deck_3165790 Flashcards
Properties of sounds
Frequency - hertzVolume - decibels
Where are the ossicles and give their function?
Lie in the upper part of the tympanic cavity- relay vibrations encountered by tympanic membrane to the internal ear- amplify and concentrate sound energy to the oval window
What are the three ossicles?Where do they articulate?
Malleus = handle attaches to the tympanic membrane and body articulate with the body of incusIncus = articulates with stapesStapes = articulates with bony labyrinth of the inner ear of the oval window
Describe the inner ear
A series of channels hollowed out of the petrous temporal bone surrounded by membranous labyrinth
What are the contents of the inner ear?
VestibuleSemi-circular ducts and canalsCochleaCochlear ductOrgan of corti
Describe the vestibule
Small bony chamberContains utricle and sacculeSensitive to rotational acceleration and static pull of gravity
Describe the semi-circular canals
Communicate with the vestibuleContains receptors which respond to rotational acceleration in three different planes- canals are all set at different angles
Describe the mechanotransduction of sounds
Tympanic membrane vibrations are transmitted to oval window. Scala vestibuli converts vibrations to pressure waves. Pressure waves are transmitted from vestibular membrane to the basilar membraneStereocilia bend due to local resonance and K+ channels in the hair cells open. K+ influxHair cells are depolarisedVOCC openCa2+ influx, triggers neurotransmitter release onto afferent nerves of spiral ganglia
How are different pitches of sounds transmitted?
High pitched sounds generate high frequency pressure waves. These cause short fibres to resonate at the base of the cochlea. Low pitched sounds - low frequency pressure waves - long fibres at apex resonate.
How are different volumes of sounds generated?
Louder sounds generate more APs in more axons.
What are the principal sensory receptors in the ear?
Inner hair cells- each have 20 afferent nerves attached to each of them- single row Outer hair cells act as amplifiers- three rows
Where do you find endolymph?
In the Scala media- lies above the basilar membrane- separated from scala vestibuli by the vestibular membrane
Where do you find perilymph?
Upper scala vestibuliLower scala tympani- communicate through the helicotrema at the apex of the cochlea
