We Feel Thirsty

Why do we feel thirsty?

            Why do you think we feel more thirsty when we exercise or when we are tense? Many people think that parching of mouth or throat is only caused by thirst. But, this is not true. Such parching can occur due to many other cases also. Tension or production of less saliva by the salivary glands as also produces thirst and so can nervousness. Have you ever wondered why we feel thirsty? Present in our blood. The body tissues also contain these two substances. Under the normal condition, the proportion of these two materials in blood remains constant. If due to some reason, the amount of water in blood gets reduced, the proportion of these two materials in blood remains constant. If due to some reason, the proportion of the two materials also changes. In such a situation, the thirst center located in the brain sends signals to the throat. As a result of this, the throat starts contracting. This contraction makes it dry ad we start feeling thirsty and want to drink water.
We feel thirsty when the amount of water in blood gets reduced
            However, sometimes, the salivary glands secrete enough saliva and our stomach and blood too have enough water and yet we feel thirsty. For example, when man drinks liquor he takes enough quantity of slated preparations along with the drink. Though the amount of water goes on increasing with the intake of liquor, consumption of salted foods also increases the quantity of salt in blood. As a result of this, the amount of salt in blood exceeds the normal level. This disturbs the normal proportion of salt and water in the blood. In such a situation, we feel thirsty. Excessive thirst may be a symptom of diabetes or kidneys ailments. In such cases, immediate medical check up should be undertaken.

One of our Feet Bigger than the Other

Why is one of our feet bigger than the other?

            You may not believe this but our feet differ in size from each other. Have you even measured or compared one of your feet with the other? What did you notice? If we carefully measure our feet we will observe that the right foot is slightly bigger than the left one. Do you know why it is so?

            The structure of our body is not completely symmetrical. There is a little symmetry between the left and right sides of the body. If we notice carefully, we find the right side of our face is slightly more developed than the left side. The length of the right leg is slightly more than that of the left one. The right hand is slightly bigger than the left one. Our heart is located on the left while the liver on the right. The inner constitution of the body is not in complete symmetry. That is why even the development of bones is slightly a symmetrical. Because of this a symmetrical development, our right foot is slightly bigger then the left foot.
Our right side is slightly more developed than the left side
            The asymmetrical structure of the body affects us in many ways. One of the effects of this is that we are not able to walk in a straight line if we are blind folded. We start moving in circles. This is true of animals also.

            Are you curious about why the right side is slightly more developed than the left one? Though nothing can be said with certainty about this, scientist hold the view that since most of the people use their right limbs more often for any work, their right side gets more developed than the left. 96% of the total population of the world uses right hands more than left ones. Only 4% are left handed. The brain controls the use of the right or the left hand. It is the left part of the brain, which regulates the functioning of the right limbs, and the right part of the brain controls the left limbs of the body. In the world, greater number of people has the left side of their brain more developed than the right one. Hence, the number of right hander’s is also large.

Human Skin has Different Colors

Why does the human skin have different colors?

            Have you noticed that people form different countries and race have different skin colors? For example, people in the northern Europe have white skin whereas those in the western Africa have black skin. People in the Southeast Asia have yellowish skin. Do you know the reason for the variation in this skin color?
Color of human skin depends on the pigments present in the body

            The color of the human skin depends mainly on three pigments or coloring materials found in the body. The first of these is called melanin which is a brown substance. If concentrated, it appears black. The second is called carotene which is a yellow substance. And the third is called hemoglobin which is the red pigment of the blood. In the absence of these pigments the color of the skin will be creamy white. The mixture of these three in different proportions produces the different colors of the skin. A man having more melanin will have dark complexion while the man having more of carotene will have yellowish skin. Melanin and carotene are found in the deep epidermis in all skin types.

