Wed fitz ear prerecorded lecture Flashcards
4 nerves that innervate pinna
great auricular
auricular branch of vagus
auriculotemporal branch of V3
lesser occipital
special glands in the ear canal. how do they work
function of what they make?
ceruminous glands
combine sebaceous fluid with aqueous fluid to make cerumen.
thought to be antimicrobial
how does conductive hearing loss come about
when the tympanic membrane doesn’t work
e.g. you pushed wax up against it.
lowest point of concavity of the tympanic membrane
umbo
two primary components of middle ear
ossicles - bones that connect the tympanic membrane to the oval window of the middle ear. physical connection that allows the transmission of sound from the tympanic membrane to the cochlea.
z
3 main parts of the ossicle bones
malleus, incus, stapes.
stapes attaches to the oval window of the middle ear
two muscles that connect to ossicle bones
what do they do
innervation?
tensor tympani - connects to malleus. innervated by V3
Stapedius - facial nerve
makes ossicle bones tense, harder to vibrate.
involved in the sound reflex: they effect middle ear transmission, may be involved in protection
auditory tube
connects to pharynx, keeps air pressure equal between external autidory canal and the middle earspace
Main function of the middle ear
3 mechanisms of this
AMPLIFIES VIA IMPEDENCE MATCHING
(minimize loss of energy that occurs at and air to water interface. (cochlea is full of fluid) normally water reflects 99.9% of sound that hits it (40-55dB))
40-55 Db is the loss in hearing of someone with conductive hearing loss.
1 - tympanic membrane»_space;> oval window, all the forces applied to the tympanic membrane is transferred to a smaller window amplifying the sound
2 - malleus lever arm»_space;> incus
3 - tympanic membrane buckles, force concentrated at umbo
what physical characteristics of the middle ear determine the mass and stiffness of it?
mass - bones (mass transmits low pitch, inhibits high pitch)
stiffness - volume of air space (transmits high pitch, inhibits low pitch)
two labyrinths of the inner ear and what they contain
bony labyrinth - contains Na rich perilymph
membranous labyrinth (inner labyrinth) - contains unique K rich endolymph. hair cell apical surface is in the endolymph. Doesn’t open out into anything - is completely enclosed.
cochlear aquduct
connects perilymph to the csf, mechanism for communication of menengitis to move from the inner ear to the CSF and vice-versa
scala media
where the cochlear duct is in the membranous labyrinth
where do the semicircular canals come off of?
the utricle
the 6 receptive areas in the inner ear and where are they found
Which deals with hearing, which with balance
3 cristae ampularis - semicircular canals
balance
2 maculae - one in saccule and one in utricle
balance
1 organ of corti - cochlea
hearing
vestibulocohclear nerve
functions
branches?
sensory afferents to brainstem to hair cells (esp type 1)
motor efferents from brainstem to hair cells (type 2)
1 - auditory (cochlea)
2 - superior vestibulo (utricles, anterior and lateral semicircular canals)
3 inferior vest. (sacule)
4 - posterior vest. (posterior SC canal)
where do efferent signals of type 1 hair cells go?
to the dendrites.
function of the adaptation motor in the inner ear
keeps tension in the ear so that you can hear really quiet stuff (keeps hyperpolarization possible)
Where are hair cells found in the semicircular canal?
in the ampula, coming off the ampulary crest, which is a bony protrusion. the cupula is above them
in what types of hair cells are kinocilium located?
vestibular hair cells
what types of hair cells have a calyx and what does it do?
type 1, it is the nerve endings of the primary afferent nerves. provides a secure route of info transfer
how does the vestibular system in the ear detect acceleration?
when the hair cells and the cupula are at different positions, that is when you head is accelerating (hair cells more faster than the cupula, but the cupula eventually catches up when you reach a constant velocity.)
what are the otolith organs and what do they do?
What is the middle of the organs called? orientation of things on both sides of this
utricle and saccule - respond to gravity, tells where you head is in space
saccule: steriocilia are orientated horizontally, they can tell if you are right side up or upside down.
Utricles are oriented downwards, they can tell if you tilt your head
middle is called the striola - in the saccule the steriocilla are orientated away from it. in the utricle they are orientate towards it
function of otoconia
pull on the steriocilia in the otolith due to gravity pulling on them. made of calcium carbonate.
what are the “threads” of the cochlea called and what are the components of it? what fluid do they contain?
spiral lamina, 3 components
scalae vestibulae (this is nearest to the "tip of the screw") pressure waves go up here scalae tympani pressure waves go back down here have perilymph
scalae media
has endolymph
membranes that separate the scalae in the cochlea
Basilar - scalae tympani and media
vestibular - scalae vestibulae and media
Where do the nerves in the cochlea run and where do they terminate
run up the center of modiolus to get to the hair cells in the basilar membrane
What membrane in the cochlia vibrates when a sound is heard?
in what organ is this membrane located?
membrane on the top of hair cells in the cochlea?
What vibrates and what doesn’t?
basilar - vibrates
organ of corti
tectorial membrane - doesn’t vibrate
what structure of cells produces endolymph?
stria vascularis
dieter cell
underneath the outer hair cell, contributes a process to the reticular lamina
