Why do we yawn?
Yawning occurs without any effort. It is a reflex action that forces oxygen into our lungs. The body’s oxygen supply is depleted after a long period of shallow breathing, which commonly occurs when we are tired, under stress, or have been sitting still for a long time. Yawning is believed to be induced by a high level of carbon dioxide in the blood. The wide opening of the mouth followed by a slow deep breath increases the oxygen level in the blood which helps relieve the tiredness.
Why is edible salt iodized?
Iodine is an essential nutrient which is required in minute amounts for normal growth of animals and humans. Iodine deficiency results in impairment of the functioning of the thyroid gland which produces ‘thyroxine’ hormone. Since thyroxine controls the rate of body metabolism and growth, iodine deficiency leads to a variety of disorders like goiter in children or adults and impaired mental functioning, poor intellectual performance and muscular disorders in children. Women with iodine deficiency give birth to still-born babies.
Iodization of salt offers the most convenient way of combating iodine deficiency. Firstly, because salt is an essential ingredient of our diet and secondly one can never take too much of it. So by iodization of common salt a minimum intake of iodine can be ensured for the entire population thereby minimizing the incidence of iodine deficiency.
Why do we perspire?
Perspiration is a mechanism for keeping the body cool in a hot environment. This is important, because if body temperature rises above the average temperature of by more than a few degrees, it could be life threatening. When the body temperature rises above the normal in hot surroundings, the sweat glands produce sweat which evaporates on the skin. This transfers the heat from blood vessels in the skin to the surrounding air. Sweating may also be triggered by pain, by intense emotions, fear or after eating very spicy food.
Why does water cause our skin to wrinkle?
The skin forms an elastic protective cover on our body. It consists of three layers; the upper layer of dead cells, the middle one of living cells and the lower most layers connected to muscles and fat. Normally the upper layer of dead cells acts as an effective water-proof barrier. But on prolonged immersion in water, the dry cells in the layer absorb water and swell. This causes the skin to form wrinkles which disappear when the skin dries out again.
Why does skin come in different colours?
Skin colour is due to the dark pigment melanin which is produced by pigment cells in the lowest layer of the skin. There is the same number of pigment producing cells in the skin of all races but the amount of melanin produced varies. In dark-skinned people of tropical regions, there is more melanin because intensity of the ultraviolet radiation from the sun is stronger in the tropics. The extra melanin protects the skin from the harmful effects of ultraviolet radiation. In people living in the higher latitudes, the skin colour is lighter as they have less pigment. The lighter skin also helps in the production of vitamin D in the body under the low intensity of sunlight available. Other factors contributing to skin colour are the blood in the blood vessels of the skin and the natural yellowish tinge of the skin tissue.
Why does sun bathing tan?
The outermost layer of the skin contains cells called melanocytes that produce the pigment melanin. When the skin is exposed to the sun, the melanocytes get stimulated by the ultraviolet rays and produce more of melanin. This acts as a filter to block ultraviolet rays from penetrating the skin. The increased production of the brown-coloured melanin gives a darker colour to the skin, which appears as suntan.
Why do we have two eyes?
The two eyes working together enable us to perceive depth which is not possible to do with only one eye. Our two eyes view an object from approximately the same height but they see the object from slightly different horizontal angles. When processed by the brain these two slightly different images gives rise to perception of depth and make the object appear in three dimensions. This ability, called stereoscopic vision, also allows us to judge distances, to estimate how far an object is, which is essential to enable us to go about in our daily chores.
EYE CONTACT
Of all the ways we communicate with people, eye contact is the most powerful. Eye contact can be a loving gaze, a hostile stare, a nervous glance, or a refusal to look at a person Looking at a people and meeting their eyes are the first steps toward striking up friendships and making a good impression. But if you look at a person for too long, he or she may feel threatened.
Failing to look at others causes suspicion as they wonder whether you are hiding something. Refusing to make eye contact also sends messages of arrogance, for it may convey that you do not consider the other person important.
There are subtle, silent rules to eye contact and they vary from culture to culture. Most Asians prefer minimal eye contact whereas in America, the UK and most of Northern Europe moderate eye contact is preferred. The Hispanic cultures, along with cultures in the Middle East prefer very direct eye. So if you travel to another country, be sure to know what form of eye contact they are comfortable with, so that you don’t offend anyone!
Why do we get headache?
Why do we blink?
Blinking helps to keep the eye lubricated and also to sweep away foreign particles. Lubrication helps maintain the transparency of the cornea – the transparent outer layer in front of the eyeball. Along the edge of each eyelid are tiny glands that release a watery fluid each time the eyelid closes. Each time one blinks, the tear glands also release some fluids. The fluids flush out the eye and also keep it moist. A sudden movement in front of the eye also makes one blink. This has protective value. It has been estimated that an average person blinks about 250 million times in a lifetime.
Why do men become bald?
Why is body temperature measured under the tongue?
Why do bruises appear blue?
Why do veins appear blue?
The red pigment of blood – haemoglobin serves two purposes; it carries carbon dioxide from body tissues to the lungs where it gives out carbon dioxide and takes up oxygen. Secondly, it carries the oxygen to various body tissues. Veins carry deoxygenated blood which has given up the oxygen. Deoxygenated blood appears slightly blue-red or purplish in colour. Since veins are thin walled and are usually located near the surface, they are visible through the skin and the deoxygenated blood coursing through them gives them bluish colour.