Physiology of Auditory and Vestibular Systems Flashcards
What is the ion distribution for endolymph?
High [K+}
Low [Na+]
What is the ion distribution for perilymph?
Low [K+]
High [Na+]
Where do higher frequency sounds displace the basilar membrane?
Near oval window where basilar membrane is narrow and stiff
Where do low frequency sounds displace the basilar membrane?
Near helicotrema (tip of cochlea) where the membrane is wide and flexible
What CN transmits central axons from the primary auditory neurons of the spiral ganglion to the brainstem?
CN VIII (vestibulocochlear)
What mechanoreceptors are rich in actin?
Hair cells
What motion of the hair cell stereocilia causes depolarization?
Deflection towards the Kinocilium
What motion of the hair cell stereocilia causes hyperpolarization?
Deflection away from the kinocilium
What neurotransmitter is released by the hair cells?
Glutamate
What channel on the stereocilia allows entry of K+?
TRPA1
What part of the cochlea is the stria vascularis located in? What is its function?
Scala media
Maintains electrochemical properties of endolymph by pumping K+ in
What cells act as the primary source of auditory information?
Type 1/Inner hair cells
What is the function of the 3 rows of outer hair cells?
Act as amplifier, boost mechanical vibrations of basilar membrane
What protein allows outer hair cells to be contractile?
Prestin
What is the source of otoacoustic emissions?
Outer hair cells (Type II)
What type of hair cells both send afferent neurons and receive efferent neurons?
Outer hair cells (send Type II afferents)
What hair cells send Type I afferent neurons?
Inner hair cells
What is the function of the dorsal cochlear nuclei?
Integrate acoustic information with somatosensory information to localize sound
What is the function of the ventral cochlear nuclei?
Process temporal and spectral features of sound
What part of the brainstem is the first site where information from both ears converge? What is this convergence called?
Superior olivary complex
Binaural processing
What structure is important for generating a map of interaural intensity differences to localize sound?
Lateral Superior Olivary Nucleus
What structure is important for generating a map of interaural time differences to localize sound?
Medial Superior Olivary Nucleus
Which colliculus is involved in localizing sound vertically? Horizontally?
Superior colliculus - Vertical
Inferior colliculus - Horizontal
What is the role of the medial geniculate nucleus of the thalamus in the auditory pathway?
Processing speech inflection
What is the role of the primary auditory cortex in the auditory pathway?
Conscious perception of sound (volume, rate of frequency modulation)
What region of the primary auditory cortex responds to low frequency? High frequency?
Rostral responds to low frequency
Caudal responds to high frequency
What areas are contained within the auditory (secondary) association cortex (A2)?
Broca’s, Wernicke’s
Which hair cells receive medial olivocochlear efferents?
Outer hair cells
What efferent fibers do the inner hair cells receive from the superior olivary complex?
Lateral olivocochlear efferent fibers
What efferent input fibers are responsible for reducing the response to noise and shifting response to higher sound levels?
Olivocochlear Efferents
What parts of the middle ear send efferents to the auditory system? From what cranial nerves?
Tensor Tympani to malleus (CN V)
Stapedius to stapes (CN VII)
What is the main function of middle ear efferents?
Prevent damage - decrease transmission of sound (act at low frequencies)
Evoked otoacoustic emissions are used for what?
Test for hearing loss in newborns (no emissions if damage present)
Tinnitus
Ototoxicity
Damage to what structures causes sensorineural hearing loss?
Outer hair cells, especially at the base end (high frequency) of the cochlea
Damage to what structures will cut off sensorineural auditory input to the CNS?
Inner hair cells
What is a cochlear prosthesis?
Electrode array threaded through the cochlea to stimulate nerve fibers and provide sound
What types of rotation are detected by the horizontal, posterior, and anterior semicircular canals?
Horizontal - rotation in horizontal plane
Vertical - rotation backwards in the vertical plane (falling backwards)
Anterior - rotation forwards in the vertical plane (falling forward)
When falling backward, what is the reflex of the eye muscles?
Posterior semicircular canal detects falling backward => Superior oblique M. is activated, inferior oblique inhibited => Eyes move down to maintain gaze on horizon
When falling forward, what is the reflex of the eye muscles?
Anterior semicircular canal detects falling forward => Superior rectus m. activated, inferior rectus muscle inhibited => Eyes move up to maintain gaze on horizon
What is the basic action of cortex and cerebellum on the vestibulooptic reflex?
Inhibitory - allows for voluntary motion
