  The Hodgkin-Huxley (HH) model is a powerful model to explain different
aspects of spike generation in excitable cells. However, the HH model was
proposed in 1952 when the real structure of the ion channel was unknown. It is
now common knowledge that in many ion-channel proteins the flow of ions through
the pore is governed by a gate, comprising a so-called selectivity filter
inside the ion channel, which can be controlled by electrical interactions. The
selectivity filter is believed to be responsible for the selection and fast
conduction of particular ions across the membrane of an excitable cell. Other
(generally larger) parts of the molecule such as the pore-domain gate control
the access of ions to the channel protein. In fact, two types of gates are
considered here for ion channels: the external gate, which is the voltage
sensitive gate, and the internal gate which is the selectivity filter gate
(SFG). Some quantum effects are to expected in the SFG due to its small
dimensions, which may play an important role in the operation of an ion
channel. Here, we examine parameters in a generalized model of HH to see
whether any parameter affects the spike generation. Our results indicate that
the previously suggested semi-quantum-classical equation proposed by Bernroider
and Summhammer (BS) agrees strongly with the HH equation under different
conditions and may even provide a better explanation in some cases. We conclude
that the BS model can refine the classical HH model substantially.
