Our sense organs 45

The brain
– the most complex structure
in the universe
“For thousands of years people have tried to
understand the brain. The ancient Greeks thought
it was like a radiator to cool the blood. In this
century it has been compared to a switchboard,
a computer, and a hologram – and no doubt it
will be likened to any number of machines yet to
be invented. But none of these analogues is adequate,
for the brain is unique in the universe
and unlike anything men have ever made.”
(Robert Ornstein / Richard F Thompson: The
Amazing Brain. Houghton Miffin Company,
Boston, 1984)
The human brain, located inside our skull and
weighing about 1.5 kg, is described by professors
Robert Ornstein (University of California) and
Richard F. Thompson (Stanford University) in the
above words. It can rightly be called the most
complex physical structure in the universe.
The brain is the central controlling organ of our
nervous system. It controls, watches over, and
coordinates nearly all the processes occurring in
the body. It collects, evaluates and stores sensory
impressions, and effects meaningful responses.
Practically nothing is known about the way
information processing actually takes place in
the brain. Nobody knows how the perceived
semantic information is derived from the incoming
electrical signals. We do know that certain
activities originate in the cerebral cortex (the
outer layer of the cerebrum), and we also know
that certain memories are stored there. But we
do not know how they are stored, nor how we
recall specific memories. We also do not know
how novel ideas originate, nor what happens in
the brain when something new is learnt. The little
we do know about the functions of various parts
of the brain has essentially been obtained by
observing the changes resulting from brain damage
or tumours. The only real knowledge we have
of the brain is on the statistical level, like the
number of structural elements and the estimated
number of interconnections. Even this statistical
information highlights the astounding properties
of the most complex structure in the universe.
The number of structural units: The brain comprises
about one hundred thousand million nerve
cells (100 x 10 9 ). The term “neurons” coined by
W. von Waldeyer in 1891, is used as a synonym
for nerve cells. They are the structural elements
of the brain, and their number is of the same
magnitude as the number of stars in our local
galaxy. No two of them have exactly the same
shape. In addition to this immense number of
neurons, there are also one hundred thousand
million other cells, providing metabolic functions
and structural support.
Every neuron is connected to thousands of others
by means of synapses (Greek synapsis = connection).
Even though each nerve cell is not in
direct contact with every other one, it is indirectly
linked with all others via intermediate connections.
It follows that the number of possible
pathways linking the nerve cells in every human
brain is extremly large: 5 x 10 21 (= 5,000 million
million million). It would require 40 printed pages
simply to list the number of direct connections of
a single neuron. In order to list all direct neuronal
links, 40 pages times the number of neurons =
4000 x 10 9 pages, would be required.
Assuming that one book comprises 400 pages,
the required number of books would be 4000 x
10 9 / 400 = 10 x 10 9 . This result is breathtakingly
large. Such a list would require a library containing
ten thousand million books of 400 pages. The
largest library in the world, namely the Library of
Congress in Washington, contains about 20 million
volumes. This means that we would require
500 such libraries just to list the direct connections
in the human brain!
The number of synapses is thus appreciably
greater than the number of neurons. One neuron
receives information from several hundreds, up
to thousands, of other neurons, and transmits it
to a similar number of other nerve cells.
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