Lecture 20


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Lecture 20

  1. 1. Electrolyte<br />Substance when dissolved in solution separates into ions & is able to carry an electrical current<br />Solute substances dissolved in a solution. These may be electrolytes or non-electrolytes<br />Electrolytes have an electrical charge when they are dissolved in water <br />Electrolytes that have a positive charge are called cations <br />Electrolytes with negative charge are anions<br />
  2. 2. Cations<br />Cations include sodium (Na+), potassium (K+), calcium (Ca+), Magnesium (Mg+), and hydrogen (H+)<br />The number of cations must equal the number of anions<br />The combining power of electrolytes is measured in milliequivalents (mEq)<br />It is the measure of charge concentration<br />
  3. 3. Anions<br />Include chloride ions, bicarbonate ions, phoshate ions, sulphate ions, organic acids, and proteins<br />Measurement of solute concentration in body fluids is based on fluid’s osmotic pressure, expressed as osmolarity<br />Osmolarity is the number of osmols (standard unit of osmotic pressure) per liter of solution<br />
  4. 4. Electrolyte<br />Electrolytes are the major components of body fluids. They enter the body through the food we eat and the beverages that we drink.<br />Electrolytes leave the body by way of urine, skin and feces.<br />The concentration of electrolyte must be maintained within specific limits<br />
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  6. 6. Solute Overview: Intracellular vs. Extracellular<br />Ionic composition very different<br />Total ionic concentration very similar<br />
  7. 7. METHODS OF FLUID & ELECTROLYTE MOVEMENT<br />Diffusion<br />Osmosis<br />Active Transport<br />
  8. 8. Electrolyte Functions<br />Controlling fluids movements between compartments<br />The movement of fluids across cell membrane differs from the movement of fluids between interstitial compartment and plasma<br />
  9. 9. Fluid Movements across cell membrane<br />Electrolytes moves across cell membrane through ion channels and ion pumps that are selective for specific ions<br />Na-K ATPase in the membrane: move ions against their concentration gradients <br />Channels specific for Na ions allow the ions to diffuse from area of higher concentration to areas of lower concentration<br />Channels specific for K allows K ions to move across the membrane from areas of higher to lower concentration<br />Differences in ion concentration between intercellular and intracellular fluids are caused by these selective ion channels<br />
  10. 10. Water move freely through water channel, which moves from higher water concentration to lower concentration<br />Through osmosis water moves to the side of membrane of higher solute concentration<br />Na exerts significant effect on water movements.<br />
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  12. 12. Fluid movement between ISF and Plasma<br />Ions and water can move freely between plasma and ISF <br />Proteins too big to leave the capillaries<br />Protein concentration in the plasma is higher than in ISF<br />Protein in the plasma exerts colloid osmotic pressure. Water moves from ISF to plasma<br />Capillary hydrostatic pressure forces fluid out of the capillary <br />
  13. 13. Sodium<br />Major cation in ECF (positively charged)<br />Responsible for extracellular osmotic pressure<br />Regulated by Aldosterone and the kidneys<br />Increases sodium reabsorption in DCT of nephron<br />Normal serum concentration in ECF ranges from 135-146 mEq/L<br />
  14. 14. Sodium Functions<br />Sodium maintains ECF osmolality, ECF volume, and influences water distribution (where salt goes water follows)<br />It affects the concentration, secretion, and adsorption of potassium<br />It also help aid the impulse transmission of nerve and muscle fibers<br />
  15. 15. Imbalances<br />Hyponatremia less than 130 mEq/L)-low sodium level-may cause headache, hypotension, decreased body temp, nausea, vomiting, and possible coma. <br />Hypernatremia occurs when plasma Na more than 150 mEq/L) -high sodium level-usually indicates water deficit in ECF-symptoms include thirst, dry sticky tongue, confusion, disorientation, hallucination, lethargy, seizures, coma, agitation<br />
  16. 16. Sodium Regulation<br />Na is filtered through glomerulus<br />Na is reabsorbed to plasma at proximal convoluted tubule (PCT) and the loop of Henle<br />In the presence of Aldosterone, Na reabsorbed at the distal convoluted tubule (DCT) <br />
  17. 17. Mechanism of Na+ Selective Reabsorption in Collecting Duct<br />Aldosterone: steroid H from adrenal cortex<br />Stimulates Na+ uptake (& K+ secretion)<br /> channel synthesis<br />
  18. 18. Mechanism of Na+ Selective Reabsorption in Collecting Duct<br />