WHAT ARE HARMONES?

HORMONES -

Hormones have been called the 'chemical messengers' of the body. They are substances that regulate certain bodily functions such as, growth, development, reproduction, and metabolism. There are eight well-defined endocrine (or ductless) glands in the body. The main endocrine glands are the pituitary, thyroid, parathyroids, pancreas, adrenals, testes and ovaries. In all, they secrete at least 25 hormones into the bloodstream. The absence or excess of hormones causes certain bodily malfunctions such as diabetes, goiter, dwarfism, and gigantism. What are these different endocrine glands and what are the hormones they produce?

An endocrine gland is groups of cells., which take away certain raw materials from the blood and convert them into hormones. The hormones are then released directly into the bloodstream. The pituitary gland is situated near the base of the brain. This gland produces a number of hormones, which control most of the functioning of other glands. One of these hormones controls the growth of the body. If it is overactive, it causes an abnormal growth or gigantism. Similarly, if it is underactive it leads to dwarfism.

The thyroid gland secretes a hormone called 'thyroxin', which is rich in iodine. An abnormality in its secretion can cause serious disorders in the body. If the secretion is insufficient in children then they do not grow in a normal way, either physically or mentally. It controls the oxidation of food in the body. If too little thyroxin is produced, people become very fat. This is because their food is changed into fat instead of being oxidized to produce energy. If the diet lacks iodine, the thyroid gland can get enlarged. This is called 'goitre'. Consuming iodized salt may help to prevent goitre. Our body has four parathyroid glands. Each is about the size of a rice grain. Their hormones enable the teeth and bones to make use of calcium. It is also necessary for proper functioning of the nervous system.

The thymus gland is located in the chest region. To begin with, it is large but becomes progressively smaller as the child grows up. The thymus produces thymosin. Although its function is not clearly understood the hormone apparently protects babies from disease. The adrenal glands are located just above the kidneys. These glands produce a hormone called 'adrenaline' in times of a anger, fear or tension. This increases heartbeat and the amount of energy available to the muscles. The pancreas produces two hormones - pancreatic juice and insulin. Pancreatic juice is used in the digestion of food while insulin controls the amount of sugar in the blood. Insufficiency of insulin results in a disease called 'Diabetes Mellitus'. Its excess, however, can cause hypoglycemia, which is characterized by low blood sugar.

Testes and ovaries are male and female sex glands, respectively. Testes produce testosterone, a male sex hormone. The ovaries produce three hormones-estrogen, progesterone (which controls menstrual cycle) and relaxing. Progesterone plays an important role during pregnancy. Relaxin helps widen the birth canal (vagina) just before the birth of a baby. Hormones control the amounts of various chemical constituents in the body; they regulate the rate of chemical reaction inside the body cells during normal and stressful activities and they control the chemical process involved in growth. One of their most important functions is to maintain functions is to maintain the body's internal environment in a steady state. Specific hormones control the balance of water, important minerals such as, sodium, potassium, calcium, and glucose, which is the main source of energy.

Scientists have now developed synthetic methods for producing hormones. These are used to treat hormonal deficiencies. Synthetic sex hormones are used in birth control pills. Cortisone hormone is often used to treat arthritis and allergies.

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WHY DO TEARS COME OUT WHILE WEEPING?

TEARS -

You must have noticed that whenever somebody weeps, tears begin to fall from his eyes. When someone is very happy even then come to his eyes. Do you know why it happens?

When we blink our eyes, many muscles come into play and the eyelids close and open just like stage curtains. The movement of the eyelids is so fast that it does not disturb our vision. The blinking of the eyes is an involuntary action that takes place every six seconds throughout our life. In each eye, there is a 'tear gland' located at the outer corner. There are small tubes or ducts, which carry the tears to the upper eyelids, and from there they fall out of the eyes through other ducts.

Every time we blink our eyes, some fluid comes out through the openings of the tear ducts. This keeps the eyes lubricated and prevents them from drying. When we weep, more fluid comes out through openings of the ducts in the form of tears. It is a reflex action that occurs without our control.
Sometimes tears come out even when we laugh a gra=eat deal. That is because, when we laugh, the muscles squeeze the tear glands, due to which tear begin to flow out.

Tears also come to our eyes when we cut onions because the onion gives off an irritating volatile substance. When it reaches our eyes, tears are produced to protect the eye from irritation. The tears 'wash' the irritating substance away. The same thing happens in the case of smoke. Some sad news also produces tears by reflex action. This happens only when do not have words to express our feelings.

