The Endocrine System - Part 1

The control centers. The endocrine glands secrete chemicals which control the growth and development of the body. These chemicals are secreted into the blood stream and are carried to all parts of the body. Because they are in general circulation, these chemicals, called hormones, can act in areas far from the gland that secreted them. They may even act on several organs at once.

The endocrine glands have a certain similarity to the nervous system because they help to integrate the activities of widely separated organs. Emotional strain, for example, causes one of the endocrines to enlarge and secrete a chemical which speeds up the action of the heart.

The master gland. In the base of the skull is a tiny gland called the pituitary, or hypophysis. This gland is called the master gland because it controls growth and the action of the adrenal, thyroid, and male and female glands. Through these glands, it has an enormous effect on the other systems of the body.

The pituitary gland secretes at least eight hormones in order to exercise its control over body functions. Each hormone controls a particular body function. Examine the chart below to see what functions these eight hormones control.

The adrenals. The adrenal glands are two of the glands that are regulated by the pituitary. The adrenals are two glands located above the kidneys. Each adrenal is composed of two parts: an inner part, called the medulla, and an outer layer, called the cortex.

The hormone secreted by the medulla, called epinephrine, is probably the best known hormone in the body. Commonly called adrenalin, this hormone stimulates most of the emergency reactions within the body. It increases the heart beat, releases sugar from the liver into the blood stream, delays fatigue in the skeletal muscles, raises the blood pressure, and performs many other functions.

In view of these effects you would think that epinephrine is essential to the function of the body. Such is not the case, however. Parts of the autonomic nervous system can control these functions even when the adrenal medulla is removed from the body! It is likely that the medulla serves only to help the autonomic nervous system in times of danger, but that it is not necessary for the body’s functioning.

The adrenal cortex. The adrenal cortex, on the other hand, secretes substances which’ are vital to the body. A person deprived of his adrenal cortex would die within a few days. It is the secretion of the hormone from the adrenal cortex that is controlled by ACTH, a hormone secreted by the pituitary. Scientists are not sure why the cortex is essential, although they have found that cortisone is very useful in alleviating some symptoms of disease.

The Nervous System

Control center. Your nervous system is like a general’s headquarters in the army. It has an intelligence division to find out information, a messenger division to deliver orders to the proper units, and a general headquarters, where all but the least important decisions are made.

The general headquarters of the brain is composed of the cerebrum and cerebral cortex. These two parts of the brain control your thinking and voluntary actions.  These structures and their associated nerves are called the central nervous system. This system controls your conscious actions. These parts are in control when you lift an ice cream cone to your mouth or when you think about the answer to a math problem.

The cerebellum and cerebrum are connected to two kinds of nerves. The first, afferent nerves, pick up information from the sense organs. The second, efferent nerves, relay impulses from the conscious center to the muscles. These nerve pathways enable you to sense your surroundings and carry out your activities.

Other parts of the brain control involuntary actions such as maintaining balance, focusing the eyes, and regulating internal organs. Look at the illustration to see what areas the parts of the brain control.

The spinal cord. Within the thirty-three bones of the spine is the spinal cord. This cord is the largest central nerve trunk of the body. The nerves begin at the base of the brain and branch off the spinal cord. They connect various internal organs with the brain.

Your spinal cord also takes part in body reactions. Whenever a quick but automatic reaction is required, the reaction is made in the spinal cord. It is the spinal cord, for instance, that directs your muscles to jerk your hand away from a flame or makes you lift your foot hurriedly if you step on a tack.

Your nerves are the spies and messengers of the body. They sense the temperatures, pressures, sights, sounds, and smells around you and send tiny electrical impulses to the brain or spinal cord to be interpreted. When the control center interprets the messages, it sends back an answer along other nerves to the muscles, which carry out the body’s activities.

Regulation of the body. Some nerves and parts of the brain are part of the autonomic nervous system. This system controls the internal organs. It regulates your breathing, digestion, rate of perspiration, and even the way in which you digest your food.

The autonomic system works in the same way that the central nervous system works. There are afferent nerves that are stimulated by heat, pressure, or pain; control centers in the spinal column and the base of the brain; and efferent nerves to send the messages to muscles that can carry out the necessary action.

