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Human Brain

What weighs about three pounds but has more parts than there are stars in the

    Milky Way galaxy (Flieger)? What fills the space occupied by only three pints

    of milk yet includes components that, laid end to end, would stretch several

    hundred thousand miles (Diagram 19)? What looks like an oversized walnut

    made of soft, grayish-pink cheese but contains the equivalent of 100 trillion tiny

    calculators (Restak, Brain 27)? What, according to James Watson,

    co-discoverer of the helical structure of DNA, is "the most complex thing we

    have yet discovered in our universe" (qtd. in Begley 66)? To all four of these

    intriguing questions there is but one surprising answer: the human brain. This

    miraculous organ is remarkable in its structure, its function, and its chemical composition.

          What is the brain? According to Richard Restak,

the human brain is the master control center of the

body. The brain constantly receives information from

the senses about conditions both inside the body and

outside it. The brain rapidly analyzes this information

and then sends out messages that control body

functions and actions.   ("Brain" 561)

    According to Tether, the brain is divided into three main parts: the cerebrum, the

    cerebellum, and the brain stem (421). These parts, in turn, are largely made up of

    nerve cells, called neurons, and helper cells, called glia. Researchers have

    discovered that there may be as many as 100 billion neurons in the brain and a far

    greater number of glia, possibly as many as one trillion (Kolb and Whishaw 1).

          Important discoveries throughout the decade of the 1990's in molecular biology

    and genetics are revolutionizing our understanding of how the human brain works

    (Kotulak ix). Advances in imaging technology are allowing us to learn more about

    the human brain than ever before in...