Organization David Keene

Organize each step of hearing

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Solution

Postsynaptic sensory neuron (branches of CN VIII) sends information to CNS

Sound waves amplified by outer ear

Sound waves reach oval window that vibrates

Waves produced in perilymph of scala vestibuli

Stereocilia of hairs cell bends, K+ influx depolarizes the cell and it releases neurotransmitter

First step

Second Step

Third step

Fourth step

fifth step

Sixth step

Seventh step

Eighth step

Ninth step

Tenth step

Endolymph in cochlear duct displaced (also perilymph of scala tympani displaced as waves exit the cochlea at round window)

Sound waves strike tympanic membrane

Basilar membrane vibrates

Sound waves travel through ossicles (malleus, incus, stapes)

Four orders of sensory neurons carry auditory to the temporal lobe (two stops in the pons, one in the midbrain and one in the thalamus)

10

Process of hearing

from auricle to brain

The process of hearing begins as sound waves are amplified by the outer ear and directed toward the tympanic membrane, causing it to vibrate. These vibrations travel through the ossicles—malleus, incus, and stapes—which further amplify the sound and transmit it to the oval window. The movement of the oval window generates waves in the perilymph of the scala vestibuli, leading to the displacement of endolymph in the cochlear duct and perilymph in the scala tympani as waves exit through the round window. This displacement causes the basilar membrane to vibrate, bending the stereocilia of hair cells. The bending opens K+ channels, resulting in depolarization and the release of neurotransmitters. The auditory signal is then transmitted via the postsynaptic sensory neurons of the vestibulocochlear nerve (CN VIII) to the central nervous system. Finally, four orders of sensory neurons carry the auditory information through the pons (two stops), midbrain, and thalamus before reaching the temporal lobe for processing.