Taste and smell are senses that are linked together. For example, when you taste food part of the enjoyment comes from your sense of smell. This is shown to be true when you get a bad cold. Then your nose becomes blocked up and meals are not as enjoyable, because without smell you cannot appreciate the full flavor of the food.
By means of the senses of taste and smell, we are able to detect chemical substances, such as those in food and drink, or those in the air we breathe. For this reason, taste and smell are known as chemical senses.
To many animals the sense of smell is much more important even than to ourselves. Wolves for example find their food largely by smell and their sense of smell is more acute than our owns.
Even so, we are able to detect the odors of very small amounts of some chemical substances. These include pleasant smelling substances such as perfume and unpleasant odors such as rotten eggs. We can smell such substances even when they are present only as one part in many million parts of air. In addition, we can detect very many different kinds of smells.
By comparison, our sense of taste is very crude. We can taste substances only when they are present in food and drink in large amounts, usually in more than one part in a thousand. In addition, we know of only four different kinds of taste: bitter, salt, sweet, and sour. The various flavors of food are actually combinations of these four tastes with many different odors.
We detect odors by the means of millions of tiny nerve endings. These can be found high up in the lining of the nose, and send messages to the brain about these smells. The part of the brain that receives these messages is the olfactory lobe, and the main nerve that carries them there is the olfactory nerve.
We detect tastes with small nerve ending call taste buds. We each have approximately ten thousand of these, and they are found all over the tongue and various parts of the mouth and throat.
The lining of the nose, mouth, and throat are always moist. This helps us to smell and taste, because the chemical substances dissolve in the moisture, so reaching the sensitive nerve ending.
Touch and Pain
When any part of the body touches something, you feel a sensation.This is called you sense of touch.
Some parts of the body are more sensitive to touch than others. For example, your fingertips are very sensitive. You can use your fingers for any delicate works. On the other end the buttocks, is not that sensitive. For this reason, if you need an injection the doctor will usually give it to you in the buttocks.
Parts of the skin, which are very sensitive to touch, contain many nerve endings, and parts which are less contain fewer nerve endings. These nerve endings are not at all alike, because the sense of touch is actually several senses. With the nerve endings in your skin, you can also feel pain, tickling, itching heat and cold.
Touch messages often bring us comfort, as when we lie snug and warm in a bed. The message â€œhotâ€ makes us draw away from a hot object quickly and automatically.
Someone who is blind will usually develop an extra keen sense of touch, this is vital for reading Braille, which consists of a series of tiny raised dots.