions are vital for nerve impulse conduction, muscle fiber contraction, and maintenance of cell membrane permeability

• Sodium ions account for nearly 90% of the positively charged ions in extracellular fluids

22

Regulation of Electrolyte Output

23


Potassium ionconcentration increases

Adrenal cortex is signaled

Aldosterone is secreted

Renal tubulesincrease reabsorption ofsodium ions and increasesecretion of potassium ions

Sodium ions areconserved and potassiumions are excreted

Calcium ionConcentration decreases

Parathyroid glandsare stimulated

Parathyroid hormoneis secreted

Intestinal absorptionof calcium increases

Renal tubules conservecalcium and increasesecretion of phosphate

Calcium ion concentrationreturns toward normal

Normal phosphateconcentration is maintained

Activity of bone-resorbingosteoclasts increases

Increased phosphateexcretion in urine

Addition of phosphateto bloodstream

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21.2 Clinical Application

Sodium and Potassium Imbalances

Read through these imbalances carefully

Pg. 820 12 e & pg. 811 13e

Hyponatremia - PubMed Health

http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001431/




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21.5: Acid-Base Balance• Acids are electrolytes that ionize in water and release hydrogen ions• Bases are substances that combine with hydrogen ions • Acid-base balance entails regulation of the hydrogen ion concentrations of body fluids• This is important because slight changes in hydrogen ion concentrations can alter the rates of enzyme-controlled metabolic reactions, shift the distribution of other ions, or modify hormone actions• pH number indicates the degree to which a solution is acidic or basic (alkaline). • The more acid the solution, the lower its pH• The more alkaline the solution, the higher its pH

26

Sources of Hydrogen Ions


H+

Hydrolysis ofphosphoproteinsand nucleic acids

Internal environment

Oxidation ofsulfur-containingamino acids

Incompleteoxidation offatty acids

Anaerobicrespirationof glucose

Aerobicrespirationof glucose

Phosphoricacid

Sulfuricacid

Acidic ketonebodies

Carbonicacid

Lacticacid

27

Strengths of Acids and Bases

• Acids:• Strong acids ionize more completely and release more H+

• Ex: HCl• Weak acids ionize less completely and release fewer H+

• Ex: H2CO3

• Bases:• Strong bases ionize more completely and release more OH-

or other negative ions• Weak bases ionize less completely and release fewer OH-

or other negative ions

28

Regulation of Hydrogen Ion Concentration

• Either an acid shift or an alkaline (basic) shift in the body fluids could threaten the internal environment• Normal metabolic reactions generally produce more acid than base• The reactions include cellular metabolism of glucose, fatty acids, and amino acids• Maintenance of acid-base balance usually eliminates acids in one of three ways:

• Acid-base buffer systems• Respiratory excretion of carbon dioxide• Renal excretion of hydrogen ions

29

Chemical buffer systems are in all body fluids and are based on chemicals that combine with excess acids or bases. •Bicarbonate buffer system

• The bicarbonate ion converts a strong acid to a weak acid• Carbonic acid converts a strong base to a weak base H+ + HCO3

- H2CO3 H+ + HCO3-

• Phosphate buffer 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+ + HPO4

-2 H2PO4- H+ + HPO4

-2

• Protein buffer system• NH3

+ group releases a hydrogen ion in the presence of excess base• COO- group accepts a hydrogen ion in the presence of excess acid

Chemical Buffer Systems

30

31

• The respiratory center in the brainstem helps regulate hydrogen ion concentrations in the body fluids by controlling the rate and depth of breathing• If body cells increase their production of CO2…

Respiratory Excretion of Carbon Dioxide

Cells increase production of CO2

CO2 reacts with H2O to produce H2CO3

H2CO3 releases H+

Respiratory center is stimulated

Rate and depth of breathing increase

More CO2 is eliminated through lungs


Respiratory System

32

33

• Nephrons help regulate the hydrogen ion concentration of body fluids by excreting hydrogen ions in the urine

Renal Excretion of Hydrogen Ions


High intake of proteins

Increased metabolismof amino acids

Increased formationof sulfuric acid andphosphoric acid

Increased concentrationof H+ in body fluids

Increased secretionof H+ into fluid ofrenal tubules

Concentration of H+

in body fluids returnstoward normal

Increased concentrationof H+ in urine

Urinary System

34

35

• Various regulators of hydrogen ion concentration operate at different rates• Acid-base (chemical) buffers function rapidly• Respiratory and renal (physiological buffers) mechanisms function more slowly(Resp.-takes several minutes.Renal- up to 1 to 3 days.)

