My Science School

          The heart is a vital organ that pumps blood to different parts of the body. The outflow of the blood takes place when the heart’s left ventricle contracts. Then blood is forced into the arteries which expand to receive blood. These arteries have a muscular lining which resists this pressure. Thus blood is squeezed out of them into the smaller vessels of the body. By blood pressure we mean the amount of pressure that blood exerts on the walls of the arteries. The amount of pressure depends upon the strength of the heart muscle, the amount of blood in the circulatory system and the condition of the arteries. 

          There are two kinds of pressures – systolic and diastolic. Systolic is the maximum pressure that occurs when the left ventricle contracts. Diastolic is the minimum pressure that occurs just before the heartbeat which follows.

          When a doctor measures blood pressure, he uses an instrument in which a column of mercury rises or falls under the pressure. It is marked in millimeters. The average systolic pressure in a young man is about 120 mm of mercury and the diastolic pressure is about 80. These figures are usually stated as 120/80 or 120 over 80.

          Blood pressure usually rises with age because the arteries become less flexible. Anxiety or exercise may also cause pressure to rise temporarily. It is also increased by a number of diseases. A. person is said to have high blood pressure or hypertension if it exceeds the figure of 100 plus his age or if the diastolic pressure exceeds 100. High blood pressure can cause heart failure, apoplexy, or kidney diseases. It may also burst a blood vessel in the eye or the brain, thus causing blindness or a hemorrhage. Symptoms of high blood pressure are headaches, hot flashes and anger.

          Abnormally low blood pressure occurs when a person has a heart attack or loses large amount of blood because of some injury etc. When the blood pressure falls considerably, the oxygen supply to the brain and other parts also gets reduced. This can cause death. Physicians use drugs which contract the muscular walls of the blood vessels to raise the blood pressure.

          Abnormal high blood pressure may be due to the constriction of arteries or due to damage to one or both kidneys. Excessive weight and lack of exercise can also contribute to hypertension. Temporary high blood pressure can be due to excitement or emotional stresses.

 

          A squint is a physical defect in which both eyes do not point in the same direction. This is also called strabismus or heterotropia – a disorder of the eye in which the alignment of the two ocular axes is not parallel.

          A person with this defect may have an inward squint (one eye may be directed towards the other eye), an upward or a downward squint. The squint is called ‘comitant’ if the deviation remains constant no matter in what direction the gaze is directed. It is called ‘noncomitant’ if the degree of misalignment varies with the direction of the gaze.

          Long-sightedness in children often causes an inward squint. On the other hand short-sightedness may produce an upward squint. If one or more of these muscles are paralyzed, the noncomitant squint occurs. 

          A squint is most often the result of some abnormality in the nervous controls. Acquired squints are usually due to nerve or muscle disease and cause double vision. In fact, the movement of the eye balls depends upon the action of six muscles – four of which are straight and two slanting. If the nerves of these eye muscles have developed some defect, the eye can develop a squint.

         With the progress in medical sciences now it has become possible to treat this defect. But it must be done at an early stage by wearing special glasses. These have a dark glass to cover the good eye to stop it from being used. This prevents the bad eye from becoming worse.

         Squint can also be treated by some orthoptic exercise which helps to strengthen the eye muscles. In some cases, an operation is necessary to strengthen a weak eye muscle or to weaken an extra strong one. The good eye is covered for some period before the correctional surgery. This is to enable the patient to use the previously unused eye and build up its vision.

          An interesting observation about squint-eyed people is that it is often difficult to judge the direction in which they look. 

          The iron-lung machine was one of the earliest life-saving machines. It was invented by Philip Drinker of Harvard, U.S.A in 1929. This device is meant to aid those who have difficulty in breathing, either due to a paralysis of chest muscles or due to some disease or an accident.

         This machine has an air-tight chamber on wheels. The patient lies on a foam-rubber bed with an adjustable head and foot rests. It is operated by electricity, but has a safety device which gives a warning signal in the vent of power failure. The machine can then be operated by hand. It has a cover which can be opened to give access to the patient. The patient’s head is usually enclosed in a plastic dome.