            The tissues of the body produce more melanin when exposed to the ultraviolet rays in sunlight. That is why the color of the skin of the people who live in tropical regions is very dark. When we work in the sunlight continuously for days, our skin becomes dark. People living in the colder countries have white skin, because their skin contains smaller quantities of melanin. The deficiency of these pigments in the body produces white spots on the body. This disorder is called leucoderma.

            The color of the skin depends partly on the amount of blood circulating through the dermis and the texture of the dermis. Since the texture varies considerably in different people, the light that falls on the skin is not always reflected in the same way. This is why the color of a person’s skin varies from place to place.

Process of Respiration

How do we breathe?

            Breathing is essential for all living beings. It is an involuntary reaction that takes place continuously. Men, animals, birds, insects and plants- all need oxygen, which they get form the air through respiration. However, different creatures breathe in different ways. Some breathe through lungs, some others breathe through their skin. The earthworm is one animal that breathes through its skin. Do you known how man breathes and what happens in the body during the process of respiration?
When diaphragm pulls down, it gives lungs more space to suck sufficient air, when it relaxes, it forces some of the air out of lungs.
            We, human beings, inhale air through the nose or mouth. The nose and mouth are jointed in the back of the mouth in an area called pharynx. The air inhaled goes to the lungs through the windpipe. There are two lungs in our body- one on each side of our chest. They are made up of tissues shaped like soft bags. Each lung has millions of air sacs, which get filled and enlarged when air is inhaled. When it is exhaled, they contract.

            The energy releasing process, which utilize the oxygen and produces carbon dioxide, is termed as tissue respiration or external respiration. In man, external respiration is the process where by air is breathed from the environment into the lungs to provide internal respiration.

            The oxygen, which is inhaled, is circulated throughout the body by the blood. It oxidizes the food materials. During the process of oxidation, carbon dioxide, water and other substances are produced. The same carbon dioxide is expelled when we breathe out. When we do some physical work or exercise, we need more energy. For the production of more energy, we need more oxygen. That is hwy the rate of breathing becomes fast when we do any hard work or physical exercise.

            Normally, a newly born child breathes 60 items per minute. A 15 years old child breathes 20 times a minute and an adult 16 to 18 times. The rate of breathing is faster in adults than in old people. The respiratory center in the brain controls the process of breathing. This center is sensitive to the amount of carbon dioxide in the blood. If there is an increase in carbon dioxide such as during exercise, this center sends signals to control breathing. As a result, the person breathes faster.

Urine Formed in our Body

How is urine formed in our body?

            Our urinary system consists mainly of two bean shaped glandular organs in the lumbar region of the abdominal cavity, which are called kidneys. They are reddish brown in color. Each kidney is approximately 11 centimeters long, 5 centimeters wide and 2.5 centimeters thick. Each of them weighs about 150 grams. Do you know what the function of the kidney is?
Human Kidney
            The main function of the kidney is to purify our blood by removing the impurities from it. They work as filters. The kidneys also maintain proper proportion of every constituent in the blood. If sometimes the level of sugar salt or water in blood excesses the normal level, the kidneys excrete the excess amount from it. They also regulate the formation of urine according to the exigencies of the situation and thus do not allow the blood to become extra thick or thin. The undesirable acids and bases of the blood come out of the body as urine.

            Each kidney has millions of coiled capillaries. Blood enters the kidneys through the renal artery and passes through these capillaries and the dissolved impurities are filtered our. The purified blood returns to the lungs. About 200 liters of blood pass through the kidneys every day. The impurities removed from the blood pass form the kidneys to a bag where they are stored for some time. This bag is known as the bladder. When the bladder is sufficiently filled, one feels the urge to empty it. We pass urine primarily to empty this bladder. Normally, an ordinary person passes 1.5 liters of urine in one day.

