Explain the effects of H concentration on pH levels in the body A PII Objectives pH Basics Acidic High H concentration pH of arterial blood 7 35 Acidosis More acidic metabolites and CO2 are present Basic Alkaline Low H concentration pH of arterial blood 7 45 Alkalosis Arterial Blood 7 4 Venous Blood Interstitial Fluid 7 35 Intracellular Fluid 7 0 All functional proteins and enzymes are influenced by H ions so almost all reactions are influenced by pH of fluid environment interstitial fluid blood etc Ex Hg will bind to Hydrogen atoms or as in the case of High of H ions in our blood diabetic ketoacidosis can occur Definitions to review Strong Acid HCL Dissociates completely b c acids are proton donors which releases all of its H individually into the water Weak Acid H2CO3 Only dissociates partly o Note Acidity of a solution is reflected by FREE H and not those bound to anions thus a weak acid is efficient at preventing a change in pH Strong Base Dissociates easily and accepts H Hydroxides Weak Base Bicarbonate ammonia Explain how the 3 major buffering systems work as well as the subsystems of the protein buffering system We have 3 MAIN Buffering Systems 1 Chemical Buffers a These chemical buffers are our FIRST line of defense and act within a fraction of a second to try and resist pH changes b A compound will bind to H when the pH drops and will release H when the pH rises While a chemical buffer can only tie up acids or bases temporarily ONLY the KIDNEYS can remove the excess from the body c Generally the change is not significant but there is an attempt worth noting so A for effort but you didn t really have a notable effect d B alanine increases our Muscle Carnosine and L Histidine i Bicarbonate Buffer System H2CO3 and NaHCO3 THE ONLY ECF BUFFER 1 1 Carbonic acid doesn t dissociate completely and Bicarbonate ties up 2 H from HCl this results in a lower pH If a strong base is added i e NaOH Carbonic acid will dissociate a little more and pH will rise 3 Buffering power is related to concentration of a substance ii Phosphate Buffer System H2PO4 2 and HPO4 1 Phosphate concentrations are low in the blood so this is a very effective buffer in the urine and ICF 2 Do we need to know the full details of this mechanism iii Protein Buffer System Hemoglobin most powerful Chemical Buffer 1 75 of buffering power of all bodily fluids is in the cells and this mostly reflects the buffering capabilities of intracellular proteins a COOH is a strong acid which releases H when pH rises to counteract it and decrease pH b Amino Group NH2 binds w H to become NH3 and pH rises 2 This is our MOST powerful system in the Chemical Buffers due to the 3 Amphoteric Molecule Amine and COOH group depending on pH of environment Hemoglobin is this a protein that can act as an acid or a base a Hemoglobin is negatively charged after released O2 H dissociates from Carbonic Acid but H rapidly binds to Hg so pH change is minimal 2 Brain Stem Respiratory Centers a These act within 1 3 minutes to counteract acidosis or alkalosis Respiratory Buffer but has 2x the buffering capacity of all the chemical buffers combined which is pretty neat A drop in CSF activates medulla chemoreceptors this activation b Hypercapnia increases our Respiratory Rate Chemoreceptors will also increase plasma H to counteract alkalosis i Acidosis increase in respiratory rate and depth Decrease CO2 shift LEFT and raise pH ii Alkalosis decrease in respiratory rate and depth Increases CO2 shift 3 Renal Mechanisms Kidney RIGHT we want to lower pH a Requires hours days to respond but this system has a very large capacity to alter our pH b Only our kidneys can get rid of metabolic acids i e nitrogen regulator blood levels of alkaline substances and renew chemical buffers that are used up c H is proportional to CO2 in ECF and CO2 is inversely proportional to blood pH i HCO3 is lost when CO2 leaves lungs ii H is retained as HCO3 is secreted which increases H shifting equation to the right iii Na is reabsorbed from filtrate to maintain balance iv Need to replenish HCO3 to counteract H retention d Carbonic acid production in tubule lumen and CO2 diffusion e Bicarb production in cell f Na and Bicarb reabsorption into ECF with no net acid secretion decreases luminal pH from 7 4 to 6 7 2 Explain how the amount of CO2 in the blood affects pH levels Also what is the ventilation response to high and low CO2 levels in the blood LOW We have metabolic acidosis we will start to HYPERVENTILATE and increase bicarbonate LOW CO2 results in an increase in pH reabsorption HIGH excretion HIGH CO2 results in a decrease in pH We have metabolic alkalosis we will start to HYPOVENTILATE and increase bicarbonate Explain the ventilation response to pH levels If pH is under 7 4 we are in acidosis we will have an increase respiratory compensation to decrease both our H and our HCO3 and shift the reaction to the left to raise the pH If pH is over 7 4 we are in alkalosis we will have decreased respiratory compensation to increase both our H and our HCO3 and shift the equation to the right to lower our pH CO2 H2O H2 CO3 H HCO3 How do acidosis and alkalosis occur Respiratory Acidosis pH under 7 35 Can be caused by exchange Respiratory Alkalosis pH over 7 45 PCO2 35 mmHg Can be caused by o Impaired lung function i e chronic bronchitis cystic fibrosis or impaired gas o Impaired ventilatory movement paralysis of respiratory muscles o Narcotic or barbiturate overdose or injury to brain stem depression of respiratory centers resulting in hypoventilation or respiratory arrest o Strong emotions pain anxiety fear panic attack o Hypoxia asthma pneumonia high altitude represents effort to raise PO2 at the expense of excessive CO2 excretion o Brain tumor or injury abnormality of respiratory control 3 Determine the levels of bicarbonate with acidosis and alkalosis Metabolic Acidosis HCO3 Causes 22 mEq L o Severe Diarrhea bicarbonate rich secretions rush through digestive tract before they can be absorbed o Renal Disease failure of kidney to rid body of acid from normal metabolic process o Untreated Diabetes lack of insulin or to respond with proper fuels ketoacidosis o Starvation lack of nutrients o Excess alcohol ingestion results in excess acid in blood o High ECF Potassium potassium competes with H for secretion in renal tubes When ECF K is high H secretion is inhibited Metabolic Acidosis HCO3 Causes 26 mEq L o Vomiting or gastric suctioning loss of HCl requires H be withdrawn from blood to
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