My Science School

          Like air and water, food is also essential for all living beings. From the smallest insects to the biggest animals - all need food for their survival. So much so that even plants and trees can not live for long without food. Each person requires a certain amount of food daily, according to size, weight, age and amount of activity. Most of us feel upset if we skip just one meal, and if we try to go without food for 12 hours we would really be uncomfortable.

           Energy required for doing work is obtained from food. Cells and tissues damaged in doing work are repaired and replaced by it. It is very much needed for the growth and development of the body. In short, food is very essential for the proper functioning of the body.

          Now the question arises: how long can we survive without food? There are some animals which can store food in their bodies and live on it for a long time. It has been observed that the smaller and the more active the animal is more rapidly it consumes its stored food. Warm blooded animals use up their stores of food in the body more quickly. A dog can survive without food for 20 days at the most. However, the bug is such a wonderful creature that it can survive without food for one full year.

          But man cannot store food in his stomach. If he misses one meal, his condition becomes bad. Food is required to maintain the flow of blood. All the constituents of blood are obtained from food. The moment, the blood lacks nutritional materials, a signal, via blood, goes to the hunger centre of the brain and we start feeling hungry.

        There are a few examples of persons who survived for a very long time without food. Angus Warviern of Scotland survived without taking any food for 382 days i.e. from June 1965 to July 1966. During this period, he took only coffee, tea, water and soda water. One South African woman survived for 102 days on water and soda water only. Stefan Taylor of New Zealand remained alive for 40 days in 1970 on a daily intake of one tumbler of water only. These are some uncommon examples. Such people are endowed with exceptional power. Common man can at the most survive without food for three week. 

            All mammals have some hair on their bodies and man is also a mammal. In some mammals hairs cover the whole body but in humans, hairs grow only in certain parts.

            Hairs on our body preserve the body warmth and protect the skin and body openings. They also help us in realizing the sensation of physical touch. The hair on our eyebrows and eye lashes, ear and nose help guard these body cavities against dust and insects.

            Now the question is, why do men have beards, and women do not? This can be understood as follows. When a child is born, he has only fur like hair on the body.

           As he grows, hair becomes harder. Boys and girls reach puberty at the age of 11 to 13 years. There is faster growth of sex glands at this age. In man, the testes and other sex glands, produce a group of hormones known as ‘androgens’. In woman, the ovaries and other sex glands, produce another group known as ‘estrogens’. The function of the androgens is to regulate secondary male sex features such as the growth of facial and chest hair and deepening of the male voice at puberty. The function of the estrogens is to regulate secondary female features, such as the change in the size of breasts, growth of pubic hair and onset of the menstrual cycle. There are various other changes in men and women brought about by these hormones. For example female body becomes soft and tender whereas, male body turns hard and strong. A special group of hormones called the ‘progestrogens’; are responsible for the regulation of pregnancy. Hence women do not have beards due to the absence of androgens.

 

            Man has five senses of perception – skin, ears, eyes, nose and tongue. The tongue tells us the taste of food and drink warns us if food has gone stale or is bad.

            The tongue is located inside the mouth and is an important muscle in our body. It is red in colour. If you examine it minutely, you will see granular bumps or projections on its upper surface, sides and back. These are called papillae. These papillae contain groups of contact called taste buds (chemoreceptors). They are composed of cells. Hairs like fibres emerge at the upper side of our tongue. At the lower end of the tongue, they end in nerve fibres of cells. These join the nerves of taste that lead to the brain.  

            The taste of food is known only when it is in the liquid state. As we chew our food, a portion of it dissolves in the saliva. This dissolved form of the food activates the particular taste buds. These generate nerve impulses and the nerve fibres carry these messages to the “taste centre” in the brain. The brain then perceives the taste.

            In addition to the tongue, our nose, which smells the food, also helps in perceiving the total taste of food. Smell is also a part of the taste. In the case of wine, cocoa and fruit juices, it is the smell which helps in the realization of the real taste. When liquids are taken into the mouth, the tongue experiences the taste while their smell enters the nose and through the “smell nerves”, it reaches the brain. In this way is derived the total pleasure of taste.

