Download The Inner Ear

The Inner Ear
SPA 4302
Summer 2006
INNER
EAR
Sensory
Endorgans
encased within
very dense bone
Two Halves:
• ____________--transduces motion and pull of gravity
• ____________-transduces sound energy
(Both use Hair Cells)
Subdivision into spaces containing ___________
(blue), and spaces containing __________ (red)
Cochlea is Divided into 3 “Scala”
• Scala Vestibuli
– __________ Membrane
• Scala Media
– __________ Membrane
• Scala Tympani
• ___________ - the
opening between 2
outer Scala
Fluids filling the Inner Ear
• ___________- in S. Vestibuli and S.
Tympani
– High Sodium / Low Potassium concentrations
– Low Voltage (0 to +5 mV)
• ___________- in S. Media
– High Potassium / Low Sodium concentrations
– High Positive Voltage (85 mV)
Cross-Section of the Cochlea
Third Turn
Second Turn
A Cross Section Shows the 3 Scala
Within S. Media is the Organ of Corti
I = Inner Hair Cells
O = Outer Hair Cells
P = Pillar Cells
D = Deiter’s Cells
The Stereocilia on IHCs and OHCs
• ________ (at top)
• V or W shaped ranks
• ________ (at bottom)
• straight line ranks
Stereocilia bent toward tallest row
• ________ flows into cell
• ________ flows into cell
• Voltage shifts to a less
__________ value
• More neurotransmitter is
released
Cochlear Afferent (Sensory) Neurons
• __________ (95%)
– synapse w/ IHC
– 1 IHC to 20 neurons
– well myelinated
• __________ (5%)
– Synapse with OHCs
– Many OHCs to 1 neuron
– unmyelinated
Cochlear Functions
• __________- Converting acousticalmechanical energy into electro-chemical
energy.
• ___________- Breaking sound up into its
component frequencies
Development of the Inner Ear
• Beginning in week 3,
________________
develops,
• Invaginates to form
_______________,
• Which then closes off,
leaving an
_________________.
• Capsule divides into
saccular, utricular
divisions
– ________: cochlea
(begins forming in
week 6)
– ________: semicirc.
canals,
endolymphatic sac &
duct
• Organ of Corti forms
from week ___
• Inner ear fully
formed by ___ weeks
Hearing Loss and Disorders of
the Inner Ear
• Vast majority of SNHL results from inner
ear disorder.
• Cochlear pts often hear, but cannot
distinguish what they hear very clearly:
____________.
– Arises from frequency and other distortions
associated with changes in inner ear function.
Inner Ear Disorders: Prenatal Causes
•
•
•
•
•
•
Genetic mutation/inheritance
Cytomegalovirus (CMV)
__________
Rubella
Rh incompatibility
__________
Anatomical Anomalies
Often seen as
Bony
malformations
Examples:
Mondini
(incomplete
cochlea)
Enlarged Duct
(shown here)
Age Effects
Noise Damage
• Temporary Threshold Shift (TTS)
• Permanent Threshold Shift (PTS)
• Duration, Timing and Intensity influence
• Typical “Noise Notch” often seen between
____________ first.
• Notch widens and deepens over time, with
hearing loss spreading to adjacent
frequencies, and increasing in degree.
Ototoxicity
Substances poisonous to the ear
• Medicines
– ___________ antibiotics
– ___________ drugs for CA
– ___________
• Industrial Chemicals (tolulene, etc)
May affect __________
Degree of hearing loss varies
Synergy with noise or other ototoxic agents
Meniere’s Disease
• Really a Syndrome:
–
–
–
–
_________ Vertigo
Roaring, Low Freq. Tinnitus
Fluctuating ___________ Hearing Loss
Sensation of Aural Fullness
• Thought to be produced by
____________________, a condition in which
too much endolymph accumulates in the inner
ear.