Auditory System Flashcards
Sound travels through the ____ ____, then hits the ____ ____, also called the ____ ____. What does this cause the latter structure to do?
Auditory canal
Tympanic membrane
Ear drum
Pulse back and forth
The ear drum is connected to how many bones? The last of these pushes on the ___ ___, a membrane. On the other side of this membrane is a ______ that sloshes back and forth, pushing the ____ ____ (other membrane) (in/out).
3 Oval window Solution Round window Out
Information from each ear travels to the (ipsilateral/contralateral/both) auditory cortices.
Both
It takes ___-___ synapses to reach the auditory cortex. How does the number of synapses required to reach the auditory cortex differ from the ipsilateral and contralateral side? What ability does this give?
4-5
One less synapse to reach ipsilateral side than contralateral side
Ability to localize sound
Auditory pathway: information enters through the ____ nerve, then travels to the _____ where it has its first synapse. The information is carried to the ____ where the second synapse occurs. That information travels to the ____ (direction) ____ where the third synapse occurs. The information then goes to the ____ (direction) _____, where the fourth synapse occurs. The information finally travels to the _____ ____.
Auditory Medulla Pons Caudal midbrain Rostral midbrain Auditory cortex
What cranial nerve (name and number) carries auditory information to the brain?
Vestibulocochlear nerve
Cranial nerve VIII
The auditory cortex is located in which lobe? Is it located on one or both sides of the brain?
Temporal lobe
Both
The auditory cortex contains _____ area. What is this area responsible for?
Wernicke’s area
Understanding speech
Broca’s area is responsible for what? It uses _____ and _____ abilities. Is it located in the temporal lobe or in a different lobe of the cortex? If so, which one? Is it located on one or both sides of the brain? Is it considered to be part of the auditory cortex?
Production of speech Auditory and motor Different lobe of cortex- frontal One side of brain only No
Tonotopy in the auditory cortex: high frequency (high pitched) sounds map to the more (rostral/caudal) part of the auditory cortex, whereas low frequency (low pitched) sounds map to the more (rostral/caudal) part of the cortex.
Caudal
Rostral
When the oval window moves in and out in response to sound waves causing the sloshing of fluid, this triggers vibration of the ____ ____, which is part of the _____.
Basilar membrane
Cochlea
What part of the basilar membrane vibrates best to high frequency sounds and where is it located along the basilar membrane? What part of the basilar membrane vibrates best to low frequency sounds and where is it located along the basilar membrane?
Base
Front
Apex
Back
How many fluid-filled chambers are in the cochlea? What are the 2 types of fluid in these chambers called? Which one has high ion concentration and which one has low ion concentration?
3
Perilymph- low ion concentration
Endolymph- high ion concentration
What chamber of the cochlea is filled with endolymph? It contains what structure?
Scala media
Organ of Corti
The organ of Corti in the cochlea converts ____ to ____ signal.
Mechanical
Electrical
The organ of Corti has what 2 types of hair cells? How many rows of each? Which is responsible for detecting sounds and which acts as an amplifier in conditions of low sound?
Inner hair cells- 1 row, detecting sounds
Outer hair cells- 3 rows, amplifiers
The inner and outer hair cells synapse on (the same/different) neurons. They are called (afferent/efferent) because they carry information to ___ ___ ___, or the ____ nerve. What neurotransmitter does the hair cells release?
Different Efferent Cranial nerve VIII Vestibulocochlear nerve Glutamate
The hair cells in the organ of Corti are arranged from (long to short/ short to long). What is the name of the longest stereocilium, or hair cell, in the bunch?
Short to long
Kinocilium
The tip link of the stereocilia links the tip of the (shorter/longer) stereocilium to the (shorter/longer) one nearest by. What is the purpose for this?
Shorter
Longer
Ensure that if one stereocilium bends, the others will as well
The stereocilia of the hair cells are protrusions of the ___ ___ of the hair cells.
Cell bodies
In the absence of bending, hair cells (don’t fire at all/ fire at a constant rate). Hair cell firing is a(n) (all or none response/ graded response).
Fire at a constant rate
Graded response
When the basilar membrane moves up and down in response to sound waves, it causes the whole ____ of ____ to move up and down. At the peak of upward motion, the hair cells are bent from (shortest to longest/ longest to shortest), which is when the cells are (depolarized/hyperpolarized). At the peak of downward motion, the hair cells are bent from (shortest to longest/ longest to shortest), which is when the cells are (depolarized/hyperpolarized).
Organ of Corti Shortest to longest Depolarized Longest to shortest Hyperpolarized
The hair cells’ highest rate of firing is when the organ of Corti is at its peak (upward/downward) position and the hair cells are bent from (shortest to longest/ longest to shortest).
Upward
Shortest to longest
Bending towards the longest stereocilium causes what type of ion channels to open?
K+
When the outer hair cells are depolarized, they experience an influx of ____ (ion) and an activation of a signaling pathway that causes them to _____. Because they are attached to the ___ ____, when this happens, the ____ of this structure is enhanced, which causes increased deflection of the ____ ____ cells, which are attached to the same structure.
K+ Contract Basilar membrane Bend Inner hair
Excitation of the (inner hair cells/ outer hair cells/ both) causes firing onto the auditory nerve.
Inner hair cells only
The endolymph in the ___ ____ bathes the (top of hair cells/ cell bodies of hair cells) and has (low/high) K+ concentration. The perilymph bathes the (top of hair cells/ cell bodies of hair cells) and has (low/high) K+ concentration. The hair cells themselves have relatively (low/high) intracellular K+ concentration.
