The Human Body
The study of the human body. Many years ago people explained some processes in the human body by saying that a "vital spirit" within the body controlled some body functions. They used this term to explain processes that they could not understand. They believed that this vital spirit could not be explained by the physical laws of science.
Today, scientists know that the human body functions according to the laws of nature. There is no mysterious vital spirit within the body that causes the heart to beat or the brain to operate. Scientists now explain the working of the body by discovering the physical principles behind its operation.
A physiologist is a modem scientist who studies the body and the ways Its parts function. He seeks scientific explanations for the ways the parts of the body operate. He is interested in the ways the parts of the human body work together to help a human to live.
The body is the most complicated organism known. Its many parts interact in so many ways that physiologists must simplify the organisation for purposes of study. In order to understand the functions of the major organs and tissues of the body, physiologists usually divide them into six major systems. These are the skeletal-muscular system, which controls the basic shape and movement of the body; the gastrointestinal system, which controls the progress of foods within the body; the respiratory system, which controls the oxidation of food in the body; the circulatory system, which is the blood circulating mechanism; the nervous system, which is the voluntary and involuntary control center for the body; and the endocrine system, which is a chemical control system for the other systems.
These systems are linked in many ways. For example, the blood in the circulatory system carries the oxygen from the respiratory system to the muscles in the skeletal-muscular system.
The organs. Each of these six systems is composed of organs, such as the heart, liver, stomach, and brain. Most of the important organs of the body are included in one of the six systems. Each of the organs carries out a special function, but it is so related to many other organs in the body that it often depends on them to help in the process.
Thus, the lungs cannot act without the brain, because the brain sends the impulses which regulate breathing. The stomach is worth nothing without the blood to carry the food it digests to the tissues. Virtually every organ depends on other organs to help it carry out its function.
Tissues and cells. The tissues that make up the organs are likewise dependent on other tissues and organs in the body. Tissues are made of cells, the smallest bits of living matter in a human body. The cells need nourishment and a way to cast off their wastes. This nourishment is provided by various organs of the body.
The tissues of the body, like the organs and the systems, are specialized. Each of the four kinds of tissue looks different from the others, and each makes up different organs. For instance, the epithelial cells in your skin are similar to the epithelial cells in your lungs. The muscle cells in your arm are similar to the muscle cells in your stomach. Look at the illustration to see the four shapes of tissue cells. These cells make up the tissues of the body.
When you read about each of the six systems of the body, you should keep one point in mind. The explanations of the six systems are simplifications. The systems are so complicated and so interrelated that they cannot be described in a few pages. In fact, doctors are still searching for functions of many parts of the six systems of the body.
Think for Yourself
What systems have structures that are dependent on the skin? You may find that there is more than one system.
The Systems of the Body
When you are well, your whole body feels well However, when one part of your body becomes injured or diseased, your whole body may feel ill Do you know why your whole body feels terrible when your stomach is violently upset? This feeling occurs because your stomach is connected to the other parts of your body. Your stomach is part of one system of organs that depends on other systems la control it and supply oxygen, food, and moisture.
The stomach is only one of the many Darts of the body that are interrelated. The parts of the body are so dependent on one another that an injury to any one part almost always has several effects in other parts of the body.
Almost two thousand years ago a Greek physician named Galen realized that the parts of the body are interrelated. Because there were laws against dissecting, or cutting apart, dead bodies, Galon could only guess about the ways the parts of the body are related.
He decided that the muscles worked because the brain sent "animal spirits" to them. He thought that the lungs cooled the heart by their fanning motion. He thought that the liver made the blood (called "natural spirits"), that the lungs pumped bright red "vital spirits" into the blood, and that the heart provided heat for the body and blended the spirits.
Although medical science has proved these theories incorrect, they influenced doctors for centuries. Scientists are still studying the ways the parts of the body influence one another. Perhaps some day we will be able to describe all the ways the body systems are interrelated.
Can You Find Out?
Place two fingers on the pulse on the inner side of your wrist and count the number of beats you feel in sixty seconds. Then repeat the bouncing ball exercise ten times. Take your pulse again. How does muscular activity affect your heartbeat?
Maintaining Mental Health - Understanding feelings of rebellion
Understanding feelings of rebellion. When you have become as old as you are now, you may find that you disagree with some of your parents’ and teachers’ values and ways of doing things. You feel that you want to make decisions for yourself and do not want someone to make them for you. You are learning to become independent and are forming more of your own personality.
The most important thing to keep in mind is that sooner or later you will work out your own ways of doing things. Instead of going your own way and ignoring the advice of adults completely, talk over some of your problems with your parents, clergyman, guidance counselor, and teachers. It may surprise you to find that they can be a great help in finding answers to your problems.
Never forget the possibility that you may be rebelling against people just for the sake of rebellion. You may be so eager to show that you are mature that you forget that most of your parents’ values are extremely sound. It is a mature person who can look at his own feelings of rebellion and realize that sometimes they have little basis in reality. If you can look at your feelings in this way, you have taken a giant step toward adulthood.
After you have considered these four areas of mental health–maintaining self-confidence, making adjustments, controlling emotions, and understanding feelings of rebellion—-you may have a better idea of the ways to change your personality and maintain good mental health.
Try This
Make a list of all the emotions you have felt today. Check the ones you think were not controlled as well as they could have been. Check the emotions you have felt today that you feel were of value to you.
