A short encyclopedic definition
The brain of an adult human contains 100 billion nerve cells - more than the number of stars in the Milky Way galaxy. Each of the neurons in the brain is connected to up to 100,000 other neurons. The brain, which weighs almost 1.4 kg, is only 2% of the body's weight, but consumes about 25% of the energy available to it.
The nerve impulses are not electrical, but are transmitted by rapid chemical changes in the nerve fibers. While the light from the computer screen flows to the user at a rate of 297,600 km per second, the nerve impulses that transmit the images from the eyes to the brain, for example, move comfortably at a rate of only 400 km per hour.
{Appeared in Haaretz newspaper, 31/7/2000{
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