the “ear” is housed within the temporal bone. the outer ear consists of: §the pinna -...
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The Outer Ear Consists of:
The Pinna - cartilaginous, highly variable in appearance, some landmarks.
External Auditory Canal (or external auditory meatus) - 2.5 cm tube.
External Auditory Canal
lateral portion-cartilagemedial portion-osseous lined with epidermal (skin)
tissuehairs in lateral partcerumen (ear wax) secreted
in lateral part.
The Middle Ear:A cleft within the temporal bone
Lining is mucous membraneTympanic Membrane separates it from EACEustachian tube connects it to nasopharynxAlso Connected to Mastoid Air Cells
Middle Ear Structures
1- Malleus
2- Incus --Ossicles
3- Stapes
4- Tympanic Membrane (Eardrum)
5- Round Window
6- Eustachian Tube
Middle Ear Muscles
1. The Stapedius Attaches to Stapes,Contracts in Response to Loud sounds, chewing, speaking; Facial (VIIth cranial) nerve
2. The Tensor Tympani Helps open Eustachian tube
Two Halves:Vestibular--transduces motion and pull of gravityCochlear--transduces sound energy
(Both use Hair Cells)
INNER EAR
The Stereocilia on IHCs and OHCs
OHCs (at top) V or W shaped ranks
IHC (at bottom) straight line ranks
Cochlear Functions
Transduction- Converting acoustical-mechanical energy into electro-chemical energy.
Frequency Analysis-Breaking sound up into its component frequencies Bekesy’s Traveling Wave Active Tuning from OHCs
Major Components of the Central Auditory Nervous System (CANS)
VIIIth cranial nerveCochlear NucleusSuperior Olivary ComplexLateral LemniscusInferior ColliculusMedial Geniculate BodyPrimary Auditory Cortex
Brainstem
Thalamus
Mid-brain
Temporal Lobe
<Trapezoid Body>
COCHLEAR NUCLEUS
LATERAL LEMNISCUS
INFERIOR COLLICULUS
MEDIAL GENICULATE BODY
AUDITORY CORTEX
SUPERIOR OLIVARY COMPLEX
Cortical Processing
Pattern Recognition
Duration Discrimination
Localization of Sounds
Selective Attention
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