Table of Contents
How many ears do you have?
Illustrations not to be taken as scientific replications.
An ear by any other name will hear differently
The Pinna is the most visible parts of the Ear
The most critical part of the Outer Ear is the External Auditory Meatus.
A Conductive Hearing Loss can occur if the External Auditory Meatus is obstructed.
Wax impacted in the External Auditory Meatus can cause a Conductive Hearing loss
If children put objects in their ears, they can get a conductive hearing loss that can last a long time.
The Tympanic Membrane is the first important structure in the Middle Ear.
The three Ossicles are the second important structure in the Middle Ear.
Using principles of leverage the Middle ear amplifies the sound signal.
Diagram Figure A-16 from the text, page 395 of the Middle Ear (colors added).
The major contribution of the Middle Ear is the amplification of sound.
The Eustachian Tube equalizes the air pressure in the Middle Ear Cavity.
The Eustachian Tube is also a passage way for germs from the nose to the Middle Ear cavity.
A Middle Ear infection can cause a Conductive hearing called Otitis Media.
A Middle Ear infection can last for months and retard language development in very young children.
Otosclerosis is a conductive hearing loss caused by plague on the ossicles.
The Inner Ear (Cochlea) is where transduction takes place.
Diagram Figure A-17 from the text, page 396 of the Inner Ear or Cochlea (colors added).
The Cochlea is a double layered tube filled with fluid
The floor of the Cochlea has the Basilar Membrane on which are four rows of hair cells.
The celia on some hair-cells on the Basilar Membrane are bent by each sound wave that enters the fluid.
Diagram Figure A-18 from the text, page 397 showing a cross section of the Cochlea (colors added).
The hair-cells along the Basilar membrane respond selectively to specific frequencies.
A hair-cell and the nerve connected to it is called a Basic Sensory Unit.
A sensory neural loss usually begins in the higher frequencies and works it way down.
An Audiogram is a chart of hearing ability.
An audiogram showing a significant loss above 4000 Hz. Speech is still intelligible but many fricatives are not heard.
An audiogram showing a significant loss above 2000 Hz. Speech is almost unintelligible. Most consonants are not heard.
An audiogram showing a significant loss above 1000 Hz. Speech is not intelligible because no consonants can be differented.
An audiogram showing a significant loss above 500 Hz. Only some prosodic features of speech are discriminable like rhythm and stress.
Amplification will not always improve speech discrimination affected by a sensory neural loss.
It is important to identify a hearing loss as early as possible and to develop a program of auditory training.
A sensory neural loss is not reversible.
The Cochlear Implant is an artificial cochlea that has considerable promise for adults and children.
Nerves connecting with hair cells emerge from the Cochlea as the VIII (Acoustic) nerve.
Connecting nerves never touch but are separated by a gap called a Synapse.
The chemistry of the Synapse creates a vital switch which provides inhibition or control of neural pathways.
Neural function is more a chemical reaction than it is an electrical transmission.
The Acoustic Nerves enter the brain stem in the Medulla where most nerves cross to the opposite side.
The Lateral Lemniscus carries the input and the Reticular formation alerts the Cerebrum that it is coming.
|