BS545 - Auditory
Terms
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- What is the name of the first first membrane an air pressure wave will see in the ear?
- Tympanic membrane
- What are the names of the bones? Start with the one touching the tympanic membrane.
- Malleus bone -> incus -> staples
- What does the footplate of the stapes cover?
- A hole in the temporal bone called the oval window.
- What structure is found on the other side of the oval window?
- Bony laybrinth
- What is fluid is contained within the vetibule of the bony labyrinth?
- perilymph
-
Regarding hearing, to what structure does the vetibule lead?
What hearing structure is found in this area? -
cochlea
organ of Corti - What liquid surrounds the hair cells?
- endolymph
-
What are the three cavities within the organ of Corti?
In which of these are the hair cells located? -
Scala vestibuli, Chochlear duct,
Scala tmpani
Chochlear duct -
The hair cells are attached to this structure: ______.
What structure touches the top of the outer hair cells and may touch the top of the inner hair cells? -
Baslar membrane
Tectorial membrane - Name the structures found in the organ of Corti.
-
Tectorial membrane
Outer and inner hair cells
Basliar membrane
Fibers of choclear nerve - What happens after the pressure wave results in the movement of the oval window?
- The stapes goes in-out-in, the secondary tympanic membrane (round window) goes out-in-out, and the basilar membrane goes down-up-down. The result is vibration of hair cells and the generation of an electrical signal.
- What is the name of the structures attached to a hair cell which result in electrical activity when moved?
- Stereocillum
- What happens as the sterecillum of hair cells are moved?
- Each stereocillum is mechanically linked to its neighbor by a tip link. When the stereocillum is bent, the tip link will open a gated K+ channel on a neighboring stereocillum. The inflow of K+ leads to depolarization of the hair cell which results in an influx of Ca++. This in turn releases glutamate on the basilar side of the cell and this leadds to stimulation of the postynaptic cochlear nerve.
- What special effect is exhibited by outer hair cells?
- They are contractle. Vibration of their basilar membrane results in a change of their membrane potential. This in turn increases the stimulation of inner cells, i.e. amplifies their signal.
- How is a tonotopic distribution obtained in the cochlear duct?
- The basilar membrane increases in thickness versus distance along the chochlear duct. Higher frequencies will tend to resonate at the thinner regions of the membranes.
- What is the pathway followed by the vestibulocochlear nerve as it leaves the Cochlea?
- Synapse in Cochlear nuclei in the pons -> synapse in the inferior colliculus of midbrain -> synapse in the medial geniculate nucleus of the thalamus -> synape in primary auditory cortex.
- What is the pathway which leads to cochlear tuning?
- vestibulocochlear nerve -> synapse coclearn nuclei -> synapse superior olivary nucleus of pons -> synapse in cochlea.
- What is the pathway for the tympanic reflex?
- Vestibulocochlear nerve -> syanpse superior olivary nucleus of pons -> CN V3 and VII -> synapse tensor tympani and stapedus muscles.
- What is the pathway for the auditory reflex (head turning)?
- Vestibulocochlear nerve -> synapse inferior colliculus of midbrain -> synapse neck muscles.
- What is conduction deafness?
- There is some type of blockage or mechanical problem in delivering the sound to the labyrinth.
- What type of deafness has damage to the hair cells, cochlear nerve firbers or cochlear nuclei?
- Sensorineural deafness
- What two mechanisms does the brain use to perform sound localization?
-
1) Shadowing (head attenuates signal from one side)
2) Distance (time of arrival differences) - What structure in the brainstem compares signals fromt eh right and left ears to identify the direction from which a sound is coming?
- Superior olive
- What is the major ascending auditory pathway of the brainstem? Where does it mostly terminate?
-
lateral lemniscus
inferior colliculus - What structure carries fibers fromt eh inferior colliculus to the medial geniculate nucleus?
- brachium of inferior colliculus
- What three things are done by the superior olive?
-
1) Involved in cochlear tuning
2) Controls tensor tympani and stapedius mm
3) Compares signals from teh right and left ears to identify the direction from which sound is coming.