1. 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

2. 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

3. 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

4. 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

6. Solute Overview: Intracellular vs. Extracellular Ionic composition very different Total ionic concentration very similar

7. METHODS OF FLUID & ELECTROLYTE MOVEMENT Diffusion Osmosis Active Transport

8. 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

9. 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

10. 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.

12. 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

13. 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

14. 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

15. 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

16. 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)

17. Mechanism of Na+ Selective Reabsorption in Collecting Duct Aldosterone: steroid H from adrenal cortex Stimulates Na+ uptake (& K+ secretion)  channel synthesis

18. Mechanism of Na+ Selective Reabsorption in Collecting Duct