Auditory System Flashcards
What three sections is the ear divided into?
Outer, middle and inner ear
Which cranial bone is the ear embedded into?
Petrous portion of temporal bone
What are the 3 functions of the outer ear?
A) To capture sound and to focus it on the tympanic membrane.
B) To amplify some frequencies by resonance in the canal
C) To protect the ear from external threats
What anatomical structures reside within the outer ear?
The pina (auricle) and the external auditory canal (meatus).
What function is performed by ear cilia?
Cilia prevents external elements from entering into the ear
What is the main function of the middle ear?
Amplification of sound
How does the middle ear amplify sound?
Focusing vibrations from the tympanic membrane to a smaller surface area (oval window). The change in surface area means the pressure is increased
Using leverage from the incus-stapes joint to increase the force on the oval window.
What structure connects the outer ear with the middle ear?
The tympanic membrane.
What is the oval window?
The oval window (or fenestra vestibuli) is a membrane-covered opening from the middle ear to the cochlea of the inner ear. Vibrations that contact the tympanic membrane travel through the three ossicles and into the inner ear.
What are the three ossicle bones?
Stapes, incus and malleus
What is the function of the inner ear?
The inner ear is concerned with transducing vibration into nervous impulses, producing a frequency and intensity analysis of the sound.
What structure within the inner ear is associated with hearing?
The cochlea
How many compartments comprise the cochela?
3
What are the three compartments of the cochlea?
Scala vestibuli
Scala tympani
Scala media
Which two cochlea structures contain perilymph?
Scala vestibuli
Scala tympani
Which ion concentration is high within the perilymph?
Sodium
Which ion concentration is high within the endolymph of the scala media?
Potassium
Which hearing organ is located within the scala media?
Organ of Corti
Within which structure does the Organ of Corti reside?
Basilar membrane
How is the basilar membrane arranged?
Arranged tonotopically, using the same principles as a xylophone
-Sensitive to different frequencies at different points along its length.Therefore, cell stimulation occurs at specific frequencies.
At high frequencies, where does the basilar membrane vibrate the most?
At the base.
At low frequencies, where does the basilar membrane vibrate the most?
At the apex, low frequency cells within the apex are participating in the transduction of sound.
Which hair cells comprise the organ of Corti?
Inner hair cells (IHC)
Outer hair cells (OHC)
How are inner hair cells arranged?
Arranged on one column
How are outer hair cells arranged?
Arranged on three columns
Which membrane is in constant contact with the outer hair cells?
The tectorial membrane.
What is the function of inner hair cells?
Transmit 95% of the afferent information of the auditory nerve, their function is the transduction of the sound into nerve impulses.
What is the function of outer hair cells?
Behave as an amplifier, the larger the vibration the more the basilar membrane is displaced (Membrane proteins contract, altering the lengths to allow the tectorial membrane to be brought closer to inner hair cells.)
Transmit 95% of efferents of the auditory nerve, modulation of the sensitivity of the response.
What hairs reside on the surface of hair cells?
Stereocilia
The deflection of the stereocilia towards the longest cilium will cause what?
Mechanical stimulation causes opening of the potassium ion channels.
The ionic interchange depolarises the cell, and the neurotransmitter is liberated onto the afferent nerve.