The Ear And Hearing Loss

The Ear and Hearing Loss


        The ear is the organ of hearing and balance in vertebrates.  The ear

converts sound waves in the air, to nerve impulses which are sent to the brain,

where the brain interprets them as sounds instead of vibrations.  The innermost

part of the ear maintains equilibrium or balance.  The vestibular apparatus

contains semicircular canals which in turn balance you.  Any movement by the

head, and this apparatus sends a signal to the brain so that your reflex action

is to move your foot to balance you.

     The ear in humans consist three parts: The outer, the middle, and the

inner portions.  The outer ear, or pinna, is the structure that we call the ear.

It is the skin covered flap of elastic cartilage, that sticks out from the side

of the head.  It acts like a funnel catching sound and sending it to the middle

portion of the ear.  The middle portion contains the ear drum and the connection

between the pharynx and the drum, the Eustachian tube.  The inner ear contains

the sensory receptors for hearing which are enclosed in a fluid filled chamber

called the cochlea.  The outer and middle ears purposes are only to receive and

amplify sound.  Those parts ofd the ear are only present in amphibians and

mammals, but the inner ear is present in all vertebrates.

     The ear can hear in several different ways.  They are volume, pitch, and

tone.  Pitch is related to the frequency of the sound wave.  The volume depends

on the amplitude or intensity of the sound wave.  The greater the frequency, the

higher the pitch.  Humans can hear about 30 and 20,000 waves or cycles per

second.  High pitch sounds produce more of a trebly sound, while low pitch

sounds produce a rumbling bass sound.

     When a person loses these abilities to comprehend sound, it is referred

to as deafness.  It can be caused by disease, toxic drugs, trauma, or an

inherited disorder.  Those causes can be classified as conductive, sensorineural,

or both.

        A conductive hearing loss results from damage to those parts of the ear

which transmit sound vibrations in the air to the fluids of the inner ear.  This

type of damage is usually to the eardrum or small bones known as ossicles.

Ossicles conduct sound from the eardrum to the cochlea.  They cannot perform

such an action if the eardrum is perforated, if the middle ear cavity is filled

with fluid, or if the bones become separated, are destroyed by disease, or are

overgrown by a spongy bone ( a disorder called otosclerosis).  In conductive

hearing loss, sound intensity is reduced, but sound isn't distorted.

     Sensorineural hearing loss is more resistant to therapy because it

involves damage to the delicate sensory cells of the organ of Corti, which is

located in the cochlea.  Sensorineural hearing loss has to do with both

distortion of sound and loss of sound intensity.  The closer the damaged tissue

is to the auditory cortex, the more complex and subtle are the types of

distortions.  The hair cells of the organ of Corti cannot grow once they are

damaged.  Sensorineural hearing loss is rarely reversible.

        The hearing losses caused by salicylates such as asprin and the early

stages of Meniere's Disease are reversible, however.  The latter condition
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