My Science School

          It is a matter of common experience that when we feel cold or frightened, tiny bumps, causing a tingling sensation, appear on our skin. These tiny bumps are called goose pimples. Do you know why these occur?

          The ‘goose pimples’ get their name from the actual bumps which appear on a goose’s skin when its feathers are plucked.

          If you have a close look at the bumps, you will see a hair in the middle of each bump. Attached to each hair inside your skin is a tiny muscle. When you get scared or chilled, messages go shooting off from nerve endings that pick up the feel of cold. In a flash, signals come back to the muscles and as a result each of these muscles tightens up and gets taut. The skin around each hair is also pulled up. The result is little bumps.

          This action of the hair standing on its end - actually keeps the outside air closer to the body and helps to keep it warm in case of chill. If you rub your skin the goose pimples disappear due to the warmth produced by the rubbing.

          The fur of the animals also rises up due to the same reason. The erector muscle of each hair automatically contracts and the hair stands upright. This is why a cat looks bigger on cold days. This serves a definite purpose in case of animals having fur on their skin. When our ancestors, millions of years ago, had more hair on their body, probably the hair helped them in keeping their body warm. 

            Sexual reproduction is a naturally gifted process by which human beings as well as other higher animals produce their offspring. This process involves the meeting of a male cell with a female cell to produce a fertilized egg which grows and develops into a new creature. The growth of a human body inside its mother’s womb, starting from the fertilization of cells till the birth, is a nine-month long process.

            To begin with, a fertilized egg is formed by the union of male and female sex cells called sperm and ovum respectively. The fertilized egg is termed as zygote. It settles inside a specific place in the mother’s body called the uterus. Almost immediately after it is formed, the zygote begins to divide - and in less than 30 hours two cells are formed, called blastomers. These two cells are absolutely alike. The repeated cell division, rapidly increase the number of blastomers. But then all these cells are not alike. Some are muscle cells, some are bone cells some others are nerve cells, blood cells and so on. In short, all the different kinds of cells that make up a human body are present. 

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          The scope of heart surgery has vastly increased ever since the introduction of the heart-lung machine in the 1950s. This machine pumps blood from the veins to the arteries without having to pass through the heart. Most of these machines oxygenate the blood, thus completely bypassing the lungs as well. By using this machine, the heart can be stopped and opened for upto four hours.

          In human heart transplant, the main problem was that the body’s natural defence system tended to reject a new organ. The problem was eventually eased by the discovery of the fact that if the tissue types and the blood group of both people were carefully matched, the person receiving the heart had a much better chance of survival. 

          It was because of the use of such modern techniques and apparatus that the first human hearts transplant became possible. It took place on December 3, 1967, at Groote Schuur Hospital, Cape Town, South Africa. A team of 30 surgeons, headed by Dr. Christian Barnard, operated on Louis Washkansky, aged 55. The donor was 25 year old Denise Ann Darvall who had been killed in a road accident. 

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It has been scientifically proved that sunlight has several medicinal values that help in the prevention, cure and treatment of many diseases. Apart from its general benefits these are some special cases where sunlight plays an effective role.

Sunlight destroys certain particular fungi and bacteria that may settle on our skin. Secondly, it acts as a protective agent by further activating the white blood cells. The white blood cells defend the body from the attack of disease-causing germs, thus sunlight helps us to develop a greater resistance to fight diseases.

When sunlight falls on the skin, it causes certain substances to move into the blood and give the muscles a new tone. The muscles become tenser and thus work better. In fact, our nervous system gets a kind of ‘charge’ from sunlight and thus we feel stimulated and want to move about.

There is a substance in the skin called ergosterol that is transformed into Vitamin D by the ultraviolet rays of the sun. This vitamin is very useful for bones, particularly, in diseases like rickets.

Exposure to sunrays is just like swallowing a tea-spoon full of medicine every five minutes. But it is important to remember that this ‘medicine’ is by no means harmless.

