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The mystique of the brain continues to intrigue modern biologists and psychologists
even as it did the philosophers of antiquity. Aristotle dismissed the brain
as merely a radiator for cooling the blood. Generations earlier, however, Hippocrates
had expressed a more accurate view of its functions. "Men ought to know,"
he argued, "that from the brain, and from the brain only, arise our pleasures,
joy, laughter and jests, as well as our sorrows, pains, griefs and tears. Through
it, in particular, we think, see, hear, and distinguish the ugly from the beautiful,
the bad from the good, the pleasant from the unpleasant." Brain function
is so strongly associated with what it means to be alive and human that the
cessation of brain activity is considered a clinical criterion of death even
when other organs of the body are still functioning.
With its hundreds of neuronal pools, 35 billion neurons, and trillions of synapses,
the brain performs sophisticated tasks beyond our present understanding. Still,
all of our mental functions, no matter how complex, are ultimately based on
the cellular activities described in the previous chapter. The relationship
of the mind or personality to the cellular function of the brain is a question
that will provide fertile ground for scientific and philosophical debate long
into the future.
The previous chapter discussed the nervous system at the cellular level. We
now move up the structural hierarchy to consider the central nervous system
at the organ and system levels. This chapter will lay a foundation for understanding
some relatively simple reflex actions of the spinal cord and brainstem considered
in the next chapter, and it will plumb some of the mysteries of motor control,
sensation, emotional drives, analytical thought, language, personality, memory,
dreams, and plans. Your study of this chapter is essentially one brain's attempt
to understand itself.
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