My Science School

               When we see an object the light falls on the light-sensitive cells that form the retina. These send nerve impulses to the brain which ‘sees’ the picture or an image that is formed at the back of the eye. This is how we see the object.

               The lens of our eye is very soft and its shape is altered by the ciliary muscle. These muscles control focussing in the eye and this alters the shape of the lens. Some people cannot focus on distant objects and some other on nearby things. In such cases the object appears blurred and we say that eye has a defect of sight.

               For testing the eyes, the eye specialist makes use of a chart in which different letters in different sizes are written. Below these is written 6/36, 6/24, 6/18, 6/12, 6/ 9, 6/6 and 6/5 etc. Specialists ask the person under test to read the different letters or numbers on the chart and upto the row the patient reads the chart is marked as his eyesight. All these letters have a common digit of six. This indicates that this chart should be placed at a distance of 6 m or 20ft from the eye. If a person’s eyesight is 6/12, it shows that this man can read this letter from a distance of 6m while a man of normal sight can read it from a distance of 12 metres.

               In this way the eye specialist tests the sight and prescribes a number. For example if a person has a number -2D, it indicates that he cannot see the distant objects clearly and he needs a concave lens for his spectacles that brings light rays together. Similarly if the number is in plus sign, he cannot see nearby objects clearly and needs a convex lens that diverge light rays before they can enter the eye. The letter ‘D’ stands for dioptre which is the unit of power of a lens. Two dioptre mean a lens of 50 cm focal length.

               If a person is not able to see clearly both the near and distant objects, he needs spectacles of compound lenses. If someone delays the use of spectacles his sight may further deteriorate. In modern techniques, computers are used to ascertain the unit of power needed for individual patients.

 

            Influenza is a common ailment caused by different kinds of virus and spreads very rapidly from one person to another. When a large number of people in the same area are affected it is called an epidemic of influenza. Do you know what causes influenza?

            Influenza is caused by three types of viruses, categorized as groups A, B and C. These groups also have some subgroups. Influenza of ‘A’ group virus tends to reappear in cycles of two to three years and influenza of ‘B’ in cycles of four to five years.

            Influenza may affect individuals of all ages and is generally more frequent during the colder months of the year. The infection is transmitted from one person to another through coughing and sneezing. The influenza virus settles in the lining of nose and throat. It causes sneezing, coughing and sore throat. It also causes fever, sudden chills and headache. Often the patient has pain in the body. People with influenza feel weak, their muscles and joints ache and they have a dry painful cough. In most cases, influenza lasts from three days to a week. Mortality is usually low and those who die die from other complications such as pneumonia etc.

            Some kinds of influenza are very mild but others even fatal. The epidemic ‘Spanish flu’ after World War I killed more people than the numbers of people killed in the war itself. Fortunately there has not been a recurrence of such epidemic.

            There is no specific treatment for influenza. If subsides on its own after a few days. However, drugs such as aspirin and codeine sulphate are used to relieve discomfort and control the fever. People who are usually susceptible to influenza and of weak constitution may develop serious complications in case of infection. Normally it is not a serious disease and one should not worry much about it.

 

          Genetics is the science of heredity, dealing with resemblances and differences between parents and their offspring. In genetics we study inheritable characteristics of plants and animals.

          The serious studies in genetics started during the last two centuries. In 1860, Gregor Mendel, an Austrian monk, made various experiments on pea plants and drew certain conclusions. He concluded through his studies that certain characteristics passed on from one generation to the next.

          The Danish Biologist Wihelm Johannsen called these factors Genes. It is now known that genes not only transmit hereditary traits but also control all the processes of life.

          In 1910, an American geneticist Thomas Hunt Morgan proved that genes are located in chromosomes and they are passed on to the offspring along with chromosomes. After this, Edward Tatum, Hargobind Khurana and others made significant contributions to the science of genetics. The scientists have discovered that nucleic acids (DNA and RNA) determine the characteristics of an organism.

          Today better varieties of food plants with stronger and more productive abilities have been developed by using genetic methods. Even better breeds of animals have been produced by this method. The study, named as ‘Genetic Engineering’ is now a modern branch of biological science.

          By using genetic engineering, the genetic structure of an organism can be changed. Subjects in modern genetic engineering include deletions, inventions, and transpositions of genes including micro-surgery. Pioneer attempts in this direction have been successful.

