The Five Senses

THE FIVE SENSES Senses are the physiological methods of perception. The senses and their operation, classification, and theory are overlapping topics studied by a variety of fields, most notably neuroscience, cognitive psychology (or cognitive science), and philosophy of perception. The nervous system has a specific sensory system, or organ, dedicated to each sense.

Sight.

The eye is the organ of vision. It has a complex structure consisting of a transparent lens that focuses light on the retina. The retina is covered with two basic types of lightsensitive cells-rods and cones. The cone cells are sensitive to color and are located in the part of the retina called the fovea, where the light is focused by the lens. The rod cells are not sensitive to color, but have greater sensitivity to light than the cone cells. These cells are located around the fovea and are responsible for peripheral vision and night vision. The eye is connected to the brain through the optic nerve. The point of this connection is called the "blind spot" because it is insensitive to light. Experiments have shown that the back of the brain maps the visual input from the eyes. The brain combines the input of our two eyes into a single three-dimensional image. In addition, even though the image on the retina is upside-down because of the focusing action of the lens, the brain compensates and provides the right-side-up perception. Experiments have been done with subjects fitted with prisms that invert the images. The subjects go through an initial period of great confusion, but subsequently they perceive the images as right side up. The range of perception of the eye is phenomenal. In the dark, a substance produced by the rod cells increases the sensitivity of the eye so that it is possible to detect very dim light. In strong light, the iris contracts reducing the size of the aperture that admits light into the eye and a protective obscure substance reduces the exposure of the light-

sensitive cells. The spectrum of light to which the eye is sensitive varies from the red to the violet. Lower electromagnetic frequencies in the infrared are sensed as heat, but cannot be seen. Higher frequencies in the ultraviolet and beyond cannot be seen either, but can be sensed as tingling of the skin or eyes depending on the frequency. The human eye is not sensitive to the polarization of light, i.e., light that oscillates on a specific plane. Bees, on the other hand, are sensitive to polarized light, and have a visual range that extends into the ultraviolet. Some kinds of snakes have special infrared sensors that enable them to hunt in absolute darkness using only the heat emitted by their prey. Birds have a higher density of light-sensing cells than humans do in their retinas, and therefore, higher visual acuity. Color blindness or "Daltonism" is a common abnormality in human vision that makes it impossible to differentiate colors accurately. One type of color blindness results in the inability to distinguish red from green. This can be a real handicap for certain types of occupations. To a colorblind person, a person with normal color vision would appear to have extrasensory perception. However, we want to reserve the term "extrasensory perception" for perception that is beyond the range of the normal. What is nearsightedness and farsightedness? How is it corrected? ➢ When people grow older, their lens loses its elasticity. The flattened shape and the viewing of the near objects get difficult when distance objects are still clear. This condition is called presbyopia (or farsightedness). You can use corrective glasses. They bring near objects to focus. There is another type of farsightedness called hypermetropia. Hypermetropia can be caused by having an eye ball that is shorter than normal. People with myopia (or nearsightedness) have eye balls that are longer than normal. A nearsighted person has difficulty seeing distant objects but can read books easily. Nearsightedness is caused by the stress of working for a long period of close work. Nearsightedness usually begins when you are a kid. When you have nearsightedness or farsightedness, there is a way to cure you. Most older people wear contact lens to make them see better. You can use glasses when you are younger. For contact lens or glasses, there are certain types. For correcting nearsightedness, you use concave lens and for farsighted people, they use convex lens. What is color blindness? ➢ Color blindness is one of the diseases some humans have. Color blindness is when they can't really notice the colors red, green, blue-violet, and other combinations. Color blindness is always an inherited disorder caused by genetic defect on X Chromosome. Color blindness mostly occurs primarily in males. Most males have color blindness because they have one X Chromosome and females have two X Chromosome. What are other disorders/diseases associated with sight? ➢ Other disorders/diseases we have with sight are cataracts, astigmatism, and blindness. Cataracts are a disorder that gradually develops in your lens of your eye. It gets cloudy or darkened. Cataracts develop by change in the chemical composition of the lens. Cataracts are most often found around people over the age of 55. Astigmatism is a vision that occurs at the front surface of your eye (the cornea). It is not irregular shape when your eye is focusing properly on the back of your eye. Astigmatism could occur at all ages. Blindness is a disorder that people of all ages suffer from. Usually, it is caused by either improper birth or an injury. When you are blind, it may be caused by a blockage of light or by a disease of the optic nerve.

CARE AND PREVENTION: ➢ Prevention continues to remain the primary measure. ➢ Wear protective safety glasses, especially for sports such as tennis, baseball and basketball. ➢ Wear 100% ultraviolet light- absorbing sunglasses, preferably with wraparound sides and a wide- brimmed hat. ➢ During eclipse of the sun, avoid looking directly at the sun.

Hearing.

The ear is the organ of hearing. The outer ear protrudes away from the head and is shaped like a cup to direct sounds toward the tympanic membrane, which transmits vibrations to the inner ear through a series of small bones. The inner ear, or cochlea, is a spiral-shaped chamber covered internally by nerve fibers that react to the vibrations and transmit impulses to the brain via the auditory nerve. The brain combines the input of our two ears to determine the direction and distance of sounds. The human ear can perceive frequencies from 16 cycles per second, which is a very deep bass, to 28,000 cycles per second, which is a very high pitch. In addition, the human ear can detect pitch changes as small as 3 hundredths of one percent of the original frequency in some frequency ranges. Some people have "perfect pitch", which is the ability to map a tone precisely on the musical scale. Bats and dolphins can detect frequencies higher than 100,000 cycles per second. What can cause deafness? ➢ Deafness can be caused before a baby is born. A child can inherit deafness. A mother who has rubella or some over viral infection while she is pregnant can have deaf or otherwise a handicapped child. A premature baby, before the full nine months, or a full-term baby experiencing a difficult birth accompanied with a lack of oxygen has a possibility of being deaf. One other thing is after birth. A person can have an illness that can result in hearing loss. What other disorders/diseases are associated with hearing?