          The machine helps in breathing by alternately reducing and increasing the air pressure around the patient’s body. When the pressure is reduced, his chest expands and air comes into his lungs through the normal air passages, as his head remains outside the machine. When the pressure is increased, the chest contracts and air is automatically expelled from the lungs.

          During a heart operation, a heart-lung machine is used. This takes over the function of the heart and lungs and the surgeon can perform the surgery safely. The technical name for this machine is the cardiopulmonary bypass machine, since it takes over the job of both heart and lungs. Blood returning along veins, from the body’s organs to the heart, is led out of the body along a tube to a gas exchange unit. Here carbon dioxide is removed from the blood and oxygen is added – thus doing the lung’s job. The blood then flows through a rotary pump which does the heart’s job and back into the main arteries. This is a very important device during heart surgery. 

          Asthma is a chronic disease of the lungs in which a person has sudden attacks of shortness of breath, wheezing and coughing. It is one of the most common diseases affecting respiration. It affects all races and both sexes equally. It usually begins in childhood or early adult life.

          Asthma is caused by a blocking of the bronchial tubes in the lungs. This blocking is caused by shrinking of the bronchial muscles, swelling of membranes lining these muscles and the presence of thick mucus called phlegm.

          Allergic bronchial asthma is the most common type of the disease. It is caused by adverse reaction to things like house dust, pollen, feathers, animal dandruff, drugs and certain foods. Strong odours or smoke may also cause its attacks. Asthma is often linked with however, another type of allergy. Different kinds of asthma may even harm other parts of the body. 

          Asthma attacks often occur after heavy physical work or in case of emotional disturbance. An infection of the nose and throat can trigger off an attack. A drastic change in the weather may also prove troublesome in this regard. Exposure to sudden changes in temperature and humidity or both may also cause an attack. Common symptoms of asthma are wheezing, a sense of suffocation, dry cough and an inability to expel air easily from the lungs.

          Asthmatic attacks usually last for half an hour to several hours. Prolonged or frequent attacks may prove dangerous if the patient is weak or suffers from malnutrition. Some 35-40 percent of childhood asthma cases improve at puberty.

           A physician identifies asthma by physical examination and allergy skin tests. From these tests, the substance to which the patient is allergic can be detected. Most doctors usually prescribe drugs such as epinephrine or ephedrine to treat it in the initial stages. Patients with very serious cases of asthma however may need to take ACTH or cortisone. Some doctors prescribe small doses or injections of asthma-causing substances. And they slowly increase the strength of these injections until the patient’s body develops a natural resistance to the allergic substances. Sometimes oxygen becomes essential for such a patient. To avoid asthma attacks one should avoid substances to which one is allergic and the situations that precipitate attacks.

 

          Physiotherapy is that branch of medicine which makes use of some physical agents or exercises to treat a disease or an injury. It is also called physical therapy. More strictly it is a branch of rehabilitation medicine. Doctors who specialize in this branch of medicine are called physiotherapists.

          Physiotherapy is helpful in treating many kinds of disabilities and diseases. It is often used to treat paralysis and muscle weaknesses, such as caused by poliomyelitis and multiple sclerosis. It is also used in treating heart and lung diseases. It can also be used as a treatment aid for amputations, fractures and other injuries. With the help of this treatment, the disabled person may lead a constructive and creative life.

          Many kinds of devices and treatments are used in physiotherapy. Radiant heat lamps are used for warming up the body to remove the pains in the backbone. Electric heating pads, diathermy, hydrotherapy (water treatment) and special baths are used to apply heat to the diseases or damaged parts of the body.

           Warming up of the body relieves the pain and improves the blood circulation in the body. Soon after certain injuries cooling methods are also used to reduce pain and swelling. Ultraviolet lamps are used to kill certain germs and to help healing because ultraviolet light has more energy and can destroy germs. Ultrasonic waves are used to treat inflammatory conditions of muscles and joints.

           Exercise is the most important part of physiotherapy. In fact, a layman believes that physiotherapy is concerned only with different kinds of physical exercises. However, the physiotherapists make use of various equipments such as pulleys, weights, parallel bars, stationary bicycles and dumb bells. Splints, braces, crutches and wheel chairs are also used to help disabled persons. Physiotherapists help people learn how to use these devices and develop confidence in doing daily tasks.

