Nervous System
Development and functions

Long Evolution of Human Brain

December 14th, 2009

When reading the works of the ancient scholars, one cannot help being surprised at the number of scientific discoveries that were made merely as the result of observation and subsequent conjecture. More than two thousand years ago, scholars and physicians possessed quite a profound knowledge of how most of the human organs function. Nevertheless, they did not even suspect the real function performed by the brain. Strange as it may seem, Aristotle, a prominent Greek scholar who lived in the fourth century В. С, considered the brain to be merely a large gland for cooling the blood. Now we know that the brain is by no means a refrigerator. We also know what purpose this so-called “gland” serves, but the way it operates still remains largely a mystery.

The human brain developed as the result of long evolution of the nervous system which originated in the primeval oceans when individual biological molecules finally merged to produce little conglomerates of living matter. Those primary living particles, as well as the subsequent more complex unicellular organisms which settled in large colonies, already possessed two main properties, irritability and conductivity, i. e. the ability to transmit excitation to neighbouring cells.

Later, in multicellular animals there emerged a dineren-tiation between these functions. The Coelenterata were the first to develop special nerve cells with a high degree of irritability and conductivity. The function of these cells was to become ever more sensitive to external influences and to transmit the excitation to those cells or organs which could react in a way beneficial to the organism.

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December 14th, 2009 13:30:22