We have to be just as careful about sunbathing as we would have to be about taking medicine. Sunbathing raises the blood pressure, so people who have heart trouble or certain lung diseases run the risk of physical harm by excessive exposure to sun. In fact, everyone should expose himself to sunlight only in phases. For instance, while taking sunbaths the best thing is to begin by exposing one-fifth of the body for about five minutes. The next day, expose another one-fifth of the body for an extra five minutes, and so on. In this way one can get all the benefits of sunlight without running into unnecessary risk.

            Jaundice is a disease of the liver in which the skin and the eyes become yellow. It occurs when some of the fluid produced by the liver, called bile, flows back to the bloodstream and gets deposited in the deeper layers of the skin.

            Jaundice is best seen in natural daylight and may not be apparent under artificial lighting. The degree of colouration depends upon the concentration of the bile pigments in the blood, its rate of tissue diffusion and the absorption and binding of bile pigments by the tissue. The bile pigments enter the tissue fluids and are absorbed more readily where there is already inflammation and edema. 

            The most common cause of jaundice is the extra secretion of bile by the liver. Congenital defects which impair the removal of bile pigments may also cause jaundice. Some liver diseases may also cause malfunctioning of the liver cells which would explain the presence of extra liver cells in the blood stream. Jaundice is usually of two types: retention jaundice and regurgitation jaundice. In retention jaundice, the pigments are retained in the bloodstream because of some removal problem. In regurgitation jaundice, there is an abnormal leak back into the bloodstream after it has been removed from the blood or directly from the bile ducts.

            Some of the diseases that can lead to jaundice are anaemia, congestion in the circulatory system, pneumonia, degeneration of the liver cells, scarring of the liver tissues and tumour in the liver and bile ducts. Newborn babies often have mild jaundice for a few days after birth. This is, however, generally harmless and soon disappears. 

 

          Electroshock therapy is a method of treating certain psychiatric disorders through the use of electric current to induce shock. This therapy is generally used in treating severe endogenous depressions and some forms of schizophrenia. How it achieves its effects is still not clear?

          The electroconvulsive therapy was introduced in Rome in 1938 by U. Cerletti and L. Bini for treating psychiatric disorders. After that it has been widely used to treat manic-depressive psychosis and various other types of depression. In the electroshock therapy, two electrodes are placed in appropriate positions on the head of the patient and 50 or 60 hertz alternating current at about 70 volts is passed for about 0.1 sec. There have been modifications and variations in the basic technique. The passage of the current causes an immediate loss of consciousness and the induction of a convulsive seizure. The treatment is given three times a week for two to six weeks. In some serious cases, the doctors even resort to two or three treatments in a single day.

          This therapy can have serious side-effects and complications. Hence it should be given to a few selected patients and with great skill and proper judgement. Although, it is a valuable therapeutic method in psychiatry, in certain cases it is not effective and sometimes it may even make matters worse.  

            The term ‘Rh factor’ stands for Rhesus factor. In biology it is known as a group of antigens which exists in the red blood cells of human beings. The Rhesus system was discovered by Landsteiner in 1940 while doing research on the Rhesus monkeys regarding blood groups. The Rhesus factor in human blood involves reaction with the blood of the Rhesus monkey. In fact it refers to the presence or absence of substances or factors in the red cells. There are half a dozen Rhesus factors, but ‘D’ factor is especially important in this regard. In majority of people this factor is present and they are known as Rhesus positive (Rh+). But about 15% of the human population, however, inherits blood that lacks in Rhesus factor. Their Rh factor is thus described as Rhesus negative (Rh-).

            There is no naturally occurring anti-Rh antibody. But if by mistake Rh+ blood is transfused into a Rh- person’s system, it can stimulate production of an antibody against the foreign ‘D’ factor and this antibody may eventually destroy the donated cells. The reaction is very slow in first transfusion, but becomes fierce in second or subsequent ones.

