4. Hearing Disorders
Deafness is the loss of hearing.
Conductive hearing loss occurs when something blocks sound waves from reaching the inner ear,
Sensorineural hearing loss is caused by damage to the inner ear or to the nerves that send sound to the brain,
sensorineural hearing loss is more likely to be permanent and to cause deafness,
Deafness is caused by noise (noise is the cause of about half of all cases of hearing loss), age, if the sensitive
hair cells inside the cochlea are damaged, and damage to the auditory nerve (the nerve that transmits sound to
7. Sight Disorders
Blindness is caused by cataracts.
Cataracts are formed in the lens of the eye which is behind the pupil.
As people get older, the lens of the eye gets cloudy.
When people have cataracts it is as if they are looking through a fog.
As the cataracts get worse, the fog gets thicker.
Although older people more often get cataracts, sometimes kids can have them as well.
Cataracts can be removed by taking out the lens of the eye with surgery and having an artificial lens put
13. Taste Disorders
Phantom taste perception; that is, a lingering, often unpleasant taste even though
you have nothing in your mouth.
We also can experience a reduced ability to taste sweet, sour, bitter, salty, and
umami, a condition called hypogeusia.
Some people cannot detect any tastes, which is called ageusia. True taste loss,
however, is rare. Most often, people are experiencing a loss of smell instead of a
loss of taste.
Within the skin, there are different types of "receptors" that are activated by different stimuli. When a receptor is activated,
it triggers a series of nerve impulses. For a person to "feel" the stimulus, the nerve impulses must make their way up to brain.
17. Touch Disorders
Touch Disorders: Touch disorders include the loss of pressure sensitivity, elevated twopoint discrimination, and loss of vibratory sense or deficits in proprioception. The causes are
Synesthesia is a condition in which one sense (for example, hearing) is simultaneously
perceived as if by one or more additional senses (such as sight).
Another form of synesthesia joins objects such as letters, shapes, numbers or people's names
with a sensory perception such as smell, color or flavor.
The word synesthesia comes from two Greek words, syn (together) and aisthesis (perception).
synesthesia literally means "joined perception."
A person might see a number as this:
1, 2, 3, 4, 5, 6, 7, 8, 9, 0.
Some people might think like this:
pain, cold, heat, pressure, light touch.