          By adding DNA from certain animal cells to the DNA of bacteriological cells we can even produce insulin. Genetic screening helps in determining several diseases. By taking some fluid from the uterus of a pregnant woman it can be determined whether the unborn child is a male or a female. Diseases such as haemophilia and sickle cell anemia can often be diagnosed in uterus by genetic counsellors. Early detection of genetic diseases helps doctors to treat the child for these diseases shortly after his birth.

 

               It is well known that vitamins are chemical substances that our body needs to stay healthy. Vitamins are found in different kinds of food. Scientists call the six kinds of vitamins as ‘A’ ‘B’ ‘C’ ‘D’ ‘E’ and ‘K’. In fact vitamin ‘B’ is a group of vitamin.

               Do you know who pioneered the discovery of vitamins? The need for vitamins was discovered accidentally by the Dutch Bacteriologist, Christiaan Eijkman (1858-1930). He first identified that chickens fed on polished rice became ill. He realized the reason that after removing the outer layer of the grains, the polished rice lacks substances now we call vitamins. His reasoning was further confirmed when Eijkman visited Indonesia in 1886 to investigate the causes of the epidemic disease ‘Beriberi’ that took a heavy toll there. He was able to show that the disease ‘Beriberi’ was caused due to a dietary deficiency. This led to the discovery of vitamins and also the recognition of vitamins as essential to health.

               Eijkman, however, did not fully realize the wider perspective of the importance of vitamins. It was Fredrick Hopkin, the British Scientist, who put forward the theory that human beings need certain amount of such substances to keep them healthy. He suggested that diseases such as rickets or scurvy could be cured by providing necessary substances in food or by other methods containing different vitamins. This was found to be true and names of vitamins were given accordingly. 

Continue reading "Who discovered vitamins? "

          Our lifecycle is closely related to ecology. Austrian geologist Eduard Suess first studied this relationship nearly a century ago. The word “ecology”, however, was derived from the Greek words “Oikos” meaning the house and logos meaning study.

          Now the question arises what actually “ecology” means? Ecology is the study of animals and plants in their natural surroundings or environments and how each species fits into its ecosystem. An ecosystem is a community of plants and animals spreading over a certain area together with the soil and other non-living materials. Therefore, the whole earth can be considered as a large ecological unit. Within an ecosystem, the organisms make up the balance with the environments.

          We all know that the most important factor for any organism is its source of energy or food. Thus within any such system a complex pattern of feeding relationship which we call food-chain, is built up to maintain the ecological balance. For instance, plants are a primary source of food and energy — the herbivores obtain their foods by eating plants. In their turn, herbivores are played upon by carnivores, which may also be a source of food for other carnivores.

          A typical example of an ecosystem is a pond, a desert or a forest. Within such an area are the major factors determining the type of ecological system that develops? In any ecological system, each organism however large or small plays a vital role in maintaining the stability of the community. Within this system carbon, nitrogen, oxygen and hydrogen (in water) are continually being recycled, through a number of processes. These are known as Carbon cycle, Nitrogen cycle and Photosynthesis.

          Over millions of years nature has moved towards the overall creation of a stable ecological balance. Natural changes such as adaption to the slow-changes tend to be gradual. But man is often responsible for causing sudden ecological imbalances through activities like deforestation; polluting the atmosphere, rivers, lakes and seas; by rapid industrialization or sometimes through the outbreak of a new disease. The effects of such types of change can be fast and irreversible. Upto now these changes have not been too serious except in some areas like disturbances of carbon cycle in the atmosphere. This is seen as a serious threat that may lead to the Global warming to change the ecology and thus an impending danger to the humanity all over the world.

          However, there is an increasing awareness of what could happen if a worldwide disturbance in ecological balance could not be checked in time.

 

            It is a matter of common experience that we see spots of light when hit on the head or eyes. This is referred to as seeing the stars. In fact these are flashes of light produced when our brain gets confusing signals from our eyes, after being hit on the head or eye.

            When a nerve carries a signal, it has an electric current flowing through it. And thus every signal is in the form of an electric current. But its meaning depends upon its place of origin and destination.

            When we are hit on the eye, the pressure on the eye ball upsets the nerve cells. These nerves are connected with parts of the brain that receive eye signals. Normally these signals mean light. In this case they are caused by pressure, but our brain cannot identify them. It interprets the signals as light and we see the flashes or stars.

