Fluid, Electrolyte, and Acid-Base Balance: Introduction to Body Fluids Essay

Fluid Compartmentswater placement occupies 2 main fluid compartmentsintra mobile phoneular fluid (ICF) about two thirds by majority, contained in cells Extracellular fluid (extracellular fluid) consists of two major subdivisions Plasma the fluid portion of the ocellusInterstitial fluid (IF) fluid in spaces between cellsOther extracellular fluid lymph, cerebrospinal fluid, eye humors, synovial fluid, serous fluid, and gastrointestinal secretions Extracellular and intracellular FluidsWater is the universal solventSolutes be broadly class intoElectrolytes in constitutional salts, all acids and bases, and some proteins Electrolytes determine the chemical and physical reactions of fluidsElectrolytes have greater osmotic advocator than nonelectrolytes Water crusades according to osmotic gradientsNonelectrolytes examples al down spirited glucose, lipids, creatinine, and urea Each fluid compartment of the eubstance has a typical pattern of electrolytes Extracellular fluids are similar (except for eminent protein content of plasma) sodium is the chief cationChloride is the major anionIntracellular fluids have low sodium and chloridePotassium is the chief cationPhosphate is the chief anionProteins, phospholipids, cholesterol, and neutral fats account for 90% of the bus of solutes in plasma60% of the mass of solutes in interstitial fluid97% of the mass of solutes in the intracellular compartmentFluid Movement Among CompartmentsCompartmental exchange is regulated by osmotic and hydrostatic twinges Net leakage of fluid from the prodigal is picked up by lymphatic vessels and returned to the strainstream Exchanges between interstitial and intracellular fluids are complex due to the selective permeability of the cellular membranes Two-way water string up is substantialIon fluxes are restricted and move selectively by active transport Nutrients, respiratory gases, and wastes move uni careally Plasma is the only fluid that circulates throughout the body and links external and internal environments Osmolalities of all body fluids are tolerable changes in solute concentrations are quickly followed by osmotic changesWater equilibrate and extracellular fluid OsmolalityTo remain properly hyd arrayd, water inspiration must equal water siding Water intake sourcesIngested fluid (60%) and solid food (30%)Metabolic water or water of oxidation (10%)Water proceedsUrine (60%) and feces (4%)Insensible losses (28%), sweat (8%)Increases in plasma osmolality trigger thirst and clit of antidiuretic drug hormone (ADH) ordinance of Water HomeostaisisIntake Hypothalmic Thirst CenterThirst is quenched as soon as we begin to drink waterFeedback signals that inhibit the thirst centers includeMoistening of the mucous membrane of the mouth and throatActivation of stomach and intestinal orbit receptorsInfluence and Regulation of ADHWater reabsorption in salt away ducts is proportional to ADH release Low ADH takes produce elongate urine and redu ced the great unwashed of body fluids High ADH levels produce concentrated urinehypothalamic osmoreceptors trigger or inhibit ADH releaseFactors that specifically trigger ADH release include prolonged fever excessive sweating, vomiting, or diarrhea severe blood loss and traumatic burn down Disorders of Water BalanceDehydrationWater loss exceeds water intake and the body is in electronegative fluid balance Causes include hemorrhage, severe burns, prolonged vomiting or diarrhea, profuse sweating, water deprivation, and diuretic abuse Signs and symptoms cottonmouth, thirst, dry flushed skin, and oliguria Prolonged dehydration may lead to weight loss, fever, mental wonder Other consequences include hypovolemic shock and loss of electrolytes Hypotonic HydrationRenal insufficiency or an some amount of water ingested quickly buns lead to cellular overhydration, or water intoxication extracellular fluid is diluted sodium content is normal but excess water is present The resulting hypo natremia promotes net osmosis into wind cells, causing swelling These events must be quickly reversed to prevent severe metabolic disturbances, oddly in neurons Edema.Atypical accumulation of fluid