            When we suffer from cold, fever, or even constipation/indigestion, the taste buds get covered by some impurities and do not get properly activated. Heat of the body (in fever) or even hotness of food, also deactivates the taste buds. Hence, we do not perceive the real taste under such unhealthy conditions.

            The number of taste buds on the tongue of an adult is about 3000 which is much more than that of a child. As we grow older, the taste buds start losing vitality and, finally, become inactive, thus decreasing in number. In a 70-year-old man, for example, the number of taste buds is only 40. The taste buds, like all skin cells, are constantly being replaced. About half of the taste buds are replaced every ten days.

            

 

            Sleep is a bodily need that takes up about one third of life-span. After a whole day’s toil, both brain and body get tired. Sleep is necessary to restore energy and freshness to the tired organs and tissues of our body. It enables the body to repair worn out tissues and cells.

            Do you know how sleep comes to us and what happens to our body during sleep? According to scientific facts, there is a very complex area in the brain called “sleep centre”. Calcium ions present in the blood, control this centre. When an optimum quantity of calcium is received by the “sleep centre”, we get sleep. It has been observed from experiments on animals that they start sleeping when calcium is injected directly into the sleep centre. But if calcium is injected into the blood stream, this does not happen. During sleep, the sleep centre does two things. Firstly, it blocks off the brain so that we have no will-power or consciousness left and secondly, it blocks all nerves leading from the brain so that our internal organs and limbs fall asleep.

            In sleep, our body continues doing many types of movements. A man on an average changes his sides 20 to 40 times during sleep in one night. Blood circulation continues during sleep. Heart beat slows down a little bit. The digestive system works normally. Liver and kidneys perform their functions. The effects of sound, light, heat, smell etc. in sleep are the same on every sleeping person. During sleep, the body temperature is lowered by about one degree centigrade and the body cells are quietly engaged in getting rid of waste materials that have accumulated during the active part of the day.

How many hours a healthy person should sleep? The number of sleeping hours needed varies with individuals. The average adult needs from 7 to 9 hours of sleep. Boys and girls of 15 years of age need about 10 hours sleep each night. It is wise to form the habit of going to bed at the same time each night. Insomnia is the condition in which a person has difficulty in falling asleep. Such sleeplessness is often associated with pain, but worry can also keep a person awake. A dark, quite room that is well ventilated and cool is good for sound sleep. 

               We often see that people faint on hearing some sad news or on getting frightened suddenly. The bodies get drenched in sweat and become cold. Their faces turn pale. Physical consciousness diminishes. Unconsciousness can be caused not only by a shocking news or terrible fear, but by many other factors also. People may faint because of confinement in a close and poorly ventilated room, or because of hunger, fatigue, severe pain, emotional shock certain heart condition of sudden fall in blood sugar. Now the question arises: why do people become unconscious?

               In order to know the reasons of fainting, it is essential to know what consciousness is. For the normal functioning of the brain, it is essential that there should be proper circulation of blood in the brain. As long as the brain is in receipt of proper supply of blood, all our physical activities remain normal. The normal functioning of the brain is in fact consciousness. If there is some obstruction in the supply of blood to the brain, the common physical processes get disturbed. Whatever may be the cause of fainting, man will become unconscious when normal supply of blood to the brain is disrupted. Hence, fainting or syncope is a temporary loss of unconsciousness resulting due to the insufficient supply of blood to the brain.

               The state of unconsciousness can be prevented by some measures. If somebody feels that he is about to faint, he should immediately lie down. If that is not possible, he should bend downwards and enclose his head in between the knees. Both these measures enhance the blood supply to the brain and as soon as the brain starts receiving proper quantity of blood, the chances of one’s becoming unconscious reduce.

               If somebody has become unconscious, he should be laid down and his clothes should be loosened so that he can breathe easily. His head should be kept at a little lower level than rest of his body. This will increase the blood supply to his brain and he will regain consciousness. Once he is conscious, he should be given tea or coffee. If somebody has fainted because of head injury or heat stroke, he should be taken to the hospital immediately. 

