PET3323 Exam 4 Study Guide Mia Newlin Spring 2012 Body Fluid and Electrolyte Balance o Affected by age body mass gender relative amount of body fat o Body mass accounts for a larger portion of H2O men tend to have more water percentage for Body Water Percentages Infants approx 75 Young adults approx 50 60 Older adults approx 45 this reason Fluid Compartments Intracellular accounts for about 2 3 of all body H2O Extracellular accounts for about 1 3 of all body H2O o Composed of Interstitial Fluid and Plasma Composition of Body Fluids Non electrolytes o Do not dissociate in solution have no electrical charge o Don t contribute much to osmolarity Electrolytes o Dissociate into ions in solution electrical charge present o Primarily make up the changes in osmolarity greater osmotic power than non electrolytes o Ions conduct electricity Extracellular Fluid o Na is primary cation o Cl is primary anion Intracellular Fluid o K is primary cation o HPO4 o Contains many more proteins is primary anion Na K pumps primary job is to balance Na and K levels throughout the body Movement of Fluid Lungs Oxygen from lungs into blood into interstitial fluid CO2 moves in opposite direction Gastrointestinal Tract one way movement of nutrients from GI tract to blood and into interstitial fluid H2O and ion flow is bidirectional to maintain osmolarity levels Kidneys Nitrogenous wastes from interstitial fluid into blood into kidneys H2O and ion flow is again bidirectional to maintain osmolarity levels pressure also contributes to the bidirectional flow of H2O and cations PET3323 Exam 4 Study Guide Mia Newlin Spring 2012 Hydrostatic Pressure think of blood pressure causes fluid to be pushed out of capillaries Osmotic Pressure allows for fluids to be drawn back in These two pressures work together to maintain overall pressure balance Fluid Intake Fluid Output Fluctuates from day to day primarily 60 made up of beverages we consume and liquid in the foods we eat 30 o Metabolism aerobic cellular activity contributes a minor portion 10 Urine is the largest contributor 60 o Insensible losses via skin lungs 28 and sweat 8 An increase in temperature increase in overall water loss thru sweat insensible o Feces accounts for smallest portion 4 Water Balance An increase in plasma osmolality dehydration o Triggers thirst center in the hypothalamus thirst mechanism this thirst center is dampened VERY quickly the moment you drink something your urge to drink is quickly diminished even though you may still be dehydrated thirst is not a reliable signal of hydration or dehydration o Also triggers release of ADH kidneys reabsorb water A decrease in plasma osmolality hydration o Inhibits thirst center in hypothalamus o Inhibits ADH large outputs of urine water not reabsorbed An increase in plasma osmolality dehydration decrease in saliva triggers thirst center water from drinking moistens throat stretches stomach water absorbed decrease in plasma osmolality A decrease in plasma volume decrease BP dehydration triggers renin angiotensin mechanism angiotensin II triggers hypothalamus thirst center A decrease in plasma osmolality hydration causes osmoreceptors in hypothalamus to stimulate the release of ADH water is reabsorbed osmolality increases An increase in plasma volume increase BP stimulates release of ADH as well water is reabsorbed plasma volume decreases Water Imbalances Dehydration o Negative fluid balance o Caused by hemorrhage severe burns prolonged vomiting diarrhea profuse sweating diuretic abuse and water deprivation o Hypovolemic shock condition in which severe blood and fluid loss make the heart unable to pump enough blood to body can cause severe organ damage Hypotonic Hyperhydration o Cellular overhydration too much water o Caused by renal insufficiency extraordinary intake of water o Hyponatremia low sodium causes cells to swell with too much water PET3323 Exam 4 Study Guide Mia Newlin Spring 2012 Edema o Atypical accumulation of fluid in the interstitial fluid causes swelling that can be seen externally typically swollen hands feet o Increase in capillary hydrostatic pressure and permeability o Hypoproteinemia decreased fluid return happens when low amount of protein in blood Easy way of seeing differences between dehydration Dehydration ultimately a fluid loss in extracellular fluid hypotonic hydration shrinkage of cells Hypotonic hydration excess water in extracellular fluid swelling of cells due to excess water being absorbed sweating or vomiting coupled with normal intake of water decreased Na concentration decreased osmolarity osmosis from interstitial fluid into intracellular fluid leads to swelling of cells water intoxication Water Intoxication hypotonic hyperhydration excessive Electrolyte Balance Sodium is most abundant cation in extracellular fluid o Sodium can be lost in urine sweat feces etc Regulation of salt is linked to blood volume and pressure Nearly all Na can be reabsorbed primarily influenced by aldosterone and ANP o Estrogens progesterone and cortisol can also effect Addison s Disease adrenal insufficiency decrease in Aldosterone decrease Na reabsorption Regulation of Sodium by Aldosterone Secreted in response to decrease in Na or increase in K K reabsorption is set we absorb same amount of K regardless of the bodies needs excess K is secreted by the kidneys for excretion Increase in K or decrease in Na renin angiotensin mechanism stimulates adrenal cortex to release aldosterone causes increase in Na and decrease in K to return to homeostasis PET3323 Exam 4 Study Guide Mia Newlin Spring 2012 Atrial Natiuretic Peptide ANP Secreted in response to overhydration increase in BP stretch of heart due to excess fluid Targets and inhibits renin angiotensin mechanism inhibits ADH inhibits aldosterone Ultimately results in a decrease in BP secretion of H2O and Na Chloride Potassium and Bicarbonate Chloride o Most abundant anion in extracellular fluid o Relatively easy movement between intracellular and extracellular fluid Can be used to exchange an antiporter for other anions cations o Chloride shift change in CO2 levels causes equilibrium shift Contributes to maintenance and o Most abundant cation in intracellular fluid o Establishes resting membrane potential regulates pH via exchange for H o Can cause problems with heart increased or decreased activity of heart nerve conduction gas exchange Potassium etc Bicarbonate o Second most abundant anion in extracellular fluid o Level of bicarbonate is
View Full Document
Unlocking...