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WHICH IS THE MOST DANGEROUS BIRD IN THE WORLD?

DANGEROUS BIRD -

The cassowary is the most dangerous bird in the world. Its inner toe has a long dagger-like claw that acts as a weapon and can slash open a man's stomach! the cassowary is found in New Guinea and Northern Australia. it is a secretive forest dweller and is seldom seen, but often heard croaking and bellowing. It can't fly but runs at a great speed on its powerful legs. On each foot, it has three toes, the inner one having a long straight claw. It can often be seen giving furious kicks at the trunk of trees without any apparent reason. because of this strange habit, the cassowary is regarded as having a very bad temper. In dense forests, it can grow up to a height of 6 feet and weigh as much as 180 pounds. When it gets annoyed, it jumps in the air and delivers a vicious kick.

It is a bony-headed bird. Its naked blue head is protected by a bony helmet. Its body is covered with coarse hair-like feathers. It is the only member of the family casuariidage. Unlike other birds, the male incubates eggs. At a time 3-6 legs are laid. The eggs are green in color and 13 centimeters long. They are incubated for 50 days in a leafy nest and on the ground. the adult provides parental care to live young ones.

Cassowaries live in family groups or in pairs. they like to be near water, for they swim readily. They are also good fishers. According to zoologists. the cassowary's ancestors were able to fly. But in the process of evolution, it became flightless. It has adapted itself to make the most sufficient use of its environment. Emu, kiwi, weka, and takahe are also flightless birds. Most of the flightless birds are found in Australia and New Zealand.

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WHAT THE DIFFERENT TYPES OF RHINOCEROS?

RHINOCEROS -

The name rhinoceros' has Greek origin. In Greek, rhino means 'nose' and keros mean 'horned'. The animal has one or more curved horns on its long nose. The horns grow throughout its lift. Rhinoceros belongs to the 'odd-toed' group of ungulates. Rhinoceroses are found in Africa and South-East Asia.

The animal carries its large body on the four stouts, short legs. It has three toes on each foot, each toe ending in the separate hoof. Each front foot actually has the fourth toe, too. that is no longer used. The skin of the rhinoceros is very thick and has little hair. They look as if they are wearing heavy armor plating held together with rivets. The horns are composed entirely of hair-like structures at above thickenings of the nasal bones and frontal bones. They are not attached to the skull and may even be torn off infighting. When this happens, they quickly grow again. The horn may be up to 107 centimeters in length.

There are five different kinds of rhinoceroses existing today - two from Africa and there from Asia. The Sumatran rhinoceroses have two horns whereas the other two Asian species - Indian and Javan - have only one. They are all on the verge of extinction but the most endangered is the Javan rhinoceros, which survives only in one small reserve.

The largest of all these is the white rhinoceros from Africa. It stands 1.8 meters (6 feet) high at the shoulder and can weigh over 3 tonnes. An interesting difference between the white and black rhinoceros lies in the shape of their lips. The white rhinoceros has a wider, square-mouth which is very suitable for dropping grass. The black rhinoceros is more of browser and has a pointed upper lip for grazing and plucking leaves and shoots from shrubs and bushes. The other two-horned species, the Sumatran rhinoceros, is the smallest of all, standing only about 4.5 feet at the shoulder and weighing less than a tonne.

Rhinoceros feeds on grass, twigs, and shrubs. It does not hunt other animals for food. During the afternoon heat, it usually buries itself in muddy water. And from here, it emerges with a layer of mud on its skin. This dries and forms a protective coating against insect bites. The huge animal is usually quiet and retiring. But if it is cornered, it can become very fierce and dangerous. A rhinoceros can run at a speed of 30 miles an hour, and use its strong, pointed horns to attack its enemy. In captivity, the rhinoceros may live up to 50 years. A female bears only one young at a time. The calf is born about 18 months after the mating season and remains with the mother for several years.

Now, unfortunately, the rhinoceros is a rare species. Over the centuries, it has been hunted by man for its horns. This is because according to an ancient belief, its horn imparted magical properties to its owner. However, now this second largest land mammal is being protected by law to prevent it from becoming extinct.

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WHY DOES DOG GO MAD?

DOG GO MAD - 

Dogs are regarded as faithful animals and were probably among the first animals to be domesticated by man. But if it goes mad, it becomes very dangerous. A person who is bitten by a mad dog may die if not treated promptly and properly.

