Figure 1.

Circuit diagram for one of the basic units. The unit circuitry was the same for both the surface units and junctional units, but the values of the various components were adjusted to reflect the long surface membrane and short junctional membrane. These values are listed in Table 1. The GTABLE values for the two types of membrane were also different, and these are listed in Table 2. Note that there are two black-boxes (BB) in the basic unit, and both are in the same leg of the Hodgkin-Huxley circuit, namely the Na⁺ conductance leg. The first BB produced activation of the Na⁺ conductance, and the second produced deactivation of the Na⁺ channel conductance. It was necessary to produce a time delay (RC time constant) before the second BB came into play to cause deactivation. The two operational amplifiers (unit gain) acted as buffers. In the K⁺ leg, the K⁺ conductance is in series with E_K, the K⁺equilibrium potential.