Damaris Alas Lusine Zhamharyan Matt Marquez Period 3

• Made up of three parts • Outer ear (external) • • Middle ear Inner ear

• • Pinna (outer ear cartilage) • External Auditory Canal Lined with hairs and ceruminous glands, which prevent objects and insects from entering. • Both funnel sound waves towards the tympanic membrane (eardrum), causing it to vibrate.

• • • • • Air filled space located in the temporal bone of the skull • • • Contains 3 small auditory bones: Malleus Incus Stapes Auditory Tube Drains fluid Adjusts ear pressure

• • • • Inter-articulated bones of the middle ear that amplify the vibration of the eardrum and send them to the internal ear Attached by ligaments Malleus attached to ear drum Stapes attached to oval window of inner ear

• • The auditory tube maintains equal pressure in the ear Does this by:  Draining fluid from the middle ear into the throat  Allows the air to pass between the tympanic cavity and the outside of the body by way of the throat and mouth

• Tympanic Reflex • Involuntary muscle contractions after loud sounds • Ossicles are pulled on causing them to become more rigid and less effective • Vibrations are dampened

• • Composed of a labyrinth • Osseous Labyrinth (Bony) • Secretes Perilymph • Membranous Labyrinth • • Lies within the osseous Contains Endolymph Main Structures: • Cochlea • Semicircular Canals • Vestibule

• • • Shaped like a snail shell Bony labyrinth is divided in two • Upper: Scala Vestibuli • • Oval Window to the apex Vestibular Membrane • Lower: Scala Tympani • • Apex to the round window Basilar Membrane • Both connected by helicotrema Membranous labyrinth lies in the middle, called the Scala Media (cochlear duct)

• Houses the organ of Corti • 16,000 hearing receptor hair cells • Lies on the upper surface of the basilar membrane • Hair cells extend into the cochlear duct

• • • • Carries the signal into the brainstem and synapses in the cochlear nucleus From there the auditory information splits into motion and form procession Auditory nerve fibers going to the ventral cochlear nucleus synapse on their target cells with giant, hand like terminals Two streams: • Cells project to a collection of nuclei in the medulla called the superior olive

• Vestibulocochlear • located in the internal auditory canal • responsible for both hearing and balance and brings information from the inner ear to the brain • Two special organs help the nerve function properly: • cochlea and vestibular apparatus

•

Comes from 2 senses:

•

Static Equilibrium

• • Senses position of the head Maintains stability and posture • • •

Dynamic Equilibrium

Senses motion Aids in maintaining balance

• Comes from: • Utricle and Saccule in Vestibule • Contain Macula • Hair cells which act as sensory receptors • Covered in layer of a gelatinous matrix • Otoliths embedded on surface • Weigh down on membrane making it more responsive to changes

• Comes from: • Ampullae in semicircular canals • Communicate with the utricle • Contain Crista Ampullaris • Also contains hair cells that extend into a gelatinous matrix (cupula)

Outer Ear

• Sound waves enter the pinna and travel down the auditory

canal

Middle Ear

• The waves strike the ear drum • The ear drum passes the waves onto the auditory ossicles (malleus, incus, & stapes) which amplify the waves

Inner Ear

• The waves enter the oval window and pass through the

cochlea

• In the cochlea, the waves trigger the hair receptor cells from the organ of corti • The organ of corti passes the signal onto the cochlear nerve which goes all the way up into the auditory cortex, where it’s processed.

• The waves continue on, out the round window

• Can be: • • Acquired • Picked up, and caused by outside factor • Exposed to intense, pure tone Inherited • Born with • • More than 100 types One in a thousand newborn are deaf because of genetic defects • 2 Types: • • Sensorineural • Damage to the cochlea or auditory nerve Conductive: • Interference with transmission of vibrations in inner ear

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