ch27ppt - 27-1Chapter 27Fluid, Electrolyte and Acid-Base...

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Unformatted text preview: 27-1Chapter 27Fluid, Electrolyte and Acid-Base HomeostasisBody fluidall the water and dissolved solutes in the bodys fluid compartmentsMechanisms regulatetotal volumedistributionconcentration of solutes and pH27-2Balance Between Fluid CompartmentsOnly 2 places for exchange between compartments:cell membranes separate intracellular from interstitial fluid.only in capillaries are walls thin enough for exchange between plasma and interstitial fluidsVolume of fluid in each is kept constant. Since water follows electrolytes, they must be in balance as well27-3Body Water Gain and Loss45-75% body weightdeclines with age since fat contains almost no waterGain from ingestion and metabolic water formed during aerobic respiration & dehydration synthesis reactions (2500 mL/day)Normally loss = gainurine, feces, sweat, breathe27-4Regulation of Water GainFormation of metabolic water is not regulatedfunction of the need for ATPMain regulator of water gain is intake regulationStimulators of thirst center in hypothalamusdry mouth, osmoreceptors in hypothalamus, decreased blood volume causes drop in BP & angiotensin IIDrinking occursbody water levels return to normal27-5Dehydration Stimulates ThirstRegulation of fluid gain is by regulation of thirst.27-6Regulation of Water and Solute LossElimination of excess water or solutes occurs through urinationConsumption of very salty meal demonstrates function of three hormonesDemonstrates howwater follows saltexcrete Na+ and water will follow and decrease blood volume27-7Hormone Effects on SolutesAngiotensin II and aldosterone promote reabsorption of Na+ and Cl- and an increase in fluid volumestretches atrial volume and promotes release of ANPslows release of renin & formation of angiotensin IIincreases filtration rate & reduces water & Na+ reabsorptiondecreases secretion of aldosterone slowing reabsorption of Na+ and Cl- in collecting ductsANP promotes natriuresis or the increased excretion of Na+ and Cl- which decreases blood volume27-8Hormone Regulation of Water BalanceAntidiuretic hormone (ADH) from the posterior pituitarystimulates thirstincreases permeability of principal cells of collecting ducts to assist in water reabsorptionvery concentrated urine is formedADH secretion shuts off after the intake of waterADH secretion is increasedlarge decrease in blood volumesevere dehydration and drop in blood pressurevomiting, diarrhea, heavy sweating or burns27-9Movement of WaterIntracellular and interstitial fluidsnormally have the same osmolarity,so cells neither swell nor shrinkSwollen cells of water intoxicationbecause Na+ concentration of plasmafalls below normaldrink plain water faster than kidneys canexcrete it replace water lost from diarrhea or vomitingwith plain watermay cause convulsions, coma & death unless oral rehydration includes small amount salt in water intake27-10...
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This note was uploaded on 04/10/2010 for the course BIO 222 taught by Professor Brooks during the Spring '10 term at Prairie State College .

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ch27ppt - 27-1Chapter 27Fluid, Electrolyte and Acid-Base...

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