in the interstitial space, leading to tissue swelling Caused by anything that increases flow of fluids out of the bloodstream or hinders their return.Factors that accelerate fluid lossinclude Increased blood pressure, capillary permeabilityIncompetent venous valves, localized blood vessel blockageCongestive cheek failure, hypertension, high blood volumeHindered fluid return usually reflects an imbalance in colloid osmotic pressures Hypoproteinemia low levels of plasma proteinsForces fluids out of capillary beds at the arterial endsFluids fail to return at the venous endsResults from protein malnutrition, colorful disease, or glomerulonephritis Blocked (or surgically removed) lymph vesselsCause leaked proteins to accumulate in interstitial fluidExert increase colloid osmotic pressu re, which draws fluid from the blood Interstitial fluid accumulation results in low blood pressure and severely impaired circulation sodium in Fluid and Electrolyte Balance atomic number 11 holds a central opinion in fluid and electrolyte balance Sodium saltsAccount for 90-95% of all solutes in the ECFContribute 280 mOsm of the core 300 mOsm ECF solute concentration Sodium is the single to the highest degree abundant cation in the ECFSodium is the only cation observeing significant osmotic pressure The role of sodium in controlling ECF volume and water distribution in the body is a result of Sodium being the only cation to exert significant osmotic pressure Sodium ions leaking into cells and being pumped out against their electrochemical gradient Sodium concentration in the ECF normally remains stableChanges in plasma sodium levels appropriatePlasma volume, blood pressureICF and interstitial fluid volumesRenal acid-base control mechanisms are coupled to sodium ion transport Reg ulation of Sodium BalanceAldosteroneThe renin-angiotensin mechanism triggers the release of aldosterone This is mediated by juxtaglomerular apparatus, which releases renin in receipt to Sympathetic nervous system stimulationDecreased permeate osmolalityDecreased stretch due to rock-bottom blood pressureRenin catalyzes the production of angiotensin II, which prompts aldosterone release Ad nephritic cortical cells are directly horny to release aldosterone by elevated K+ levels in the ECF Aldosterone brings about its effects (diminished urine output and increased blood volume) easyCardiovascular System BaroreceptorsBaroreceptors alert the brain of increases in blood volume (hence increased blood pressure) Sympathetic nervous system impulses to the kidneys declineAfferent arterioles dilateGlomerular filtration rate risesSodium and water output increaseThis phenomenon, called pressure diuresis, decreases blood pressure Drops in systemic blood pressure lead to opposite actions and sy stemic blood pressure increases Since sodium ion concentration determines fluid volume, baroreceptors can be viewed as sodium receptors Atrial Natriuretic Peptide (ANP)Reduces blood pressure and blood volume by inhibitingEvents that promote vasoconstrictionNa+ and water retentionIs released in the heart atria as a response to stretch (elevated blood pressure) Has potent diuretic and natriuretic effectsPromotes excretion of sodium and waterInhibits angiotensin II productionInfluence of Other Hormones on Sodium BalanceEstrogensEnhance NaCl reabsorption by renal tubulesMay cause water retention during menstrual cyclesAre responsible for edema during pregnancyprogesteroneDecreases sodium reabsorptionActs as a diuretic, promoting sodium and water lossGlucocorticoids enhance reabsorption of sodium and promote edema Regulationof Potassium BalanceRelative ICF-ECF potassium ion concentration affects a cells resting membrane potential Excessive ECF potassium decreases membrane potentialToo diminutive K+ causes hyperpolarization and nonresponsiveness Hyperkalemia and hypokalemia canDisrupt electrical conduction in the heartLead to sudden close henry ions shift in and out of cellsLeads to corresponding shifts in potassium in the opposite direction Interferes with activity of excitable cellsInfluence of AldosteroneAldosterone stimulates potassium ion secretion by principal cells In cortical collecting ducts, for each Na+ reabsorbed, a