Auditory System
Jackson, Kaitlynn
Miranda, Fermin
A. Outer Ear
•Pinna- the pinna refers to the visible part of the ear,
outside of the head. It is made of cartilage covered by
skin. The function of the pinna is to capture any sound
waves and lead it towards the inner ear. It also helps
determine where sound is coming from.
•Ear Canal- (external auditory meatus) the purpose of
the ear canal is to direct sound to the more sensitive
part of the outer ear; the tympanic membrane.
•Tympanic Membrane- is a cone-shaped membrane
between the external ear and the middle ear.
B. Middle Ear
1. The primary purpose of the middle ear is so that when
sound waves move through this area, it can be
transferred into fluid so it can move through the cochlea:
•
2.
Three bones known as the anvil (incus), hammer
(malleus), and stirrup (stapes) act as a lever system.
Once the tympanic membrane senses sound, it
vibrates letting the middle ear get into motion.
The hammer is connected to the tympanic membrane,
and collects larger sound which is also connected to the
anvil in a hinged shaped structure.
3. The stirrup is fused with the anvil and acts as one bone.
The stirrup transmits sound vibrations from the incus.
C. Inner Ear
•
Cochlea- the cochlea contains nerve
endings needed to convert sound
patterns into electrochemical pulses to
the brain.
•
The vestibular system gives animals a
sense of balance.
•
Semicircular canals-three fluid-filled loops
with tiny hairs covering each canal. When
head is tilted, the fluid moves which cause
the hairs to translate movement to the
nerves that send messages to the brain.
C. Inner Ear (Cochlea
Function)
•After sound passes through the middle ear, sound waves are
transferred into the oval window that connects to the cochlea.
As the fluid (the sound) moves through the cochlea, hair cells
are set in motion converting the fluid into electrical signals so
that nerve cells can be translated by the auditory cortex for
further processing.
D. Brain Processing
• Once sound has been released from the
cochlea, into the cochlear nerve to the
brain, brain neurons in the auditory cortex
translate sound
• From here, sound is sent to the brain,
nervous system, and spinal cord.
E. Deafness
1. Deafness- is the state of somewhat or completely lacking the ability to hear.
• Deafness can be caused by many different factors, including age, heredity, noise, and physical
trauma.
Age- Presbycusis, also known as age-related hearing loss is common and
begins in adulthood, but does not become a problem until much later on.
Heredity- Deafness can be inherited, and both dominant and recessive
genes exist where hearing impairment is found.
Noise- Noise is the cause for half of all the instances for deafness.
Although we experience sound everyday, we may be taking in a unsafe
amount of noise levels.
E. Deafness Cont.
Physical Trauma- Anyone who has suffered brain, or head damage may have
temporary or permanent hearing loss, depending how badly the auditory cortex was
injured. The auditory cortex is a vital piece in processing the sound so any damage to
the cortex is fatal.
• Several parts of the ear may be damaged when someone is deaf since most parts
share the role of sending sound to the brain.
• The parts of the ear that can be damaged and affect hearing are the following: the
auditory nerve, the cochlea, the eardrum, and the middle ear ossicles.
Bibliography
•
InteractiveBiology. “037 How Sound is Transferred to the Inner Ear.” Youtube. Web. 2o Feb. 2011.
•
How do the hammer, anvil and stirrup bones amplify sound into the inner ear?. Douglas E. Vetter. 31 Jan. 2008
<http://www.scientificamerican.com/article.cfm?id=experts-how-do-the-hammer-anvil-a#add-comment>
•
Johnson, George, and Peter Raven. Biology. Austin: Holt, Rinehart and Winston, 2007
•
Semicircular Canals. Kids Health. 1995-2013 <http://kidshealth.org/kid/word/s/word_semicircular_canals.html>
•
Hear. Kriten Hayes. 13 April 2009 <http://ent.about.com/od/entanatomybasics/ht/How_We_Hear.htm>