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OBJECTIVES

Review - Weeks 1 & 2. OBJECTIVES. Electrical components, current, voltage, resistance, conductance, capacitance . Principle of equilibrium. Osmolarity vs. tonicity: how they affect cell volume Principle behind the following equations: Nernst equation Hodgkin/Huxley equation

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OBJECTIVES

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  1. Review - Weeks 1 & 2 OBJECTIVES • Electrical components, current, voltage, resistance, conductance, capacitance . • Principle of equilibrium. • Osmolarity vs. tonicity: how they affect cell volume • Principle behind the following equations: • Nernst equation • Hodgkin/Huxley equation • Gibbs-Donnan Equilibrium • Measurement of membrane conductance : • Current clamp conditions • Voltage clamp conditions • Patch clamp conditions

  2. Direction of current • [ ] [] [] [] []  • [] [ ] [] [] []  • [] [] [ ] [] []  • [] [] [] [ ] []  • [] [] [] [] []

  3. A NON-CONDUCTIVE ELEMENT B CAPACITANCE

  4. C R Vout Vin RC CIRCUIT

  5. DIFFUSION EQUILIBRIUM A B 0.1 M K+ 0.01 M K+ 0.1 M Cl- 0.01 M Cl-

  6. OSMOSIS A B 0.1 M K+ 0.01 M K+ 0.1 M Cl- 0.01 M Cl-

  7. Why consider osmolarity and tonicity? ↑ [K+]e→ [Na+]e

  8. Why consider osmolarity and tonicity? ↑ [K+]e ↓[Na+]e

  9. ELECTROCHEMICAL GRADIENT AND EQUILIBRIUM A B 0.1 M K+ 0.01 M K+ 0.1 M Cl- 0.01 M Cl-

  10. GIBBS-DONNAN EQUILIBRIUM A B 0.1 M K+ 0.1 M K+ 0.1 M Cl- 0.1 M Anions

  11. Em ∆Em STIM CABLE PROPERTIES AXON Current ∆Em= 5 15 20 15 5

  12. Membrane / Cytosolic Resistance & Capacitance

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