➢ Other than deafness, there are many diseases associated with hearing. Some of these are otitis media (infection of the middle ear), otosclerosis (infection of the auditory ossicles), and meniere's disease (disorder of the inner earmarked by periodic attacks of hearing loss). All of these diseases are caused by birth defects or injuries.

Taste.

The receptors for taste, called taste buds, are situated chiefly in the tongue, but they are also located in the roof of the mouth and near the pharynx. They are able to detect four basic tastes: salty, sweet, bitter, and sour. The tongue also can detect a sensation called "umami" from taste receptors sensitive to amino acids. Generally, the taste buds close to the tip of the tongue are sensitive to sweet tastes, whereas those in the back of the tongue are sensitive to bitter tastes. The taste buds on top and on the side of the tongue are sensitive to salty and sour tastes. At the base of each taste bud there is a nerve that sends the sensations to the brain. The sense of taste functions in coordination with the sense of smell. The number of taste buds varies substantially from individual to individual, but greater numbers increase sensitivity. Women, in general, have a greater number of taste buds than men. As in the case of color blindness, some people are insensitive to some tastes. What disorders/diseases are associated with taste? ➢ There are many tongue disorders. Lumps or ulcers on your tongue can be a problem for people of all ages. It is caused by a papillae disorder. When you have lumps or ulcers on your tongue, you can get tumors if they aren't treated quickly. Glossitis and a geographical tongue are also cause by papillae disorder. It affects all people and results in inflammation of the tongue. It is caused by bacteria build-up and leads to fungal infection and a dark-colored tongue. CARE AND PREVENTION: ➢ Proper oral hygiene. ➢ Avoid any spicy foods when experiencing glossitis.

Smell.

The nose is the organ responsible for the sense of smell. The cavity of the nose is lined with mucous membranes that have smell receptors connected to the olfactory nerve. The smells themselves consist of vapors of various substances. The smell receptors interact with the molecules of these vapors and transmit the sensations to the brain. The nose also has a structure called the vomeronasal organ whose function has not been determined, but which is suspected of being sensitive to pheromones that influence the reproductive cycle. The smell receptors are sensitive to seven types of sensations that can be characterized as camphor, musk, flower, mint, ether, acrid, or putrid. The sense of smell is sometimes temporarily lost when a person has a cold. Dogs have a sense of smell that is many times more sensitive than man's. What disorders/diseases are associated with smell? ➢ There are many smell diseases/disorders. One of them is Sinusitis. People of all ages can have Sinusitis. It is when there is an inflammation or infection of the air pockets on either side of and behind the nose. It is caused by viruses, fungi (molds), and maybe allergies. Another disease/disorder is phantom sensations. People of all ages also can have this. Phantom sensations are when there is presence of unpleasant or disordered tastes and smells. They can also be the presence of tastes or smells that other do not perceive. Lastly, halitosis (also all ages) is when there are burning sensations in your mouth or nose. It can be perception of bad breath.

Touch.

The sense of touch is distributed throughout the body. Nerve endings in the skin and other parts of the body transmit sensations to the brain. Some parts of the body have a larger number of nerve endings and, therefore, are more sensitive. Four kinds of touch sensations can be identified: cold, heat, contact, and pain. Hairs on the skin magnify the sensitivity and act as an early warning system for the body. The fingertips and the sexual organs have the greatest concentration of nerve endings. The sexual organs have "erogenous zones" that when stimulated start a series of endocrine reactions and motor responses resulting in orgasm. What disorders occur in your skin? ➢ Three basic disorders occur in your skin (there are too many to mention all). They are acne, skin cancer, and dermatitis. ➢ Acne usually occurs in teenagers. It is when extra keratin is made, leading to blackheads then acne. ➢ Skin cancer can come to people of all ages. It is when your skin is exposed to too many ultraviolet rays. ➢ Dermatitis (including eczema) occurs in children aged 5 and up. A rash forms, usually on the chest, elbow, and/or knees. Skin looses water and becomes dry which causes itchyness. This skin disorder is very hard to cure and is may be caused by the body's immune response attacking itself. What disorders/diseases are associated with touch? ➢ There are three main disorders/diseases that are most common. Here is a quick review telling about all of them: ➢ Attention Defict Disorder, otherwise known as ADD occurs in people of all ages. It can be associated with making your sense of touch much more sensitive than other people. It is caused when things aren't being filtered through your brain properly. ➢ Another disorder is Tactile defensiveness, which also can be a problem for people of all ages. People with this disorder have a tendency to react negatively to the sensation of touch and possibly trigger anxiety or panic. ➢ Sensory Intergrative Dysfunction is another disorder. It usually occurs in kids. It makes people uneasy, have poor balance, and have under or over sensitivity to touch. The main cause is that there is a dysfunction in the central nervous system.

CARE AND PREVENTION: ➢ Principles of good nutrition, exercise, rest, and sleep are emphasized in any teaching program focused on skin care. ➢ Avoid too much exposure in the sun, to avoid skin cancer. ➢ Use sun block. ➢ Proper hygiene is encouraged. ➢ Adequate fluid intake (8-12 glasses a day). ➢ Any unusual ties noted, consult the physician.

RESEARCH

IN PSYCHOLOGY “THE FIVE SENSES”