            The Rh factor plays a significant role during pregnancy. Some or all of the children of an Rh- mother and an Rh+ father may inherit the factor from the father. When a Rh- mother conceives a Rh+ baby and the blood supplies of the mother and the baby mix during the delivery resulting in some of the baby’s blood mixing with the mother’s blood, her blood may form antibodies against the Rh factor. Although these antibodies disappear after a few months, the mother is sensitised. In subsequent pregnancies, she may produce anti-Rh bodies which would attack the baby’s red cells. As a result the child might be stillborn or may die at birth due to a heart failure or a damaged brain or jaundice. In extreme cases so many red blood cells are destroyed that the foetus may die before birth.

            It is possible to overcome the problem with an exchange transfusion, the gradual removal of the baby’s blood, a few millilitres at a time and its replacement with Rh negative blood. In this way, some 95% of the affected babies can be saved.

            The condition brought about by the Rh incompatibility is known as ‘hemolytic disease’ of the neonate. The risk has been lessened by the development of a vaccine made from the anti-Rh antibody (known as Rh immune globulin). If this is administered to the mother within 24 hours of the birth of an Rh+ baby, it removes from her blood any Rh+ cells which may have seeped in. This saves her from becoming sensitised.

            The vaccine is now given as a preventive measure to Rh- mothers and it is repeated at each pregnancy. Thus due to these precautions the number of deaths of newborn babies caused by haemolytic disease is falling rapidly.

 

            Cirrhosis is a liver disease which renders a part of the spongy liver tissue scarred and useless. It can be caused by excessive alcohol consumption, poor diet, poisonous fumes, hepatitis, or inflammation of the liver. Once the liver tissue gets scarred, it cannot be repaired. The liver is the largest and a very important organ in the body since it helps to digest food and keeps the blood clear. Once the liver tissue gets scarred the liver may become useless and stop making proteins and purifying the blood. 

            The commonest type of cirrhosis is known as Laennec’s cirrhosis. Although it can occur at any age, it usually affects the people between 40-60 years of age. It is more commonly found among the males than among the females. To begin with, this involves an abnormal increase in liver fat. Soon the liver starts degenerating and in the end only a little fat is left.

            Cirrhosis can block the blood vessels of the liver and cause internal bleeding. Many people afflicted by cirrhosis become weak and lose weight. In certain cases the abdomen gets swollen with excess body fluids. The patient’s skin and eyes may become yellow. 

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           The nervous system is a network of nerve cells called neurons that send information to and from all parts of the body. All animals have special cells to perform this function. The messages are in the form of electric signals or nerve impulses. They travel through the cell and are passed on to the other cells. In the animal body there are millions of nerve cells linked together to make up the nervous system. The human brain itself contains about ten thousand million nerve cells.

          The human nervous system is divided into two parts: the central nervous system and the peripheral nervous system. The central nervous system comprises the brain and the spinal cord, whereas the peripheral nervous system consists of all nerve cells and nerve fibres at the periphery. The brain is protected by the tough bones of the skull and the spinal cord is protected by the bones of the spinal column.

          There are two kinds of nerve cells or neurons: sensory neurons and motor neurons. Sensory neurons carry messages from distant parts of the body towards the brain. These relate to pain, temperature, pressure and other messages from the sense organs. The motor neurons carry messages to the muscles, telling them to contract; and to the glands, telling them to produce the secretions. The nerves of the central and peripheral nervous system are a mixture of sensory and motor neurons travelling together.

          The nervous system can also be divided on the basis of the nature of work of the neurons. If the nerves are all concerned with conscious sensations, it is called the voluntary nervous system. They carry out orders given by the brain that are directed by will. When we want to walk, write or talk we use the neurons of the voluntary system. The neurons of the autonomic system are the ones that help in carrying out the routine activities we don’t normally think about. The autonomic system regulates the heart beat, respiration, digestion, blood pressure, and other unconscious activities.

