to raise pH kidneys and lungs excrete CO2 Phosphate Buffer System H2PO4

To raise ph kidneys and lungs excrete co2 phosphate

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to raise pH, kidneys and lungs excrete CO2 Phosphate Buffer System H2PO4- (dihydrogen phosphate ion) HPO42- + H+ as in the bicarbonate system, reactions that proceed to the right release H+ and ↓ pH, and those to the left ↑ pH Important in the ICF and renal tubules where phosphates are more concentrated and function closer to their optimum pH of 6.8 constant production of metabolic acids creates pH values from 4.5 to 7.4 in the ICF, avg.. 7.0 Protein Buffer System More concentrated than bicarbonate or phosphate systems especially in the ICF Acidic side groups can release H+ Amino side groups can bind H+ Explain how the respiratory system affects pH Neutralizes 2 to 3 as much acid as chemical buffers can Collaborates with bicarbonate system CO2 + H2O → H2CO3 → HCO3- + H+ lowers pH by releasing H+ CO2(expired) + H2O ← H2CO3 ← HCO3- + H+ raises pH by binding H+ Higher CO2 and lower pH stimulate pulmonary ventilation, while an ↑ pH inhibits pulmonary ventilation Explain how the urinary system controls pH Most powerful buffer system (but slow response) Renal tubules secrete H+ into tubular fluid, then excreted in urine Limiting pH
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Tubular secretion of H+ continues only with a concentration gradient of H+ between tubule cells and tubular fluid if H+ concentration ↑ in tubular fluid, lowering pH to 4.5, secretion of H+ stops This is prevented by buffers in tubular fluid bicarbonate system Na2HPO4 (dibasic sodium phosphate) + H+ NaH2PO4 (monobasic sodium phosphate) + Na+ ammonia (NH3), from amino acid catabolism, reacts with H+ and Cl- NH4Cl (ammonium chloride) Describe the causes and effects of acidosis and alkalosis Acidosis H+ diffuses into cells and drives out K+, elevating K+ concentration in ECF H+ buffered by protein in ICF, causing membrane hyperpolarization, nerve and muscle cells are harder to stimulate, CNS depression from confusion to death Alkalosis H+ diffuses out of cells and K+ diffuses in, membranes depolarized, nerves overstimulate muscles causing spasms, tetany, convulsions, respiratory paralysis Disorders of Acid-Base Balances Respiratory acidosis rate of alveolar ventilation falls behind CO2 production Respiratory alkalosis (hyperventilation) CO2 eliminated faster than it is produced Metabolic ↑ production of organic acids (lactic acid, ketones), alcoholism, diabetes, acidic drugs (aspirin), loss of base (chronic diarrhea, laxative overuse) Metabolic alkalosis (rare) overuse of bicarbonates (antacids), loss of acid (chronic vomiting) Compensation for Imbalances Respiratory system adjusts ventilation (fast, limited compensation) hypercapnia (↑ CO2) stimulates pulmonary ventilation hypocapnia reduces it Renal compensation (slow, powerful compensation) effective for imbalances of a few days or longer acidosis causes ↑ in H+ secretion alkalosis causes bicarbonate and pH concentration in urine to rise
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  • Fall '18
  • pH, ICF, ECF, Bicarbonate

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