Anatomy and Physiology of the Ear
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Transcript Anatomy and Physiology of the Ear
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)
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