           Physiotherapists work in clinics, hospitals and schools for the handicapped. Nowadays the use of physiotherapy is constantly increasing.

 

Blood must reach every cell in the body to provide it with food and oxygen, and to remove waste products. The group of organs which circulate blood through the body is called the circulatory system.

In the human beings, the circulatory system has a muscular pump called heart. It pumps the blood through long, tube-like blood vessels. Blood vessels carry the blood throughout the body to the cells. In our circulatory system there are five types of blood vessels: arteries, arterioles, capillaries, venules and veins. An artery is a large vessel that carries blood away from the heart to the cells. It branches off into the smaller arterioles which further divide into very small capillaries. The capillaries carry blood to the cells. These reunite to form larger tubes called venules. These venules merge to form large tubes called veins. Veins carry impure blood back to the heart. According to a rough estimate if all the blood vessels are joined together in a single-line they would stretch to 60,000 miles.

Blood is pumped from the right ventricle of the heart into the pulmonary artery. The pulmonary artery carries it to the lungs where it absorbs oxygen and releases carbon-dioxide. The blood returns to the left auricle of the heart through the pulmonary vein. The left auricle pumps the oxygenated blood into the left ventricle of the heart which pumps it into aorta. The aorta is the largest artery in the body. It carries blood to other arteries and arterioles. The blood absorbs food when it passes near the small intestines. The wastes from the cells are removed from the blood when it passes through the kidneys. After the blood passes through the cells of the body, delivering food and oxygen and removing wastes, it returns to the heart through the vena cava. The vena cava is the largest vein in the body. The unoxygenated blood enters the right auricle which returns it to the right ventricle. It is then pumped to the lungs to receive more oxygen.    

The muscular walls of the arteries are thick and elastic. They carry bright red, oxygen-rich blood. As the heart pumps, a wave of pressure travels along the walls of arteries and can be felt as pulse. Their walls can contract and release and can regulate the amount of blood flowing to the body tissues.

The walls of veins have three layers: elastic, muscular and lining. The veins are thinner and less muscular than the arteries. In the arms and legs the veins have valves that prevent the back flow and pooling of blood due to gravity. The veins that are swollen, stretched or coiled on themselves are called varicose veins. These can sometimes be found on the legs of older people as well as those whose jobs involve a lot of walking. Blood in the veins is under low pressure and flows slowly. Since it contains less oxygen, it turns purplish red in colour. 

          Electrocardiography is a system of tracing graphically, the electric impulses generated by the heart muscles during a heartbeat. The graphic record is called electrocardiogram (ECG).

          The working of the heart is regulated by electrical impulses. It’s each part including the various valves from where the blood flows in and out produces its own electric wave pattern. These electrical impulses are recorded by a machine called electrocardiograph.

          Electrocardiogram provides extremely useful information regarding the condition and performance of the heart. It is very useful in the treatment of heart ailments.

          Electrocardiograms are made by attaching electrodes to various parts of the body. These lead off the feeble heart current to the recording instrument. The four extremities and the chest become standard places for attaching the electrodes. When the electrocardiogram is switched on, an automatic pen recorder moves up and down on a chart paper and records each wave impulse. 

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          No two persons in the world have exactly the same voice! Do you know why it differs from person to person?

          The act of speaking involves movements of hundreds of muscles in split-second co-ordination. The speech organ called larynx or voice-box is capable of producing an infinite number of sounds. It is part of the throat through which air passes. When we breathe, air passes through the larynx downwards through mouth and nose into trachea (windpipe) and finally to the lungs.

          The larynx is made up of a tough wall of cartilage. It’s inside lining has two folds of tissue stretching on each side and leaving a gap between them. These are called vocal cords. In case of simple breathing, the gap between the cords remains wide open. The cords are slack. But talking, singing or shouting involves tightening of the cords. The exhaled air causes the cords to vibrate and produce sound. Our vocal cords can be found in any of about 170 different positions.