Phosphatebuffer system

Proteinbuffer system

First line of defenseagainst pH shift

Second line ofdefense againstpH shift

Chemicalbuffer system

Physiologicalbuffers

Bicarbonatebuffer system

Respiratorymechanism(CO2 excretion)

Renalmechanism(H+ excretion)


Time Course of pH Regulation

36

• Various regulators of hydrogen ion concentration operate at different rates• Acid-base (chemical) buffers function rapidly• Respiratory and renal (physiological buffers) mechanisms function more slowly(Resp.-takes several minutes.Renal- up to 1 to 3 days.)

Phosphatebuffer system

Proteinbuffer system

First line of defenseagainst pH shift

Second line ofdefense againstpH shift

Chemicalbuffer system

Physiologicalbuffers

Bicarbonatebuffer system

Respiratorymechanism(CO2 excretion)

Renalmechanism(H+ excretion)


Time Course of pH Regulation

37

21.6: Acid-Base Imbalances

• Chemical and physiological buffer systems ordinarily maintain the hydrogen ion concentration of body fluids within very narrow pH ranges• Abnormal conditions may disturb the acid-base balance


Acidosis Alkalosis

pH scale

6.8 7.0 8.07.87.35 7.45

Normal pH range

Survival range

38

Acidosis

• Acidosis results from the accumulation of acids or loss of bases, both of which cause abnormal increases in the hydrogen ion concentrations of body fluids• Alkalosis results from a loss of acids or an accumulation of bases accompanied by a decrease in hydrogen ion concentrations


Loss ofbases

Accumulationof acids

Acidosis

Increased concentration of H+

pH scale

pH drops

pH rises Alkalosis

Decreased concentration of H+

Accumulationof bases

Loss ofacids

7.4

39

• Two major types of acidosis are respiratory acidosis and metabolic acidosis

Acidosis


Decreasedgas exchange

Decreased rateand depth ofbreathing

Obstruction ofair passages

Accumulation of CO2

Respiratoryacidosis

Excessive production of acidicketones as in diabetes mellitus

Kidney failureto excrete acids

Accumulation of nonrespiratory acids

Metabolic acidosis

Excessive loss of bases

Prolonged diarrheawith loss of alkalineintestinal secretions

Prolonged vomitingwith loss of intestinalsecretions


40

Alkalosis• Respiratory alkalosis develops as a result of hyperventilation• Metabolic alkalosis results from a great loss of hydrogen ions or from a gain in bases, both accompanied by a rise in the pH of blood


• Anxiety

• Fever

• Poisoning

• High altitude

Hyperventilation

Excessive loss of CO2

Decrease in concentration of H2CO3

Decrease in concentration of H+

Respiratory alkalosis

Gastricdrainage

Vomiting with lossof gastric secretions

Loss of acids

Net increase in alkaline substances

Metabolic alkalosis

• Normal Arterial Blood Gas Values

• pH 7.35-7.45

• PaCO2 35-45 mm HgPa

• O2 80-95 mm Hg

• HCO3 22-26 mEq/LO2

• Saturation 95-99%

• BE +/- 1

Four-Step Guide to ABG Analysis

• Is the pH normal, acidotic or alkalotic? • Are the pCO2 or HCO3 abnormal? Which

one appears to influence the pH? • If both the pCO2 and HCO3 are abnormal,

the one which deviates most from the norm is most likely causing an abnormal pH.

• Check the pO2. Is the patient hypoxic? \• manuelsweb.com

• http://orlandohealth.com/pdf%20folder/Inter%20of%20Arterial%20Blood%20Gas.pdf

• ABG interpreter – calculator

• http://manuelsweb.com/abg.htm

pH control and ABG’s (Arterial Blood Gases)

http://orlandohealth.com/pdf%20folder/Inter%20of%20Arterial%20Blood%20Gas.pdf

http://orlandohealth.com/pdf%20folder/Inter%20of%20Arterial%20Blood%20Gas.pdf

http://manuelsweb.com/abg.htm

• Interp. of Arterial Blood Gases.pdf

• ABG interpreter - calculator.mht

pH control and ABG’s (Arterial Blood Gases)

pH control and ABG’s Practice

• Analyze the following:

• pH 7.35

• pCO2 33

• HCO3 15

• ABG interpreter - calculator.mht• (Must allow blocked content for interpreter to work.)



• pH 7.35

• pCO2 49

• HCO3 28




• pH 7.48

• pCO2 40

• HCO3 30




• pH 7.30

• pCO2 49

• HCO3 28


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Chapter 21 Bio 202 Anatomy & Physiology Part 2 Tim Pimperl A & P Instructor Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction