The Physics Factbook™
Edited by Glenn Elert -- Written by his students
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|Bibliographic Entry||Result |
|Glencoe Health 2nd Edition. Mission Hills: Glencoe Inc., 1989: 252.||"Weighing around three pounds (1.35kg), the brain contains nearly 100 billion cells."||100 billion|
|World Book 2001. Chicago: World Book Inc., 2001: 551.||"The human brain has from 10 billion to 100 billion neurons."||10–100 billion|
|Magill's Medical Guide Revised Edition. Salem Press, 1998: 221.||"It has been estimated that the adult brain has around one hundred billion neurons and an even larger number of glial cells."||100 billion|
|The Science Times Book of the brain. New York: The Lyons Press, 1987: 150.||"The human brain holds about 100 billion nerve cells."||100 billion|
|The Scientific American Book of the Brain. New York: Scientific American, 1999: 3.||"An adult human brain has more than 100 billion neurons"||> 100 billion|
One of the most remarkable aspects of the adult nervous system is the humanbrain. The human brain controls memory, vision, learning, thought, consciousnessand other activities. By means of electrochemical impulses the brain directlycontrols conscious or voluntary behavior. It also monitors, through feedback circuitry,most involuntary behavior and influences automatic activities of the internalorgans.
During fetal development the foundations of the mind are laid as billions ofneurons form appropriate connections and patterns. No aspect of this complicatedstructure has been left to chance. The basic wiring plan is encoded in the genes.It has been shown from previous studies that in developing embryos of animals,nerve cells are created in or travel to designated regions of the brain, and oncein place send out axons along preprogrammed paths to make contact with specifictargets.
The brain's billions of neurons connect with one another in complex networks.All physical and mental functioning depends on the establishment and maintenanceof neuron networks. A person's habits and skills -- such as nail-biting or playinga musical instrument -- become embedded within the brain in frequently activatedneuron networks. When a person stops performing an activity, the neural networksfor the activity fall into disuse and eventually may disappear.
Differences in weight and size of a person's brain does not correlate withdifferences in mental ability. The adult human brain normally weighs from 1.0to 1.5 kg (2¼ to 3¼ lbs).
The work of the brain is similar to a combination of a computer and a chemicalfactory. So take good care of your PC!
Anicia Ndabahaliye -- 2002
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