Neuroquantology, the Ultimate Quest - Brain Theory from a Circuits and Systems Perspective - page 151

Fig. 9.1 Expected waveform distortion
When an ion channel opens, lower speed positive ions, which are by far the most
plentiful, are stopped and reversed by a strong repelling electric field as soon as the
internal neural voltage goes positive. A typical potential approaches +40 mV across
the membrane; assuming a 4 nm long channel, this amounts to a repelling force of
about +10MV/m, which is very high indeed, higher than the field for lightening in
the sky (air breaks down at roughly 3 MV/m). Consequently ions are repelled,
forced to drift back to where they came from. This should result in a sharp
reduction, a distortion in the risetime of a neural pulse as internal voltage goes
positive. Without electron capture the neural pulse might appear as in Fig. 9.1 . But
no such distortions are observed.
Pictured in Fig. 9.2 is an artist's rendition of an ion reversing direction in a
channel, and capturing an electron as it leaves. Note that the electric field that repels
outside positive ions also attracts inside electrons. Electrons still may diffuse into
the channel if the electric field is not too high, or they may tunnel into the channel
even for higher potential barriers. Captured electrons contribute to a neural pulse
just like a transfer of positive ions, since losing negative charge is equivalent to
gaining positive charge. Numerous such events would strengthen a neural pulse
making it rise smoothly as commonly observed.
Once the possibility of tunneling is considered, this suggests other possibilities.
For instance, depending on electric fields, stray electrons might tunnel through the
phospholipid bilayer membrane without a transmembrane protein, resulting in
charge transfer. 3 However, the possibility of direct tunneling through the bilayer
membrane is not developed here.
3 Probability of quantum penetration of stray electrons with energy 2 eV going through 1 nm of
membrane barrier presenting a potential barrier of 5 eV is about 10 10 . Because electrons are so
numerous, this is more than enough to build up significant amounts of charge.