Auditory System Flashcards
What is the function of the conductive apparatus?
Transform sound pressure waves into mechanical vibrations
What is the path of sound from environment to inner ear?
External auditory meatus
Tympanic membrane
Ossicles: malleus, incus, stapes
Oval window
What is the function of the ossicles?
Amplify the force at the oval window
Compensate for difference in impedance between air filled middle ear and fluid-filled inner ear
What is the function of the round window?
Point of relief that allows fluid to vibrate the oval window
What is otosclerosis?
Footplate of the stapes gets locked in place as a result of bone growth around the annular ligament
What does Weber’s test tell you, assuming the patient complains of R hearing issues?
If complaining of R problems:
Louder on L: sensorineural
Louder on R: conductive hearing loss
What is a positive Rinne’s test?
Sound is heard louder outside the ear vs. on mastoid process (AC > BC)
What does a negative Rinne test indicate?
conductive hearing loss on the side of testing, or sensorineural on the opposite side (CHECK)
In the weber test, which side is the sound louder on for a) sensorineural hearing loss and b) conductive hearing loss?
SN: Unaffected side
Conductive: damaged side
What are sensory receptors in the cochlea, and where are they located?
Hair cells in the organ of Corti
What is the make-up of receptors in the organ of Corti?
Inner: 1 row of hair cels
Outer: 3 rows of hair cells
Which types of hair cells are embedded in the tectorial membrane?
Stereocilia of the outer hair cells (NOT inner hair cells)
How does the cochlea work to transmit sound?
as basilar membrane vibrates, stereocilia are bent: outer hair cells by shearing action, inner hair cells by fluid movements
What is the greatest danger to hair cells?
Excessively loud sound!
Do auditory hair cells have kinocilium?
No, lost during development and replaced by basal body
What is the arrangement of stereocilia in auditory hair cells?
Clusters of stereocilia at their apical end, ordered in terms of size
Which direction of bending stereocilia leads to depolarization?
Toward the basal body
How do stereocilia depolarize the neuron?
Bending of the stereocilia opens mechanosensitive ion channels, depolarizing current by opening K+ channels
What is the function of inner hair cells?
Detection of sound
What is the function of outer hair cells?
Participate in amplifying and dampening of the sound stimulus
How do outer hair cells move in synchrony with sound-evoked receptor potentials?
Motor protein prestin allow them to contract and elongate!
Why are ototoxic agents important?
They can significant impair auditory and vestibular functions
What is an example of ototoxic agents?
Aminoglycoside antibiotics
What is the cochlea innervated by?
VIII
