lecture 17 (test 2) Flashcards
role of the outer ear
- funnels sound
- conducts sound vibrations
- prevents damage to the tympanic membrane
what is the role of the pinna
- part of the outer ear
- channels sound to the eardrum
- lined with wax secreting glands that protect the ear
the middle ear is made up of the …
malleus
incus
stapes
malleus
“hammer”
attached to eardrum
head connected to the incus
incus
“anvil”
the shaft is connected to the stapes
stapes
oval shaped footplate makes a tight connection with the oval window
the function of the middle ear
conduct vibration to the inner ear
eustachian tube
equalizes pressure across eardrum
connects the ear to the back of the throat
the lever effect
joints between bones are hinged
movement of the long part of incus creates a greater force on the incus
the condensation effect
sound collected my tympanic membrane and channeled through the ossicles
surface area or the eardrum is ______ than the oval window
18 times bigger
muscles in the middle ear
tensor tympani (attached to malleus) stapedius (attaches to stapes)
what activates the middle ear muscles and when
motor neurons in response to loud sounds
what does tensing middle ear muscles do
reduce ossicle movement
middle ear muscle reflex has a ______ delay
200ms (arent activated in time for loud sudden noises)
3 canals of inner ear
vestibular canal
typanic canal
middle canal
3 canals of inner ear separated by what
basilar membrane and Reissner’s membrane
sound transmission from the middle ear to the inner ear
1) displacement of stapes on oval window, increases pressure in the vestibular canal
2) pressure gradients transmitted across resiner’s membrane into middle canal
3) causes movement of the basilar membrane, on which the transduction apparatus sits
4) increased pressure on the tympanic membrane is relieved by the outward movement of the round window
where is the organ of Corti located
along the top of the basilar membrane
how does the organ of Corti work
recieves vibrations from basilar membrane
what is the organ of Corti mad of
a scaffold of the cells that supports the specialized neurons called hair cells
arch of Corti separates into ____ and _____
the inner and outer portion
the organ of Corti is arranged in what matter
bilaterally symmetrical
tectorial membrane attaches where
at the end of the tallest stereocilia
inner hair cells
single row
transform vibrational energy to electrical energy
innervated by the afferent auditory nerve fibers
the inner side of arch of Corti
outer hair cells
3 rows
the outer side of arch of Corti
the tectorial membrane is a
gelatinous structure
what happens when stereocilia are flexed
release of neurotransmitters
stereocilia bend in which direction
the direction of the force
a traveling wave causes the basilar membrane to move _________ and _______
up and down
which direction do hair cells and tectorial membrane move and what is it called
the opposite, shearing force
what is the result of the shearing force
ion channels open
what are tip links
fine filaments that run parallel to the plane of bilateral symmetry
how are inner hair stereocilia arranged
tallest to shortest
steps to auditory transduction
1) displacement of hair bundles towards tallest stereocilia
2) tip links open cation-selective channels
3) entry of cation (mainly K+) depolarizes the hair cell
4) voltage-gated Ca2+ channels open and allow Ca2+ entry
5) Neurotransmitter (glutamate) released onto cochlear nerve fibers that innervate the hair cells
6) AP in cochlear nerve carry info to higher processing areas
what is mechanoelectrical conduction
mechanical displacement converted to an electrical signal is fast (10 μs) is sensitive (hair cell movements detected on atomic nm scale)
sensory recptors of the auditory system
hair cells
how do we detect greater amplitude in the cochlea
- HOW MUCH BASILAR MEBRAN MOVES UP AND DOWN
- the tympanic membrane will move farther
- greater deflection of basilar and tectorial membranes
- greater shearing force
- greater depolarization and more neurotransmitters released
place code
- a complex tone will cause the basilar membrane to vibrate where each of its harmonics frequencies that make up the complex sound
vibrations start at what end of the basilar membrane
base
the base is for what frequency
high
apex is for what frequency
low
which end of the basilar membrane is wider
apex
what frequencies are stimulated earlier in a complex sound
higher
when will the sound be heard
when vibration reaches the apex
tonotopic map
how frequencies are mapped on the basilar membrane
what acts like a Fourier analyzer in the ear
basilar membrane
