1. OBJECTIVES 1. 1.Electrical components, current, voltage, resistance, conductance, capacitance. 2. 2.Principle of equilibrium. 3. 3.Osmolarity vs. tonicity: how they affect cell volume 4. 4.Principle behind the following equations: Nernst equation Hodgkin/Huxley equation Gibbs-Donnan Equilibrium 5. 5.Measurement of membrane conductance : Current clamp conditions Voltage clamp conditions Patch clamp conditions Review - Weeks 1 & 2

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

3. CAPACITANCE NON-CONDUCTIVE ELEMENT A B

4. RC CIRCUIT V in V out RC

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

6. OSMOSIS BA 0.1 M K + 0.1 M Cl - 0.01 M Cl - 0.01 M K +

7. Why consider osmolarity and tonicity? [K + ] e (mM) Change in Fiber water (%) [K + ] i (mM) 31491 61492 1226101 1823107 3017120 6012142 9013184 ↑ [K + ] e → [Na + ] e

8. Why consider osmolarity and tonicity? ↑ [K + ] e ↓[Na + ] e [K + ] e (mM) Change inFiber water (%) [K + ] i (mM) 100119 208 3014120 4030119 5045 6062 7095117

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

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

11. CABLE PROPERTIES 20155 EmEm 5 STIM ∆Em ∆Em= AXON Current

12. Membrane / Cytosolic Resistance & Capacitance RmRiCm   cm 2   cm  F/Cm 2 Black lipid1.0 Axon (lobster) Homarus vulgaris 229060.51.3 Axon (crab) Carcinus maenas 326354.71.2 Sartorius muscle Rana pipiens 20802485.2