Acid Base Regulation

the control of free H+ ion concentration in body fluids what is acid base regulation - strong acids = greater % of molecule which type of acid has greater chance of dissociates into free H+ ions dissociating - weak acid = greater % of molecule remaining intact measure of separation of H+ ions K = [H+] [HCO3-] / [H2CO3] what is the dissociation constant - a base binds to H+ ions to remove them how are H+ ions removed from a solution from solution - strong bases bind more readily pH = -log[H+] what is the calculation for pH what are the pH's for acids and bases - acid pH < 7 - base pH > 7 what is the pH of arterial vs venous blood and what is the average blood pH - arterial = 7.45 - venous = 7.35 - average = 7.4 - condition where there is too much acid what is acidosis and what pH classifies it in the body fluids - pH < 7.35 - when blood and body fluids contain an what is alkalosis and what pH classifies excess of bases or alkali it - pH > 7.45 at what pH does death occur at outside pH 6.8-8.0 for more than a few seconds - increased H+ reduces CNS activity producing disorientation and coma - decreased H+ excites CNS producwhat are the consequences of acidosis ing action potential generation (pins and and alkalosis needles, twitches, spasms...) - changes protein shape and activity which changed metabolism - the kidney can exchange Na+ ions for 1/5 H+ or K+ ions. if H+ high then K+ not excreted. high K+ impairs heart function what is the major source of H+ and its equation carbonic acid formation CO2 + H20 <-> H2CO3 <-> H+ HCO3- reversible - in capillaries forward reaction from middle - in lungs backward reaction from middle how do the lungs help with acid base regulation lungs regulate CO2 to influence acid base status inorganic acids - meat proteins sulphur/phosphorus produce sulphuric and phosphoric acids - ^ produce lots of H+ - fruits and veggies produce bases to explain how H+ is produced through meneutralise acids tabolism organic acids: - fatty acids - amino acids - lactic acid what are the two other ways that we input H+ ingested acids: - citric acid - acetic acid disease - diabetes mellitus produces keto acids - drugs produce H+ ions what are the three lines of defence for pH regulation 1. chemical buffer systems 2. the respiratory system 3. kidneys what are the 4 chemical buffer systems - carbonic acid- bicarbonate buffer - protein buffer - haemoglobin buffer - phosphate buffer 2/5 - 1st line of defence - most important buffer for extracellular fluid as H2CO3 and HCO3- are abundant in this fluid explain the carbonic acid - bicarbonate - if H+ added (fall pH) they bind with buffer in the chemical buffer system HCO3- to give H2CO3 - if H+ removed (increase pH) H2CO3 gives H+ forming Hco3- kidneys regulate HCO3- lungs regulate H2CO3 pH = pKa + log [A-]/[HA] - calcs pH of solution with known amounts of acid and base - pKa = dissociation constant of acid - [A-] = base - [HA] = acid Henderson-Hasselbalch equation -main intracellular mechanism explain the protein buffer system in the - high protein coc in intracellular fluid - proteins have acidic and basic groups chemical buffer system - these grps give up or accept H+ - haem buffers H+ from metabolically produced CO2 - deoxygenated haem accepts H+ - H+ released in lungs as haem picks explain the haemoglobin buffer system oxygen - H+ combines with bicarbonate in lungs producing carbon dioxide and water which is exhaled - main urinary buffer - acidic NaH2PO4 donated H+ explain the phosphate buffer system in - basic Na2HPO4 accepts H+ the chemical buffer system - if high phosphate consumes it is put in urine and used to remove H+ in kidney to make excretion more efficient - 2nd line of defence controls rate of CO2 removal 0 regulates plasma pH 3/5 - acts in minutes - respiratory abnormalities reduce effects explain the respiratory system as a line of defence for pH regulation - stimulates peripheral and central chemoreceptors in medulla what happens when there is increased - increases pulmonary ventilation via inarterial H+ ions creased frequency of ventilation and tidal volume - results in: removal of CO2, H2CO3, H+ - pulmonary ventilation reduced via rewhat happens when there is decreased duced frequency of ventilation and tidal arterial H+ ions volume via chemoreceptors -results in: increased CO2, H2CO3, H+ explain kidney regulation as a line of defence for pH regulation - 3rd line of defence - takes hours - days - most potent regulators how do kidneys excrete H+ - H+ originating from sulhuric, phosphoric, lactic acid removed - secreted into proximal, distal, collecting tubules. - H+ can not be reabsorbed - more H+ secreted so urine contains more H+ how does the kidney respond to acidosis - less HCO3- filtered as exists in blood plasma as H2CO3 - more newHCO3- is put in plasma how does the kidney respond to alkalosis - more HCO3- filtered - less H+ secreted - HCO3- can't all be reabsorbed - more HCO3- excreted in urine respiratory acidosis A drop in blood pH due to: - hypoventilation - compensation respiratory alkalosis Arise in blood pH due to: - hyperventilation - compensation 4/5 metabolic acidosis decreased pH in blood and body tissues as a result of an upset in metabolism metabolic alkalosis elevation of HCO3- usually caused by an excessive loss of metabolic acids 5/5