120 likes | 311 Views
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
E N D
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
Direction of current • [ ] [] [] [] [] • [] [ ] [] [] [] • [] [] [ ] [] [] • [] [] [] [ ] [] • [] [] [] [] []
A NON-CONDUCTIVE ELEMENT B CAPACITANCE
C R Vout Vin RC CIRCUIT
DIFFUSION EQUILIBRIUM A B 0.1 M K+ 0.01 M K+ 0.1 M Cl- 0.01 M Cl-
OSMOSIS A B 0.1 M K+ 0.01 M K+ 0.1 M Cl- 0.01 M Cl-
Why consider osmolarity and tonicity? ↑ [K+]e→ [Na+]e
Why consider osmolarity and tonicity? ↑ [K+]e ↓[Na+]e
ELECTROCHEMICAL GRADIENT AND EQUILIBRIUM A B 0.1 M K+ 0.01 M K+ 0.1 M Cl- 0.01 M Cl-
GIBBS-DONNAN EQUILIBRIUM A B 0.1 M K+ 0.1 M K+ 0.1 M Cl- 0.1 M Anions
Em ∆Em STIM CABLE PROPERTIES AXON Current ∆Em= 5 15 20 15 5