K+ is secreted Increased K+ in the ECF around the suprarenal gland cortex causesRelease of aldosterone Potassium secretionPotassium controls its own ECF concentration via feedback regulation of aldosterone release Regulation of CalciumIonic atomic number 20 in ECF is important forBlood clottingCell membrane permeabilitySecretory behaviorHypocalcemia Increases excitability, causes muscle tetanyHypercalcemia inhibits neurons and muscle cells cause heart arrhythmias Calcium balance is controlled by parathyroid hormone and calcitonin PTH pro motes increase in calcium levels by targetingBones PTH activates osteoclasts to break down bone matrixSmall intestine PTH enhances intestinal absorption of calcium Kidneys PTH enhances calcium reabsorption and decreases phosphate reabsorption Calcium reabsorption and phosphate excretion go overhaul in hand Influence of calcitoninReleased in response to rising blood calcium levelsCalcitonin is a PTH antagonist, but its contribution to calcium and phosphate homeostasis is minor to negligible Acid Base BalanceIntroduction to Acids and BasesStrong acids all their H+ is dissociated completely in water Weak acids dissociate partly in water and are efficient at preventing pH changes Strong bases dissociate easily in water and quickly tie up H+ Weak bases accept H+ more slowly (e.g., HCO3 and NH3)Normal pH of body fluidsArterial blood is 7.4Venous blood and interstitial fluid is 7.35Intracellular fluid is 7.0Alkalosis or alkalemia arterial blood pH rises above 7.45Acidosis or acid emia arterial pH drops down the stairs 7.35 (physiological acidosis) Sources of Hydrogen Ions Most heat content ions originate from cellular metabolism Breakdown of phosphorus-containing proteins releases phosphoric acid into the ECF Anaerobic respiration of glucose produces lactic acidFat metabolism yields organic acids and ketone bodiesTransporting carbon dioxide as hydrogen carbonate releases hydrogen ions Hydrogen Ion RegulationConcentration of hydrogen ions is regulated sequentially by Chemical buff systems act at heart secondsPhysiological modify systemsThe respiratory center in the brain stem acts within 1-3 minutes Renal mechanisms require hours to days to effect pH changes Chemical soften SystemsBicarbonate Buffer SystemA mixture of carbonic acid (H2CO3) and its salt, sodium bicarbonate (NaHCO3) (potassium or magnesium bicarbonates achievement as well) If strong acid is addedHydrogen ions released combine with the bicarbonate ions and form carbonic acid (a pr omiscuous acid) The pH of the solution decreases only slightlyIf strong base is addedIt reacts with the carbonic acid to form sodium bicarbonate (a weak base) The pH of the solution rises only slightlyThis system is the only important ECF bufferPhosphate Buffer SystemNearly identical to the bicarbonate systemIts components areSodium salts of dihydrogen phosphate (H2PO4), a weak acidMonohydrogen phosphate (HPO42), a weak baseThis system is an effectual buffer in urine and intracellular fluid Protein Buffer SystemPlasma and intracellular proteins are the bodys most plentiful and powerful buffers Some amino acids of proteins haveFree organic acid groups (weak acids)Groups that act as weak bases (e.g., amino groups)Amphoteric molecules are protein molecules that can function as both a weak acid and a weak base Physiological Buffer Systemsrespiratory Buffer SystemThe respiratory system regulation of acid-base balance is a physiological buffering system on that point is a reversible equ ilibrium betweenDissolved carbon dioxide and waterCarbonic acid and the hydrogen and bicarbonate ionsCO2 + H2O H2CO3 H+ + HCO3During carbon dioxide unloading, hydrogen ions are incorporated into water When hypercarbia or rising plasma H+ occursDeeper and more rapid breathing expels more carbon dioxideHydrogen ion concentration is reducedAlkalosis causes slower, more shallow breathing, causing H+ to increase Respiratory system damage causes acid-base imbalance (respiratory acidosis or respiratory alkalosis) Renal Mechanisms of Acid-Base BalanceIntroductionChemical buffers can tie up excess acids or bases, but they cannot eliminate them from the body The lungs can eliminate carbonic acid by eliminating