The Ear Flashcards
Sound frequency
Measured in Hz
Cycles/sec
What is sound?
Audible variations in air pressure
Sound range
20 Hz to 20,000 Hz
What is infrasound?
Low frequency sound that can be felt but not heard by humans
Where is the organ of Corti located?
In the cochlea of the inner ear
What is the auricle and what does it do?
Outer ear cartilage
Collects sound waves
What is the external auditory meatus and what does it do?
Ear canal
Receives vibrations of sound waves and directs them towards tympanic membrane
What is the function of the middle ear?
Amplifies and concentrates sound waves
What is the tympanic reflex?
Protective mechanism
Requires loud and repetitive sound
Muscle tenses to keep ossicle from pushing stapes to oval window
What is the tympanic cavity?
An air-filled space behind the eardrum that separates outer and inner ear
What part of the ossicle is connected to the tympanic membrane?
Malleus
What part of the ossicle connects the malleus to the stapes?
Incus
What is the smallest bone in the body?
Stapes
What part of the ossicle connects the incus to the oval window?
Stapes
What structure is the entrance to the inner ear?
The oval window
What structures does the Eustachian tube connect?
Middle ear to nasopharnyx
Equalizes pressure on both sides
Why does our hearing decline with age?
Ossicles become ossified
What is the bony canal in the temporal bone in inner ear?
Osseous labyrinth
What is the membrane within the osseous labyrinth?
Membranous labyrinth
How do lymphs of the ear differ?
Different ionic concentrations
Endolymph is high in K+
Which fluid fills the space between the osseous and membranous labyrinth?
Perilymph
Which fluid fills the membranous labyrinth?
Endolymph
Why are there more outer hair cells?
They are responsible for amplification of sound
Fluid in scala vestibule and scala tympani
Perilymph
Fluid in scala media
Endolymph
Basilar membrane contains:
: 16000 hearing receptor cells
How the cochlea works:
: pressure from oval window -> pushes perilymph into scala vestibuli -> round window membrane bulges out
What type of projection does the auditory nerve have?
Bilateral projection
CNS structures associated with hearing
Inferior colliculi
Medial geniculate nucleus of thalamus
Insular cortex
Lesion in the auditory cortex causes:
: normal auditory function because of bilateral projection
With a cochlear implant :
: hair cells bypassed
Utricle hair cells
Depolarization inward
Saccular macula hair cells
Depolarization out wards
What type of crystals are within the saccule and the utricle?
Calcium carbonate crystals
Head movement is :
: opposite of fluid movement
Push-pull arrangement of semicircular canals
Rotation causes excitation of a semicircular canal on one side and the inhibition of a semicircular canal on the other side
What responds to gravitational pull?
Otoliths within gelatinous material
What does the kinociliumdo?
Keeps otoliths embedded in gelatinous material
Balance is a ________ pathway
Descending, controls motor
All signals are _________ in brainstem and midbrain but __________ within cortex
Bilateral
Contralateral
What are cupula?
Long rows with hair cells embedded in the crista ampullaris
What is the vestibulo-ocular reflex?
Line of sight fixed on visual target
Senses rotation of head and commands compensatory movement of eyes in opposite direction
How are the EOMs excited by the VOR?
Semicircular canals -> vestibular nucleus -> CN nuclei -> EOMs
What are the movement detectors of hearing and balance?
Periodic waves
Rotational
Linear force
