Quiz 3 Flashcards
Gain provided by Middle Ear
60 dB
Acoustic Stapedial Reflex
-Stapedial muscle contracts in response to intense, long duration sounds
-Middle ear reflex by tone above 85 dB SPL
-Bilateral reflex
-May improve hearing in presence of ongoing loud sounds and head noises (speaking/chewing)
-Controlled by CN VII
-Tightens ossicular chain
Number of cochlea turns
2.5
3 compartments of the cochlea
-Scala Vestibuli (upper)
-Scala media (middle with neural components)
-Scala tympani (lower)
-Fluid in scala vestibuli is displaced by the movement of the stapes against the oval window. It travels to the apex of the cochlea and then travels back to the round window via the scala tympani.
-This causes basilar membrane to move
Tonotopic Organization
-Pitches the basilar membrane (and other structures) are arranged in order
-BM decomposes complex sounds into their component sine waves
Traveling Wave Envelope
-Low frequency almost all of BM undergoes displacement
-High frequency- restricted region is displaced
Hair Cells
First neural component of auditory system
Hair Cell Types
Three rows of outer hair cells, a ridge, and then one row of inner hair cells
Inner Hair Cell Role
transduce sound into a neural impulse to the brain
-send signals to spiral ganglion
Prestin shape change
The voltage-sensitive shape change feeds mechanical energy back into the basilar membrane
OHC role
causes both an increase in amplification and frequency selectivity
-OHC allow you to focus in on frequency regions you care about
Population coding
-Each neuron responds to the same phase of a sound
-Each neuron does not respond to the same period of the sound
-Timing of action potentials can tell you what the frequency was
Ratio of IHC to spiral ganglion
1-to-10 ratio
Cochlear Nucleus
-This is the first place where info from two ears are combined
-First stop for auditory information in the brainstem
-First major transformations of the signal occur here (Onset and Offset neurons)
Superior Olivary Nucleus
-This structure is critical for azimuth based localizaton
-Plays a large role in descending pathway (jumping off point to OHC)
-Initiates pathways for processing interaural time differences
Lateral lemniscus
the tracts formed of axons that project up to the midbrain from the superior olivary nucleus
Inferior Colliculus
-Lateral lemniscus projects here
-Receives somatosensory inputs
-End of pathway for encoding interaural time differences
Medial Geniculate Body
-Thalamic relay for auditory information
-Last stop before auditory cortex
-Interactions between auditory and visual information here
Heschel’s Gyrus
-Auditory Cortex largely resides in superior region of the temporal lobe
-Primary auditory cortex located in Heschel’s gyrus
-First cortical processing of sound happens here
What and Where pathways
-What: Identifying what you heard
-Where: Identifying where it came from
Descending Pathway
-Allows you to selectively attend to sounds
-OHC most directly influenced by superior olivary nucleus
-Skips largely over cochlear nucleus on the way down
Lateral olivocochlear pathway
efferents inhibit inner hair cell function
Medial olivocochlear pathway
efferents inhibit outer hair cell function
Both olivoochlear pathways
Reduce responses to soft sounds
