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. 

How Much Sleep is essential? Age and timings of sleep

HOW MUCH SLEEP?

 Sleep is essential, but the amount required varies. The usual sleeping time for the adult is eight hours, but some people need less, some need more. Everyone has heard the story of Thomas A. Edison sleeping only two hours a night-and the romantic picture of Edison working on through the night to invent the electric light bulb suggests that any of us, strong willed enough, could cut down on sleep and have more time to become famous and rich. The fact is that Edison, though protesting that sleep was a loss of time and opportunity, was concerned about getting his own quota of sleep, according to his own diaries.

He napped often, and frequently drifted back to sleep for another hour or so after waking in the morning. Some physicians are firmly convinced that if shortchanging yourself on sleep does not catch up with you quickly, it will, and there will come the day when you suddenly appear to lose your energy, become prone to ailments, and suffer a general deterioration of health. There is no simple answer to the question of how much sleep is best. The essential test is whether you feel rested in the morning and have enough energy to carry on the day's activities.

Eight hours, as we have noted, is an average figure. If you do very heavy physical work or extremely exacting mental work, you may need more. Children need more sleep than adults since they are growing fast and are very active. Old people often have been thought to need less sleep; this is not necessarily true. They may need more, depending upon their activity and health. It could be a most worthwhile exercise to make your own investigation into your sleep needs, on the simple basis of experimenting to determine how much sleep makes you feel good, how much less makes you feel out of sorts, irritable, fatigued. 

Sleep and Good health - Sleeping Pattern and Sleeping process

SLEEP

SLEEP IS fundamental to good health and yet, it would appear, many of us need a refresher course in sleeping. According to recent surveys, about half of all men and women in the United States have trouble sleeping at night, and about one fourth of the population use some form of sleeping medicine. Before considering how sound, healthy sleep may best be encouraged, let's get some basic understanding of this long-mysterious process which has come in for scientific exploration only in recent years.

How much sleep do you need? Have you ever really tested yourself over a period of time?

What is the nature of sleep?

Are sleeping patterns inborn or acquired habits?

What happens in sleep?

THE SLEEP PROCESS

As you have discovered when you do not get adequate sleep, sleep is necessary for both physical and psychological well-being. Even now, however, scientists are unable to explain why about one third of our lives must be spent in sleep and why in our sleep we dream. In trying to get sound insights into the mysteries of sleep, investigators in many sleep laboratories use volunteers to whose scalp they tape electrodes to detect tiny currents in the brain.

 Amplified many hundreds of thousands of times, the impulses are registered on graph paper as an electroencephalogram (EEG).

 In addition, equipment records pulse, eye movements, breathing, body movements, and muscle tensions while the in sleep, it is now known, is not a state of oblivion, of complete.

Rather, it is a progression of rhythmic cycles.  Equipment, scientists have been able to establish that sleep. That a newborn baby alternates between sleep and wakefulness at about hourly intervals; that gradually, as the child grows older, the cycles stretch out until eventually they becomes 90-minute cycles in adulthood.

 These 90-minute cycles are beyond conscious control. It used to be thought that we fall into deeper and deeper sleep during the night until we arrive at a turning point, and then sleep lightens progressively until we wake up. But it is now clear that this is not so. Instead, throughout the night, we shift from one gradation of sleep to another and are even awake several times during the night without necessarily remembering the wakefulness.