          The autonomic nervous system has two main divisions: the sympathetic and parasympathetic systems. Their activities balance each other. Nerve impulses in the sympathetic system tend to increase the rate of heart beat and the blood pressure. On the other hand the impulses in the parasympathetic system tend to have the opposite effect. Under different conditions, each system takes control of the unconscious activities.

          With the help of prescribed physical exercises, training and to some extent will power, it is possible to control some of the activities of the autonomic nervous system.

 

          Anaemia is a particular physical condition in which the amount of haemoglobin in the blood or the number of red blood cells in a person falls below the normal level. More specifically, it is a condition caused by the deficiency of iron in the blood. In fact, haemoglobin is a protein in the red cells that contains iron. It is carried in the red blood cells of the human blood and imparts it the red colour. Haemoglobin makes it possible for the blood to carry oxygen. The body’s tissues need oxygen to function properly. The lack of the minimum amount of red blood cells or haemoglobin would result in a poor oxygen supply to the body and hence people suffering from anaemia look pale and feel tired as they become oxygen-starved.

          In every healthy human being, haemoglobin maintains a certain level of concentration. The mean values of haemoglobin for males are 15 gm per deciliter and for females 13.5 gm per deciliter. Values which are less than 2.5 or 3 standard deviations below the mean value are indicative of anaemia. The mean values are greater for males than for the females and again greater in adults as compared to children.

          To detect anaemia, the concentration of three things in the blood is measured. These are: the haemoglobin, the red-cell count and hematocrit. If the values of these things are below the normal level, the person is said to be anaemic.

          This disease may have several causes. The major ones are: (i) defective blood formation, (ii) cell destruction, and (iii) extensive loss of blood. Moreover there are a number of physical disorders, any of which can cause different types of anaemia. Some of the specific types of anaemia are: (i) microcytic anaemia (red cells are smaller than the normal size), (ii) macrocytic anaemia (red cells are larger than the normal size), (iii) normocytic anaemia (red cells are of normal size), and (iv) hypochromic anaemia (cells contain very little haemoglobin). Anaemia resulting from sudden blood loss are generally normocytic in nature.

          Red cells have an average lifespan of 120 days in the circulation. Each day about 45,000 red cells per microlitre are removed from the blood circulation in a healthy person. They are replaced with new cells from the bone marrow. Anaemia occurs when this rate of removal of red cells from the circulation exceeds the replacement or when the production of red cells is impaired or is ineffective in delivering cells to the circulation. Anaemia also occurs due to the lack of iron in the diet. Some kinds of anaemia can be treated by eating iron-rich foods. Medicines are also available to supply iron required to maintain the desirable level.

          Anaemia which results from the increased red blood cell destruction is known as hemolytic anaemia. This may be caused by poisoning, a kind of malaria, poor diet, allergy or some hereditary condition. 

 

          Belly button is the little dent that we have in the belly. Though it does not serve any purpose in our daily life, yet it is a matter of interest to know what it is and why we have it.

          Before birth, a child passes through embryo and foetus stages. In these stages, its abdomen is connected to the mother’s body by a rope-like tube called the umbilical cord. Everything which an embryo or a foetus needs to survive and grow during the pre-natal phase of nine months is supplied to the unborn baby from the mother’s body through this cord. Oxygen and food from the mother’s blood are carried to it through the vein in the umbilical cord. And the wastes are excreted through the two arteries in the umbilical cord. The cord remains attached to the spot where the belly button is.

          After the child is born the role of the umbilical cord ends because the child can now eat, drink, breathe and get rid of the body’s waste by itself, using the specific organs. Hence at the time of delivery, the cord is carefully cut off as close to the belly as possible. It does not hurt the mother or the baby. A tiny piece of cord left after cutting the long umbilical cord dries within a week and falls off, leaving a scar or a dent on the abdomen. It is called the navel or belly button. 

