Chapter 6.3: AUDITORY Remote Sensing Flashcards
the middle ear bones form a ___ system that converts ____ vibrations into ____ ___
the middle ear bones form a LEVER system that converts AIRBORNE vibrations into PRESSURE WAVES
___ ___ from the middle ear travel through the fluid filled ___ in the inner ear that induce vibrations on the ___ membrane
PRESSURE WAVES from the middle ear travel through the fluid filled COCHLEA in the inner ear that induce vibrations on the BASILAR membrane
vibrations in the basilar membrane bend the ___ of hair cells on the membrane, depolarizing them, causing them to release ___ onto the axons of neurons in the ___ nerve.
vibrations in the basilar membrane bend the STEREOCILIA of hair cells on the membrane, depolarizing them, causing them to release GLUTAMATE onto the axons of neurons in the AUDITORY nerve.
explain the cochlea’s tonotopic map
the tonotopic map allows for sound discrimination.
High frequency sounds excite hairs on the BASE of the cochlea, and low frequency sounds excite hairs on the APEX
2 main parameters of sound
1) intensity (dB) aka amplitude of waves
2) frequency (pitch) (Hz)
two components of the outer ear
pinna and ear canal
the ___ membrane vibrates at the ____ frequency as the sound wave, and separates the outer and middle ear.
the TYMPANIC membrane vibrates at the SAME frequency as the sound wave, and separates the outer and middle ear.
three components of the middle ear. How do they work together to convey info the inner ear?
include the malleus incus and stapes. They are all connected by ligaments and vibrate TOGETHER when the tympanic membrane vibrates.
They AMPLIFY sound waves before sending it to the fluid filled inner ear and oval window membrane. Amplification is necessary so the sound waves can move through the fluid.
what membrane separates the middle ear and inner ear?
the OVAL WINDOW
role of middle ear muscles
they are in the middle ear and contract in response to extremely loud sounds to prevent further amplification and damage to the middle and inner ear
the inner ear is comprised of the __ and ___ ___
cochlea and vestibular labrynth.
the cochlea is divided into two portions folded onto itself into the scala ___ and scala ____
scala vestibuli and scala tympani
scala vestibuli
part of the cochlea that extends from the OVAL WINDOW to the apex of the cochlea
scala tympani
part of the cochlea that ectends from the apex to the round window
cochlear sound waves travel from the oval window up the ___ and down the ___ toward the round window
up the vestibuli and down the tympani
how does the round window allow for sound wave propagation in the cochlea?
if there was no opening, the fluid in the cochlea would not be able to be compressed/moved by the sound waves. The round window essentially provides an opening for the soundwaves to move to.
scala ___ lies between the scala vestibui and typanica of the cochlea
scala media
the ___ membrane’s width, tension and stiffness DECREASES to the APEX of the cochlea. What does this allow for?
the basilar membrane characteristics changes as it moves from the base to the apex. This allows for the relationship between sound frequency and location of maximal basilar vibration.
sound vibrations in the cochlea are sensed by ____ of the hair cells which sit on top of the ___ membrane and project onto the scala ___
sound vibrations in the cochlea are sensed by STEREOCILIA of the hair cells which sit on top of the BASILAR membrane and project onto the scala MEDIA
each hair cell has __ stereocilia with dif heights for further differentia
3 rows of stereocilia
sounds cause the basilar membrane on the cochlea to vibrate up and down, but the stereocilia vibrate SIDEWAYS. What causes this change in vibrational direction?
the tectorial membrane lies just above the hair cell stereocilia. The outer edge is attached to the basilar membrane where the outer hair cells attach. This causes the basilar membrane to slide sideways against one another.
Hair cell’s stereocilia is bathed in ___ that contains large amounts of ___.
bathed in endolymph that contains large amounts of K+
Explain hair cell depolarization
the shortest stereocilia contain K+ and Ca2+ channels that open up when the shortest stereocilia bend towards the tallest stereocilia. They are connected together by TIPLINKS. When the sound waves cause vibration of the basilar membrane which cause sideways vibration of the stereocilia, the K+/Ca2+ ion channels in the short stereocilia open, and K+ from the K+-rich endolymph move into the hair cell from the stereocilia channels.
How can tip link tension be adjusted? what does this cause?
small myosin motors can adjust tip link tension and alter sound sensitivity. The more tension in a tip link, the larger the vibrations in the cochlea are required to open hair cell ion channels.
the K+ and Ca2+ channels on the hair cells are ___ gated
mechano-gated- they open when the stereocilia is physically moved
explain how the hair cells in the cochlea release neurotransmitters after depolarization
after mechanogated K+ and Ca2+ channels open promoting initial depolarization, VOLTAGE GATED Ca2+ channels opn and promote further Ca2+ influx.
Vesicle exocytosis of glutamate occurs through the RIBBON SYNAPSE network that is close to the post synaptic cell (SPIRAL GANGLION) which conveys APs into the COCHLEAR NUCLEUS BRAINSTEM REGION
Ribbon synapse from hair cells –> ___ ___ —-> ____ nucleus (in brainstem)
Ribbon synapse from hair cells –> SPIRAL GANGLION —-> COCHLEAR nucleus (in brainstem)
How is the hair cell in the cochlea repolarized?
opening of K+ permeable channels when the tiplinks pull short stereocilia to the tall stereocilia causes K+ influx into hair cell and flows from the endolymph (causes depolarization and glut release to the spiral ganglion), then K+ moves down into body of hair cell and OUT into the perilymph.
stereocilia is bathed in ____, where as the hair cell BODY is bathed in _____. These 2 fluid compartments are separated by cells with ___ ___ between them
stereocilia is bathed in ENDOLYMPH, where as the hair cell BODY is bathed in PERILYMPH. These 2 fluid compartments are separated by cells with TIGHT JUNCTIONS between them
Which ions do hair cells use for depolarization?
Ca2+ and K+, not Na+ like neurons.
How is the high potassium concentration of the endolymph maintained?
the stria vasciliaris cells that are located on the peripheral wall of the scala media. Has a rich capillary bed and contains ATP pumps to maintain the K+ concentration in the scala media’s endolymph.
explain cochlear tonotopy
the higher the frequency of a tone, the closer to the cochlear base will be the hair cells that are most activated by the tone
T/F: loudness is also mapped tonotopically on the cochlea
false. loudness is not mapped. varying amplitude of constant pitch (frequency) will be on the same portion of the cochlea.
Label lined code
APs in a particular set of axons are interpreted by other neurons according to the label associated with the axon type
ex/ poke yourself in the eye and stimulate the optic nerve. optic nerve fires in response to light. in addition to feeling pain, you will also see stars because your brain think the photoreceptors are firing.
benefit of sensory maps
minimizes the connection lengths between neurons encoding similar stimuli.
