PowerPoint Presentation

Hearing

Anatomy of the Ear

Sound

Sound Waves

Middle Ear

Auditory Ossicles

Inner Ear

Organ of Corti

Cochlear ductTympanic ductCochleaBasilar membrane: between the cochlear duct and the tympanic canal. Tough but flexible membrane that moves itself in direct response to the frequency of the incoming sound. Much stiffer at the base (near the stapes).It becomes wider toward the apex of the cochlea.

Basilar membraneOrgan of CortiFound within the cochlear duct. Its where transduction from mechanical waves to neural signals takes place. Contains columns of hair cells.Inner hair cells (3500): single column.Outer hair cells (20,000): three columns.Each hair cell has about 100 tiny filaments called stereocilia. Organ of Corti

Organ of Corti

Basilar Membrane

Traveling waveFunction of the inner earThe Place Code Theory:Hair cells of the organ of Corti are organized in a strictly tonotopic fashion.Different vibration frequencies in the cochlea displace different regions of the basilar membrane.Georg von Bekesy.

Georg von Bekesy

Basilar Membrane

Traveling waveThe Auditory NerveOriginate along the basilar membrane.Basilar membrane is frequency-specific.Auditory nerve near the apex of the basilar membrane (near the helicotrema) encodes low-frequency sound.Auditory nerve fibers near the base of the basilar membrane (near the oval window) encode high-frequency sound.Tonotopic Organization. Tonotopic Organization

Cochlear implants

The Auditory NerveOriginate along the basilar membrane.Basilar membrane is frequency-specific.Auditory nerve near the apex of the basilar membrane (near the helicotrema) encodes low-frequency sound.Auditory nerve fibers near the base of the basilar membrane (near the oval window) encode high-frequency sound.Tonotopic Organization. Medial Geniculate Nucleus of the Thalamus

Auditory Cortex