hearing Flashcards
the external ear ends at
the tympanic membrane
the air-filled middle ear extends
from the tympanic membrane to the round and oval windows and contains the ossicles
the internal ear includes
the body and membranous labyrinths
pressure within the middle ear is normally equal to atmospheric pressure because
the Eustachian tube connects the pharynx to the middle ear
bony labyrinth
the outer bony framework of the inner ear
a maze of passageways “cut” into the temporal bone that forms a cavity that contains the membranous labyrinth
is divided into a cochlea, a vestibule, and three semicircular canals
is filled with perilymph, which is similar to cerebrospinal fluid
membranous labyrinth
a continuous series of winding, saclike, membranous ducts and sacs within (lining) the bony labyrinth
is divided into a cochlear duct (within the cochlea), a utricle and saccule (within the vestibule), and three semicircular ducts (within the semicircular canals)
is surrounded by perilymph and filled with endolymph, which is similar to intracellular fluid and rich in potassium
the endolymph-filled cochlear duct is surrounded by
perilymph (which is within the cochlea but not within the cochlear duct)
if the cochlea were unrolled, the perilymph-filled space “above” the cochlear duct is the _____ and the perilymph-filled space “below” the cochlear duct is the ____
scala vestibuli
scala tympani
the cochlear duct begins near the ____
and extends to the “end” cochlea
oval window, a membrane-covered opening between middle and inner ears
the cochlear duct has a ceiling called the ____
and a floor called the ____
vestibular membrane
basilar membrane
round window
membrane-covered opening where the inner ear’s scala tympani connects to the middle ear
the scala tympani and scala vestibuli are
continuous with one another at the far end of the cochlea
within localized areas of the membranous labyrinth are
hair cells
sound is transmitted through a medium by
producing a vibration of the medium’s molecules
wave amplitude is related to the sound’s
loudness
wave frequency determines the sound’s
pitch
sound waves hitting the tympanic membrane cause it to
vibrate at the same frequency as the frequency of the wave
vibrations from tympanic membrane are transferred to
malleus to incus to stapes to oval window
this amplifies the sound pressure (necessary because liquid is harder to move than air)
the tensor tympani is attached to the ____
the stapedius is attached to the ____
they are both
malleus
stapes
skeletal muscles that contract to dampen bone movements and thus protect the cochlea from damage due to continuous loud noises
the vibrating stapes causes the
oval window to bow into the scala vestibuli and back out rhythmically
the vestibular membrane is so thin that vibrations in the perilymph within scala vestibuli move easily into the
endolymph within the cochlear duct
a low-frequency sound wave travels all the way down the scala vestibuli, turns the corner, and travels back along
scala tympani to the round window (which bulges to dissipate the wave). this sound wave is not heard
the vibrations of audible sound waves are transferred
from the scala vestibuli across the cochlear duct and then to the basilar membrane
sitting atop the basilar membrane is the
organ of corti, which contains the inner and outer hair cells that are the receptor cells for hearing
protruding from the hair cell’s border that is furthest from the basilar membrane are
stereocilia
the stereocilia extend either into ____ or into ____
endolymph
an overlying, gel-like tectorial membrane
the vibrating basilar membrane moves the bulk of a hair cell but its stereocilia are
embedded in the tectorial membrane which remains stationary. this causes the stereocilia to bend or shear, back and forth
stereocilia bending in one direction opens
mechanically gated cation channels (in the stereocilia), and an influx of K+ from the endolymph depolarizes the hair cell
the depolarization of hair cells open voltage-gated channels near the cell’s base, and the influx of ____ triggers the hair cell to release
Ca 2+
glutamate onto associated sensory neurons – thus the membrane potential of the hair cell oscillates rapidly, and glutamate is released in bursts
glutamate increases action potential production in the sensory neurons, the axons of which are bundled into the
cochlear branch of the vestibulocochlear nerve (cranial nerve VIII)
the louder the initial sound, the greater the frequency with which action potentials are sent to the brain
the basilar membrane contains about 25,000 stiff but elastic fibers that are
fixed at one end but not the other, thus they can vibrate like the reeds of a harmonica
fibers in cochlear duct, near the oval window are ____ while fibers near the cochlea’s apex are ____
short and stiff
longer and floppy
the stiff fibers in the cochlear duct resonate best (are ‘tuned to’)
the floppy fibers resonate in time with
high-frequency pressure waves (high-pitch sounds)
lower-frequency pressure waves (low-pitched sounds)
place principle
brain determines which position along the basilar membrane is most stimulated (by paying attention to which incoming fibers are carrying the most action potentials), and thereby produces the sensation of the pitch of the particular sound
fibers of the sensory neurons synapse with
interneurons in the brainstem (medulla)
sensory input from both ears may converge on the same interneuron (in the medulla) and the different times of input arrival and different intensities of the sound can be used to
determine the direction from which the sound came
pathway of hearing information to temporal lobe of cerebrum
inferior colliculus of the midbrain –> medial geniculate nucleus of the thalamus where all fibers synapse with interneurons that carry the information to the primary auditory cortex in the temporal lobe of the cerebrum
much but not all of hearing information crosses the body’s midline by the time it reaches the
midbrain
different regions of the auditory cortex are specialized to
analyze location, movement, loudness, or duration of sound, to respond to complex sounds such as those used in speech, and to focus selectively on one sound in a noisy or complex group of sounds
