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Lecture 20

Lecture 20






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    Lecture 20 Lecture 20 Presentation Transcript

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