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Module 1.6c
The Ear
1.6-10 How does the ear transform sound energy into neural messages?
1.6-10 How does the ear transform sound energy into neural messages?
How does vibrating air trigger nerve impulses that your brain can decode as sounds? The
process begins when sound waves strike your eardrum, causing this tight membrane to middle ear the chamber
vibrate ( Figure 1.6-18 ). between the eardrum and the
cochlea containing three tiny
In your middle ear a piston made of three tiny bones — the hammer (malleus), anvil bones that concentrate the
,
(incus), and stirrup (stapes) — picks up the vibrations and transmits them to the cochlea , vibrations of the eardrum on the
a snail-shaped tube in your inner ear . cochlea’s oval window.
The incoming vibrations then cause the cochlea’s membrane-covered opening (the oval cochlea [KOHK-lee-uh] a
window ) to vibrate, jostling the fluid inside the cochlea. This motion causes ripples in the basilar coiled, bony, fluid-filled tube
membrane, bending the hair cells lining its surface, rather like grass blades bending in the wind. in the inner ear; sound waves
The hair cell movements in turn trigger impulses in the adjacent nerve cells, whose axons traveling through the cochlear
fluid trigger nerve impulses.
converge to form the auditory nerve. The auditory nerve carries the neural messages to your
Copyright © Bedford, Freeman & Worth Publishers.
thalamus and then on to the auditory cortex in your brain’s temporal lobe . From vibrating air, inner ear the innermost
part of the ear, containing the
to tiny moving bones, to fluid waves, to electrical impulses to the brain: Voila! You hear! cochlea, semicircular canals, and
vestibular sacs.
(a) OUTER EAR MIDDLE EAR INNER EAR
Semicircular canals
Bones of the
middle ear Bone
Auditory nerve
Sound Distributed by Bedford, Freeman & Worth Publishers. Not for redistribution.
waves Cochlea
Eardrum
Auditory Oval window
canal (where stirrup attaches)
Hammer Anvil Cochlea, Auditory cortex
(malleus) (incus) partially uncoiled of temporal lobe
(b)
Enlargement of middle ear
and inner ear, showing Auditory nerve
cochlea partially uncoiled Sound
for clarity waves Nerve fibers to auditory nerve
Protruding hair cells
Basilar membrane
Eardrum Stirrup Motion of fluid in the cochlea
(stapes) Oval window
Figure 1.6-18
Hear here: How we transform sound waves into nerve impulses that our brain interprets
(a) The outer ear funnels sound waves to the eardrum. The bones of the middle ear amplify and relay the eardrum’s vibrations through the
oval window into the fluid-filled cochlea. (b) As shown in this detail of the middle ear and inner ear, the cochlear fluid’s resulting pressure
changes cause the basilar membrane to ripple, bending the hair cells on its surface. Hair cell movements trigger impulses at the nerve cells’
base, whose fibers converge to form the auditory nerve. That nerve sends neural messages to the thalamus and on to the auditory cortex.
Sensation: Hearing Module 1.6c 137
03_myersAPpsychology4e_28116_ch01_002_163.indd 137 15/12/23 9:26 AM