Other Endocrine Glands and Functions

The parathyroid glands, each about the size of a pea, are located at the four corners of the thyroid gland. They secrete Para hormone, which helps regulate the body's use of calcium and phosphorus. Too little of this hormone reduces the calcium level in the blood. Too much Para hormone, on the other hand, may prompt excessive calcium deposits in other than bone tissue, which is what is happening to the circus freak said to be "turning in­to stone."

The islet cells of the pancreas are only one part   of this   much   larger   internal   organ, which also manufactures digestive juices released through ducts. The hormone elabo­rated by the islet cells is insulin. It is essen­tial to the carbohydrate metabolism of the body. Without adequate insulin supply, the body cannot properly utilize starches and sugars. The failure of the islet cells to produce enough insulin is the direct cause of the dis­ease diabetes mellitus.

The thymus gland, situated on the wind­pipe, is classified as an endocrine, but it has no acceptably proved function. Large at birth, it generally withers and shrinks until at pu­berty it has practically disappeared.

One more observation about the endocrine system as a whole is pertinent. Since it in­fluences so much the course of physical growth and development as. for example, the advent of sex characteristics  it can also be said to underlie the psychological develop­ment of the individual, which waits on bio­logical readiness.

SLEEP

"God bless the man who first invented sleep," said Sancho Panza. voicing a senti­ment that echoes down the ages. Sleep, like mental health, is a phenomenon that invokes both mind and body. Furthermore it is indic­ative of a reasonable state of mental health, for sleeplessness is frequently a symptom of anxiety or other psychosomatic maladjust­ments that do not bespeak a good level of mental health. We have therefore chosen to deal with the subject of sleep in this place.

A human being spends approximately a third of his life in sleep. Yet for an activity or perhaps lack of activity so common and universal, we still know surprisingly little about its fundamental mechanisms. The most scientific explanations of the function of sleep hardly surpass Shakespeare's seventeenth-century description:

Sleep that knits up the raveled. of care, The death  of each   day's   life, sore labor 's

bath, Balm  of hurt  minds, great nature's second (nurse, ('hie) nounsher in life's feast.

There are many theories about sleep, but none is universally accepted. On the other hand many extended and acute scientific ob­servations have been made to illuminate the nature of sleep and the effects of lack of it. The longest that a man has been known to go without sleep and survive is a little over 9 days.

Sleep

During sleep the sleeper becomes uncon-scioufl unaware, and more or less unrespon­sive to the environment about him. However, this is a relative matter Some senses and some parts of the body remain more alert and more in function than others. For example, a sleeper may sleep through a loud noise but awake at the lightest touch. Again, while the lungs and heart may work more slowly dur­ing sleep, the sweat glands and some parts of the brain and nervous system may become more active. This increased, even though tem­porary, activity of the nervous system is the explanation of dreams, sleepwalking 'som­nambulism), and talking in one's sleep. Ex­actly why these events occur to a specific per­son on a given night cannot be explained, but the fact of their occurrence demonstrates that sleep and waking are both part of the same cycle of living It is questionable whether the unconscious mind ever completely rests. Anx­iety, certainly, is one of the great enemies of sleep.

Most of the measurable physiological func­tions of the body are diminished during sleep. The body temperature falls, indicating a gen eral decline in metabolism and a decrease in the tone of muscles. Muscular relaxation is one of the key components of sleep. During sleep also the heart beats more slowly, blood pressure    and    pulse    rate    fall,   breathing is   slower,   and   secretion   from   nearly   all viands diminishes

But sleep is more than a time of rest and relaxation. It is also a time of recuperation and repair, of growth and regrowth. During the normal course of living, cells of the body wear out and must be replaced This regener­ation takes place more rapidly during sleep. It has been shown, for example, that the cells of the skin divide and make new cells about twice as fast during sleep.

The amount of sleep a person needs is therefore influenced by his rate of growth Rapidly growing infants need more sleep than children, children more than adults. Again in old age, when the reparative processes of the body are less active, an increase in sleep may be required. Furthermore during the period of recovery from a debilitating illness or opera­tion (convalescence), and in some stages of pregnancy, added increments of sleep or rest may be essential.