           Generally most of the people are of normal height, but sometimes we come across people who are exceptionally tall or small. Persons who are exceptionally small are called dwarfs. In circus you must have seen such dwarfs who entertain you.

          Do you know why some people lack normal height? The growth of a person depends on many factors. Heredity plays an important role in determining the height of a man or a woman. Children of tall parents are generally tall while of dwarf parents are dwarf. In Africa, some tribes such as the Watusi and the Masai have many men who are about 200 cm tall. At the same time, there are Pygmy tribes in Africa, whose people are only about 130 cm tall. These variations are due to heredity only.

            Disease is also a reason causing dwarfness. There are cases of dwarfness in which head and trunk are normal in size, but arms and legs are short. This is caused by disease of cartilage. A normal body skeleton increases in length during childhood and adolescence because cartilage changes into bone at the growing ends of the bones. Disease of the cartilage prevents arms and legs from growing to a normal size.

            Dwarfness is often caused by the lack of hormones produced by pituitary gland. The underactive pituitary gland during childhood does not allow the body to grow normally. This type of dwarfness can be treated by injecting hormones. Too much or too little growth is also determined by some disorder in adrenal, pituitary, thyroid and male and female sex glands (testes and ovaries). The growth retardation may also be due to inadequate nutrition and intake of vitamins. The restoration of an inadequate diet, vitamins and mineral intake will also cause the child’s growth to spurt. A dwarf, named Jeffery Hudson, eighteen inches tall served as a captain of cavalry in the British Army. He lived from 1619 to 1692.

 

          Memory can be defined as the capacity to keep information available for later use. The process of memory can be divided in to the four aspects - learning, retention and forgetting, and retrieval. The initial storage of information is called learning, keeping the new information available is called retention, the loss of new information over a period of time is called forgetting and utilization of stored information is called retrieval.

            According to psychologists there are four kinds of learning. Classical conditioning is the simplest kind of learning. Ivan Pavlov studied it during the early 1900. He offered a dog food and at the same time rang a bell. The sight of food made the dog’s mouth water. Pavlov called this an unconditioned response because it was not learned. Soon, however, ringing the bell was enough to cause the dog’s mouth to water. This was called conditioned response. Classical conditioning is often called respondent learning.

            Another form of learning is called instrumental learning. Often a person learns to do something as a result of what happens after the person does it.

Multiple response learning is the third type and it takes place when a skill is learned. A sequence of simple things must first be learned. Using a typewriter is our kind of multiple-response learning. At first, a person has to type letter by letter. With practice, the person learns to type word by word or phrase by phrase.

            Fourth type of learning is insight learning. It means solving a problem through understanding how the different parts of a problem fit together. A simple example is that of a young child wanting to climb on the top of a table. The child may use a stool to get on to the chair and then use the chair to climb onto the table.

           There are two basic theories to explain the process how we memorise events. According to one theory, memory is said to be stored in the brain as a memory trace. When we learn or experience something, impulses are generated in the nerves of the brain. These impulses impart their effects in the brain in the form of a record. According to the other theory, sensations created by learning produce some permanent changes in the brain which remain there in the form of memory. According to some biologists, the R.N.A. (ribo-nucleic acid) present in the brain keeps the record of events. It has been observed that the quantity of R.N.A. present in the brain keeps on increasing from the age of three to the age of forty. During these years, the memory of the man also increases. The quantity of R.N.A. is almost constant from the age of 40 to 55 or 60. Therefore man’s memory is almost consent during this period. After the age of 60, the quantity of R.N.A. starts decreasing and so does the memory.

           The only effective way of remembering something is to repeat it many times Interest is very important. Boring things are much more difficult to remember than something that we understand and are interested in. Motivation or desire to do something is also important.

 

          Every man in this world wishes to live long and nobody wants to grow old. But this desire of man is never fulfilled. Growing old is a process that begins with birth itself and continues throughout the life.

          When the child is born, all the parts of his body are tiny. All the biological processes continue with a fast speed. As man grows older, biological changes take place in the body. These changes cannot be prevented. Old age is the culmination of these biological changes. Do you know which are the biological changes brought about by old age?

