Cochlea Hearing
Cochlea spiral chambers coils around a bony pillar - modiolus running through center of coils like a wedge shaped worm is cochlea duct (scala media) it plus a shelf like extension of modiolus divides the cavity into 3 regions
cochlear duct scala vestibuli scala tympani scala vestibuli - superior continuous with vestibule and abuts the oval window and the scala media or cochlear duct scala tympani – inferior which ends in round window scala tympani
cochlear duct scala vestibuli vestibular membrane scala tympani endolymph perilymph both the scala vestibuli and scala tympani have perilymph vestibular membrane - “roof” of cochlear duct thought to secrete endolymph vestibular membrane scala tympani perilymph
the “floor” is cochlear duct and basilar membrane, which supports the organ of Corti
A branch of the cochlear nerve (joins vestibular nerve to form vestibulocochlear nerve) runs from the organ of Corti, through the modiolus → brain.
Vibrations from oval window → perilymph → basilar membrane
Vibrations from oval window → perilymph → basilar membrane scala vestibuli Organ of Corti scala tympani
When maximum vibrations occur, the organ of Corti hair cells are pulled by attached “awning” – tectoral membrane.
When maximum vibrations occur, the organ of Corti hair cells are pulled by attached “awning” – tectoral membrane.
Their movement causes ion channels in hair cell membranes to open. Neurotransmitters are released and nerve endings below hair cells are stimulated.
Cerebral cortex “processes” sounds.
hair cells nearest oval window = high pitch near cochlear apex = low pitch amplitude = more hair cells in the area are vibrated
Sound Pathway
Tympanic Membrane Auditory Canal What is the scientific name for ear wax? cerumen Tympanic Membrane Auditory Canal Pinna Collects sound Transmits vibrations
Tympanic Membrane Auditory Canal What is its function? Trap foreign objects Tympanic Membrane Auditory Canal Pinna Collects sound Transmits vibrations
Malleus Incus Stapes Amplifies vibrations Ossicles What prevents the eardrum from rupturing? Ossicles Tensor tympani muscle tightens ossicles Malleus Incus Stapes Amplifies vibrations
Malleus Incus Stapes Amplifies vibrations Ossicles What is the function of the Eustachian tube? Ossicles Equalizes pressure between middle ear and throat Malleus Incus Stapes Amplifies vibrations
What is behind the stapes? Oval Window
What is behind the oval window? Perilymph
Vestibular membrane Basilar membrane
Endolymph Vestibular membrane Endolymph Organ of Corti Basilar membrane Endolymph
Tectorial membrane Hair cells
Hair cells scrape against the tectorial membrane.
Action Potential Cochlear Nerve
Vestibulocochlear Nerve Cerebral (Auditory) Cortex Of Brain