Water, Electrolyte, and Acid-Base BalanceBody Fluid DistributionComposition of Body FluidsWater BalanceWater Intake/OutputRegulation of Water BalanceElectrolyte BalanceSodium/Potassium RegulationCalcium RegulationAcid-Base BalanceRegulating Acid/Base BalanceAcid-Base Buffering SystemRespiratory Excretion of CO2Renal Excretion of H+Suggested Homework QuestionsWATER, ELECTROLYTE, AND ACID-BASE BALANCEChapter 21BODY FLUID DISTRIBUTIONBody ~ 50-60% waterIntracellularFluid/electrolytes within cellular membranesExtracellularPlasmaLymphInterstitial fluidTranscellular fluidCSF, humors of eye, synovial fluid, serous fluidCOMPOSITION OF BODY FLUIDSWATER BALANCEWATER INTAKE/OUTPUTIntakeRegulated by thirst mechanismIntake primarily via mouthWater loss of 0.5-1% triggers osmoreceptors in hypothalamusAs stomach fills, distension inhibits thirst mechanismOutputSources of water lossSweat, evaporation, feces, urineUrine best means of controlOutput = intake to maintain proper balanceREGULATION OF WATER BALANCEELECTROLYTE BALANCEElectrolyteSubstance that ionizes in solutionNaCl  Na+ + Cl- SignificanceCellular functionEx. Muscle contraction, nerve stimulationMost abundant/necessaryNa+, K+, Ca2+, Mg2+, Cl-, SO42-, PO43-, HCO2-, H+ • Most significant loss  urinegreatest source for regulation• Deficiency  salt cravingSODIUM/POTASSIUM REGULATIONAldosterone stimulated by:Decrease in sodium ions Increase in potassium ionsNegatively charged ions (Cl-) largely reabsorbed with positively chargedCALCIUM REGULATIONACID-BASE BALANCEAcids – ionize in water; release H+Bases – react with H+Regulation of acid/base balance  regulation of H+ ionsAccumulation  acidic pHREGULATING ACID/BASE BALANCEAcid-Base buffering systemRespirationRenal secretionACID-BASE BUFFERING SYSTEMBuffers in bodily fluids that neutralize acids and basesStabilize pHBicarbonate buffer systemIntracellular and extracellular fluidsH+ + HCO3-  H2CO3  H+ + HCO3- Phosphate buffer systemIntracellular and extracellular fluidsH+ + HPO42-  H2PO4-  H+ + HPO42- Protein buffer systemPlasma–COOH  COO- + H+  –COOHRESPIRATORY EXCRETION OF CO2Regulation of H+ concentration via control of rate and depth of breathingRENAL EXCRETION OF H+Tubular secretion of H+SUGGESTED HOMEWORK QUESTIONSChapter Assessments1-3, 5, 7-20, 24-25 Integrative