          If the vocal cords are slack, they may vibrate about 80 times per second and the result is deep tones. If they are tensed, they vibrate rapidly, perhaps thousand times a second, and produce short sound waves or high tones or high pitch sounds.

          As a child has short vocal cords, they produce short air waves and consequently a high pitched voice. As a child grows, the vocal cords become longer and that causes the voice to become deeper. Thus the voices of adults are heavier and deeper than children’s voices.

          Similarly the voices of most adult men are deeper than those of women. This is because a man’s larynx is larger than that of a woman with longer cords.

          The pitch of a voice depends upon the length of the vocal cords. Each voice has a certain range of frequencies. It is this range that determines what kind of voice a person has. Voices can be divided into six groups: bass, baritone, and tenor for men; and alto, mezzo-soprano and soprano for women.

          The quality of human voice also depends on many other things, such as resonating spaces, lungs, nasal cavities etc. The nose, sinuses, pharynx and the oral cavity act as resonating chambers, and modify the vocal tone produced by the vocal cords. The movement of the tongue against palate, the shaping of the lips, and the arrangement of teeth also produce changes in the voice.

           Since the structures and movements of all these organs are different in different persons the voices of no two persons in the world can be the same.

 

            You must have heard of the great service, Mother Teresa of India, the Nobel Prize winner, is rendering to lepers. Even international organizations such as the World Health Organization, UNICEF, etc are engaged in a continuous worldwide fight against leprosy. What is leprosy and how is it caused?

            Leprosy is caused by certain bacteria called Mycobacterium leprae bacillus. They attack the skin and nervous system, causing lumps and patches of discolouration on the skin. These occur mainly on the ears, face, testes and the limbs. The inner surface of the mouth and nose also get affected. When the disease spreads to the eyes, it causes blindness. The affected nerves are destroyed. The fingers and the toes may lose all sensation and become paralyzed. 

            Leprosy is mainly of two types: Lepromatous or Cutaneous; and Tuberculoid. Lepromatous is marked by wide-spread infiltration of grainy masses of inflamed tissue under the skin, face, testes and mucosal membranes of the upper respiratory tract. But the tuberculoid is marked by stain-like lesions with raised, reddish borders and patches that become insensitive to physical stimulus as they spread. The symptoms of this disease are thickening of the skin, loss of hair, deformities of bones and joints and loss of sensation in various areas of the body.

            Leprosy’s treatment involves a long-range use of Sulfone drugs to bring an immediate stop to the infection. Severe cases, however, might also need surgery. Other drugs used to treat it are sulfoxone and solapsone. An ointment named ditophal ointment is also used with some success by rubbing on the affected areas in the body. This is a volatile substance which is lethal to the leprosy bacteria. It is generally used with another therapy which is called dapsone therapy. These drugs are fairly inexpensive. According to rough estimates one in every five patients ever receives proper treatment.

            Today the reported cases of leprosy throughout the world number at least 2,000,000 and the actual number of infected-people may be as large as 10,000,000. It is still not clear how its germs spread the infection. It appears that prolonged, close physical contact with an infected person usually precedes active infection in susceptible persons. According to the experts the disease is mildly contagious. Infants born of infected parents do not develop the disease if separated from them at an early stage.

            Leprosy occurs mainly under humid, tropical and subtropical climates. The majority of lepers are found in different parts of Asia that include Japan, Korea, and the Pacific Islands.

 

We all know whether we are right-handed or left-handed. But only a few of us know whether we are right-eyed or left-eyed. This means that we do not use both our eyes equally. One eye is dominant or stronger than the other. It has been found from several studies that 65% people have an unconscious preference for the right eye, 32% for the left eye and only 3% are ambicular i.e. they use both eyes equally.

By the following experiment, you can know whether you are a right-eyed person or left-eyed.

Hold a pencil in your hand and stretch the arm in front of you at eye level. Keep both your eyes open and line the pencil up with a picture or shelf or some object on the wall. First close one eye and see the object. Then close the second eye and see the object with first. If the object remains lined up with your right eye opened, and seemed to move to the left when your left eye was opened, then your right eye is dominant and if it happens the other way, then you are left-eyed.