Nerve cells. All nerve cells, whether they are in the nerves, the spinal cord, or the brain, are similar in structure. Nerve cells have a nucleus and cell body like all cells, and they have two special structures that allow them to send and receive electrical impulses. These are the dendrites and axons.

The dendrites receive impulses from a sensory organ and pass them through the cell body to the axon, which passes them to the dendrite of the next cell in the chain. Thus, a nerve fiber is like a long bucket brigade in which an impulse is transmitted from a sensory organ to a control center. However, the "bucket" travels at 300 feet per second, much faster than a bucket has ever traveled in any human bucket brigade.

These chains of nerve cells penetrate every part of the body. The nerves that make up the central nervous system, or conscious control centers, constitute the five senses and are connected to the skeletal muscles that you can control. The nerve chains that are part of the autonomic nervous system are concentrated in the organs inside the body. You seldom feel the effects of these nerves, but their activities are essential to the operation of your organs and systems.

Have you ever had perspiring palms when you were about to take a very important examination? This condition is evidence that there is a link between the sweat glands in your hand and the higher conscious control centers of your brain. Other evidence of the great complexity of the nervous system is seen in the many ways the rest of the organs react to emotional stress.

Think for Yourself
What internal organs are controlled by the autonomic nervous system? Which by the central nervous system?

Maintaining Mental Health - Controlling emotion

Controlling emotion. The third aspect of good mental health is the ability to control the emotions. Undoubtedly you have occasionally lost your temper when your parents have forbidden you to go somewhere or do something. This could be serious, if you could not control your temper, or habitually lost your temper.

Because people your age are likely to become very enthusiastic about some things and extremely critical of others, it is a good idea to "stand back and look at yourself." Can you see yourself usually losing control of your enthusi­asm when your team wins a basketball game? Can you see yourself always arguing heatedly with an umpire? If you can answer yes to these questions, you need to practice controlling your emotions.

It is important for you to recognize that everyone has feelings of anger, and that nearly everyone occasionally loses his temper. However, a mature person does not allow himself to lose his temper habitually. Neither does he allow himself to become angry every time something happens he doesn’t like. If you think of the adults you like and admire, you will probably find that they control their feelings well enough so that they are pleasant peo­ple to be with.

Methods of control. There are many ways you can control your emotions. One is to talk over the situation with a friend, your parents, or a teacher. This way is often a good one because it can make you understand ways to deal with similar situations in the future.

Physical activity is a good way to get rid of your anger. If you are angry with someone and you cannot talk to anyone about it, it will feel good to perform some vigorous activity, such as washing the family car, playing basketball, swimming, cleaning the house, or mowing the lawn. This method of releasing strong feeling is called sublimation. You will be surprised to see how much better you will feel after sublimating your anger.

There are other ways of letting go of angry feelings. Creative work, such as woodworking, painting, or sculp­ture, is fun and useful. Writing is an­other way to get rid of your feelings of anger, rebellion, or discouragement. It sometimes helps to write down the reason for your feelings. Then you can control them because you know why you feel so strongly.

Another emotion that you can at­tempt to control is fear. Everyone has felt worried or afraid when he has ap­proached a difficult test or unfamiliar situation. However, this fear should not be allowed to become too strong. If it does, you will not be able to do your best. The easiest way to get rid of such feelings is to make sure you have studied adequately. Then, if you are still worried, try doing something re­laxing. If you are too worried to relax, you might go outside and play a game. It might be good to call a friend to see how he is progressing with studying. These methods will take your mind off your problems and help you to control your fear.

The important thing to remember about controlling your emotions is that you should do something about them. It never helps just to sit by yourself worrying about a disappointment or situation that made you angry.

Value of emotions. It has been said that emotion is the stuff of life. Any person who had not felt the joy of success, the anger of frustration, or the pride of victory has not lived very much or very well.

When properly controlled, your emo­tions are of great value. If you become supremely enthusiastic about support­ing a friend who is running for the student council, you are using your emotions. Probably no one has ever been elected to anything unless his friends were a little emotional about his strong points.

Your emotions are helping you right now. When you become worried about your grades on a science test, your fears cause you to do something— study harder or obtain special help from your teacher. Have you noticed that when you are playing a game the excitement has helped you to perform a little better?

The important thing to remember about emotions is that they should not be hidden or forgotten, but should be used well.