hearing pt2 Flashcards
What is the human amplitude range?
0 dB - 120 dB (130 dB = pain level)
What is the transmission pathway of sound to the inner ear?
air –> external auditory canal –> tympanic membrane (ear drum) –> ossicles (malleus, incus, stapes) –> oval window of cochlea –> vibration of cochlear fluid –> basilar membrane of cochlea
What occurs during the resonance of the basilar membrane?
- Vibration of oval window -> perilymph vibration
- For 20 - 20,000 Hz only, vibration of vestibular membrane
- Vestibular membrane vibration -> endolymph vibration
- Endolymph vibration -> vibration of basilar membrane
- Basilar membrane fibers have different lengths, thicknesses, and tensions like piano strings.
What is the significance of the different fibers of the basilar membrane?
Different fibers of the basilar membrane have different natural frequencies, and specific parts vibrate only at specific frequencies (pitch).
How are hair cells of the Organ of Corti excited?
Cochlear hair cells rest on the basilar membrane, containing stereocilia that project into the tectorial membrane. Basilar membrane vibration causes hair cell vibration, leading to the opening/closing of channels and depolarization/hyperpolarization of the cochlear nerve.
How is pitch perceived?
Pitch is perceived based on the location of vibration on the basilar membrane.
How are differences in loudness perceived?
As amplitude increases, more hair cells of the basilar membrane (with the same pitch) are activated.
What is the superior olivary nucleus?
It is the first point where sound from both ears comes together, processing relative intensity and timing of sound waves.
What is the vestibule in the inner ear?
The vestibule is a bony cavity between the cochlea and semicircular canals, containing saccule and utricle.
What are maculae?
Maculae are patches of supporting cells and hair cells along the utricles and saccules that respond when bent.
What is the function of otolithic membrane?
It is a jelly-like sheet that abuts the stereocilia of hair cells, with otoliths (ear stones) resting on top.
How do maculae respond to horizontal acceleration?
The maculae of the utricle are in the horizontal plane; hairs bend when motion is forward or backward.
How do maculae respond to vertical acceleration?
The maculae of the saccule are in the vertical plane; hairs bend when motion is up or down.
What are semicircular canals?
Three bony ‘hula-hoop’ extensions of the vestibule in three different planes.
What is the crista ampullaris?
Like maculae, it contains hair cells that respond to the flow of endolymph in the canals.
What is the cupula?
A gelatinous ‘cap’ into which hair cells project, similar to the otolithic membrane.
How is angular acceleration monitored?
Movement of the head in a non-linear (circular or angular) direction is monitored by the three semicircular canals.
What is vestibular nystagmus?
Movement of the eyes to remain fixed on an object when on a merry-go-round.
What is vertigo?
A false feeling of gravity or motion.
What is the equilibrium pathway in the brain?
Activated hair cells of crista ampullaris send signals via afferent axon fibers (vestibulocochlear nerve) to the vestibular nuclear complex or cerebellum.
What role do vestibular nuclei play?
They receive input from eyes and somatic proprioceptors, coordinating information to help control motion of eyes, neck, and limbs.
What role does the cerebellum play in equilibrium?
It receives input from eyes and somatic proprioceptors, coordinating information to help regulate head position, posture, and balance.
