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ADVANCED PHYSIOLOGY FLUID & ELECTROLYTES Part 1 Instructor Terry Wiseth

ADVANCED PHYSIOLOGY FLUID & ELECTROLYTES Part 1 Instructor Terry Wiseth. NORTHLAND COLLEGE. FLUID ELECTROLYTE HOMEOSTASIS. In a healthy individual fluid volume and electrolyte concentrations are maintained within strict homeostatic limits through the interaction of several organ systems.

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ADVANCED PHYSIOLOGY FLUID & ELECTROLYTES Part 1 Instructor Terry Wiseth

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  1. ADVANCED PHYSIOLOGYFLUID & ELECTROLYTESPart 1Instructor Terry Wiseth NORTHLAND COLLEGE

  2. FLUID ELECTROLYTE HOMEOSTASIS • In a healthy individual fluid volume and electrolyte concentrations are maintained within strict homeostatic limits through the interaction of several organ systems

  3. FLUID ELECTROLYTE HOMEOSTASIS • Total body water (TBW) can be divided by cell membranes into two main compartments: • 1) Extracellular fluid (ECF) • fluid outside cells • 1/3 of total body water • 2) Intracellular fluid (ICF) • fluid inside cells • 2/3 of total body water

  4. FLUID ELECTROLYTE HOMEOSTASIS • The ECF is further divided into: • 1) Blood plasma (80%) • 2) Interstitial fluid (20%) • These two ECF compartments are separated by a capillary membrane Interstitial fluid

  5. FLUID COMPARTMENTS • Effectively there are three compartments • 1) Intracellular • 2) Interstitial • 3) Plasma

  6. FLUID COMPARTMENTS Cell CYTOPLASM PLASMA (Intracellular) (Extracellular) INTERSTITIAL FLUID Capillary

  7. ELECTROLYTES • Dissolved ions in the: • Cell, interstitial fluid, blood • Potassium (K) • Sodium (Na) • Calcium (Ca) • Magnesium (Mg) • Chlorine (Cl) • Bicarbonate (H2CO3) • Proteins (Pr)

  8. ELECTROLYTES • There are three key concepts in consideration of fluid and electrolyte management: • 1) Cell Membrane Permeability • 2) Osmolarity • 3) Electroneutrality

  9. CELL MEMBRANE PERMEABILITY • Refers to the ability of a cell membrane to allow certain substances to pass freely • Other substances like charged ions (Na+) cannot cross the membrane and are trapped on one side of it H2O Na+ H2O H2O H2O Na+ H2O Na+ H2O Na+ Na+ H2O Na+ Na+ H2O Na+

  10. CELL MEMBRANE PERMEABILITY • In other words • “No Trespassing” • Cell membranes allow some things to pass and blocks passage of others

  11. OSMOLARITY • Osmolarity is a property of particles in solution • If a substancecan dissociate insolution, it willcontribute to theosmolarity of thesolution

  12. OSMOLARITY • In other words • “Water, water every where but not a drop to drink” • If you are thirsty, you cannot drink salt water

  13. ELECTRONEUTRALITY • The principle of Electroneutrality means that the overall number of positive and negative charges balances • For instance, in conditions like renal tubular acidosis where HCO3- is lost, chloride is retained Cl-

  14. ELECTRONEUTRALITY • In other words • “Cells do not make good batteries” • Positive and negative charges inside and outside the cell must be equal Click to show a charged battery - + - + - + - + - + - + - + - + - +

  15. ELECTROLYTES • When the body is in “fluid balance” it means that the various body compartments (cells, tissues, organs) contain the required amount of fluids to carry out normal bodily functions

  16. ELECTROLYTES • Fluid balance and electrolyte balance are inseparable • In a healthy individual, the volume of fluid in each compartment remains stable

  17. ELECTROLYTES • Loss of electrolytes can have serious consequences for the body • In severe dehydration, the loss of electrolytes can result in circulatory problems such as tachycardia (rapid heart beat) and problems with the nervous systemsuch as loss ofconsciousnessand shock

  18. ELECTROLYTES • Electrolytes serve three general functions to maintain: • 1) Normal metabolism • 2) Proper fluid movement between compartments • 3) The acid-base balance

  19. ELECTROLYTE COMPOSITION OF PLASMA AND INTERSTITIAL FLUID

  20. ELECTROLYTES

  21. ELECTROLYTES PLASMA INTERSTITIAL FLUID

  22. Na+ Cl- IONS AND MOLECULES • Ions are charged atoms • ex: Na+, Cl-, Mg++ • Molecules are formed when two or more atoms or ions are combined • ex: H2O, C6H12O6, NaCl

  23. MOVEMENT OF BODY FLUIDS • Fluid moves between the compartments of the body through various mechanisms • Substances leave and enter capillaries via three mechanisms: • 1) Vesicular transport • 2) Diffusion • 3) Bulk flow

  24. VESICULAR TRANSPORT AND DIFFUSION • Vesicular transport and diffusion are associated with the movement of solutes (electrolytes)

  25. BULK FLOW • Bulk flow is the most important process for the maintenance of relative volumes (fluids) of blood and interstitial fluid • Bulk flow involves the movement of both solvent (fluids) and solute into the interstitial space

  26. MOVEMENT OF IONS AND MOLECULES • Ions and molecules pass through membranes by: • Simple Diffusion • Passage through channels • Facilitated Diffusion • Active Transport (Na-K pump)

