THE BRAIN AND NERVOUS SYSTEM

THE BRAIN AND NERVOUS SYSTEM 

EVERYTHING YOU does in, and every awareness and impression you have of, life is the result of activity in the brain and nervous system. To call it a remarkable system is to understate the obvious. It is so complex that scientists are only making a beginning at penetrating its mysteries. And yet enough has been determined, and it is now possible to understand sufficiently the broad outlines of the makeup and functioning of the system in health and disease, to permit you to do much to preserve its health.

THE BRAIN 

Of all things known in the universe, the human brain is, by far, the most intricate. Although it weighs only about 12 ounces on the average at birth and in an adult only about 3 pounds, its storage capacity is phenomenal. It has been estimated that the brain can store more facts, impressions, and total information than are contained in all the 9 million volumes in the Library of Congress. It's another indication of the brain's complex organization that, if necessary, you can get along with only half of it. The fact is that after removal of much of one side of the brain because of tumor, doctors, lawyers, and others have been able to carryon with their regular work.

And in one study with 62 soldiers who suffered penetrating head wounds during World War II, the men, upon being retested for intelligence, showed little or no change in scores they had made in the Army General Classification Test upon first entering service. Although at various times there has been some belief that the brain is compartmentalized, with specific areas for specific functions, the evidencemany studies is that when some brain area is damaged, another area may be able to take over its functions. 

The brain has 15 billion nerve units which permit storage of memory images and all the learning we accumulate. In addition, it has huge numbers of connections which control the more than 600 muscles in the body. Other connections into the brain from the eyes, ears, and nerves in the skin permit us to record and remember what we see, hear, feel, smell, and taste.

The brain is made up of several parts. 

The cerebrum, largest and most familiar, takes the form of two hemispheres divided by a groove. The surface, or cortex, of the cerebrum is the gray matter we hear about, formed by the cell bodies of nerve cells. Fibers from these bodies lead inward and form the white matter of the cerebrum. Some of these fibers lead to the center of the brain; others extend from front to back and from side to side; and deep in the brain, complicated junctions are formed.

 Actually, most of the fibers cross over so that one entering the brain from the left side of the body crosses to the right side of the brain, which is why the right lobe of the cerebrum controls most of the left side of the body, while the left lobe controls the right side. At the base of the cerebrum are three structures: pons, medulla, and cerebellum.