          With the advancement of age, biological processes slow down, due to which the strength and sensitivity of man also diminish. This is because of the fact that the rate of production of proteins in the body decreases. Changes in the enzymes are also responsible for aging process. With reduced physical activity, man starts losing weight, his eye sight becomes weak and hair go grey. All these are the signs of the old age.

         In old age, changes occur in all the cells and tissues of the body. The cells of kidneys, liver and intestines become weak. Blood vessels become old and consequently they are not able to carry blood and other nutrients adequately to all parts of the body. As a consequence aging increases. As the age advances, eyes, ears, skin, teeth and digestion become weak. Blood circulation becomes irregular. Finally life comes to an end.

          The rate of growing old may be different with different people but old age spares none. This is a definite biological change which cannot be prevented. However, with the help of nutritional food, pure environment and proper exercises, early onset of old age can be prevented.

           There are many theories regarding baldness. Some people treat baldness as the indication of the arrival of old age while some are of the view that bald men are intelligent. Baldness is also treated as a sign of richness. Some people think that bald men are fools. Whatever may be the significance of baldness, one thing is certain that by losing hair, man is deprived of his natural charm.

           Baldness or alopecia is mainly of two types: permanent and temporary. Heredity, age and male sex hormone (androgens) production are three main factors causing permanent baldness. Other causes of permanent baldness are scar producing skin diseases, injuries, inborn lack of hair development and severe injury to hair growing centers caused by chemical or physical agents. Disease of the scalp is one important cause of baldness.

           Temporary baldness may be due to high fever, typhoid, pneumonia, influenza etc. Hairs start falling due to weakness also. Baldness caused by disease and weakness can be cured by nutritive diets and tonics. X-rays, ingestion of meals and drugs, malnutrition, skin disease and endocrine disorders are some other causes of temporary baldness.

          Baldness can be controlled to some extent through proper care of hair and a balanced diet. No successful drug or therapy has yet been developed to treat baldness. Don’t waste money on advertised patent medicines or so called, “cures”!

 

Just as carbohydrates, proteins, fats, inorganic salts and water are the essential parts of our food, vitamins are also necessary to keep the body in good health. Lack or deficiency of vitamins can cause many disorders and diseases like loss in digestive power, weakening of eye-sight, general weakness, tiredness, dryness of skin, inflammation of gums, weakening of bones, beriberi, rickets, etc.

What are vitamins? The word vitamin was coined in 1912 after the Latin word ‘vita’, which means life. In fact, vitamins are organic materials which are found in many food substances and are extremely essential for the proper functioning of the body. They are of many kinds and each vitamin has a separate role in keeping our body healthy. Twenty kinds of different vitamins have already been isolated, out of which six vitamins are most important. These are vitamins A, B, C, D, E, and K.

Vitamin A: Vitamin A is mainly found in milk, butter, cream, cheese, eggs, fish-oil, cabbage etc. It is very essential for the development of the body. Deficiency of vitamin A weakens eye sight and leads to night blindness. Vitamin A protects us from infections, skin diseases and many eye diseases.

Vitamin B Complex: Vitamin B consists of many water soluble vitamins of the same nomenclature. They are known by their chemical names. Their constitution and functions are also different.

Continue reading "Why are vitamins essential for us? "

          The normal body temperature of a healthy man is 98.4°F (37°C). Fever is a condition in which the body temperature rises above the normal. It is a common symptom of disease.

          The heat energy produced by the chemical reactions taking place inside the body is controlled by brain and skin. As long as there is no disease or malfunctioning in the body, the temperature remains 98.4°F. When germs of some specific disease attack the body, pyrogens are produced in the body cells. Consequently, the centres controlling the body temperature are affected and, as a result, body temperature starts rising. This rise in temperature is called fever. The first signs of fever are chills, loss of appetite and a feeling of weakness.

          Fever is a body mechanism that helps us in destroying the germs of diseases. During fever, some of the body organs start working fast and some physiological processes get accelerated. The rate of production of hormones, enzymes and blood cells increase considerably. These hormones, enzymes and blood cells start fighting the germs causing fever. During fever, blood circulation and respiration become faster. Both these processes help the body in getting rid of the poisonous germs present in the body. Fevers are often the symptom of a serious infection.