  27. CELL MEMBRANE

  28. FLUID COMPARTMENTS • Describes the distribution of water in the body • Fluid compartments are separated by semipermeable membranes • Capillary wall separates the plasma and the interstitial fluid • Cell membrane separates the cytoplasm and interstitial fluid

  29. SEMIPERMEABLE MEMBRANE

  30. SEMIPERMEABLE MEMBRANE

  31. FLUID COMPARTMENTS PLASMA CAPILLARY WALL CELL MEMBRANE INTERSTITIAL FLUID CYTOPLASM

  32. FLUID SHIFTS • Fluid shifts may occur as the result of disease or injury

  33. FLUID SHIFTS • Accumulations of fluids in a tissue or in a body cavity is called third space compartment • Ex: liver disease may lead to significant accumulations of fluid in the peritoneal cavity • Represents a fluid loss as it is trapped

  34. FACTORS CONTROLLING EXCHANGES OF FLUIDS • 1) Diffusion • 2) Filtration • a) Hydrostatic Pressure • b) Osmotic (Oncotic) Pressure

  35. DIFFUSION • Water, small molecules and ions • Movement of molecules from areas of higher concentration to areas of lower concentration Click to View Animation

  36. FILTRATION • Net flow of water is due to overall effect of pressure on both sides of a membrane • Fluid is filtered out of capillaries in response to changes in: • 1) Hydrostatic Pressures • 2) Oncotic (Osmotic) Pressures H2O H2O H2O H2O H2O H2O H2O H2O H2O

  37. HYDROSTATIC PRESSURE (HP) • Fluid pressure • Ex: blood pressure in the capillaries 6 4 H2O H2O H2O H2O 8 6 H2O H2O H2O H2O H2O H2O H2O H2O

  38. HYDROSTATIC PRESSURE (HP) • Fluid pressure • Ex: blood pressure in the capillaries • Ex: pressure exerted by interstitial fluid 8 6 H2O H2O H2O H2O H2O 6 4 H2O H2O H2O H2O H2O H2O H2O

  39. HYDROSTATIC PRESSURE IN PLASMA • Blood Pressure at Arterial end of capillaries is 30 mm Hg • Blood Pressure at Venous end of capillaries is 10 mm Hg • Difference in pressure forces fluid out of plasma to the interstitial fluid

  40. HYDROSTATIC PRESSURE IN PLASMA Osmotic Pressure H2O H2O H2O H2O Click to View Osmotic Pressure NetPressureon Fluids Click to View Hydrostatic Pressure Click toView Net Pressureon Fluids Venule side Net Pressure on Fluids Arteriole side Hydrostatic Pressure H2O H2O H2O H2O Osmotic Pressure

  41. HYDROSTATIC PRESSURE ININTERSTITIAL FLUID • The lymphatic system drains interstitial fluid creating a negative interstitial pressure • Hydrostatic pressure in interstitial space is - 6 mm Hg • Supplies a pulling force (suction) drawing fluid out of the capillaries

  42. OSMOTIC (ONCOTIC) PRESSURE • Drawing force resulting from the pressure created by presence of protein dissolved in the: • Cytoplasm • Plasma • Interstitial fluid • Pressure which develops when there is net movement of water across a membrane (osmosis)

  43. OSMOTIC (ONCOTIC) PRESSURE • Pressure created is directly proportional to solute concentration • Thus osmotic pressure is dependent on the concentration of urea, glucose, amino acids, electrolytes and proteins • Oncotic pressure definespressures which are the resultof protein concentration differences

  44. Solute Solvent HIGHOSMOTIC PRESSURE LOWOSMOTIC PRESSURE OSMOTIC (ONCOTIC) PRESSURE Click to View Change Semi-permeable membrane

  45. Capillary ONCOTIC PRESSURE IN PLASMA • Oncontic pressure at the arterial end of capillaries is 28 mm Hg • Oncotic pressure of interstitial fluid is5 mm Hg • Due to a higher protein concentration in plasma (albumin) Pr- Pr- Pr- Pr- Pr- Pr- H2O H2O Pr- Pr- Pr- Pr- Pr- Pr- Pr- Pr- Pr- Pr- Pr- Pr- Pr- Pr- Pr- H2O H2O H2O H2O H2O

  46. Capillary ONCOTIC PRESSURE PROTEIN (OP) INTERSTITIAL FLUID PROTEIN (OP) H2O H2O Opposing oncotic pressure (OP) inside and outside of a capillary. A higher protein concentration in plasma as compared to interstitial fluid, thus it has a greater oncotic pressure

  47. Capillary CAPILLARY-INTERSTITIAL FLUID EXCHANGES • Hydrostatic and osmotic (oncotic) pressures create opposing inward and outward forces on the capillary Hydrostatic Pressures Osmotic Pressures

  48. Capillary OUTWARD FORCES • Arterial end of capillary exerts hydrostatic pressure (30 mm Hg) 30 Hydrostatic Pressures

  49. Capillary OUTWARD FORCES • Interstitial fluid oncotic pressure (5 mm Hg) • Negative interstitial fluid pressure (-6 mm Hg) • Total outward pressure 41 mm Hg 5 30 Osmotic Pressures Hydrostatic Pressures 6 Interstitial Fluid (Pull)

  50. Capillary INWARD FORCES • Plasma oncotic pressure (28 mm Hg) 28 Osmotic Pressures

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