The human body is comprised of five senses. These senses are necessary to the survival of mankind in all aspects of life. This is because the senses help man to adapt to the enviroment5. These five senses include; the sense of smell, taste, touch, hearing and sight. In this paper, the main focus will be on the sense of sight and the sense of hearing as well as the problems that affect their working.
Sense of sight
A Cataract is an eye condition that makes the eye lens become cloudy. The eye lens becomes cloudy like frost on a window pane hence the individual cannot see clearly. This is because; light rays passing through the cloudy lens are distorted before they get to the visual receptors located in the retina. Cataracts are most common in old people. This is because; the protein composition in the eyes changes with old age causing the lens to get cloudy. However, old age is not the only cause of cataracts, smoking, eye injury, poor diet, excessive exposure to sunlight and certain medical conditions are also known causes.
Cataracts are divided into three main types. These are nuclear cataracts, cortical cataracts and the subcapsular cataract. The most common type experienced is the nuclear cataract. Nuclear cataract is a condition that occurs when proteins in the center of the nucleus disintegrate and darken. This causes light rays to scatter hence vision becomes blurry. The second most experienced type of cataract is the cortical cataract. This type of cataract affects the periphery or cortex of the lens. Cortical cataract occurs when the arrangement of fibers in the cortex are altered or disturbed. The gaps between the fibers then fill with water and debris. This result in the path physiology being altered hence scattering light rays. This eventually leads to blurry vision. The least common type of cataracts is the subcapsular type. This type affects the back part of the eye lens. This alters the path light rays take causing blurry vision.
Cataracts progresses slowly and are therefore hard to detect early. Some of the earliest symptoms include; blurry vision, light sensitivity and poor night vision. The most obvious sign is that most people claim that they feel as if their eyes are covered with a film. The cloudy film over the eyes alters the manner in which light is focused in the eyes. This causes temporary improved vision for long sited people. People with difficulties seeing near objects are favored by this as they experience “second sight”. However, the condition worsens with time. People are advised to consume vitamins C and E in order to reduce the risk of cataracts. This is because; the vitamins reduce the risk of eye proteins getting damaged. In addition to this, avoiding the causative agents like UV rays and smoking can help (Kirschmann, 2006).
Sense of hearing
Hearing is usually underestimated until a problem occurs. Sound waves pass through the ear through three key parts. Any damage to either one of these structures results in hearing loss. Hearing begins in the outer part of the ear. When a sound or noise is made in the vicinity of the outer ear, the sound waves transmit down the external auditory canal. As a result, the sound waves strike the tympanic membrane on the eardrum. In response to this, the eardrum vibrates. These vibrations are further transmitted to the ossicles. The ossicles are made up of three tiny bones found in the middle ear. The ossicles in return amplify the sound. Finally, they transmit the sound waves to the inner ear and into the cochlea. The cochlea is a part of the ear that is filled with fluid. Once these vibrations or waves get to the inner ear, they are transformed into electrical impulses. It is in this form that the auditory nerve transmits information to the brain. The brain then deciphers these electrical impulses as sound (Moore, 2007).
There are four main types of hearing loss. These are; conductive, mixed, central and sensorineural hearing loss. Sensorineural hearing loss is a type of hearing loss that affects the inner ear or auditory nerve. Conductive hearing losses usually change all sound wave frequencies to the same degree. However, this type of hearing loss is not severe. Mixed hearing loss entails a combination between the conductive and the sensorineural types of hearing loss. Central type of hearing loss is caused from a defect in the canal between the inner ear and the auditory region of the brain. The problem can also be as a result of an infection in the brain itself. A sensorineural loss often interferes with an individual’s ability to listen to certain frequencies. This results in sound appearing distorted. Sensorineural losses can range from mild to profound. In this type of hearing loss, sound waves reach the inner ear proper hearing is not achieved. This could be as a result of a problem in the inner ear or the auditory nerves. This type of hearing loss accounts for 90% of the known cases of hearing loss in the world. However, hearing loss resulting from old age is the most common (Roland, 1996).
Hearing loss may either be unilateral or bilateral. This means that it may affect either one or both ears and may be and may vary from ear to ear. The four major causes of hearing loss are extremely loud sounds, infections, toxic drugs and old age. Development of a hearing loss can be gradual or sudden. This may be coupled with the aging process, noise exposure or to other medical issues.