Lecture 16: Hearing Flashcards
Define hearing
the brains interpretation of sound energy
Energy of sound waves is a combination of their ______ and _____
Frequency and Amplitude
Pitch is the brains interpretation of ____ where as loudness/ intensity is the brains interpretation of _____
Frequency ; Amplitude
Sound Transduction is
The conversion of mechanical energy in sound waves to electrical energy (AP’s)
True or False; Our brains Can not distinguish distance and direction of sounds
False
What structures are in the external ear
Pinna, Ear canal, Tympanic membrane
What is located in the Middle ear
Eustachian tube The Ossicles (malleus, incus, stapes)
What is located in the Inner ear
Cochlea, bony tabyrinth, Membranous labyrinth, saccule and Utricle
Crista Ampullaris
Vestibular Duct, Oval window, stapes on one end, Helicotrema on other
Coachlear duct (Organ of corti, on tympanic side) (tectorial membrane on vestibular side)
Tympanic duct
What is the first, second and major role in transduction
1) Tympanic membrane
2) Ossicles vibrating
Major) Vestibular apparatus
What cochlear duct has hair cells
Organ of corti
What is the 6 steps of transduction of sound via hair cells?
1) Sound waves strike the tympanic membrane and become vibrations
2) The sound wave energy is transferred to the three bones of the middle ear (Malleus, Incus and stapes) which vibrate
3) The stapes is attached the membrane of the oval window, vibrations of the oval window create fluid waves within the cochlea
4) The fluid waves push on the flexible membranes of the cochlear duct. Hair cells bend and ion channels open, creating an electrical signal that alters neurotransmitter release
5) Neurotransmitters release onto sensory neurons creates action potentials that travel through the cochlear nerve to the brain
6) The energy from the waves transfer across the cochlear duct into the Tympanic duct and is dissipated back into the middle ear at the round window
What duct has endolymph
Cochlear duct
Movement of tectorial membrane results in what
movement of hair cells within organ of corti
What are the 4 important things that happens when transduction in organ of corti occur
1) Vestibular and Tympanic ducts contain perilymph (Plasma)
2) Cochlear duct contains endolymph (very high in K+) secreted by epithelial cells
3) Coachlear duct and vestibular duct are separated via vestibular membrame
4) Cochlear duct and tympanic duct are separated via basilar membrane
The tallest sterocilium is called
the Kinocilium
The sterocilia are connected via
Tiplinks
Sterocilia have very special K+ channels on their surface which are
mechanically gated
At rest only ____ % of channels are open
10%
Describe Excitation
When all stereocilia bend towards the kinocilium. Cell depolarizes increases AP frequency in associated sensory neuron
Describe Inhibition
When all sterocilia bend away from the Kinocilium, ion channels close, cells hyperpolarizes
The Basilar membrane has ______ sensitivity to sound wave frequency along its length
variable
Where do the signals go after the cochlea via what
To the medulla oblongata via vestibulocochlear nerve
Secondary sensory neurons, send information from the medulla oblongata to the _____ then the ______ and then project to the _____ ____
Midbrain
Thalamus
Auditory cortex
Conductive hearing loss is problems with
External ear or the middle ear
Central hearing loss is from
Either damage to the neural pathways, between the ear and cerebral cortex
Or the cerebral cortex itself
Sensoryneural hearing loss if from
Damage to the structure in the inner ear
Old age/ loud music
Inner ear is made up of
Bony labirynth
Membranous labyrinth
What is in the membranous labyrinth
1) Cochlear duct with ogan of corti
2) semicircular ducts with 1 crista ampullaris in each
3) utricle and saccule with 1 macula in each
Semicircular canals detect what
rotational acceleration
The vestibular apparatus is filled with what
K+
The crista consist of ____
hair cells
Macula in Saccule and Utricle consist of
hair cells, and a gelatinous mass
What are the two pathways for the head tilted posteriorly?
1) Synapse with cerebellum directly
2) Project to vestibular nucleus to midbrain to thalamus to cortex
What are two areas that project to areas controlling eye movement
Cerebellum and vestibular nuclei
