The “Ear” is housed within the

TEMPORAL BONE

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.

Pinna LandmarksHelixAntihelixConchaTragus Intertragal NotchAntitragus

External Auditory Canal

lateral portion-cartilagemedial portion-osseous lined with epidermal (skin)

tissuehairs in lateral partcerumen (ear wax) secreted

in lateral part.

Outer Ear FunctionsAmplification / FilteringProtection Localization

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

Middle Ear Functions

Impedance Matching

Filtering

Acoustic Reflex

These sounds get through the middle ear most

readily

Two Halves:Vestibular--transduces motion and pull of gravityCochlear--transduces sound energy

(Both use Hair Cells)

INNER EAR

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 acoustical-mechanical energy into electro-chemical energy.

Frequency Analysis-Breaking sound up into its component frequencies Bekesy’s Traveling Wave Active Tuning from OHCs

AfferentAfferent & 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 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

Mid-Saggital View of Brain

Pons

Cerebellum

4th Ventricle

Thalamus

Corpus Callosum

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