carbon dioxide Only the kidneys can rid the body of metabolic acids (phosphoric, uric, and lactic acids and ketones) and prevent metabolicacidosis The supreme acid-base regulatory organs are the kidneysThe most important renal mechanisms for regulating acid-base balance are Conservi ng (reabsorbing) or generating new bicarbonate ionsExcreting bicarbonate ionsLosing a bicarbonate ion is the same as gaining a hydrogen ion reabsorbing a bicarbonate ion is the same as losing a hydrogen ion Hydrogen ion secretion occurs in the percentageHydrogen ions come from the dissociation of carbonic acidReabsorption of BicarbonateCO2 combines with water in tubule cells, forming H2CO3H2CO3 splits into H+ and HCO3-For each H+ secreted, a Na+ and a HCO3- are reabsorbed by the PCT cells Secreted H+ form H2CO3 thus, HCO3- disappears from filtrate at the same rate that it enters the peritubular capillary blood H2CO3 formed in filtrate dissociates to release CO2 + H2CO2 then diffuses into tubule cells, where it acts to trigger further H+ secretion Hydrogen Ion voidingDietary H+ must be counteracted by generating new HCO3-The excreted H+ must bind to buffers in the urine (phosphate buffer system) Intercalated cells actively secrete H+ into urine, which is buffered and excreted HCO3- generated isMoved into the interstitial space via a cotransport systemPassively moved into the peritubular capillary bloodIn response to acidosisKidneys generate HCO3-and add them to the bloodAn equal amount of H+ are added to the urineAmmonium Ion (NH4+) ExcretionThis method uses NH4+ produced by the metabolism of glutamine in PCT cells Each glutamine metabolized produces two ammonium ions and two bicarbonate ions HCO3- moves to the blood and ammonium ions are excreted in urine Respiratory Acidosis and AlkalosisResult from failure of the respiratory system to balance pHPCO2 is the single most important indicator of respiratory inadequacy PCO2 levels normal PCO2 fluctuates between 35 and 45 mm Hg Values above 45 mm Hg signal respiratory acidosisValues below 35 mm Hg indicate respiratory alkalosisRespiratory acidosis is the most common cause of acid-base imbalance Occurs when a person breathes shallowly, or gas exchange is hampered by diseases such as pneumonia, cystic fibrosis, or emphysema Respiratory alkalosis is a common result of hyperventilation Metabolic AcidosisAll pH imbalances except those caused by brachydactylous blood carbon dioxide levels Metabolic acid-base imbalance bicarbonate ion levels above or below normal (22-26 milliequivalent/L) Metabolic acidosis is second most common cause of acid-base imbalance Typical causes are ingestion of alike much alcohol and excessive loss of bicarbonate ions Other causes include accumulation of lactic acid, shock, ketosis in diabetic crisis, starvation, and kidney failure Metabolic AlkalosisRising blood pH and bicarbonate levels indicate metabolic alkalosis Typical causes areVomiting of the acid contents of the stomachIntake of excess base (e.g., from antacids)Constipation, in which excessive bicarbonate is reabsorbedRespiratory and Renal CompensationsAcid-base imbalance due to inadequacy of a physiological buffer system is compensated for by the other system The respiratory system will attempt to adva nce metabolic acid-base imbalances The kidneys will work to correct imbalances caused by respiratory disease Respiratory CompenstaionIn metabolic acidosisThe rate and depth of breathing are elevatedBlood pH is below 7.35 and bicarbonate level is lowAs carbon dioxide is eliminated by the respiratory system, PCO2 falls below normal In metabolic alkalosisCompensation exhibits slow, shallow breathing, allowing carbon dioxide toaccumulate in the blood Correction is revealed byHigh pH (over 7.45) and elevated bicarbonate ion levelsRisingPCO2Renal CompensationTo correct respiratory acid-base imbalance, renal mechanisms are stepped up Acidosis has high PCO2 and high bicarbonate levelsThe high PCO2 s the cause of acidosisThe high bicarbonate levels indicate the kidneys are retaining bicarbonate to offset the acidosis Alkalosis has Low PCO2 and high pHThe kidneys eliminate bicarbonate from the body by failing to reform it or by actively secreting it