Auditory and Vestibular Systems Flashcards
Hair cells do one of these two things as stereocilia are bent
Depolarize or hyperpolarize
Time taken for sound to reach from ear to ear, localization of sound in horizontal plane (left side hits left ear first)
Interaural time dealy
These receive feedback from the cortex and cerebellum to help fine tune how we use info
Vestibular nuclei
Detect changes in head angle, linear acceleration (macular hair cells responding to tilt)
Otolith organs
Duplex theory of sound localization
Interaural time delay = 20-2k Hz (compare time delay)
Interaural intensity difference = 2k-20k Hz (compare loudness)
Fluid in scala vestibuli and scala tympani of inner ear
Perilymph
What are expressed in hair cells that are opened when they bend, leading to depolarizing the hair cells and inc NT release
Mechanoreceptors
Lesion in striate cortex
Complete blindness in one visual hemifield
Pushes fluid in the cochlea, bending stereocilia on the hair cells
Movement of oval window
Pressure at the oval window pushing perilymph into the scala vestibuli causes this to bulge out and release pressure
Round window membrane bulges out
Most synaptic input of spiral ganglion comes from this
Inner hair cell
Composition similar to CSF (high Na, low K) while this is opposite
Perilymph similar and endolymph opposite
Neuronal response property meaning similar characteristic freq between neurons
Freq tuning
Present in the superior olive and get info from both ears
Binaural neurons
These aren’t neurons but they package NTs (glutamate) and communicate with spiral ganglion bipolar neurons
Hair cells
Some info from vestibular system is sent directly here
Cerebellum
Without sound force amplification by the ossicles, what would everything sound like?
Like we are under water
Sound at high freq from one side of ear, localization of sound in horizontal plane
Interaural intensity difference
Columnar organization of cells with similar binaural interaction in auditory cortex
Tonotopy
Different freq band info in the auditory cortex causes this
Parallel processing, localization deficit
Low freqs use this for encoding sound intensity and freq
Phase locking
Axons leaving the MGN project to here via internal capsule in an array
Auditory cortex
What freqs vibrate the basilar membrane best?
High freqs vibrate it best
Involved in balance, equilibrium, posture, head, body, and eye movement
Vestibular system
Lesion in the auditory cortex
Normal auditory function
Med freqs use this for encoding sound intensity and freq
Phase locking and tonotopic maps
Most lesions here don’t cause deafness bc info from each ear is represented on each side
Auditory cortex
Lesions here can cause sound localization problems, small lesions could eliminate the ability to detect sounds of only a specific freq
Auditory cortex
Did research on the inner ear
AJ Hudspeth
Firing rates of neurons and numbers of neurons firing increase with these sounds
Louder sounds
This type of sound localization is based on reflections from the pinna
Vertical sound localization
Created bc endolymph electric potential 80 mV more positive than perilymph
Endocochlear potential
Send complex info to many ares to control head movement, eye movement, and stability
Central vestibular pathways
Low freq indicates what with pitch?
Low pitch
Sound force amplification by the ossicles create greater pressure at this than this to move fluids
Greater at oval window than tympanic membrane
Sensory system detecting sound and perceiving and interpreting nuances
Auditory system
Each is paired with another on the opposite side of the head for sensing all possible head rotation angles through push pull arrangements of vestibular axons
Semicircular canals
Hair cell in the organ of Corti are arranged along this
Basilar membrane
What does movement of fluid in the cochlea cause?
Bending of hair cell stereocilia
Moves a very small amount to amplify force through ossicles onto footplate
Tympanic membrane
Involve a push pull arrangement of vestibular axons
Semicircular canals
Sterocilia on hair cells of basilar membrane in the organ of Corti project into this fluid
Endolymph
Basilar membrane base vs apex?
