Redefining Reality - The Intellectual Implications of Modern Science

Instead, we are a part of the world. We are shaped by the
world and react to it in ways that show us to be connected to
each other and to externalities in a deeper fashion than we are
accustomed to considering.
The development of the brain in the human fetus is, in part, guided
by genetics: 25,000 of our genes are active in the creation of our
central nervous system. Cells divide from the fertilized egg and
daughter cells that form the various organs of the body. To form the
brain, hundreds of types of cells must develop.
Some of these cells are neurons, which emit and absorb
electrical impulses to give rise to neurological functions.
Neuronal cells form complex webs to send particular signals.
There are also glial cells. If neurons are the bricks of the
brain, glial cells are the mortar, holding the neuronal structure
together and sustaining the necessary gaps, called synapses,
between the neurons.
Although this process is guided by our genetic make-up, the
environment plays a crucial function, as well. The effect of the
chemical environment of the mother’s body greatly affects how
the brain develops. The reason for this is that the brain has an
Around the second month, the embryo develops a thin tube of
that will ultimately give rise to all the brain cells.
Around the fourth month, these progenitor cells divide
unbelievably rapidly, creating the cells that become the brain.
Ultimately, there will be about 100 billion neurons and at least
1 trillion glial cells.
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