Chapter 15 - Auditory and Equilibrium Flashcards
outer ear is composed of
- pinna/auricle
- external acoustic meatus
function of the outer ear
collect sound waves and direct them to eardrum
middle ear is composed of
- tympanic membrane
- auditory ossicles: malleus, incus, and stapes
- oval and round windows
- pharyngotympanic tube
function of the middle ear
transmit sound waves from outer ear to inner by amplifying sound vibrations through ossicles and adjust pressure difference b/w air and fluid
where do infections occur in the ear?
middle ear
why do kids get more ear infections than adults?
their pharyngotympanic tube is more horizontal than vertical so fluid gets stuck in ear
tensor tympani and stapedius muscles
dampen sound by preventing ossicles from vibrating when there is a loud sound to protect hearing
function of pharyngotympanic tube
drains into nasal cavity and it is there to equalize pressure in the middle ear
inner ear is composed of
- cochlea
- semicircular canals
- vestibule
- vestibulocochlear nerve
- labyrinths: bony and membranous
cochlea
a hearing structure
- consists of 3 membrane-lined chambers
- houses spiral organ of corti
semicircular canals
equilibrium structure
- spinning around
vestibule
equilibrium structure
- linear balance
labyrinth of the inner ear: bony labyrinth
- semicircular canals, cochlea, and vestibule
- filled with perilymph
labyrinth of the inner ear: membranous labyrinth
- semicircular ducts, utricle, and saccule and cochlear duct
- filled with endolymph
spiral organ of corti
- tectorial memby: upper surface
- basilar memby: bottom border
- contains hair cells
hair cells have groups of what? what type of ion channels do they have?
- cilia of different lengths connected by a protein strand called tip link
- mechanically-gated ion channels
sound =
vibrations and pressure waves
frequency =
pitch
amplitude =
loudness
pathway of sound waves
- sound waves vibrate the tympanic membrane
- vibrates ossicles
- stapes pushes on oval window which sets the perilymph in cochlea in motion
- stimulates basilar memby which stimulates hair cells (depends on the frq of sound: middle range stimulates basilar memby, lower pitch doesnt, higher pitch doesnt)
- vibrations dissipate through round window
why does the basilar membrane get “punched” at different locations due to different frqs?
bc of it structure
- Base: very stiff and short fiibers —> medium frqs and high frqs are here
- apex: long floppy fibers –> lower frqs here
pathway to brain
- axons from organ of corti
- cochlear nerve
- vestibulocochlear nerve
- medulla
- inferior colliculus of midbrain
- thalamus
- primary auditory cortex of temporal lobe
what are the two different types of equilibrium?
static equilibrium and dynamic equilibrium
static equilibrium
aka linear equilibrium
- sensing movement forwards or backwards
- utricle and saccule of vestibule
dynamic equilibrium
- rotational movement of head
- semicircular canals
maculae of utricle and saccule contain what
- hair cells whose cilia project into the otolith membrane
- gelatinous substance with otolith crystals
static equilibrium at rest
constant act pots sent to the vestibular nerve
static equilibrium when head tilts back or forward
otoliths and memby move with tilt
head tilted backwards
- hair cells hyperpolarize
- decrease in act pots in vestibular nerve
head tilted forward
- hair cell depolarizes
- nerve fibers excited
- inc in act pots in vestibular nerve
dynamic movements
when you spin in one direction the flow of endolymph flows in that direction causing ampullary cupula to move to one direction and this causes it to send a certain pattern of act pots and when you spin in the other direction the flow of endolymph changes —> shifts ampullary cupula to the other side —> sends different pattern of act pots
