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Two Halves:• ____________--transduces motion and pull of gravity• ____________-transduces sound energy
(Both use Hair Cells)
INNER EARSensory
Endorgans encased within
very dense bone
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)
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 acoustical-mechanical 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)
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.
OtotoxicitySubstances 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