Ch 25 Fluid, Electrolyte, and Acid-Base Balance Learning Objectives 1.List the factors that determine body water content. 2.Describe the importance of sodium balance in the body (and the resulting factors from too much sodium being lost). Too much fluid?Not enough fluid?

Discussion How much water should we really drink per day? What happens if we drink too little? What happens if we drink too much? q=how+much+water+to+drink&total=387&start=0&num=10&so=0 &type=search&plindex=0

Small Group Activity For further information: Instructions: 1.In small groups of no more than 4 people per group, read the article “Can You Drink Too Much Water?” 2.Discuss and formulate answers to the 6 guiding discussion points (next page). 3.Be prepared to share your answers with fellow classmates.

Body Water Content Infants have low body fat, low bone mass, and are 73% or more water (In old age, only about 45% of body weight is water) Healthy males are about __% water; healthy females are around __% This difference reflects females’: - Higher body fat - Smaller amount of skeletal muscle What inference can you draw from that?

Fluid Compartments Water occupies two main fluid compartments: 1.__________ fluid (ICF) – about two thirds by volume, contained in cells 2.____________ fluid (ECF) – consists of two major subdivisions –Plasma – the fluid portion of the blood –Interstitial fluid (IF) – fluid in spaces between cells –Other ECF – lymph, cerebrospinal fluid, eye humors, synovial fluid, serous fluid, and gastrointestinal secretions

Composition of Body Fluids Q - What is the universal solvent? Q – What are solutes?

Electrolyte Composition of Body Fluids Q – What are some of the greatest electrolytes found in blood plasma?

Electrolyte Balance Electrolytes are salts, acids, and bases, but electrolyte ________ usually refers only to salt balance Salts are important for: –Neuromuscular excitability –Secretory activity –Membrane permeability –Controlling fluid movements Salts enter the body by ingestion and are lost via perspiration, feces, and urine

Electrolyte Balance continued Changes in plasma sodium levels affect: –Plasma volume, blood pressure –ICF and interstitial fluid volumes Look at Table 25.1 “Causes and Consequences of Electrolyte Imbalance” pg 916. Answer the following questions: 1.What happens to the heart when there is not enough potassium? 2.How about too much magnesium?

Fluid Movement Electrolytes have ________ osmotic power than nonelectrolytes Water ______ according to osmotic gradients To remain properly hydrated, water intake must _____ water output

Thirst Management What part of the brain regulates thirst? How?

Thirst continued _______________ is stimulated: –By a decline in plasma volume of 10%–15% –By increases in plasma osmolality of 1–2% –Via baroreceptor input, angiotensin II, and other stimuli Thirst is quenched as soon as we begin to drink water. Feedback signals that inhibit the thirst centers include: a. __________ of the mucosa of the mouth and throat b. Activation of stomach and intestinal stretch receptors

Abnormalities of Acid-Base Balance What is respiratory acidosis? Respiratory alkalosis? Metabolic acidosis? Metabolic alkalosis? Instructions: Explore the following imbalances and their possible effects with your small group. Use the text pages 927 – 928 as reference material. Note the causes in Table 25.2 page 928.