            If you want to confuse your brain and see lights or stars, close an eyelid and press your finger gently in the corner of your eye. You would see a patch of light on the side opposite to the finger. Similarly by pressing the eyelid we can see stars. Same is the case when we are hit on the head. 

               Pain is an unpleasant feeling that is usually caused by an injury, disease or other abnormality of the body. It is a warning that something is wrong somewhere in our body. Do you know why do we feel pain?

               We feel pain if something burns or presses hard on the end of certain nerves which are known as pain receptors. These receptors are located throughout the body as well as in the skin. Each pain receptor is a part of a nerve which carries pain impulses to the brain.

               Superficial pain is caused by receptors in the skin. A person can tell the location of the superficial pain as the skin has a large number of pain receptors. It is very difficult to pin-point the location of pain in internal regions because there are only a few pain receptors there. Sometimes deep inside the body, pain may be experienced that might get transferred to some other part of the body at some distance from the actual source of the pain. Toothache is one example of such pain.

               The best treatment of pain is to treat its cause. It can be controlled by some drugs called pain killers. Aspirin is one such drug. For controlling severe pain narcotics are usually used. Long term or chronic pain is treated by interrupting the pathways of the brain or spinal cord. Opium, morphine and heroine are the important narcotics used for this purpose. These drugs cut off the paths of the nerves which carry the pain messages to the brain. The biggest disadvantage of these drugs is that they lead to addiction. In modern times, chemists have invented anaesthetic drugs and other pain killers having fewer side effects to deaden pain caused by any disease and injury. 

          We know that construction of a huge structure requires thousands of slabs and other material like steel or stones to make it functional. Similarly billions of cells, tiny or long, subtle or sturdy, construct a living being. All the cells in the human body are not alike. They differ greatly according to the tasks that they have to perform. Muscle cells, for instance, are long and have the ability to contract and shorten the muscle. There are two types of muscle. Some work when our brain tells them to perform. For instances, when we pick up a load, our brain sends signals to muscles in our arms. Other muscles work even when we are asleep, for example, our stomach muscles go on churning the food we have consumed. The cells of the skin are mostly quite flat as their task is generally to cover a surface of the body. It acts as a barrier to infection and prevents the body losing water and heat too rapidly. In fact nature has designed cells to carry out every necessary bodily task.

          When many cells of the same or of different types are arranged together they form a tissue. These cells are put together by a substance called matrix. Its function is similar to that of the mortar placed between layers of bricks. The form of a tissue is determined by the nature and amount of the matrix and the type of cells. For example the quantity of matrix in the skin tissues is very small while in bone tissues it is quite large. The matrix is made from calcium phosphate and carbonate and magnesium phosphate and carbonate. They strengthen the bones. Our blood is made up of pale liquid called plasma and millions of cells or corpuscles. The blood cells float in it quite freely.

          Different types of tissues arranged together form an organ which performs a particular task. In the human eye, for example, there are many different tissues, all of which assist in the process of seeing. Though eye is a very small organ of our body, it is very complicated in structure. It is made of different types of tissues. Some organs like liver are much bigger but they are largely composed of a single type of tissue.

          When several organs work together to perform a special and complicated task, they are usually called a system. Digestive, respiratory, excretory etc. are the different systems which perform different tasks. Every system in the body helps each other and provides energy. For example, many of our activities are controlled by different parts of our brain. The hind brain, which consists of medulla oblongata, controls the heart-lings and digestive system.

          All warm blooded animals and human beings have their own system which varies in different degrees in terms of functional behaviours. 

            When we decide to get up early in the morning at a fixed time, we wake up without the help of an alarm or even a watch. Our body in fact does have a regular daily rhythm and this makes us aware of time. We usually sleep for eight hours every night. Depending upon the temperature of the surroundings our body temperature also undergoes a change and so does the speed of our heartbeat.

            Now the question arises, whether these rhythms depend on a sort of built-in-clock or on the daily changes of light and darkness? A famous experiment gave some clues to scientists to find an answer to this question. For several months the researchers lived alone in a cave where they did not even see daylight and had no idea about the time. They camped in tents, with gas heaters, lights, books and even a record player to make life in the cave bearable. Frequently they used a special phone to call the base camp above ground, reporting when they woke up, ate and went to bed.

            In another experiment people lived in specially built underground apartments. They, too, reported regularly to scientists outside.

            Most of the researchers in these experiments slept and wake up regularly on time. Only few lived on irregular schedules.

