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A&P Exam 4 Study GuideLecture #1: Acid-Base Balance pH Levels- pH—the measure of acidity in a solution: relative H+ concentration in body fluidso Greater H+acidic o Lower H+alkaline o H+ are by products of metabolism—either from lactate or ketone bodies- All functional proteins are influenced by H+, therefore almost all reactions are influenced by pH of their fluid environment - pH Balance in Body Fluidso Arterial blood—7.4 o Venous blood and Interstitial fluid—7.35 o Intracellular fluid—7.0 (neutral)- pH riseslower [H+]/ pH fallshigher [H+]o arterial pH<7.35—acidosis o arterial pH>7.45—alkalosis - Lower pH—more acidic metabolites and CO2 Acid-Base Classification- Strong Acid (SA)—dissociates completely which releases all of its H+ individually (HCl) - Weak Acid (WA)—only dissociates partly (H2CO3)- Strong Base (SB)—dissociates easily and accepts H+(Hydroxides –OH)- Weak Base (WB)—bicarbonate, ammonia Chemical buffer system—a system of one or more compounds that acts to resist changesin pH when a strong acid or base is added OVERVIEW: 1. Chemical Buffer Systems (1st line of defense)  Act within a fraction of a second to attempt resisting changes in pH Muscle Carnosine Only temporary2. Brain-Respiratory System Act within 1-3 minutes to counteract acidosis or alkalosis  Respiratory Buffer3. Renal System (Kidneys) Require hours or even a day to react to changes in blood pH Only kidneys can remove excess metabolic acids from body3 chemical buffer systems—a change in [H+] in 1 fluid compartment is compensated by a shift in another compartment (if 2 or more compounds)- Bicarbonate Buffer System— ONLY important buffer in extracellular fluid (ECF)o Substances:  H2CO3 (Carbonic Acid—WA), NaHCO3 (Sodium Bicarbonate—WB), HCl (Hydrochloric Acid—SA) NaOH (Sodium Hydroxide—SB)o Based off equilibrium: H2CO3 ↔ HCO3- + H+ o Resists a large decrease in pH when acidic substances are added to a solution  This is because only small amount of H+ remain as free ions, the rest bind to HCO3- to form carbonic acid o Resists a large increase in pH when basic substances are added to a solution  This is because most of the H2CO3 forms HCO3- and H+ when H+ isremoved o Responds quickly to addition of carbon dioxide and lactic acid from exercise, ketone bodies and fatty acids from an elevated fat metabolism, and large amounts of NaHCO3 from antacids - Phosphate Buffer System—very effective buffer in urine and intracellular fluid (ICF)o Substances: NaH2PO4 (Sodium dihydrogen phosphate—WA) NaHPO4 (Sodium monohydrogen phosphate—WB)o Similar mechanisms to bicarbonate systemo Phosphate containing molecules (such as DNA, RNA, ATP and phosphate ions) act as bufferso Two main ions fluctuate between gaining and losing H+ ions to help balance pH When pH decreases ions likes HPO4- bind H+ to form H2PO4-raising pH When pH increases H2PO4 releases H+ into solutionlowering pH- Protein Buffer System—3/4 of buffering power of all bodily fluids is in the cellso Substances: Intracellular proteins—hemoglobin, histone proteins (nucleic acids) Plasma proteinso Capacity to act as buffers is due to functional groups of amino acids (-COOH and –NH2) being able to act as acids and bases As [H+] increases (pH drops), more H+ binds to NH2 to form NH3raising pH As [H+] decreases (pH raises), COOH is a SA which releases H+ lowering pHo Amphoteric Molecules—a single protein that can act as an acid or base depending on the pH of its environment o Hemoglobin example—Hb is negatively charged after releasing O2 which causes rapid binding of H+ (from carbonic acid dissociation) to Hb causingminimal pH changesRespiratory Buffer System—influenced and achieved by bicarbonate buffer system- Acts more slowly than chemical buffers BUT has 2x buffering capacity of all chemical buffer systems combined- Decreases in body fluid pH stimulate neurons in the brainstem to cause the rate and depth of ventilation to increaseo Increased ventilation allows CO2 to be expelled from the lungs at a greater ratedecreasing body fluid CO2 levelso As CO2 level declines, bicarbonate buffer system reactso H+ binds to HCO3- to form H2CO3 which then forms CO2 and H2Oo H+ concentration decreasespH rises - Increases in body fluid pH, inhibit neurons in the brainstem and cause the depth and rate of ventilation to decreaseo Decreased ventilation allows less CO2 to be eliminated through lungso CO2 levels increase because it is continually a by-product of metabolism in all tissues o H2CO3 levels increase and dissociate to H+ and HCO3-o H+ concentration increasespH lowers- SUMMARY:o As CO2 levels increases, pH decreaseso As CO2 levels decrease, pH increases o Hypoventilation(respiratory acidosis)—increases blood CO2 levelso Hyperventilation(respiratory alkalosis)—decreases blood CO2 levels- Hypercapnia—drop in CSF pH activates medulla chemoreceptors which increaserespiratory rate and cause decreased CO2 levels which increases pH- Respiratory Compensations:o Metabolic acidosis—increased respiratory rate and deptho Metabolic alkalosis—decreased respiratory rate and depth- CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3-- Acidosis—hydrogen ions are increased and pH and bicarbonate ions are decreased- Alkalosis—bicarbonate ion are increased and the concentration of hydrogen ions are decreased- Both acidosis and alkalosis can be of two different types: respiratory and metabolico Respiratory –caused by various malfunctions of the lungso Metabolic—caused by various metabolic disorders which result in an excessive build up or loss of acids or basesRenal Buffer System—directly regulates acid-balance by altering the rate of H+ concentration and HCO3- reabsorption - Secretion of H+ into the filtrate and the reabsorption of HCO3- into ECF cause extracellular pH to raise o Carbonic acid dissociates to form H+ and HCO3-o Antiport mechanism moves H+ into nephron lumen and Na+ into nephron cello Na+ and HCO3- diffuse into ECF- HCO3- in filtrate are reabsorbedo HCO3- combine with excess H+ in ECF to form carbonic acidincreases extracellular pHo Some H+ that was secreted into filtrate combines with HCO3- (which got into the filtrate through a filtration membrane in the form of NaHCO3—bicarbonate) to form carbonic acido Which then dissociates into CO2 and H2Oo CO2 diffuses into nephron cells and forms carbonic acid which then


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FSU PET 3323C - A&P Exam 4 Study Guide

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