Chapter 10: The Inner Ear Flashcards
Inner Ear Functions
-Transduce mechanical energy from middle ear into energy that can be understood by the brain
-Maintain balance
Equilibrium
-Depends on inputs from inner ear (vestibular), visual, and proprioceptive systems
Otolith organs
Utricle and Saccule
Utricle
horizontal, linear acceleration
Saccule
vertical acceleration
Semicircular Canals
Rotational or angular movement
Ampullae
Receptor site for rotational/angular movement
How does the Vestibular System work?
When the head is moved, fluids tend to lag behind because of their inertia. This sets the fluids into motion resulting in stimulation of the vestibular system
Vertigo
True sensation of spinning
Nystagmus
Rapid rocking eye movement. Occurs with vertigo
Scala Vestibuli
-Upper portion of cochlea
-Starts at the oval window
Scala Media (Cochlear Duct)
-Middle portion of cochlea
Scala Tympani
-Bottom portion of cochlea
-Starts at the round window
Helicotrema
-Place where the scala vestibuli and scala tympani connect at the apex of the cochlea
Endolymph
-Found within the scala media, utricle, saccule, and semicircular canals
-High in potassium and low in sodium
Perilymph
-Found within the scala vestibuli and scala tympani
-High in sodium and low in potassium
Organ of Corti
-End organ of hearing
-Contains the sensory hair cells
Basilar Membrane
-Contains the auditory hair cells in its fibrous layer that in tonotopically organized
-Moves in response to fluid wave
Tectorial Membrane
-Hair cells are held between the basilar and tectorial membrane
Reissner’s Membrane
Separates the scala media from the scala vestibuli
Spiral Ligament
-Supports the scala media
Stria Vascularis
-Produces endolymph
-Supplies oxygen and nutrients to the cochlea
Modiolus
-Central core of the cochlea
-Where blood and nerve supply enter the cochlea
Low Frequency Tones
-Longer wavelengths and create maximum displacement at the apex
High Frequency Tones
-Shorter wavelengths and create maximum displacement at basal end
Hair Cell Transduction
-When the basilar membrane moves up and down in response to the fluid wave, the hair cells twist/shear
Outer Hair Cells
Amplify sound
Inner Hair Cells
Better frequency discrimination ability
Spontaneous OAE
-Recorded without auditory stimulation
Transient-Evoked OAE
-Uses a short click
-Screening approach
Distortion - Product OAE
-Frequency Specific
-More diagnostic
Causes of Perinatal Hearing Loss
-Anoxia
-Exposure to virus from infected mother
-Trauma to fetal head
Sudden Idiopathic Sensory/Neural Hearing Loss (SISNHL)
-Unilateral hearing loss that develops suddenly
-Medical emergency
Meniere’s Disease
-Suden attacks of vertigo, roaring tinnitus, vomiting, unilateral hearing loss, aural fullness
-Over secretion of endolymph
Semicircular Canal Dehiscence Syndrome (SCDS)
-More common in superior semicircular canal
-Due to weakening of the bone that covers the semicircular canals
Autoimmune Inner-Ear Disease (AIED)
-Results in bilateral, fluctuating, progressive sensory hearing loss
Presbycusis
Hearing loss due to aging
Noise Induced Hearing Loss
-Sloping Audiogram
-May occur due to work or recreational noise exposure
Ototoxic Hearing Loss
-Hearing loss caused by exposure to drugs or chemicals that are toxic to the inner ear
