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21 Cards in this Set
- Front
- Back
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State which ones are ECF or ICF buffers: bicarb, hemoglobin, organic phosphate compounds, plasma proteins, inorganic pohsphate
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ECF: Bicarb, plasma proteins, inorganic phosphate.
ICF: hemoglobin, organic phosphate compounds |
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What is the pH equation for bicarb?
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pH = 6.1 + log(HCO3/0.03CO2)
Note that 0.03mmol/L/mmHg is the solubility coefficient |
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What does increase or decrease in pH do to endogenous acid production?
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Increase in pH increases endogenous acid production; decrease in pH decreases endogenous acid production
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List the 4 acid-base disturbances, the changes in PCO2 and HCO3-, and the compensatory responses involved
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Respiratory acidosis - decrease in pH, increase in pCO2 and HCO3. Kidneys increase H+ excretion to increase blood bicarb
Respiratory alkalosis - increase in pH, decrease in pCO2 and HCO3. Kidneys increase HCO3+ to decrease bicarb Metabolic acidosis - decrease in pH, decrease in pCO2 and HCO3. Alveolar hyperventilation; kidneys increase H+ excretion Respiratory acidosis - decrease in pH, increase in pCO2 and HCO3. Alveolar hypoventilation; kidneys increase HCO3+ excretion |
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Causes of respiratory acidosis. Chemical, Respiratory and renal compensation
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Decrease in alveolar ventilation (hypoventilation due to insufficient neural drive for ventilation, inadequate movements of muscle, lung disease, etc.), V/Q mismatch, breathing CO2. Alveolar hyperventilation; kidneys increase H+ excretion
most of buffering is within the cells. Respiratory response is inadequate to prevent CO2 accumulation. Bicarb concentrations increase - 4mEq/L per 10mmHg is for chronic, 1mEq/L per 10 mmHg is for acute |
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Causes of respiratory alkalosis. Chemical, Respiratory and Renal Compensation
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Alevolar hyperventilation, due to voluntary hyperventilation, anxiety, direct stimulation of medullary respiratory center (meningitis, fever, aspirin intoxication), hypoxia caused by severe anemia and high altitude.
Chemical buffering most in cells. inhibited ventilation, but inadequate Renal excretes bicarb. Fall is 1mEq/L per 10mmHg for acute; 2mEq/L per 10 mmHg for chronic |
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Causes of Metabolic acidosis. Chemical, Respiratory and Renal Compensation
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Failure of kidneys to excrete acid (acute and chronic renal failure); excessive intake or pdouction of nonvolatile acids (keto, lactic, ingestion of acidifying agents, poisons), loss of bicarbonate.
Half of buffering occurs in cells and bone, with bicarb as primary buffer Respiratory compensation - blood pH stimulates ventilation. Renal compensation - kidneys increase H+ excretion, add new bicarbonate into blood |
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How does anion gap change with metabolic acidosis? What causes anion gap acidosis? When does anion gap NOT change for metabolic acidosis?
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anion gap takes into account unmeasured anions. Increase in phosphate, lactate, etc. causes increase in anion gap (normal range is 8-14mEq/L).
Methanol, Uremia, Lactic Acid, Ethylene Glycol, Paldehyde, Ketone Body acids, Salicylates. Hyperchloremic acidosis - GI losses of bicarbonate, renal tubular acidosis, or ingestion of NH4-Cl |
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Causes of Metabolic alkalosis. Chemical, Respiratory and Renal Compensation
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Excessive alkali intake (ingestion of antacids); loss of acid (vomiting of gastric acid juice, renal loss of H+ (hyperaldosteronism, hypokalemia).
Chemical buffers liberate H+, about 1/3rd used; Respiratory compensation - hypovolemia, limited. Renal compensation - bicarbonate excretion |
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How do you calculate net renal acid excretion?
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Urinary titratable acid + urinary NH4+ - urinary HCO3-
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What are dietary sources of metabolic acidosis? What are dietary sources of metabolic alkalosis?
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Cationic amino acids (arginine, lysine, histidine) makes hydrochloric acid; phosphorous containin proteins + phosphoesters of nucleic acids causes phosphoric acid
Incomplete oxidation of fatty acids and glucose Citrate makes bicarbonate |
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What are three mechanisms of renal compensation to urinary acidification? How are the two of the methods different from the first?
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Reabsorption of filtered bicarobnate. Uses carbonic anhydrase enzyme in apical and cytoplasm of tubular epithelium. Note that the process does not raise bicarbonate plasma concentrateion.
Formation of titratable acid. Note the proton pumps in alpha-intercalated cells. Also note that bicarbonate levels increase Excretion of ammonia. 2 ammonium ions are made from 1 glutamine molecule. Note that for each NH4+ excreted, 1 HCO3- is added to blood. |
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Where is most of H+ secreted in? Where is the steepest pH gradient established and why?
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Majority is in the PCT. Steepest pH gradient established in the collecting ducts, due to NH4+ entering the collecting duct and getting trapped there.
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Where along the nephron is ammonia made? Where and how does it go through before reaching the collecting duct?
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Ammonia is made along the proximal tubule cells and secreted. NH4+ is reabsorbed in thick ascending limb, and accumulates the medulla. NH3 diffuses into collecting duct urine where it is trapped
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How does H+ excretion change with intracellular pH?
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Decrease pH -> increase Na+-H+ exchanger, recruited H-ATPases, stimulated renal ammonia synthesis. Thus, H+ excretion increases
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How does H+ excretion change with intracellular pCO2?
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Increased pCO2 -> increased bicarb production -> increased H+ secretion.
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How does H+ excretion change with intracellular carbonic anhydrase activity?
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Inhibited of carbonic anhydrase activity will lower H+ for secretion
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How does H+ excretion change with intracellular Na+ reabsorption?
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Increased Na+ reabsorption > makes lumen more negative, favors H+ secretion.
Important in volume depletion of vomiting -> lowered Na, lowered H+, but increased Na+ reabsorption will keep lowering H+. Thus, give salt water |
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How does H+ excretion change with intracellular K+ reabsorption?
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Increased K+ -> decreased H+ secretion.
Hypokalemia results in movement of K+ from cells into ECF; H+ cell smove in exchange for H+, results in intracellular acidosis and increased H+ secretion. Hypokalemia results in increased ammonia synthesis due to intracellular acidosis Hypokalemia stimulates H/K ATPase activie |
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how does aldosterone change H+ stimulation?
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Aldosterone stimulates H+ secretion
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List the speed and quality of chemical buffering, respiratory compensation, and finally renal compensation
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Chemical buffers: rapid. Respiratory system: fairly rapid, but incomplete. Renal compensation: Slower (takes time to make ammonia), but more perfect
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