Simulation of the Action Potential in the Neuron’s Membrane in Artificial Neural Networks - Advancing Artificial Intelligence Through Biological Process Applications - page 78

gets to take the potassium ions out of the cell by
diffusion, but the strong attraction of the organic
ions trend to maintain the potassium inside.
The result of these opposite forces is an
equilibrium where there are more sodium and
chlorine ions (Cl-) outside and more organic and
potassium ions inside.
This equilibrium makes a potential difference
through the cell's membrane of 70 to 100 mV
(millivolts), being negative the intracell fluid. This
potential is called cell's repose potential.
The influences of the excitatory inputs that
arrive to one cell from another are added in the
axonal join and cause a successive depolarization
of the membrane. It is then that the potential gets
inverted up to +35 mv in only 0.1 milliseconds. The
resultant depolarization alters the permeability of
the cellular membrane relating to sodium ions.
As a result, there is an incoming flux of positive
sodium ions that enter the cell influencing even
more the depolarization.
This self-generated effect causes the action
potential (Figure 1). After an action potential, the
potential of the membrane becomes more negative
than the repose potential for some milliseconds,
up to get the ion equilibrium. To begin with the

action potential, it is required a sudden increment
of approximately 15-30 mv, considering -65 mv
the stimulation threshold. Within an excitable fiber
it can't be got a second action potential while the
membrane is depolarized.
The period during which it can't be launched
another action potential, even with a very powerful
stimulus, it is called “absolute refractory period”
and it lasts about 0.5 milliseconds. Then, it is fol-
lowed by a “relative refractory period” that lasts
from 1 to 1.5 milliseconds, while it is needed a
bigger stimulus than usually to get the action
potential, because the ionic equilibrium of the
repose potential hasn't been recovered yet.
This point can't be excited in approximately 1
millisecond, the time that it takes to recover the
repose potential. This refractory period limits the
transmission frequency of the nervous impulse
to about 1000 per second.

TIME DECREASED ACTIvATION

Obviously, the behaviour of the PE in the ANN
is not very similar, about the activation phase, to
what we have just described. In the traditional

Figure 1. Action potential in the neuron's membrane

Action Potential

40 mV

Threshold

-65 mV

Repose
Potential

-100 mV

1 2

0 3

Milliseconds