            On the basis of these experiments, we may conclude that our body has a built-in-clock. In fact the clock does not exist literarily. The most probable answer could be that our body responds involuntarily to a fixed regular time of all actions or even to any conceived time in mind. The actions in response to time may be the results of involuntary body actions or conditioned reflex actions. When the body is accustomed to a particular time for a particular action or become responsive to a pre-set time in mind then it works accordingly in set times. Researchers are going on this subject and it is hoped that someday scientists would be able to find a definite answer to these questions related with built-in-clocks in our bodies.

               Arthritis is the name given to a group of diseases that cause pain in the joints of the body. Arthritis in general, is a disorder of the joints. In fact, the word arthritis is of Greek origin, which means inflammation of a joint. In these diseases the connecting tissues of the joints get inflammed. Sometimes it can even cripple a patient.

               Although arthritis is more common in old age, it can occur to a person of any age. As per the available data the disease attacks twice as many women as men. It is not restricted to human beings only. It may even attack the animals. Today scientists have sufficient evidence to prove that dinosaurs suffered from arthritis. It may be caused by inflammation or infection in the joints.

               Sometimes it is a symptom of another disease. There are various forms of this disease but the exact cause of most kinds of arthritis is not yet known. Some types of arthritis are caused by injuries or by high content of some special chemicals in the body. It may also be caused by the wearing a way of cartilage in old age or by an allergic reaction involving joint tissues.

               A new form of arthritis has been discovered which is believed to be caused by a virus. It spreads among human beings by a bite from an insect, known as tick.

               In this disease joints get swollen and crooked. The patient feels pain and finds it difficult to move. There is no absolute cure for arthritis, although it is usually treated by aspirin-type drugs to reduce pain and swelling. Physiotherapy has also been found very helpful in its treatment. Vigorous massage and transmission of sound waves into the body is also very effective in curing this disabling disease.

               The treatment of arthritis varies according to the stage of the disease in the patient at the time of medical check-up.

               In preliminary stages the treatment is directed towards the relief of symptoms, improvement in general health and performance of some physical exercises. In some kinds of arthritis, diseased joints can be replaced with artificial ones. 

          After taking meals most of us tend to belch. Some people even belch whenever they want to. Do you know why do we belch?

          Every time we swallow food, a little air goes down with it. A muscular valve at the top of our stomach opens to let in whatever we have consumed and then closes quickly. This keeps strong stomach juices from sloshing out.

          Usually, some air is always present in our stomach. A little gas is produced during the digestion of food. Sometimes carbohydrate bubbles in soda water enter the stomach when we drink soda water. It helps to release pressure of gas generated in stomach due to indigestion. When too much of air and gas collects, our brain gets a signal that something should be done. As a result muscles of our stomach tighten up and the valve opens. Thus we get a burp. The noise is produced by the air and the gas vibrating in the pipes that go out of our stomach. Thus we see that belching is a mechanism and a kind of reflex action by which the extra gases collected in the stomach are released. 

 

          The recording of potential changes produced by the eye when the retina is exposed to a flash of light is called the electroretinogram, or in short ERG. Retina is a light-sensitive area at the back of the eye connected to the brain by the optic nerve. To record an ERG, one electrode is mounted on contact lens that fits over the cornea and the other is attached above the ear or forehead.

          An ERG signal is more complicated than a nerve signal because it is the combination of the effects taking place within the eye. The general pattern of an ERG is shown in the figure. From the medical point of view, the ‘B’ wave is the most important because it arises in the retina. If a patient is suffering from ‘Retinitis pigmentosa’ the ‘B’ wave would be absent in his ERG because of the inflammation of the retina.

          The recording of the potential changes due to eye movement is called electroculogram. In short, it is known as EOG. To record an EOG, a pair of electrodes is attached near the eye. An EOG can record horizontal and vertical movements of the eye. EOG also provides information about the orientation of the eye, its angular velocity, and its angular acceleration. Scientists have studied the effects of drugs on the eye movement. By an ERG, eye movements during sleep can also be studied. EOG is very rarely used in the routine check up for eye ailments.

          Retina is an important part of the eye. It is a layer of special cells at the back of an eye ball and contains sensory cells capable of converting light into nervous messages that pass down the optic nerve to the brain. Images of the objects are formed on the retina. So with the help of an ERG, certain major diseases of the retina can be detected. Damage to the retina can cause blindness.