            Any disorder or damage to the kidneys is very dangerous for the body. If the kidneys become defective, impurities in blood go on increasing and have poisonous effect on the body. If somebody’s kidneys stop faction, the person dies within a few days. It is, therefore, absolutely essential to have proper treatment of any defect or disease of the kidneys. It is necessary to take proper quantity of food in order to keep them healthy. Excessive eating compels the kidneys to work more to expel more excretory material and thus the chances of any damage to the kidneys increase. To keep the kidneys healthy, we should take eight to ten glasses of water every day.

Sign of Luck or Bad Omen

What makes people sneeze?

            There are many stories and superstitions connected with sneezing. Some people take sneezing as a sign of luck while some others regard it as a bad omen.

            In our country (India), sneezing in front of a person when he is living his house is considered inauspicious but sneezing behind his back is considered a good sign. The Romans thought that a person expelled evil spirits when he sneezed. Primitive people believed that sneezing was a sign of approaching death. When anyone sneezed, people said, God bless you, because it was considered a sign of danger. These are all superstitions, which do not have any truth in them.
Sneezing occurs the nerve ending of the mucous membranes are irritated

            According to physiology, sneezing is just an involuntary reflex action. It is an explosive expiration through the nose and mouth stimulated by irritation in the nasal epithelium. It occurs when the nerve endings of the mucous membrane of the nose get irritated. It happens when we catch a cold. The foreign bodies that somehow manage to get into the nose can also cause sneezing. Allergies can also produce irritation.

            The act of sneezing is an attempt by the body to expel air to get rid of the irritating substances. Sometimes sneezing also occurs when a bright light stimulates our optic nerve.

            During the act of sneezing, our whole body gets a jerk because the air comes out with a great speed- around 160 kilometers per hour. The whole body vibrates and the eyes are automatically closed. After the sneeze, the body becomes fresh and light. Some people put snuff powder of tobacco leaves in their nose and create artificial sneezing. This is a harmful practice.

Tears come out while weeping

Why do tears come out while weeping?

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

            Some times tears come out even when we laugh a great deal. That is because, when we laugh, the muscles squeeze the tear glands, due to which tears begin to flow out.

            Tears also come to our eyes when we cut onions because the onion gives off and 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 we do not have words to express our feelings.

Environment and Ecology

            Human civilization has developed very slowly. In the ancient times man was totally dependent on nature for his needs but as he learnt abut agriculture he started interfering with the laws of nature. He shaved off the forests for agriculture and tamed many wild animals for his food and clothing. He left the caves and started living in houses. With the development in man’s lifestyle, several civilizations of Summaries, Egypt and Indus valley spread over the vast areas of the world. It is a general belief that man has conquered the nature but still he cannot control natural disasters.
Eating relations in a community
            All the living beings on the earth utilize solar energy and get essential elements from atmosphere, lithosphere and hydrosphere. Animals and plants either depend on plants or on other animals for their food. A balance exists between living and non living things in the nature. Whenever any element of nature increases or decreases in large proportions, ecological balance gets disturbed. The study which deals with the relationships of life forms with each other and with their surroundings is called ecology. A group of animals living in a particular physical environment is called ecosystem.

            Today rapid industrialization and ever increasing human requirements have disturbed these natural elements and created an ecological imbalance. Increasing population, emission of carbon dioxide and other toxic gases by factories and vehicles, occurrence of acid rain, nuclear tests and poisonous chemicals have posed a serious threat to the ecological balance. The entire earth and its inhabitants are affected by pollution. Life on earth is endangered. Now, the man ahs realized the need of ecological conservation and safety of environment. Public awareness is being created for the protection of life on the earth. Many programmes for a better environment and conservation of natural resources are being carried out all over the world. The scientific conservation programmes are mainly based on the principles of ecology. We can get a better environment only when every body, specially the children, becomes aware about it.

            To study the ecosystem, it is necessary for us to acquire deep knowledge of the trees, plants, ponds, rivers, lakes; air, water and land; crops and creatures; marine animals, etc. this way we will be able to make our ecosystem even better. It is our duty as well as responsibility to ensure the safety of our food chains.

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