Auditory System Flashcards
What are the three parts of the ear?
external, middle, and inner
What are the parts of the external ear?
the external canal
What are the parts of the middle ear?
auditory ossicles and auditory tube
What are the parts of the inner ear?
cochlea and cochlear duct
What are the auditory ossicles of the ear?
the malleus, incus, and stapes
What is the function of the auditory ossicles?
to transfer vibration of tympanic membrane to inner ear, increase force, and decrease amplitude
What is the inner ear lined with?
membranous structure that divides into chambers
Where is the vestibular window (oval) located?
between the stapes and the upper chamber of the inner ear
Where is the cochlear (round) window?
between the middle ear and the lower chamber
What is the function of the auditory tube?
to connect the middle ear with the oropharynx
What are the tensor tympani muscle and the stapedeus muscle important for?
keeping the auditory ossicles in place
What is the tympanic membrane also known as?
the ear drum
What is the scale vestibuli?
the upper chamber of the cochlea
What is the scale tympani?
the lower chamber of the cochlea
What is the basilar membrane?
the seperation between the scale tympani and the cochlear duct
What is the cochlear duct?
the middle chamber of the cochlea
What is the osseous labyrnth?
the bony part of the cochlea
What is the membranous labyrinth?
the part that divides the cochlea into its three parts
What is the scale vestibuli and scale tympani filled with?
perilymph
What is the cochlear duct filled with?
endolymph
Where is the organ of corti?
in the cochlear duct on top of the basilar membrane
What is the organ of corti made up of?
stereocilia and supporting cells
Where are the stereocilia imbedded?
in the tectorial membrane
What are the spiral ganglia?
the axons that make up the auditory nerve that send axons into the stereo cilia
When the wave caused by sound reaches the scale tympani, what happens?
the basilar membrane moves up and down to move the tectorial membrane
What is the size of the base of the basilar membrane?
narrow and taut
When does the base of the basilar membrane move?
when high frequency sounds reach it
What is the size of the apex of the basilar membrane?
wide and floppy
When does the apex of the basilar membrane move?
when low frequency sounds reach it
What happens when hair cells bend?
K channels open, depolarization opens Ca channels, and a neurotransmitter is released
What is the function of the cochlear nerve?
take information from the sensory hair cell to the cochlear nuclei
What is the first stop for all auditory info?
the cochlear nuclei
Is the cochlear nuclei unilateral or bilateral?
receives information unilaterally (ipsilateral) but sends information contralaterally
What does the cochlear nuclei send information to?
the dorsal nucleus of the trapezoid body on both sides and to the acoustic stria (which ascends on the contralateral side of the body)
What sides does the dorsal nucleus of the trapezoid body get information from?
both sides
What sides does the caudal colliculus get information from and from what structures?
both sides: the acoustic stria of the contralateral side and the dorsal nucleus of the trapezoid body of the ipsilateral side
Why is there bilateral auditory input?
so that we can localize sound
What is the acoustic startle reflex?
the reflexive head towards sound
What structures are involved in the acoustic startle reflex?
caudal colliculus, rostral colliculus, tectospinal tract, and spinal lower motor neurons
What type of information goes to the caudal colliculus?
auditory information
What type of information goes to the rostral colliculus?
visual information
How does the rostral colliculus work in the acoustic startle reflex?
it coordinates with the eyes to move towards the sound
What is the middle ear reflex?
protection of the inner ear from loud sound by limiting movement of the auditory ossicles
What structures are involved in the middle ear reflex?
cochlear nuclei, dorsal nuclei of the trapezoid body, and the stapedius muscle
What is the pathway of the middle ear reflex?
sound causes the stereocilia to send information to the cochlear nuclei, the cochlear nuclei transmits information to the dorsal nucleus of the trapezoid body, the trapezoid body sends information to the motor nucleus of the facial nerve, the facial nerve then tells the stapedius to either contract or relax depending on the sound