          There are various kinds of fever – malaria, typhoid, etc. Persistence of any fever for a longer period is not good. During fever, the internal parts become hot and there is deficiency of water causing the contraction of the capillaries of blood and urinary tracts. Protein accumulated in the body gets depleted. Disorder sets in the brain due to high temperature. It is, therefore, a big mistake on the part of anybody, if he or she ignores fever. Though fever is a physiological activity aimed at fighting any disease, it is extremely essential to seek immediate medical assistance once you get it.

A fracture is a break in a bone. Bones may break or fracture in several different ways. A simple fracture is one in which the two ends remain in position, and not much damage is done to the surrounding tissue. In a compound fracture, the broken bone sticks out through the skin. A comminuted fracture is a bone that has splintered or shattered. An impact fracture involves the ends of two bones rubbing each other. A greenstick is a partial break of a bone. In other kinds of fracture large blood vessels may be damaged or the bone ends may be smashed.

A fracture causes pain and inflammation in the area around it. Usually, when a fracture occurs, a doctor must set the bone right so that it may heal properly. A plaster cast is often applied to the limb with the fracture to assure proper healing.

The healing process begins when blood from broken blood vessels clots. After a few days the broken ends of the bone become soft and the space between them is filled with sticky ‘glue’ which contains bone forming cells.

Within two or three weeks, new soft bone tissues completely fill the gap between the broken ends. They slowly harden. The complete healing of a fracture may take several months. The only necessary condition is that the two broken pieces must be held in place for several weeks so that they can grow together properly.

Older people with brittle bones are most apt to get a fracture. Children tend to resist fracture.

             When your skin gets a cut, the broken blood vessels immediately become very narrow. This stops excessive bleeding and helps to keep germs out of the blood. Then substances released into the blood cause it to clot. The blood clot holds the edges of the wound together and hardens into a protective scab.

             Meanwhile white blood cells called neutrophils rush to the wound and begin to engulf the invading germs of dangerous bacteria. Then larger white cells called monocytes appear and engulf more germs, together with any debris. Any germs that escape are dealt with by a third kind of white cells called lymphocytes. These recognize germs as being ‘foreign protein’ or antigens. Then they start the production of antibodies, which are protein substances that stop germs working.

                      In the lower layer (the dermis) of the skin, special cells called fibroblasts move into the wound and start producing new tissues. These new tissues are essential for the healing of the wound. In the upper layer (epidermis), the cells around the wound start multiplying and filling the gap. When the process of new skin tissue development beneath the scab is nearly complete, the scab falls off. In this way the wound gets healed. 

             During the past two decades bio-engineers have developed a number of artificial substitutes for diseased tissues and organs. Some of these, such as, kidney dialyzers are external devices. Other such as plastic heart valves and artificial blood vessels are implanted inside the body, replacing the diseased or damaged ones. Two devices - the dialyzer and artificial heart valves are of special interest.

           The artificial kidney or dialyzer performs the function of removing wastes from the blood of a person whose kidneys do not work properly. It is an external device and patient needs dialyses twice a week. With this machine a person can be kept alive for years.

            In April 1969, Dr. Denton A. Cooley of St. Luke’s Episcopal Hospital in Houston placed a Dacron and silastic heart (artificial heart) into a dying man. Three days later a cadaver heart became available and was used to replace the artificial device. The next day the patient died. Some 13 years later, at the university of Utal medical centre, an artificial heart powered by a 170 kilogram external system, was implanted in the chest of 62 years old Barney Clark. He died 112 days later of multiple organ collapses. The heart was in perfect working condition.

        In 1984-1985, several artificial heart implants were performed in the United States and Sweden. Good life spans have been achieved but against a tremendous cost.

       Artificial teeth have been used by humans for a long time very successfully.

       The heart, the lung, the liver, the kidney, the adrenal glands and cornea can be transplanted from one human being to another. Success rate of transplantations of human organs is much higher than that of artificial parts.