January 02, 2019 Wednesday
Bedtime Story
The Story of Action Potential
The action potential that “runs” along our
neurons and cardiac muscle cells is explained in terms of chemistry and physics
and is measured and recorded mathematically.
In the end all our actions and thoughts and
wishes are fundamentally explained by the movement of sodium and potassium ions
across channels through special voltage-gated ion channels.
The actual event that we call a nerve
impulse is a mere depolarization of the resting transmembrane potential that
exists all the time because of differential permeability of biological
membranes that enclose excitable cells to different subset of ions.
I cannot go into the depths of the action
potential or resting membrane potential since it is a topic that will carry me far
too away from the original thread which already seems to be getting lost in a
series of digresses.
The importance of the story of membrane
potential and action potential is emphasized by the very fact that this is one
of the first topics that we as medical students are taught in the physiology of
human being (most studies of action potential are actually carried out in other
species of the animal kingdom the most favorite one being the squid that
possess neuronal axons so large in diameter that they can be seen even with our
naked eyes and thus accessible to easy probing with micro electrodes).
Action potentials like genetic information
is a common thread found in all living forms including those of plants going up
to invertebrates and later vertebrates such as reptiles all the way up to
mammals and then the higher apes.
The only multicellular organisms that
perhaps lack these action potentials are sponges since their multiple
eukaryotic cells are loosely bundled up together more like a colony of
apartment blocks rather than a tightly knit family living in a single room.
Just see how life and evolution works; once
one of the multicellular organisms managed to develop this system of action
potential accidentally (differential ion concentration across lipid membrane)
it conferred to it huge evolutionary advantage in terms of survival and
replication.
Such organisms definitely were better informed
about external stimuli thereby allowing them to react in their defense and save
themselves.
This system was then carried on by the
other evolving species that followed only to be polished along the way with gradual
additions and tweakings.
Evolution rarely works by massive jumps or
radical mutations as these tend to be more lethal than useful.
The 1963 Nobel Prize for Physiology or
Medicine was given to Alan Lloyd Hodgkin (Cambridge, England), Andrew Huxley
(Cambridge, England) and Sir John Eccles (Australian who later adopted
Switzerland as his home country) for explaining the ionic basis of nerve
conduction.
And by the way just as a reminder, to sort
out the problem of biology of action potential, these men had to work with
physical apparatuses such as voltage clamps, capacitance, Faraday’s cages, fine
electrode tips and measurements were made in numbers.
Stay tuned to the voice of an
average story storytelling chimpanzee or login at http://panarrans.blogspot.com
Good night Mon Ami and my fellow cousin ape.
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Another great educator and a teacher that I am aware of is
Professor Subhashish Chattopadhyay in Bangalore, India.
While I narrate stories, Professor Subhashish an electronic
engineer and a former professor at BARC, does and teaches real mathematics and
physics.
He started the participation of Indian students at the
International Physics Olympiad.
Do visit him here:
All his books can be downloaded for free through this link:
For edutainment and English education of your children, I
recommend this large collection of Halloween Songs for Kids:
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