Acid base lecture (shortened)

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Acid base lecture (shortened)

  1. 1. Chapter 24 Acid-Base Balance Anatomy & Physiology: The Unity of Form and Function , 5th Edition. By, Kenneth S. Saladin.
  2. 2. Acid-Base Balance <ul><li>Normal blood pH = 7.35-7.45 </li></ul><ul><ul><li>Arterial blood pH = 7.4 </li></ul></ul><ul><ul><li>Venous blood pH = 7.35 </li></ul></ul><ul><li>Alkalosis : arterial blood pH rises above 7.45 </li></ul><ul><li>Acidosis: arterial pH drops below 7.35 (physiological acidosis) </li></ul>
  3. 3. Hydrogen Ion Regulation <ul><li>Concentration of hydrogen ions is regulated sequentially by: </li></ul><ul><ul><li>Chemical buffer systems – act within seconds </li></ul></ul><ul><ul><ul><li>e.g. Bicarbonate Buffer System (H 2 CO 3 /HCO 3 - ) </li></ul></ul></ul><ul><ul><ul><li>e.g. Proteins (hemoglobin) </li></ul></ul></ul><ul><ul><li>The respiratory system – acts within 1-3 minutes </li></ul></ul><ul><ul><li>The renal (urinary) system – require hours to days to affect pH changes </li></ul></ul>
  4. 4. Acid-Base Regulation by Respiratory System: <ul><li>As more CO 2 accumulates, so do H + ions, resulting in Acidosis. </li></ul><ul><li>To Compensate for Acidosis (  pH,  H + ): respiratory rate and depth are increased to eliminate more CO 2 and lower H + ions and raise blood pH. </li></ul><ul><li>To Compensate for Alkalosis (  pH,  H + ): respiratory rate and depth are decreased to accumulate more CO 2 and raise H + ions and lower blood pH. </li></ul><ul><ul><li>CO 2 + H 2 O  H 2 CO 3  H + + HCO 3 ¯ </li></ul></ul>
  5. 5. Acid-Base Regulation by the Renal System: <ul><li>Chemical buffers can tie up excess acids or bases, but they cannot eliminate them from the body </li></ul><ul><li>The lungs can eliminate carbonic acid by eliminating carbon dioxide </li></ul><ul><li>Only the kidneys can rid the body of hydrogen ions as well as metabolic acids (phosphoric, uric, and lactic acids and ketones). </li></ul><ul><li>The ultimate acid-base regulatory organs are the kidneys </li></ul>
  6. 6. Acid-Base Regulation by the Renal System: <ul><li>To Compensate for Acidosis (  pH,  H + ): the kidneys reabsorb more HCO 3 - ions and secrete more H + ions to lower H + and increase pH. </li></ul><ul><li>To Compensate for Alkalosis (  pH,  H + ): the kidneys reabsorb more H + ions and secrete more HCO 3 - ions to increase H + and lower pH. </li></ul>Renal Compensation for Acidosis
  7. 7. Respiratory Acidosis: <ul><li>Blood pH is below 7.35 </li></ul><ul><li>Due to decreased CO 2 elimination (hypoventilation) </li></ul><ul><li>Occurs when a person breathes shallowly , or gas exchange is hampered by diseases such as pneumonia, cystic fibrosis, or emphysema </li></ul><ul><li>Can be due to depressed respiration due to narcotic or barbiturate overdose </li></ul>
  8. 8. Respiratory Alkalosis: <ul><li>Blood pH is above 7.45 </li></ul><ul><li>Due to increased CO 2 elimination (hyperventilation) </li></ul><ul><li>Occurs when a person breathes quickly and/or shallowly, usually due to pain, anxiety, or asthma . </li></ul>
  9. 9. Metabolic Acidosis: <ul><li>Blood pH is below 7.35 </li></ul><ul><li>Due to increased bicarbonate loss or increased acid accumulation. </li></ul><ul><ul><li>Typical causes of acid accumulation are ingestion of excess alcohol , excess asprin intake, excessive exercise , untreated diabetes mellitis , and starvation diets. </li></ul></ul><ul><ul><li>Typical causes of bicarbonate loss are excessive diarrhea and vomiting from the lower GI . </li></ul></ul>
  10. 10. Metabolic Alkalosis: <ul><li>Blood pH is above 7.45 </li></ul><ul><li>Due to increased reabsorption of bicarbonate ion or increased hydrogen ion loss . </li></ul><ul><ul><ul><li>Typical causes of bicarbonate ion reabsorption include excessive antacid ingestion and constipation . </li></ul></ul></ul><ul><ul><ul><li>Typical causes of hydrogen ion loss include excessive vomiting from upper GI (stomach); aldosterone hypersecretion . </li></ul></ul></ul>
  11. 11. What is the effect of Acidosis / Alkalosis? <ul><li>Acidosis : CNS depressed (muscle and nerve cells are hyperpolarized)  confusion, coma, death. </li></ul><ul><li>Alkalosis : CNS overstimulation (muscle and nerve cells are easily depolarized due to xs K + )  muscle tetany, nervousness, convulsions, respiratory paralysis, death. </li></ul>

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