Glossary of SFS - Auditory

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Function of superior olivary nucleus
Localizaiton of sound
Inferior colliculus function
localization of sound
Medial geniculate function
main thalamic-relay point
Heschl's gyrus function
auditory cortex
What kind of wave is sound?
Sinusoidal, involving pressure increases and decreases. Fluctuating between compression and rarefaction in an elastic medium.
Normal frequency range in humans.
20 Hz to 20 kHz
With respect to loudness, there is approximately an equal increment between a ___ fold increase in pressure.
a. Most sensitive frequency.
b. Damage occurs at what loudness?
a. 1 kHz
b. 120 dB
What is the central auditory pathway (step-by-step)?
Cochlea > cochlear nerve > cochlear nucleus. From here, some fibers cross in trapezoidal body, or go straight to inferior colliculus > medial geniculate > cortex. This is a bilateral system.
Function of outer ear.
Collection of sound, focusing sound on eardrum
Functions of middle ear.
Air-filled, 3 bones. Transmission of sound from eardrum to oval window. AMPLIFICATION!!!
Cochlea function.
Convert mechanical energy to electrical.
What goes on in middle and inner ear?
Vibrations cause ossicles to oscillate, sending pressure waves into perilymph chambers. Pressure eventually released at round window. Scala media has endolymph.
Main transduction organ sitting on the basilar membrane and semi encapsulated by the tectorial membrane.
Organ of Corti
Ca dependent synapse with vesicle fusion and glutamate release.
Hair cell synapse
Nerve fibers from the brain heading toward inner and outer hair cells.
2 olivocohlear efferents
Innervate inner hair cells.
Primary afferents
Innvervate outer hair cells.
Secondary afferents.
Convergence of these fibers. Each cell has 10 outputs to the CNS.
Afferent fibers from inner hair cells.
Divergence of these fibers. Afferents of about 10 of these cells connect.
Afferent fibers from outer hair cells.
Change shape (contract/expand) when depolarizaed. Useful for sensitivity, dampening movements, and amplification.
Outer hair cells.
Loudness/intensity is encoded by?
Firing frequency of the APs in the nerve. Linear relationship. Saturation at around 500 Hz
Encoding frequency depends on what 2 mechanisms?
location of the cell on the basilar membrane and phase locking
The mehcanism where if a sinusoidal wave brings info into the membrane and excites the hair cells, the output is locked to the phase of the waves.
Phase locking
What can shift the dynamic range of afferent nerve fibers?
Outer hair cells stimulated directly by efferents.
Process of outer hair cells getting eliminating background noise.
In what 2 ways are outer hair cells important?
Amplification of basilar membrane and changing sensitivity of the inner hair cells and their afferent connections to the CNS.
Because the cochlear n. is split and sends info to lots of different structures, the inner hair cells have ______ afferents.
Mechanism in superior olive for knowing direction from where sound wave is coming from
interaural timing differences, which is dependent on angle to midline.
In the medial superior olive, cells respond best with _______ input and _______ and _______ innervation.
Bilateral; ispilateral; contralateral. Yes, a redundant answer.
When will cells in the superior olive respond better?
When a signal is less intense from 1 ear than from the other ear.
Input of the inf. colliculus
lateral lemnisus
Cells in inf. colliculus are sensitive to what?
Differences in aural delay and intensity. Thought to be involved in localization
Main relay station to get info to cortex.
Med. geniculate. Some cells sensitive to auditory, some multimodal.
Location of main part of auditory cortex
temporal lobe
Primary auditory cortex in Heschl's gyrus?
Area 1
Order of cell arrangement in auditory cortex
Processing of information in auditory cortical neurons.
Across frequency, location, and intensity.
Area critical to language production and speech production.
Broca's area
Area critical for speech comprehension
Wernicke's area
Area of basilar membrane responding to high frequencies.
Near oval window. narrow and less flexible.
Area of basilar membrane detecting low frequencies.
Near apex of cochlea. Wider and more flexible.
Present throughout the auditory system. Arrangement of cells to map out tones.
Tonotopic map
Oscillates differently for different frequencies
Basilar membrane.
Causes transduction of sound
Shearing forces between the cilia and the tectorial membrane
Where is endolymph derived from? Where does it reside? What is unique about it?
Stria vascularisi, scala media, high K+ concentration
Primary cells responsible for collecting auditory information
Inner hair cells
Cells responsible for modulation of signal
Outer hair cells
Where does potassium enter the hair cell?
Through the stereocilia along a HUGE driving force.
Dissipates K depolarization
Activation of voltage gated K channels allowing extrusion of K into the perilymph.
Largest cilia
Shearing between tips of cilia and tect. memb. cause...?
Tension on tip link from pressure changes and opening of mechanosensitive K channels
Important in encoding frequency
Position of hair cell along basilar membrane and properties of basilar membrane. All cells have threshold close to the baseline of sensitivity.
Allow a person to bypass hair cells by directly stimulating afferent nerve fibers. A microphone will collect sound and split it into various frequencies and send stimulation to appropriate part of basilar membrane.
Cochlear implant

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