PET3323 Exam 4 Study Guide PET3323 Fall 2011 Study Guide Exam 4 Body Fluid and Electrolyte Balance 1 Know the main fluid compartments within the body pg 996 Intracellular Fluid Fluid in trillions of compartments inside the cells Extracellular Fluid Outside the cells Plasma Fluid portion of the blood Interstitial Fluid Fluid in the spaces between tissue cells 2 Know the major components of body fluid and distinguish between the extracellular and Glucose and lipids Do not dissociate in solution intracellular compartments know what causes fluid movement between the two compartments Nonelectrolytes Electrolytes DO Dissociate into ions in solution Ions conduct electricity Greater ability to change osmolarity than electrolytes Increased osmolarity increased solutes Examples inorganic salts and some proteins PET3323 Exam 4 Study Guide Each fluid compartment has a distinctive pattern of electrolytes extracellular chief cation is sodium and the main anion is chloride intracellular chief cation is potassium and the main anion is HPO4 Electrolyte Dissociation NaCl Na Cl The continuous exchange and mixing of body fluids are regulated by osmotic pressure and hydrostatic pressures Solutes are unequally distributed because of their size electrical charge or dependence on transport proteins Anything that changes the solute concentration in any compartment leads to net water flows 3 Understand what components will regulate water intake e g the thirst mechanism and water output e g obligatory and insensible water losses pg 997 Triggers thirst Drink fluids Release of Antidiuretic Hormone ADH Causes reabsorption of water into plasma Excrete Concentrated Urine Thirst Mechanism Increase in plasma osmolarity Decrease in plasma osmolarity Inhibits thirst Inhibits ADH Large outputs of dilute urine PET3323 Exam 4 Study Guide A decrease in blood volume or pressure also triggers the thirst mechanism Obligatory water loss outputs of certain amounts of water are unavoidable Insensible water loss water that accompanies undigested food residues in feces daily kidney flush to excrete urine solutes 500ml depends highly on diet and fluid intake 4 Where is Anti diuretic Hormone ADH vasopressin produced what is its primary role in fluid balance and what will influence its secretion Osmoreceptors of the hypothalamus sense the ECF solute concentration and trigger or inhibit ADH release from the posterior pituitary gland A decrease in ECF osmolality inhibits ADH release and allows more water to be excreted in urine An increase in ECF osmolality stimulates ADH release by stimulating the hypothalamic osmoreceptors ADH causes increased urine osmolarity and decreased water excretion due to water reabsorption into the plasma from the distal collecting tubule ADH increases permeability of the distal collecting tubule Permeability is increased by ADH inserting water channels into the membrane of the tubule PET3323 Exam 4 Study Guide When osmolarity in blood stream is increased the neurons will be stimulated to release ADH from the pituitary posterior lobe ADH is an endocrine response regulating the collecting duct reabsorb water ADH causing water reabsorption into the plasma causes an increase in blood pressure due to vasoconstriction Acid Base Balance 5 Know the three primary buffer systems i e chemical respiratory renal and characteristics of each i e when are they recruited how quickly do they respond how quickly do they bring about change etc 1 Chemical Buffers 1st line of defense These act within a fraction of a second in an attempt to resist changes in pH Muscle Carnosine Definition A system of one or more compounds that acts to resist changes in pH when a strong acid or base is added Compounds bind to H when pH drops PET3323 Exam 4 Study Guide Release H when pH rises A shift in H concentration in one fluid compartment is compensated by a shift in another compartment e g hemoglobin in RBC s Bicarbonate Buffer System H2CO3 carbonic acid and NaHCO3 sodium bicarbonate The Only important buffer in extracellular fluid ECF Phosphate Buffer System H2PO4 dihydrogen phosphate and HPO42 monohydrogen phosphate Protein Buffer System Example Hemoglobin NOTE Chemical buffers can only tie up acids or bases temporarily only kidneys can remove excess from the body 2 Brain Stem Respiratory Centers Act within 1 3 minutes to counteract acidosis or alkalosis Respiratory Buffer Acts more slowly than the chemical buffers 2X s the buffering power of all of the chemical buffers combined CO2 water H2CO3 H HCO3 When blood acidity increases decreased pH chemoreceptors stimulate the inspiratory area in the medulla oblongata increased excretion of CO2 When blood acidity decreases increased pH the respiratory center is inhibited buildup of CO2 Reversible Reactions Low CO2 drives reactions to the left High CO2 to the right Respiratory Compensations Compensate for metabolic acid base imbalances Metabolic acidosis increased respiratory rate and depth Metabolic alkalosis decreased respiratory rate and depth 3 Renal Mechanisms Kidneys Require hours or even a day or more to act Only the kidneys can rid the body of metabolic acids via excretions of H in the urine Only the kidneys can regulate blood levels of alkaline substances and renew chemical buffers that are used up PET3323 Exam 4 Study Guide Renal mechanisms include Excretion of H into filtrate Buffering of H by other filtrate buffers Reabsorption of exisiting Bicarbonate Renal Compensations Compensate for respiratory acid base imbalances Respiratory acidosis kidneys will retain bicarbonate to offset Respiratory alkalosis kidneys will eliminate more bicarbonate 6 Know the three major chemical buffer systems and their components Bicarbonate buffer system Substances H2CO3 Carbonic Acid Weak Acid NaHCO3 Sodium Bicarbonate Weak Base HCL Hydrochloric Acid Strong Acid NaOH Sodium Hydroxide Strong Base The Only important buffer in extracellular fluid ECF Phosphate buffer system Similar to that of the Bicarbonate Buffer Sodium salts dihydrogen phosphate NaH2PO4 and monohydrogen NaHPO4 phosphate H2PO4 Weak Acid HPO42 Weak Base OH H2PO4 H2O HPO4 2 H HPO4 2 H2PO4 Phosphate concentrations are low in the blood so this is very effective buffer in urine and cytosol ICF Protein buffer system of buffering power of all bodily fluids are in the cells and this mostly reflects the buffering capabilities of intracellular proteins Amino Group Carbon Group COOH Organic Acid COOH is a strong acid which releases H when pH
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