There are some other methods too by which the eye dominance can be determined. In this respect, one Stanley Coren conducted some experiments at the University of British Columbia. He concluded that when we see objects with the dominant eye, they appear somewhat bigger. He selected 45 people and tested them for eye dominance. It was found that 25 people were right-eyed and 20 people were left-eyed. It was interesting to note that 17 of the right-eyed subjects viewed the object bigger with their right eyes whereas 13 of the left-eyed persons felt the same difference in size with their left eyes.

According to scientists all individuals have equal refraction for both eyes; the difference in size felt by the right-eyed and left eyed persons was only psychological. It is just a matter of unconscious individual preference practiced from the beginning that leads to the dominance of one particular eye and makes people right-eyed or left-eyed. 

          Leukemia or blood cancer is a fatal disease of the blood-forming tissues wherein abnormal white blood cells are found in the blood stream. It can occur at any age and in either sex. It is even more dangerous because its cause is still unknown. Do you know what happens in this disease?

          Blood is a vital body fluid and all its constituents have a specific function. Blood has a large number of red blood cells and a comparatively smaller number of white blood cells. The red blood cells carry oxygen to all the tissues of the body. The white cells defend the body. White blood cells are produced mainly in the bone marrow and lymph glands. In the case of leukemia, something goes wrong with the tissues that produce white cells. So these cells start multiplying at an abnormal rate. A person afflicted with leukemia may have 30 to 60 times the normal number of white blood cells that a healthy person has. Simultaneously, the rate of production of red blood cells becomes extremely slow and this causes anaemia. 

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          Normally mammals have bigger brains in relation to their size when compared with other living creatures and the human brain is the biggest and most developed among all the mammals. It controls all the activities of the body throughout our life. It remains active every moment directing and guiding all other organs of the body. That is why it is called the control centre of the body? But what is our brain made of and how does it carry out its different functions?

          The human brain is largely made up of grey and white matter. The grey matter contains nerve cells and the white matter contains the nerve fibres. The nerve fibres carry messages from the nerve cells to different parts of the body. Thousands of electrical impulses are constantly passing through these nerve cells. All messages are first sent to the brain through different nerves from the sense organs in all parts of our body. Consequently it sends signals to different muscles and glands in the body to carry out necessary actions. The most important human activity ‘thinking’ takes place in our brain. All the energy produced in the body is used by the brain. 

          The central nervous system consists of the brain and the spinal cord. Different parts of the brain are interconnected and they control different activities of the body. The medulla and hypothalamus control the involuntary activities such as breathing and heart-beat. The cerebellum controls muscles and organs of balance in activities like walking or riding a bicycle that is, carrying out work automatically once we have learnt them. The cortex controls conscious feeling and voluntary movements such as writing and running. The front part is called cerebrum which has two cerebral hemispheres – the left hemisphere and the right hemisphere. This part (cerebrum) does most of the thinking and is responsible for our memory and emotions. The left hemisphere is associated with the right side of our body and the right hemisphere, with the left side. People with a more developed right hemisphere are left-handed and vice-versa.

          Our brain works even when we are asleep. An adult’s brain weighs about 1.4 kg and has 14 billion nerve cells in it. The fastest messages pass along the nerves at a speed of 400 km/hr. 

          Immunity is described as the ability of the body to resist or to recover from the invasion of disease-causing microbes (bacteria, viruses, and protozoas) and larger parasites (helminthes). Thus a person said to be immune to a particular disease would not contact it although others might do so.

          Microbes and parasites cause several diseases in man. The disease-causing germs often release toxins (poisonous substances). Normally our body is able to defend itself against most disease-causing microbes. First the skin acts as a barrier to the entry of many microbes. And secondly the white blood cells destroy many microbes. But if the number of microbes exceeds the capacity of white blood cells they fail to protect the body against them.

