Anatomy and Physiology of the Ear

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The “Ear” is housed within the
TEMPORAL BONE
The Outer Ear Consists of:
 The Pinna  External Auditory
cartilaginous, highly
Canal (or external
variable in appearance,
auditory meatus) - 2.5
some landmarks.
cm tube.
Pinna Landmarks






Helix
Antihelix
Concha
Tragus
Intertragal Notch
Antitragus
External Auditory Canal
 lateral portion-cartilage
 medial portion-osseous
 lined with epidermal (skin)
tissue
 hairs in lateral part
 cerumen (ear wax) secreted
in lateral part.
Outer Ear Functions
 Amplification / Filtering
 Protection
 Localization
The
Middle
Ear:
A cleft within
the temporal
bone




Lining is mucous membrane
Tympanic Membrane separates it from EAC
Eustachian tube connects it to nasopharynx
Also 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
Middle Ear Functions
 Impedance Matching
 Filtering
 Acoustic Reflex
These sounds get through
the middle ear most
readily
INNER
EAR
Two Halves:
 Vestibular--transduces motion and pull of gravity
 Cochlear--transduces sound energy
(Both use Hair Cells)
Within S. Media is the Organ of Corti
The Stereocilia on IHCs and OHCs
 OHCs (at top)
 V or W shaped ranks
 IHC (at bottom)
 straight line ranks
Cochlear Functions
 Transduction- Converting acousticalmechanical energy into electro-chemical
energy.
 Frequency Analysis-Breaking sound up into
its component frequencies


Bekesy’s Traveling Wave
Active Tuning from OHCs
Afferent & Efferent Neurons
IHC activation alters firing rate
Afferent neurons have their cell
bodies in the Spiral Ganglion (4)
Major Components of the Central
Auditory Nervous System (CANS)



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
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VIIIth cranial nerve
Cochlear Nucleus
<Trapezoid Body>
Superior Olivary Complex
Lateral Lemniscus
Inferior Colliculus
Medial Geniculate Body
Primary Auditory Cortex
Brainstem
Mid-brain
Thalamus
Temporal Lobe
AUDITORY CORTEX
MEDIAL GENICULATE BODY
INFERIOR COLLICULUS
LATERAL LEMNISCUS
SUPERIOR OLIVARY COMPLEX
COCHLEAR NUCLEUS
Mid-Saggital View of Brain
4th Ventricle
Corpus
Callosum
Cerebellum
Thalamus
Pons
Cortical Processing
 Pattern Recognition
 Duration Discrimination
 Localization of Sounds
 Selective Attention
Cerebral Dominance/Laterality
 Language Processing in the left hemisphere.
(Remember the right ear has the strongest
connections to the left hemisphere)
 Most people show a right-ear advantage in
processing linguistic stimuli
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