Scala media Top of hair cells High Cell bodies of hair cells Low High
What is the charge in mV of the endolymph? The inner hair cells? The perilymph?
Endolymph: 80 mV
Inner hair cells: -45 mV
Perilymph: 0 mV
Between the endolymph and the hair cell cytoplasm, how big and in what direction is the concentration gradient and electrical gradient? Why? In what direction is the resulting driving force and in what direction does the K+ move?
Concentration gradient: small endolymph -> hair cell (endolymph has slightly higher K+ concentration than hair cell)
Electrical gradient: large endolymph -> hair cell (hair cell is much more negative than endolymph)
Driving force: endolymph -> hair cell
K+ moves from endolymph to hair cell
Between the hair cell cytoplasm and the perilymph, how big and in what direction is the concentration gradient and electrical gradient? Why? In what direction is the resulting driving force and in what direction does the K+ move?
Concentration gradient: large hair cell -> perilymph (much greater K+ concentration in hair cell than perilymph)
Electrical gradient: moderate perilymph -> hair cell (hair cell is more negative than perilymph)
Driving force: hair cell -> perilymph
K+ moves from hair cell to perilymph
From lowest to highest membrane potential (Vm), order the following: endolymph, perilymph, hair cell cytoplasm
Lowest: hair cell cytoplasm
Perilymph
Endolymph
The tip links are attached to the “lids” of ____-____ channels on the stereocilia. What ions do these channels pass?
Mechanically-gated
K+, Ca+2
When the stereocilia bend towards the tallest stereocilium, the tip links are (stretched/relaxed), leading to (opening/closing) of the ____-____ ion channels. When the stereocilia bend towards the shortest stereocilium, the tip links are (stretched/relaxed), leading to (opening/closing) of these ion channels.
Stretched Opening Mechanically-gated Relaxed Closing
- The hair cell is depolarized when ___-gated channels are opened and pass ____ (ion). At this point, driving force is mainly due to (concentration gradient/electrical gradient).
- Depolarization causes ___-gated ___ (ion) channels to open, causing an (influx/efflux) of ___ (ion).
- ____ (ion) mediates ____ fusion.
- Opening of ____ (ion) -gated ___ (ion) channels and ___-gated ____ (ion) channels causes an (influx/efflux) of ____ (ion). At this point, driving force is mainly due to (concentration gradient/electrical gradient).
- ____ (ion) is pumped out of cell through ____ ____ or stored in ____ or ____ ____.
1. Mechanically-gated K+ Electrical gradient 2. Voltage-gated Ca+2 channels Influx Ca+2 3. Ca+2 Vesicle 4. Ca+2 gated K+ channels Voltage-gated K+ channels Efflux K+ Concentration gradient 5. Ca+2 Ca+2 pumps Mitochondria Endoplasmic reticulum
At the hair cell ribbon synapse, glutamate reuptake is mediated by ____ cells. What type of glutamate receptors do the afferent neurons have? The afferent neurons have (small/big) ____-gated ___ (ion) channels, through which the ion moves (into the cell/out of the cell) due to driving force. The afferent neurons also have ____-gated ____ (ion) channels, through which the ion moves (into the cell/out of the cell) due to driving force.
Glial AMPA Big voltage-gated K+ channels Out of the cell Voltage-gated Ca+2 channels Into the cell
If the voltage-gated and Ca+2-gated K+ channels of the hair cells were blocked, what would happen to the level and length of depolarization of the hair cell? Why? What would then be the effect on vesicle fusion? Why?
Increase in level and length of depolarization: no K+ efflux means hair cells’ mV stays high for longer
Increased vesicle fusion: voltage-gated Ca+2 channels are open upon depolarization, so more Ca+2 to mediate vesicle fusion
The tip link on the side of the (shorter/taller) stereocilium is associated with what type of motor proteins? When these proteins move the tip link up the stereocilium, what happens to the tip link? When these proteins move the tip link down the stereocilium, what happens to the tip link?
Taller
Myosin
Tip link stretches
Tip link relaxes
Adaptation of stereocilia-mediated signaling enables a return to ____ potential. Fast adaptation is ____-mediated, whereas slow adaptation is dependent on ____ ____ moving the ____ ____. How does each work?
Resting
Ca+2
Motor proteins
Tip links
Fast adaptation: Ca+2 entering mechanically-gated channel causes channel closure
Slow adaptation: motor proteins move tip link down stereocilium to reduce tension, then moves it back up after stereocilium has returned to upright position
The hair cells have ____ synapses between themselves and the afferent nerves. This synapse has an ____-dense center ____ surrounded by ____ _____.
Ribbon
Electron-dense center core
Synaptic vesicles
The ribbon synapse is surrounded by what 3 groups of vesicles (ribbon attached or not, docked and primed or reserve pool)? Ca+2 influx enables fusion of which one(s) of these groups? What does this mean in terms of glutamate release?
3 groups: ribbon attached/docked and primed, ribbon attached, not ribbon attached/reserve pool
Ca+2 influx enables fusion of ribbon attached as well as ribbon attached/docked and primed
Greater glutamate release
Loud noise causes what kind of damage to hair cells? This is mediated by _____, caused by overactivity of _____ (neurotransmitter) systems.
Mechanical
Excitotoxicity
Glutamate
Drug induced hearing loss: _____, a class of antibiotics, is thought to bind and activate _____ receptors, leading to _____ and hair cell death.
Aminoglycosides
NMDA
Excitotoxicity
2 methods of hair cell damage repair
Cochlear implants
Induce new hair cell formation
