1. Equivalent Circuit of an Axon Membrane

2. Feedback Amplifier current proportional to difference (E-input)
Measured voltage
Input Signal
Measured Current
Feedback Amplifier current proportional to difference (E-input)
Hodgkin & Huxley’s voltage clamp of the squid giant axon

3. Hodgkin & Huxley’s voltage clamp of the squid giant axon:
early inward Na
late outward K
Hodgkin & Huxley’s voltage clamp of the squid giant axon:
Current response to hyper-polarization and de-polarization

4. Hodgkin & Huxley’s voltage clamp of the squid giant axon:
late outward K
early Na
Hodgkin & Huxley’s voltage clamp of the squid giant axon:
Current response to hyper-polarization and de-polarization

5. Hodgkin & Huxley separation of Na and K currents by variation of bath Na concentration

6. Separation of Na and K Current-Voltage curves

7. Separation of Na and K Ionic conductance changes
Rapid changes in gNa
Slow changes in gK
Separation of Na and K Ionic conductance changes

8. Na and K conductance at various voltage clamp steps

9. Channel openings and closings during Action Potential

10. Example of time course of changes in n & n^4 ~ gK and m, h & m^3
Example of time course of changes in n & n^4 ~ gK and m, h & m^3*h ~ gNa

11. Voltage dependence of Hodgkin-Huxley model parameters