(neuro) auditory system Flashcards
how many sections is the ear divided into?
outer, middle, and inner ear
where is the ear embedded?
petrous part of the temporal bone
why is it important that the ear is embedded in the temporal bone?
temporal bone = hardest bone in the body
so can protect the delicate structure of the ear well
what are the functions of the outer ear?
to capture sound and to focus it onto the tympanic membrane
to amplify some frequencies by resonance in the canal
to protect the ear from extrenal threats
what is the tympanic membrane also known as?
eardrum
how is the ear adapted for protection from external threats?
have cilia in the external acoustic meatus that waft to extrude unwanted elements from entering the ear
have ear wax that will trap the unwanted external elements + has a pH that is toxic for pathogenic material
what is the main function of the middle ear?
amplification
how is sound amplified in the middle ear?
vibrations are focussed from the tympanic membrane (larger SA) onto the oval window (smaller SA)
the change in surface area causes in increase in pressure
what impact does the focussing of vibrations have?
the decrease in SA from the large tympanic membrane to the smaller oval window causes an increase in pressure
how is the force increased on the oval window?
using leverage from the incus-stapes joint
what does the middle ear consist of?
tympanic membrane
ossicles (malleus, incus, stapes)
stapedius muscle
oval window
what are the ossicles?
smallest bones in the body
include the malleus, incus and stapes
name the three ossicles
malleus, incus, stapes
describe the structure of the ossicles
the malleus is attached to the inner surface of the eardrum
the malleus articulates with the incus which in turn articulates with the stapes
what is the oval window?
membrane-covered opening from the base of the stapes in the middle ear to the cochlea of the inner ear
describe the path of sound amplification in middle ear
vibration hit the tympanic membrane
transmit vibrations to the chain of connected ossicles
vibrations focussed onto the connective tissue membrane called the oval window
the focussing of the vibrations causes an increase in pressure = amplification of sound
sound is transmitted into the inner ear
what is the oval window?
connective tissue membrane located at the end of the middle ear at the base of the stapes and the beginning of the inner ear
responsible for stimulating the movement of auditory fluids in the cochlea and the activation of receptors for hearing
what is the hearing part of the inner ear?
cochlea
what is the function of the cochlea?
transduces vibrations into nervous impulses
produces a frequency (pitch) and amplitude (loudness) analysis of the sound
what does the frequency and amplitude of the sound determine?
will determine the location of the ear in which the cells will be stimulated
i.e. different frequencies and amplitudes will stimulate cells in different parts of the ear
what is the alternative function of the cochlea besides transduction?
produce a frequency (pitch) and amplitude (loudness) analysis of the sound
describe the structure of the cochlea
hollow, spiral-shaped bone found in the inner ear
cochlear duct is divided into thee compartments: scala vestibuli, scala media and scala tympani
name the three compartments of the cochlear duct
scala vestibuli, scala media and scala tympani
what structure separates the cochlea into its three compartments?
oval window
describe the structure of the scala vestibuli and the scala tympani
both scalae are bony structures that are filled with perilymph (w the membranous scala media in between them)
communicate w each other via the helicotrema (an opening at the apex of the cochlea)
what do the scala vestibuli and scala tympani contain?
perilymph (high in sodium)
what is the perilymph and why is it important?
sodium-rich fluid found in the bony labyrinth of the scala vestibuli and the scala tympani, surround the endolymph in the membranous labyrinth of the scala media
resembles extracellular fluid and transmits sound waves to the endolymph
which membranes are linked to the scala vestibuli and the scala tympani?
scala vestibuli = vestibular membrane
scala tympani = basilar membrane
how do the scala tympani and the scala vestibuli communicate?
communicate w each other via the helicotrema (an opening at the apex of the cochlea)
what is the cochlea?
hollow, spiral-shaped bone found in the inner ear
transforms the vibrations of the auditory fluids into neural signals for interpretation by the brain
what is the function of the cochlea?
transforms the vibrations of the auditory fluids into neural signals for interpretation by the brain
which mineral ion is the perilymph high in?
sodium
what structure sits in between the scala vestibule and the scala vestibuli?
scala media
what is the scala media?
membranous structure that contains endolymph, rich in potassium
what does the scala media contain?
endolymph, rich in potassium
which mineral ion is the endolymph high in?
potassium
compare the perilymph with the endolymph
perilymph = found in the bony labyrinth of the scala vestibuli and scala tympani, rich in sodium and mimics extracellular fluid, transmits vibrations to the endolymph
endolymph = found in the membranous labyrinth of the scala media, Irish in potassium and mimics intracellular fluid, transmits vibrations to the hair cells
which structure is linked to the scala media?
organ of Corti
where is the perilymph located?
in the bony labyrinth of the scala vestibuli and scala tympani
where is the endolymph located?
in the membranous labyrinth of the scala media
where is the organ of Corti found?
within the scala media
what is the helicotrema?
an opening at the apex of the cochlea
which is the point of communication between the scala vestibuli and the scala tympani
where is the organ of Corti found?
within the basilar membrane (between the scala media and the scala tympani)
