ULTIMATE COMPUTING - Quantum Consciousness Studies

From Brain to Cytoskeleton 59
4 From Brain to Cytoskeleton
4.1 Nervous System Evolution
The German philosopher Nietzsche wrote:
“Then you must be a scientist whose field is the leech” said
Zarathustra, “and you must pursue the leech to its last rock bottom,
you conscientious man!” “Oh Zarathustra!” answered the man, “that
would be an enormity, how could I take up such a huge task What I
am the master and connoisseur of is the brain of the leech: that is my
field and it is a whole universe.”
The human brain appears to have evolved from predecessors of earthworms
and leeches whose development was a milestone in eukaryotic evolution (Somjen,
1983). These organisms’ nervous systems probably consisted of a chain of
organized clumps of nerve cells called ganglia, or perhaps two chains of
symmetrically paired ganglia with an enlarged head ganglion at the front end. The
polarity and preferred axis of orientation which defined these basic nervous
systems are related to polarity and asymmetry within their component nerve cells,
or neurons, each a “universe” of its own. As will be described in the next
chapters, neuronal orientation and asymmetry are determined by the cytoskeleton
which, in many ways, is the nervous system within all higher plant and animal
cells.
Over the course of evolution the primitive leech’s head ganglion began to
dominate other members of its chain, performing “decisions” which required
cooperation of the entire assembly. Each segmental ganglion still retained some
autonomy of action and, when cut into pieces, such a creature may have been able
to regenerate complete new individual organisms like its current descendants.
Pairs of leech ganglion chains resemble sympathetic ganglion chains of
vertebrates which retain a measure of autonomy. For example, man’s autonomic
nervous system can efficiently regulate heart, intestine, blood vessels and other
organ systems even when disconnected from the brain and spinal cord.
Transition from a segmented organism to a nervous system like our own
probably occurred due to fusion of the paired chains of ganglia into a tubelike
structure of nervous tissue. Paired nerve roots then emerged from the primitive
central system similar to the spinal roots of today’s vertebrates. These roots
connected the central nervous system with the peripheral sensory organs, muscles
and glands. Eventually, the head end of the neural tube increased in size and
importance until it dominated most nervous system functions, a process termed
“encephalization” by famed English neurologist Hughlings Jackson (Somjen,
1983). Encephalization, which occurred over eons and may be continuing
presently within man, reflects development of a hierarchical organization in an
otherwise parallel, distributed system. Brain components which are more highly
organized and capable of more complex functions are generally newer on the
evolutionary scale (i.e. “neocortex”). A collective hierarchy of parallel
information processing systems based on functional organization which includes
subcellular elements (cytoskeleton and cytoplasmic ground substance) is shown in
Table 4.1.
4.2 Nervous System Organization
Brain activities have been intensively studied by various disciplines for many
years. In the following sections, essential elements of brain organization are