5. Time constant of recovery from inactivation—incomplete data
6. Magnitude of steady-state conductance—increases monotonically with increasing depolarization
7. Fall time on sudden repolarization—less than 1 msec.
[Figure 6B] shows the potassium conductance change in response to an imposed step depolarization. Four parameters are sufficient to characterize this response:
1. Delay time—decreases monotonically with increasing depolarization
2. Rise time—decreases monotonically with increasing depolarization
3. Magnitude of steady-state conductance—increases monotonically with increasing depolarization
4. Fall time on sudden repolarization—8 msec or more, decreases slightly with increasing depolarization.
In addition to the aforementioned parameters, the transient portion of the sodium conductance appears to exhibit an accommodation to slowly varying membrane potentials. The time constants of accommodation appear to be those of inactivation or recovery from inactivation—depending on the direction of change in the membrane potential [(18)]. The remaining elements in the Hodgkin-Huxley model are constant and are listed below:
- 1. Potassium potential—80 to 85 mv (inside negative)
- 2. Sodium potential—45 to 50 mv (inside positive)
- 3. Leakage potential—38 to 43 mv (inside negative)
- 4. Leakage conductance—approx. 0.23 millimhos/cm²
- 5. Membrane capacitance—approx. 1 μf/cm²
- 6. Resting potential—60 to 65 mv
- 7. Spike amplitude—approx. 100 mv