Apex = wide and floppy Base = narrow and stiff
Distance between successive compressed patches in a sound wave
Cycle
Functions as line of sight fixed on visual target
Vestibulo-ocular reflex (VOR)
Used at low freqs for encoding sound intensity and freq when neurons fire to match the freq. Fire at same part of the waves
Phase locking
Neuronal response property meaning similar characteristic freq, diversity among cells
Isofrequency bands
Characteristic freq of neurons get more complicated here
Beyond the brain stem, like in the auditory cortex
Moves the ossicles that transmit to and amplify the force on the oval window
Tympanic membrane
Cells responding to different intensities and time delays are present here
Auditory cortex
This causes the basilar membrane to move upward, reticular lamina upward and sterocilia outward
Sound
Amplification by outer hair cells in the inner ear functions to do this
Sound transduction
One of these in the inner ear has one inner hair cell and numerous outer hair cells
Spiral ganglion fiber
Contain 3 sets 90 degrees to each other; gather info on rotation from moving cilia
Semicircular canals
Receives input from both cochlea (both ears)
Superior olive
This occurs so that hair cells remain sensitive to stimulation
Adaptation
Number of cycles per second expressed in units called hertz (Hz)
Sound freq
Involved in head rotation
Semicircular canals
Human song freq detection range
20-20000 Hz
Another name for the internal capsule
Acoustic radiation
Motor proteins of outer hair cells do this
Change length of outer hair cells
Are soft or loud sounds amplified more by the outer hair cells of the inner ear?
Softer
How are delay lines used to localize sound?
Impulses from the ears reach the olivary neuron at the same time leading to summation and an action potential in that spot, where the sound was closer to
Vestibular labyrinth contains these
Otolith organs and semicircular canals
Inward flow of this at sterocilia drives depolarization of hair cells while outward flow causes hyperpolarization
K
How do hair cells get hyper polarized?
Sterocilia bend back the other way
Required for outer hair cell movements
Prestin
Gathers sound waves and transmits the changes in pressure to the tympanic membrane
Outer ear (pinna)
What is the purpose of having outer hair cells?
They act as a cochlear amplifier (motor protein best at amplifying soft sounds)
Auditory pathway stages
- sound waves
- tympanic membrane
- ossicles
- oval window
- cochlear fluid
- sensory neuron response
Contains three fluid filled chambers
Cochlea
The function of this is to adapt ear to loud sound, understand speech better (good at suppressing low sounds and drowning out background noise)
Attenuation reflex (mid ear)
Involved in gravity and tilt
Otolith organs
High pitch indicates what with freq?
High freq
High freqs (above 5k) use this for encoding sound intensity and freq
Tonotopic maps
Hair cells are 45 mV more negative than this
Perilymph
Pressure at the oval window pushes perilymph into this
Scala vestibuli
Found endolymph movement bends basilar membrane near base, wave moves towards apex
Georg and Bekesy
Info from vestibular system is first sent here
Medial and lateral vestibular nuclei ipsilaterally in the brain stem
Middle chamber of cochlea containing hair cells and auditory neurons
Organ of Corti
Two ways sound is localized in the horizontal plane
- interaural time delay
2. interaural intensity difference
Act like a lever to amplify force
Ossicles
Audible variation in air pressure
Sound
Sensory system dealing with sense of balance, head and body location, head and body movements
Vestibular system
Senses rotations of the head, commands compensatory movement of eyes in opposite direction
Vestibulo-ocular reflex (VOR)
Connections from semicircular canals, to vestibular nucleus, to cranial nerve to do this in the VOR
Excite extra ocular muscles
Movement of the basilar membrane up and down causes these to bend in alternating directions
Hair cells
Neurons have characteristic these that they are the most responsive at; they prefer to respond at certain these
Freqs
How is the fluid in the cochlea moved?
In waves by the force of the ossicles on the oval window
Structure of these similar to corresponding visual cortex areas
A1 and secondary auditory areas
Some cells here respond to similar binaural stimuli
Auditory cortex
How are channels opened by hair cells?
Bending of sterocilia which are connected by tip links
The vestibular nuclei communicate with brain areas controlling various head movement and with the cortex through this
VP nucleus of the thalamus
Show encoding sound intensity and freq on the basilar membrane, spiral ganglion, and cochlear nucleus
Tonotopic maps
How do high and low intensity frees get perceived?
High intensity is louder than lower intensity
Bending of stereocilia on hair cells releases NT onto these that transmit info through APs on a path to the brain (first place we have APs)
Spiral ganglion neurons
The vestibular labyrinth uses these, like the auditory system, to detect changes
Hair cells
Fluid in scala media of inner ear
Endolymph
Channels in the inner ear are thought to be this
Mechanoreceptors (MECH) channels
Ultimate goal of the auditory pathway
Taking sound waves and representing them as APs
Response where onset of loud sound causes tensor tympani and stapedius muscle contraction
Attenuation reflex (mid ear)
What are the two ways we encode sound intensity?
- firing rates of neurons
2. number of active neurons (more neurons start to fire)
