THE NERVOUS SYSTEM

THE NERVOUS SYSTEM

The brain is likened to a control center, then the nervous system can be thought of as a two-way communications network through which informational messages flow to the control center and command messages are transmitted from the center. The informational, or sensory, messages come from the outside world through the sense organs (eyes, ears, etc.); they also come from within the body itself-there are billions of receptors all over the body concerned with various functions. 

The nervous system is organized to give you essential voluntary control over many actions. It is also set up to relieve you of concern with routine matters. Thus, for example, you eat dinner and decide whether you like or dislike a certain dish and wish to finish it.

On the other hand, you walk along, stumble on an object; without thought on your part, the muscles of the legs are automatically commanded to react, and one leg is extended and the other flexed so you maintain your balance. How Nerves Work Messages travel along nerves, at speeds of as much as 250 miles an hour, as the result of both electrical and chemical action. 

A nerve cell, or neuron, when viewed under a microscope, looks like a tiny blob, rounded or irregular in shape, with one or more threads extending from it. The blob is the actual nerve cell body; the threads are nerve fibers. Shorter fibers, called dendrites, bring messages to the cell body; they may range from a very small fraction of an inch to several feet in length.

One fiber, longer than the others and called the axon, transmits messages away from the cell body. A nerve impulse, going through the nerve network, travels over the fibers of many cells. As it reaches the end of one fiber, it jumps a gap, called a synapse, to the next fiber. Chemicals produced and stored around synapses can help the impulse to jump the gaps or can block the impulse. Some drugs that act in the nervous system-some of those for high blood pressure, for example-accomplish their tasks by affecting the chemicals at the synapses. 

Sleep and revitalizing the Brain

Sleep is essential not alone for the body in general but for resting and revitalizing the brain in particular. Good sleeping habits (page 94) are well worth developing. Both overstimulation of the brain through excessive use of caffeine in coffee, tea, and soft drinks and depression of the brain through frequent use of sedatives such as barbiturates and bromides are best avoided. 

The brain works most effectively when freed from anxieties and mental conflicts. We suggest that a reading of the next section of this book, Preventive Mental Care, may provide you with insights you will find useful in keeping your psyche-the functional part of the brain-in the best possible condition.

Are special "brain foods" and "brain tonics" necessary? Not at all. As it will for all the rest of the body, a well-balanced and varied diet will ; 

The Brain and Nervous System / 241 provide the brain with all the nourishment it requires. Fish, a good food, is not any better for the brain, despite its reputation for being so, than any other protein food. There is no magical brain food. It bears emphasizing that the mind reacts to distress elsewhere in the body. Headaches, dizziness, fainting, impairment of memory, and other "brain" symptoms may, of course, stem from disturbances in and around the brain (for example, sinusitis or tumor).

 But they can also be the results of, for example, the circulation of poisons because of failure of damaged kidneys to remove toxic materials from the blood. In short, brain symptoms call for a complete medical checkup. Can the effects of aging on the brain be prevented? Some of the most harmful effects of hardening of the arteries can be prevented or considerably diminished by following the suggestions given in the sections of this book devoted to nutrition, obesity, high blood pressure, and aging. 

There is every reason to be optimistic about your brain function as you get on in years. You may recall that Michelangelo produced some of the greatest art of all time when he was more than 80 years old, and Arturo Toscanini at 87 directed symphonies without reference to musical scores. Many people in everyday life continue to have alert, active brains long beyond the age of 70.

Actually, a study made for the Office of Naval Research indicates that, contrary to what has been commonly thought, mentalability does not invariably decline with age but may, in fact, be greater at and after 50 than at 20. The ONR study avoided a pitfall of other studies in the past. In the latter, the same tests were given to various age groups, and the results suggested that a peak of intelligence comes at 20 and thereafter declines. 

But such studies, many scientists have thought, were faulty. In recent years, young people have been receiving more and more formal education, and it has been demonstrated that generally the more formal education, the higher the Score on mental tests. Therefore, older people, generally had had less formal education, were handicapped in test competition with younger ones.

 In the ONR study, 127 men who had taken the Army Alpha Examination upon entering Iowa State College after World War I were retested 30 years later. They were competing against their younger selves. The results showed them to be intellectually more able at mean age 50 than they had been at mean age 19 when they had been college freshmen. 

Strenth Of Human Body and Medical records - Modern day health hazards succeeding

 THE BASIC STRENGTHS OF THE HUMAN BODY 

A FASCINATING case in medical records is that of an 80-year-old man who some years ago stepped off a curb in Boston, was hit by a truck and taken to Massachusetts General Hospital where, within an hour, he died. Upon autopsy, even the physicians were astonished by what they found. The man had had almost every known major disease, including several that, individually, might have been potentially deadly. 

His blood pressure had been grossly elevated, so much so that his heart had almost doubled in size under the burden. He had generalized arteriosclerosis, or hardening of arteries. Tuberculosis had left marks on both lungs. Chronic kidney disease had destroyed large portions of both kidneys. He had had severe cirrhosis of the liver. Even more astonishing was the report of the man's wife: He had been no invalid; instead, he had been active until the day he was killed and had complained of nothing.

His is an extreme and encouraging example of the reserve powers and adaptability of the body. There are many other examples: The 7-year-old boy who survived a plunge over the 160-foot-high Horseshoe Falls at Niagara after the boat in which he was a passenger capsized in the river above the cataract. The workman who fell 150 feet from a chimney scaffold, landing on his left side near the base of the chimney, creating an impression 8 inches deep in the earth, bouncing over a 30-degree slope toward a concrete retaining wall, then dropping another 10 feet to a lower level. He fractured his jaw, both ankles, complained of chest pain for less than 36 hours, re- covered rapidly-surviving an impact that might well have crushed an airplane.  

There was also the hammer thrower, a world record holder, who while warming up to compete for a place on the U.S. Olympic team pulled a back muscle. Desperate, he persuaded a physician to give him an injection of novocaine and let him compete; he whirled out a foot throw to finish second and get his place on the team.

 In Olympic team trials, too, a swimmer won a place by qualifying in the 800-meter relay while still sore and still bandaged six days after an appendicitis operation. It is also reassuring to view the spare capacity of the body-what one can live without if necessary and, in some instances, even live without comfortably. Half the brain is a spare. This has been shown in cases of serious brain damage caused by strokes and head injuries, with loss of memory, language, speech, even understanding. Although damaged areas remain damaged, other areas can be trained to take over their function.