hearing

Question 1

the external ear ends at

Answer 1

the tympanic membrane

Question 2

the air-filled middle ear extends

Answer 2

from the tympanic membrane to the round and oval windows and contains the ossicles

Question 3

the internal ear includes

Answer 3

the body and membranous labyrinths

Question 4

pressure within the middle ear is normally equal to atmospheric pressure because

Answer 4

the Eustachian tube connects the pharynx to the middle ear

Question 5

bony labyrinth

Answer 5

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

Question 6

membranous labyrinth

Answer 6

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

Question 7

the endolymph-filled cochlear duct is surrounded by

Answer 7

perilymph (which is within the cochlea but not within the cochlear duct)

Question 8

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 ____

Answer 8

scala vestibuli

scala tympani

Question 9

the cochlear duct begins near the ____

and extends to the “end” cochlea

Answer 9

oval window, a membrane-covered opening between middle and inner ears

Question 10

the cochlear duct has a ceiling called the ____

and a floor called the ____

Answer 10

vestibular membrane

basilar membrane

Question 11

round window

Answer 11

membrane-covered opening where the inner ear’s scala tympani connects to the middle ear

Question 12

the scala tympani and scala vestibuli are

Answer 12

continuous with one another at the far end of the cochlea

Question 13

within localized areas of the membranous labyrinth are

Answer 13

hair cells

Question 14

sound is transmitted through a medium by

Answer 14

producing a vibration of the medium’s molecules

Question 15

wave amplitude is related to the sound’s

Answer 15

loudness

Question 16

wave frequency determines the sound’s

Answer 16

pitch

Question 17

sound waves hitting the tympanic membrane cause it to

Answer 17

vibrate at the same frequency as the frequency of the wave

Question 18

vibrations from tympanic membrane are transferred to

Answer 18

malleus to incus to stapes to oval window

this amplifies the sound pressure (necessary because liquid is harder to move than air)

Question 19

the tensor tympani is attached to the ____

the stapedius is attached to the ____

they are both

Answer 19

malleus

stapes

skeletal muscles that contract to dampen bone movements and thus protect the cochlea from damage due to continuous loud noises

Question 20

the vibrating stapes causes the

Answer 20

oval window to bow into the scala vestibuli and back out rhythmically

Question 21

the vestibular membrane is so thin that vibrations in the perilymph within scala vestibuli move easily into the

Answer 21

endolymph within the cochlear duct

Question 22

a low-frequency sound wave travels all the way down the scala vestibuli, turns the corner, and travels back along

Answer 22

scala tympani to the round window (which bulges to dissipate the wave). this sound wave is not heard

Question 23

the vibrations of audible sound waves are transferred

Answer 23

from the scala vestibuli across the cochlear duct and then to the basilar membrane

Question 24

sitting atop the basilar membrane is the

Answer 24

organ of corti, which contains the inner and outer hair cells that are the receptor cells for hearing

Question 25

protruding from the hair cell’s border that is furthest from the basilar membrane are

Answer 25

stereocilia

Question 26

the stereocilia extend either into ____ or into ____

Answer 26

endolymph

an overlying, gel-like tectorial membrane

Question 27

the vibrating basilar membrane moves the bulk of a hair cell but its stereocilia are

Answer 27

embedded in the tectorial membrane which remains stationary. this causes the stereocilia to bend or shear, back and forth

Question 28

stereocilia bending in one direction opens

Answer 28

mechanically gated cation channels (in the stereocilia), and an influx of K+ from the endolymph depolarizes the hair cell

Question 29

the depolarization of hair cells open voltage-gated channels near the cell’s base, and the influx of ____ triggers the hair cell to release

Answer 29

Ca 2+

glutamate onto associated sensory neurons – thus the membrane potential of the hair cell oscillates rapidly, and glutamate is released in bursts

Question 30

glutamate increases action potential production in the sensory neurons, the axons of which are bundled into the

Answer 30

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

Question 31

the basilar membrane contains about 25,000 stiff but elastic fibers that are

Answer 31

fixed at one end but not the other, thus they can vibrate like the reeds of a harmonica

Question 32

fibers in cochlear duct, near the oval window are ____ while fibers near the cochlea’s apex are ____

Answer 32

short and stiff

longer and floppy

Question 33

the stiff fibers in the cochlear duct resonate best (are ‘tuned to’)

the floppy fibers resonate in time with

Answer 33

high-frequency pressure waves (high-pitch sounds)

lower-frequency pressure waves (low-pitched sounds)

Question 34

place principle

Answer 34

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

Question 35

fibers of the sensory neurons synapse with

Answer 35

interneurons in the brainstem (medulla)

Question 36

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

Answer 36

determine the direction from which the sound came

Question 37

pathway of hearing information to temporal lobe of cerebrum

Answer 37

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

Question 38

much but not all of hearing information crosses the body’s midline by the time it reaches the

Answer 38

midbrain

Question 39

different regions of the auditory cortex are specialized to

Answer 39

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