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 Important Points in Chapter 21: Outcomes to be Assessed 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 Important Points in Chapter 21: Outcomes to be Assessed 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
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)
16 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 Dehydration headache weakness dry mouth & mucous membranes dizziness confusion nausea profuse sweating progressing muscle cramps to no sweating slurred speech increased temperature confusion loss of consciousness seizures in severe cases
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
24 21.2 Clinical Application Sodium and Potassium Imbalances Read through these imbalances carefully Pg. 820 12 e & pg. 811 13e Hyponatremia - PubMed Health
25 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
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: H 2 CO 3 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 + + HCO 3 - H 2 CO 3 H + + HCO 3 - 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 + + HPO 4 -2 H 2 PO 4 - H + + HPO 4 -2 Protein buffer system NH 3 + 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
Normal Arterial Blood Gas Values pH7.35-7.45 PaCO235-45 mm HgPa O2 80-95 mm Hg HCO3 22-26 mEq/LO2 Saturation95-99% 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/Inte r%20of%20Arterial%20Blood%20Gas.pdfhttp://orlandohealth.com/pdf%20folder/Inte r%20of%20Arterial%20Blood%20Gas.pdf ABG interpreter – calculator http://manuelsweb.com/abg.htm pH control and ABG’s (Arterial Blood Gases)
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 pCO 2 33 HCO 3 15 ABG interpreter - calculator.mht (Must allow blocked content for interpreter to work.)
pH control and ABG’s Practice Analyze the following: pH 7.35 pCO 2 49 HCO 3 28 ABG interpreter - calculator.mht
pH control and ABG’s Practice Analyze the following: pH 7.48 pCO 2 40 HCO 3 30 ABG interpreter - calculator.mht
pH control and ABG’s Practice Analyze the following: pH 7.30 pCO 2 49 HCO 3 28 ABG interpreter - calculator.mht