Audition Part 1 Flashcards
What are the three parts of the ear?
external, middle, inner ear
What is the auricle of the external ear made of?
elastic cartilage covered with skin and sebaceous glands associated with hair
What are six regions of the external ear?
helix, antihelix, tragus, antitragus, concha, lobule
What are ceruminous glands and what is their purpose?
modified apocrine glands that secrete cerumen. this protects the ear canal from physical damage and microbial invasion
What is ear wax made up of?
cerumen and desquamated meatal cells
What 5 nerves innervate the external ear (sensory innervation)?
greater auricular (majority of the auricle), lesser occipital (helix), auriculotemporal (from V3, medial auricle), Facial nerve (CN7, concha), Vagus (CNX, external auditory meatus and concha)
What nerve innervates the middle ear?
The glossopharyngeal (CN IX)
What is in the middle ear?
The tympanic cavity, ossicles, their muscles and the auditory (eustachian) tube that connects to the nasopharynx
What muscles open the auditory (Eustachian) tube?
levator/tensor palati and the salpingopharyngeus muscles
What are the three ossicles named from the tympanic membrane to the oval window?
malleus, incus, stapes
What are two muscles in the inner ear? What nerve innervates them?
Tensor tympani (dampens low frequency vibrations) innervated by V3 Stapedius innervated by VII
What is the chorda typani? What does it do?
nerve that branches from facial nerve to join V3 in the tympanic cavity. contains sensory to anterior tongue, parasympathetics to submandibular and siblingual salivary glands.
What nerve is possibly impacted by otitis media?
chorda tympani (of CN VII, facial nerve)
What is the umbo?
central depression on the tympanic membrane created by tension from the malleus
What are five visual landmarks in auriscopic view?
malleus, incus, stapes, cone of light and flaccid/tense parts
What is otitis media?
infection of the middle ear, fluid builds up in the tympanic cavity, can be drained by a tube inserted into the membrane
How can otitis media lead to meningitis or brain abscesses?
infection can spread through the tegmen tympani and through the dura into the brain from the middle ear
What is cholesteatoma?
a skin cyst from the ear canal that migrates through the tympanic membrane, grows out of control and damages the middle ear and mastoid
What is the inner ear made of?
the cochlea
What three structures can the cochlea be divided into?
the chochlear duct (scala media), the scala vestibuli and the scala tympani
What two membranes separate the cochlear duct from the other spaces?
the vestibular and basilar membranes
What kind of fluid is in the cochlear ducts and what cells secrete it?
endolymph (high K+), made by stria vascularis
What kind of fluid is in the scala vestibuli and scala tympani?
perilymph (high Na+)
Where to the scala vestibuli and scala tympani meet?
the apex (helicotrema) of the cochlea
How is sound transduced through the external, internal and middle ears?
external (air waves); middle (ossicle vibrations); internal (fluid vibrations)
What is the passage of vibrations in the internal ear?
oval window –> perilymph of scala vestibuli –> perilymph of scala tympani –> round window
What is the organ of corti made of?
tectorial membrane, inner and outer non-neural receptor cells (hair cells) with stereocilia (microvilli) that activate the cochlear nerve
How does sound in the scala tympani bend the hair cells?
vibrations in the fluid vertically push the basilar membrane, thereby pushing the hair cells against the tectorial membrane
How does the bending of hair cells initiate neurotransmitter release?
physically gated K-channels
How is the frequency (pitch) of sound coded in the cochlea?
by differences in basilar membrane stiffness and width from base to apex (tonotopic representation of sound)
What is the resonance frequency?
a unique point along the basilar membrane at which a sound wave has maximum amplitude
95% of sensory neuron axons innervate what type of hair cells?
inner hair cells
The primary sensory cells transmitting sound information to the brain are:
inner hair cells
The cochlear nerve projects inner cell activity to _____
the dorsal and ventral cochlear nuclei in the medulla
What is the function of outer hair cells?
to amplify oscillations from the basilar membrane, enhancing inner cell responses. allows distinction of frequencies that are close together
overstimulation of outer hair cells can cause:
oto-acoustic emissions OAEs- return vibrationsout through the tympanis membrane
Loud noise mostly destroys what cells?
outer hair cells
What kind of sound does the dorsal cochlear nucleus analyze?
quality of sound and distinction of tiny frequency differences
What kind of sound does the ventral cochlear nucleus analyze?
localization of sound
from the cochlear medullar nuclei, what is the pathway of auditory information?
lateral lemniscus –>inferior colliculus–>medial geniculate–>primary auditory cortex in the temporal lobe
What difference helps localizes high frequencies?
time difference
What difference helps localize low frequencies?
intensity difference
auditory information that goes to the ventral cochlear nucleus also goes to the_____
superior olive
Where does the inferior colliculus receive input from?
auditory cochlear nuclei and superior olive- for somatosensory information, head and sound localization
Where does the medial geniculate body of the thalamus do?
projects sound to the cortex tonotropically
Where is the primary auditory cortex?
superior temporal lobe
What is the ventral stream of auditory association cortices for?
speech comprehension in the temporal lobe, largely bilateral
What is the dorsal stream of auditory association cortices for?
sensory-motor integration of vocal articulations. projects to the parietal-temporal junction and the frontal lobe, Brocas area (left dominant)
What does Wernickes area do?
integrates auditory, visual and somatosensory aspects of language- understanding speech, writing, symbolism
How is wernickes area connected to Brocas area?
via the arcuate fisciculus
What is Brocas area?
the speech motor area in the frontal lobe
higher levels of auditory activity (singing, music, speech, etc) involve what lobes of the cortex?
bilateraly use of the motor, parietal and temporal cortices
Music can activate emotions in the limbic cortices. Name 5 areas that are involved in this emotional pathway.
amygdala, auditory cingulate cortex (response after OFC), orbitofrontal cortex (is it good/bad?), hippocampus and the insula
How do efferent olivocochlear neurons cause auditory selective attention?
efferent olivocochlear neurons from the superior olive terminate on outer and inner hair cells to regulate their sensitivity and responses to sound. controlling outer hair responses to the basilar membrane
Efferent control in stimulated by:
sensory input from the cochlear nuclei, reticular formation (locus ceruleus-norepi), auditory cortex
Conductive deafness is due to:
damage to the tympanic membrane, ossicles, etc
Sensorineural deafness is due to:
damage of the cochlea or cochlear portion of CN VIII
What are four possible causes of tinnitus?
disease processes (eg TMJ dysfunction, damage to hair cells), neurological, infection, drug side effect
Subjective tinnitus can be caused by what kind of abnormal acitivty?
changes to the primary auditory cortex or the dorsal cochlear nucleus conditioning
What is somatic tinnitus?
a form of subjective tinnitus usually due to two or more causes
What neural areas are involved in somatic tinnitus?
trigeminal nerve and dorsal root ganglia, the spinal trigeminal nucleus, dorsal column nuclei and cochlear nuclei