          Many persons are able to resist diseases to certain extent due to immunity mechanisms in their systems. The blood of a person produces substances called antibodies which fight the invading organisms. Each kind of antibody acts against only one type of microbe. Different antibodies have different characteristics. Some antibodies neutralize the toxins released by microbes. Certain others clump them together which can then be easily attacked by white blood cells. Some other antibodies dissolve the bacteria. Sometimes a certain amount of antibodies is permanently left in the blood plasma and this serves to protect the individual from future attacks. Such persons are said to be immune to that particular disease. 

          Immunological mechanisms are either specific or non-specific. Specific immunity, also called acquired immunity, which refers to mechanisms that are activated individually after a microbe or some other foreign material, invades the body. Non-specific immunity refers to general protective mechanisms that either kill or prevent the multiplication of microbes and other parasites.

          Some persons are immune to certain diseases right from the birth. These people are said to have natural immunity or inborn immunity. In an epidemic of a particular disease, say cholera, people with natural immunity do not suffer from cholera. If someone gets smallpox or chickenpox once, he will not get it again during his whole lifetime. The body in such a case retains adequate levels of antibodies as a protection against future infection.

          A person can also develop immunity by treatment with appropriate antigens. This is called artificial immunity. For instance, in the case of epidemics of smallpox, the health authorities vaccinate the people by which immunity is produced artificially. This vaccine was invented by Edward Jenner. It is produced by infecting a calf or horse with the smallpox virus. The virus in the calf or horse gets weakened. This weakened virus is collected as a vaccine and introduced into the human body. Since the virus is weak, it is not able to cause a severe attack of smallpox in man. But its presence induces the body, to produce antibodies and provides immunity against smallpox for several years. The introduction of weakened microbes in the body is called active immunity, the effect of which may last for even a lifetime. Immunity may also be passive. In this readymade antibodies are injected into the human body. An animal like a horse is infected with disease-producing microbes. The antibody is produced in the blood of the horse. The serum of the horse containing the antibody is extracted and introduced into the human body. The human body makes use of antibodies against the disease thus producing passive immunity. Passive immunity is produced almost instantly when the serum has been injected, but the effect lasts only for a short period.

          Vaccines are now produced to provide immunity against diseases like whooping cough, diphtheria, measles, tetanus, typhoid, polio, rabies tuberculosis, mumps, scarlet fever, German measles, and chickenpox. All infants should be provided immunity by vaccination for different diseases.

          In our country Haffkine Institute at Bombay and the Virus Institute at Poona produce several kinds of vaccines.

 

        If you look through binoculars, you will find distant objects appear nearer and larger. Why does this happen?

        Binoculars are a pair of small telescopes built into a frame or casting. The two telescopes in binoculars are exactly similar in structure and meant for each eye. Each telescope is built into a funnel-shaped tube or cylinder. It consists of one objective lens and one eyepiece. The objective lens is kept towards the object and the eyepiece near the eye. The lenses are anti-reflection coated. Two prisms are also mounted between the objective lens and the eye piece to make the image of the object erect.

        The light from the object falls on the objective lens and an inverted image is produced by it. This image is further inverted by the two prisms, thus the image becomes erect. The eyepiece further magnifies this image. This is how we see the erect and magnified image of the object.

      

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In the early nineteenth century people believed that light travelled through imaginary stationary medium called ether. It was believed that ether filled all space, and all movements could be measured absolutely with respect to it. It was also thought that the speed of light relative to a moving observer could be calculated in the same way as the relative speeds of any two moving objects. For example, just imagine two cars in the same direction: one going at a speed of 110 km/hr and the other at 80 km/hr. Passengers in the slower car would observe that the faster car is travelling at 30 km/hr.

Two American scientists, Michaelson and Morley, experimentally tried to measure the speed of earth through ether in 1887. But their result did not confirm the existence of the hypothetical medium ether. Later the explanation of negative results was offered by Albert Einstein. According to him, nothing like ether exists in the universe and the concept of absolute motion is meaningless. He also said that the speed of light is constant, no matter how fast the observer is moving. No material body can travel faster than light.

On the basis of his conclusions, Einstein formulated the Special Theory of Relativity in 1905. He showed that physical quantities like mass, length and time are also not absolute. They change as the bodies move. If a body moves with a large velocity, its mass increases and it becomes shorter. 

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