‘Pins ins and Needles’ is referred to the tingling sensation we feel in our hands, feet, arms or legs when the blood begins to circulate in those areas after being impeded for some time. For example, when we sit with our legs curled up in one position for a long time and then try to stand up, we sometimes get the feeling of numbness as if one of our leg had ‘fallen asleep’. As the blood begins to flow again, the familiar tingling sensation occurs due to the change. But why do we get this tingling sensation?

We know that the blood flows freely through the blood vessels in our body, just as water flows freely through a stretched hose. Imagine what would happen if you bent the hose! Water would only trickle through. Similarly blood is the transport system of our body and performs two important functions. It supplies food and oxygen to different parts of the body as well as collects the poisonous wastes. When a recession occurs in the flow these poisonous wastes accumulate and block the nerve cells from carrying messages from the foot to the brain. This results in the feeling of numbness. Again when the leg is stretched, the blood starts flowing again and this change causes the tingling sensation. 

          The potential threat of a population explosion made family planning a national issue in many developing countries. In the developed countries the changing role of a family to meet the demands of a hectic industrial life necessitated small families. Hence several birth control techniques were developed over the years.

          The sex glands of a man, the testes, produce sperms while the sex glands of a woman, the ovaries, produce eggs or ova. When the male sperm joins the female ovum inside a woman’s body, a new life begins to grow. Birth control methods are used to prevent this meeting of the egg-cell with the sperm. These have been divided into three broad categories: Natural methods, Spacing methods and Terminal methods.

          Natural methods are those which do not involve the use of any device or drug. These are: (i) rhythm or safe period method and (ii) coitus interruptus.

          The rhythm method is based on the avoidance of sexual intercourse during the ‘unsafe period’ or the days when there is a possibility of the egg cell meeting the sperm. Women normally produce one egg cell every month. If the male sperm do not enter the vagina at that time, then pregnancy can be avoided. The safe period is counted basing on the days of the regular menstrual cycle of 28 days. Eleven days before the expected date of commencement of menstruation are considered safe; the eight days preceding these eleven days are full of risk then again eight days before this risk period are considered safe. Since the regularity of monthly period varies from woman to woman, so also the safe period. 

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            It is a matter of common experience that we shiver in winter if we are not wearing woollen clothes. And even if we want to stop it we cannot do much about it. Do you know why do we shiver on a cold day? 

            Physiologically speaking, shivering is an automatic movement of the muscles. When we shiver our muscles tighten and relax very quickly over and over again. Each time when our muscles contract, the muscle cells burn more food for energy and as a result of this, heat is produced. Thus shivering is a mechanism of the body which helps to keep it warm. It keeps the body temperature from falling beyond a certain point. This is a process in which our muscles work hard and keep the body warm. Sometimes, shivering is not enough to warm us up properly. We, therefore, often jump up and down and flap our arms on cold days. Thus extra uses of muscles produce more heat in the body.

            We wouldn’t shiver if we do some exercise or play a physical game. Physical activities make our muscles work hard and warm up the body. Shivering, in fact, does the same job without any exercise.

 

          EEG is the abbreviated form of electroencephalography which is a bio-medical process of recording the minute electric currents produced by the brains of human beings and other animals. The instrument for detecting and recording the electric current produced by the activity of the brain is called electroencephalograph. This was discovered by Hans Berger of Jena (Germany) in 1929 and found to have important clinical significance in the diagnosis of brain diseases.

          The brain constantly generates minute electrical currents even during sleep and in deep coma. These can be recorded from the skull’s surface by means of small wires called electrodes attached to the scalp. In normal persons they have an electrical potential of about 100 microvolts. So to make such recordings the doctors use a machine that has about 20 equally-spaced electrodes which are attached to the scalp’s surface in accordance with the standard positions adopted by the International Federation of EEG. Electrode positions are carefully measured so that subsequent recordings from the same person can be compared with the earlier ones. The electrodes are connected to an amplifier which amplifies the voltages to 1,000,000 times. The current then moves an electromagnetic pen that makes a graph on a chart paper. 

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