A dog goes mad when it suffers from a disease called 'rabies'. This disease is caused by a virus, which is carried in air or by some wild animals and enter's the dog body through a wound or a cut on its skin. The virus is bullet-shaped, having a diameter of about 70 millimicrons and a length of about 210 millimicrons.

When an infected animal bites a dog, the virus contained in the saliva enters the wounds and travels through sensory nerves system. It multiplies there and then begins to destroy the brain cells. The dog becomes lazy, suffers from fever and losses interest in food. In about 4 to 6 weeks, when these viruses affect's the dog brain, the dog growls, barks and saliva forths from its mouth. During this period, the dog can bite anybody. This is the stage when the dog is said to be mad. It is likely to die within 3 to 5 days after these symptoms appear. Some infected dogs do not go mad but show signs of paralysis, a disease called 'dumb rabies'.

When a mad dog bites a man, the virus present in saliva enters the man's body through the wound. Initially, the victim experiences mental weakness and uneasiness, which is followed by fever. He suffers from lack of sleep and feels frightened. The muscles in the throat get slackened and the faces difficulties in swallowing food or liquid. He is afraid of water, being infected by a disease called 'hydrophobia' which means 'fear of water'.

These signs appear in the victim within one to three months after the mad dog's bite. In all cases of dog-bite, the affected portions should be immediately cleaned and anti-rabies injections should be given to the victim within three days of the bite, the number of injections can vary from 3 to 14 depending on the location and number of bites.

The virus of rabies also attacks foxes, jackals, monkeys, bats, cats, and rats. Louis Pasteur introduced the treatment for rabies in 1888. Pasteur Institute of France is a famous center for rabies treatment.

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IS THERE ANY ANIMAL WHICH COMMITS SUICIDE?

SUICIDE -

Lemmings are small, stout, grey or brown animals with short tails and small eyes. These mouse-like rodents live in the colder regions of Northern Hemisphere, such as the mountains of Scandinavia and Lap land. They are between 12 to 16 centimeters ( 5 to 6 inches) in length, with feet covered with fur for protection against cold. They make their nests both above the ground with dry grass and in burrows. They feed on roots, stalks, and moss.

You may have heard stories about lemmings that hundreds of thousands of them march to the sea in a long packed line and jump into the sea. This is only one part of the whole story. The lemmings live high up on the mountainside. In years, when food is plentiful, lemmings breed very quickly to produce enormous population.  This is known as 'population explosion'. The available food is quickly eaten and then large numbers of lemmings migrate in all directions in search of food. As they migrate, many many fall prey to predators while many others fall into the rivers and the seas slipping from the edges of the cliff. They swim for about 15 to 20 minutes and are finally drowned.

No lemming ever returns to the place of its origin. The migration process is repeated every third or fourth year. Scientists have proved that lemmings move away from their houses in large groups because of overpopulation, but they do not drown themselves on purpose.

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WHY DO WE DREAM?

DREAM - 

We spend about one-third of our life in sleep. Sleep is essential for the good health of both mind and body. Sleep is a state of unconscious rest. Even the conscious part of the mind is totally at rest, the subconscious part of the mind continuous working and produces dreams.

About five times during the night, we change from periods of deep sleep to periods of light sleep. And as morning approaches, the periods of light sleep become longer. We dream during the periods of light sleep. In the dream, we make rapid eye movements and some body movements. If we wake up while we are dreaming, we can often remember the dream. No one really knows why we have dreams. But they appear to be an important part of sleep. Scientists have proved that almost everyone dreams three to five times during an 8-hour sleep. Those who claim that they do not dream, in fact, do not remember what they dreamt.

Most dreams are based on events that happened during the day. Others involve fearful sights you might have seen when you were young. In other dreams, wishes you have had for a long time are also fulfilled. Some psychologists contend that during this activity, the brain 'clears its registers' to prepare for the next day's conscious activities. During this period, the pattern of brain waves also changes. It is sometimes recorded for scientific observations. Its recording is called electroencephalogram.

According to some people, their problems have been solved during dreams. Kekule, a great chemist, gave the structure of benzene molecule after having a dream. He was very puzzled about the structure and one night in his dream, he saw a snake biting its tail while in whirling motion. That gave him the idea about the molecular structure of benzene. Some people believe that dreams can foretell the future. So far, scientists have not been able to fully explain this phenomenon.

Some dreams are pleasant, while others called 'nightmares' are related to our suppressed emotions, fears, desires, and needs.

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