Daudi Langat, PhD Adjunct Professor, Kaplan University Online HS130 Unit 8 Seminar Fluid and Electrolyte Balance (Chapter 18), Acid-Base Balance (Chapter 19) Daudi Langat, PhD Adjunct Professor, Kaplan University Online Hi Class! Welcome to our eight Seminar! We will begin at the top of the hour. See you then! Seminar Topic: This week, we will discuss concepts from Chapters 18 and 19 – Fluid and Electrolyte Balance and Acid – Base Balance. We will also cover the instructions for the Unit 9 written assignment. Don’t forget to contact your instructor with any questions you have regarding this assignment.

BODY FLUIDS Water is most abundant body compound References to “average” body water volume based on a healthy, non-obese, 70-kg male Water is 60% of body weight in males; 50% in females (Table 18-1) Volume averages 40 L in a 70-kg male (Figure 18-1) Variation in total body water is related to: Total body weight of individual Fat content of body —the more fat the less water (adipose tissue is low in water content) Gender —female body has about 10% less water than male body (Figure 18-2) Age —in a newborn infant, water may account for 80% of total body weight. In the elderly, water per pound of weight decreases (muscle tissue—high in water—replaced by fat, which is lower in water)

BODY FLUID COMPARTMENTS Two major fluid compartments (Table 18-1) Extracellular fluid (ECF) Types: Plasma Interstitial fluid (IF) Miscellaneous—lymph; joint fluids; cerebrospinal fluid; eye humors Called internal environment of body Surrounds cells and transports substances to and from them Intracellular fluid (ICF) Largest fluid compartment Located inside cells Serves as solvent to facilitate intracellular chemical reactions

Fluid compartments

MECHANISMS THAT MAINTAIN FLUID BALANCE Fluid output, mainly urine volume, adjusts to fluid intake; antidiuretic hormone (ADH) from posterior pituitary gland acts to increase kidney tubule reabsorption of sodium and water from tubular urine into blood, thereby tending to increase ECF (and total body fluid) by decreasing urine volume (Figure 18-6) ECF electrolyte concentration (mainly Na+ concentration) influences ECF volume; an increase in ECF Na+ tends to increase ECF volume by increasing movement of water out of ICF and by increasing ADH secretion, which decreases urine volume, and this, in turn, increases ECF volume

MECHANISMS THAT MAINTAIN FLUID BALANCE Capillary blood pressure pushes water out of blood, into IF; blood protein concentration pulls water into blood from IF; hence, these two forces regulate plasma and IF volume under usual conditions Importance of electrolytes in body fluids Nonelectrolytes —organic substances that do not break up or dissociate when placed in water solution (e.g., glucose) Electrolytes —compounds that break up or dissociate in water solution into separate particles called ions (e.g., ordinary table salt or sodium chloride) Ions —the dissociated particles of an electrolyte that carry an electrical charge (e.g., sodium ion [Na+]) Positively charged ions (e.g., potassium [K+] and sodium [Na+]) Negatively charged particles (ions) (e.g., chloride [Cl] and bicarbonate [HCO3])

MECHANISMS THAT MAINTAIN FLUID BALANCE Importance of electrolytes in body fluids (cont.) Electrolyte composition of blood plasma—Table 18-3 Sodium —most abundant and important positively charged ion of plasma Normal plasma level—142 mEq/L Average daily intake (diet)—100 mEq Chief method of regulation—kidney Aldosterone increases Na+ reabsorption in kidney tubules (Figure 18-6) Sodium-containing internal secretions (Figure 18-7) Capillary blood pressure and blood proteins

FLUID IMBALANCES Dehydration —total volume of body fluids less than normal; IF volume shrinks first, and then if treatment is not given, ICF volume and plasma volume decrease; dehydration occurs when fluid output exceeds intake for an extended period Overhydration —total volume of body fluids greater than normal; overhydration occurs when fluid intake exceeds output; various factors may cause this (e.g., giving excessive amounts of intravenous fluids or giving them too rapidly may increase intake above output)

Fluid Disturbances Dehydration Overhydration Edema

pH OF BODY FLUIDS Definition of pH: It is a measure of the hydrogen ion concentration in the blood. The number indicates the hydrogen ion (H+) concentration of a fluid; pH 7.0 indicates neutrality, pH higher than 7.0 indicates alkalinity, and pH less than 7.0 indicates acidity. pH = -Log10[H+], i.e. pH 7.0 means hydrogen ion concentration is 0.0000001 moles per liter, or 1 x 10-7 moles per liter. Normal arterial blood pH—about 7.45 Normal venous blood pH—about 7.35 What is the reason for the difference?

-Log10[10-0] = - [-0] = 0 -Log10[10-2] = - [-2] = 2 -Log10[10-7] = - [-7] = 7 This means water has a hydrogen ion concentration of 1 x 10-7 mol/lit, or 0.0000001 mol/lit -Log10[10-14] = - [-14] = 14

Mechanisms that control pH of body fluids Buffers Definition —substances that prevent a sharp change in the pH of a fluid when an acid or base is added to it. NaHCO3 – H2CO3 buffer pair This is what happens when you add a strong acid to a bicarbonate-carbonic acid buffer pair

This is what happens when you add a strong base to a bicarbonate-carbonic acid buffer pair

MECHANISMS THAT CONTROL pH of BODY FLUIDS Respiratory mechanism of pH control —respirations remove some CO2 from blood as blood flows through lung capillaries, the amount of H2CO3 in blood is decreased and thereby its H+ concentration is decreased, and this in turn increases blood pH from its venous to its arterial level Urinary mechanism of pH control —being the body’s most effective regulator of blood pH, kidneys usually acidify urine by the distal tubules secreting hydrogen ions and ammonia (NH3) into the urine from blood in exchange for NaHCO3 being reabsorbed into the blood

pH IMBALANCES Acidosis and alkalosis: pH or acid-base imbalances Metabolic disturbances Metabolic acidosis—bicarbonate (NaHCO3) deficit Metabolic alkalosis—bicarbonate (NaHCO3) excess; complication of severe vomiting Respiratory disturbances Respiratory acidosis (H2CO3 excess) Respiratory alkalosis (H2CO3 deficit) In uncompensated metabolic acidosis, the normal ratio of NaHCO3 to H2CO3 is changed; in compensated metabolic acidosis, the ratio remains close to 20:1, but the total amount of NaHCO3 and H2CO3 changes Cardiac arrest and respiratory acidosis

END OF UNIT 8 SEMINAR Questions?? Ask ME (in Instructor Questions or E-mail) or ask your classmates!! Goodnight everyone!!!