          Just as an engine needs fuels like coal, petrol etc. to run, similarly our body also requires fuel which provides us energy to work with. The substances which act as fuel or energy for our body are fats, carbohydrates, proteins etc. — the substances which our food consists of. Whatever food we take it gets burnt with the help of oxygen which we get from in-breathing, thereby releasing energy by breaking into these constituents. This energy thus produced is used in the performance of all of our voluntary and involuntary body functions. For instance, protein is required for growth and tissue repair while vitamins and the minerals are necessary for the proper functioning of various body organs.

          So, we need to supply these substances regularly to our body for its efficient functioning. That is why we take food regularly.

          Out of these substances taken as food our body absorbs and utilizes useful ones and rejects those which are not needed, in the form of waste material. We excrete daily about 2 kg of urine and stool. Carbon-dioxide also comes out during out-breathing as a waste material. About 400 gm of water comes out through the process of sweating and out-breathing.

          Human body temperature remains constant between 98°F and 99°F. This is a wonderful equilibrium between the production and consumption of heat in the body so that the body temperature remains constant. Food is measured in units of energy, called Calories.

          Our body is a wonderful machine which works continuously without any break. Even when we are in sleep many processes such as respiration, digestion, heart beating etc. go on incessantly. These processes also consume fuel continuously.

 

               The word consciousness in psychological term refers to the condition of alertness of the organism. The brain is the control centre of the body’s nervous system and plays a major role in man’s thinking, remembering, alertness and vice-versa. Unconsciousness refers to the state of sleeping. Between these two conditions one may have varying degrees of consciousness.

               In a condition of full consciousness the level of alertness will be very high. For example if someone is playing chess and wants to win, he would try to remain in a state of high alertness and deep concentration. Similarly the circus gymnasts would have to be very alert during their performances.

               If a person is dozing he is said to be in a state of lower level of consciousness. He would be regarded as unconscious if he falls asleep.

               These are different states of consciousness we come across in our normal day-to-day life. However, unconsciousness or sub-consciousness can also be produced by artificial means. A high state of consciousness can be produced with the help of some medicines which act as a stimulant to make person more active beyond his normal ability. Such medicines affect the central nervous system and produce such abnormal conditions. Caffeine in a strong coffee or tea can act as a powerful stimulant for some people. Too much alcohol can produce dozing effect and finally unconsciousness.

               Certain diseases have a marked impact on the level of consciousness. There are some mental diseases which can lower the consciousness of a person. Emotional disturbances also affect the state of alertness of an individual. Highly emotional people often get the feeling of depression.

               Today, scientists have developed several medicines and shock therapies which can control the level of consciousness. These methods are used for treating people with lower level of consciousness. However, these should be used only when prescribed by a physician. 

          Cholesterol is an organic compound belonging to the steroid family and occurring either in a free state or as esters of fatty acid in practically all animal tissues. The molecular formula for cholesterol is. In a normal man it is about 0.3 percent of his average weight. It is the starting material from which the body produces bile acids, steroid hormones and pro-vitamin substances in the body. It is used by our body to help the digestive system as well.

          Cholesterol was discovered in 1812. Its name arises from its occurrences in gallstones derived from the Greek word chole-stereos-ol meaning bile-solid. The synthesis of cholesterol occurs in various tissues and organs particularly, the brain, liver and arteries.

          The increase in its quantity beyond a certain level can be harmful for our body. Excess of fat and cholesterol get deposited in the walls of arteries causing blockage and hardness thus obstructing the free flow of blood. Due to this, quantity of blood flowing in the arteries decreases and consequently the oxygen supply to vital parts of our body is also decreased. This condition is medically termed as arteriosclerosis. Small blood clots that would normally pass through blood vessels may get trapped by high cholesterol deposits.

          We know that coronary arteries play a vital role for the heart to function. They provide oxygen and carry blood to the heart. If a coronary artery gets blocked that particular part of the heart may stop functioning leading to a major heart attack which can even prove fatal.

          Cholesterol in blood can be controlled by a regulated diet. A high concentration of cholesterol is present in the foods of animal origin like meat, egg, butter etc. Doctors advise to avoid high-cholesterol foods by substituting unsaturated foods like fruits, vegetables, cereals and so on.

          Lowering cholesterol levels in the blood can help to reduce the risk of heart attacks. Several other measures can be taken to maintain the desirable cholesterol level. This includes giving up smoking, regular exercises, avoidance of overeating and fatty substances.