Structures of the ear
This is responsible for helping the tympanic membrane amplify sounds through their lever-like movement within the middle ear.
Ossicles
The amplitude of sound waves can be measured and perceived as this
loudness
This a coiled shaped structure that contains 3 chambers and many smaller structures that all play an important role in sensation
Cochlea
Hair cells are so-called because of this, which is a hair-like protrusions from the apex of the cell
Stereocillia
_____________ form the cochlear portion of the vestibulocochlear nerve and as they exit the cochlea.
IHC afferents
This is responsible for collecting sound and funneling sounds into the middle ear
External auditory meatus = Ear Canal
This is perceived as the pitch of the sound
Bonus: how is High pitch perceived as?
Sound frequency
The basilar membrane is ____________ organized so that higher pitched sounds deflect the membrane at the base.
tonotopically
Hair cells have their base embedded in the __________ membrane and their apex touching the __________ membrane in the middle canal
Basilar & Tectoral
This area is critical for sound localization and binaural hearing
Superior olivary nucleus
This is critical for amplifying sounds (200 fold) as they vibrate in the air (in the external ear) to the fluid of the inner ear to reduce sound loss due to impedance/resistance.
Tympanum (Tympanic Membrane; aka the eardrum) - a thin ~50 μm diaphragm that vibrates in tune with the sound
Sounds can be made up of 1 frequency
Pure Tone
The _______ end of the basilar membrane is narrow & stiff, which is sensitive to higher frequency sounds
Basal
Hair cells depolarize with specific movements of the basilar membrane resulting in graded release of this neurotransmitter
Glutamate
The auditory pathway terminates in primary auditory cortex in the _______________.
superior temporal gyrus (Heschl’s gyrus)
Connected to the tympanic membrane at one end and to the ____________ at the other. The footplate of the stapes seals the ___________ from the middle ear side.
Oval Window
This is responsible for decoding frequencies of sounds as well as converting the mechanical pressure into a neural signal (sensory transduction)
The inner ear
This canal contains the organ of corti which is responsible for sensory transduction.
Bonus: Which fluid?
Middle Canal (Scala Media)
These receive the most sensory afferent innervation and carry the majority of acoustic information to the brain
Inner Hair Cells
Outputs of the inferior colliculi go to the ________________ of the thalamus.
medial geniculate nucleus (MGN)
(2 Structures) These connect to different ossicles to dampen the ossicles sound amplifying effect. This is a protective mechanism to prevent ear damage due to dangerously loud sounds
Tensor Tympani & Stapedius Muscles
Higher frequency sounds refract, and cause an _____________ where the head physically blocks the sound
Acoustic shadow
Lower frequency sounds (<3kHz) can bend around the head so the listener will report no sound intensity differences between the two ears.
Higher frequency sounds refract, and cause an “acoustic shadow” or “sound shadow” where the head physically blocks the sound
Vibration of oval window causes pressure changes in this fluid within the vestibular canal
perilymph
____________ is the ability of OHCs to change length in response to voltage input and modifies the extent of basilar membrane displacement
Electromotility
Extra fact: Cochlear amplification in basilar membrane allows for sharper tuning/sensitivity of the CF
Superior olivary nuclei pass auditory information, from both ears, to the _______________ —the primary auditory centers of the midbrain
inferior colliculi