Auditory and Vestibular Systems Flashcards
How many stereocilia are in a bundle?
30-300
What are the different types of links possible between sterocilla?
Lateral link connectors and tip links
What are lateral link connectors?
Connections between shafts that hold the bundle together and allow it to move as a unit
How do tip links work?
Tension in the tip links distort the sterocilia mechanically, which allows channels to open and close with cilia movement
How do hair cells work?
Tip links open ion channels, that causes potassium ions to flow into the cell depolarising it.
Voltage gated calcium channels open which trigger neurotransmitter release at the synapse.
What is the lateral line system?
Hair cell system that detects water movement along the outside of fish and amphibians
What do mechanoreceptors in the lateral line system provide?
Information about movement through water or the directions and velocity of water flow
What does the internal canal under the epidermis contain?
Mechanoreceptors called Neuromasts
Where are superficial neuromasts found?
On fish/amphibians surfaces
What encases the sterocilia bundles in fluid?
A gelatinous cupola
What is the inner ear formed of?
Semicircular canals and cochlea
What system is responsible for balance and motion in mammals?
Vestibular system
Which system is the cochlea involved in?
Auditory system
What is the vestibular system?
Balance and motion in mammals
Which direction of rotation does the posterior semi-circular canal sense?
Roll around the X axis
Which direction of rotation does the anterior semicircular canal sense?
Around the Y axis
Which direction of rotation does the horizontal semicircular canal sense?
Around the z axis
How do the hair cells sense rotation?
Cilia are connected to the gelatinous cupola
Under motion, fluid in the canals lag bc inertia
Pulls the cupola in the opposite direction to the rotation of the head, displacing cilia and depolarising hair cells
How do the otolith organs work?
Hair cells are topped by a rigid layer of otoconia crystals
Under acceleration, the crystal layer is displaced, deflecting the cilia
What is the quietest sound we can perceive and how much do the sterocilia move at this volume?
20 picoamps, 0.3mm
What is the pathway of sound from the cochlea to the brain?
Change in air pressure -> change in fluid motion in the cochlea -> translated into electrical current in the cochlear nucleus-> olivary complex -> lateral lemniscus -> inferior colliculus -> medial geniculate body -> auditory complex
What is another name for the outer ear?
Pinna
What is the function of the Pinna?
Gathers sound from the environment and funnels it into the eardrum
What is the Pinna made of?
Cartilage and covered with skin
Which part of the ear filters high frequency (3000-5000 hz)?
Flange
Which part of the ear filters very high frequency (>5000 hz)?
Conchae
Which part of the ear filters low frequency?
Meatus
What is grade I microtia?
Less than complete development of the external ear with identifiable structures and a small (but present) ear canal
What is grade II microtia?
A partially developed ear with a closed stenotic external ear canal producing a conductive hearing loss
What is grade III microtia?
Absence of the external ear with a small peanut-like vestige structure and an absence of the external ear canal and ear drum
What is grade VI microtia?
Absence of the total ear or anotia
What is another name for the eardrum?
tympanic membrane
What connects the tympanic membrane to the oval window of the cochlea?
Ossicles
What are the three ossicles?
Malleus, incus and stapes
Which of the ossicles connect to the tympanic membrane?
Malleus
Which of the ossicles connect to the oval window of the cochlea?
Stapes
What are the ossicles positioned to create?
Amplification
What is the space where the bones are usually filled with?
Air
What is the swanky name for glue ear?
Otitis media
What happens in otitis media?
Middle ear fills with fluid, impeding the ossicle motion
What are the three chambers of the cochlea?
Scala vestibuli, Scala media and Scala tympani
What does the Scala media contain?
Components for sound transduction
What happens when the stapes move back and forth?
Creates compression and rarefaction in the fluid of the chambers
What does the basilar membrane do?
Filters sound according to frequency
What is the basilar membrane like far from the oval window?
Stiff and narrow
What is the basilar membrane like close to the oval window?
Stiff and narrow
What is the basilar membrane like at the non-oval window end?
Wide and compliant
What frequencies will the basilar membrane pick up close to the oval window?
High
What frequencies will the basilar membrane pick up far away from the oval window?
Lower
What is the organ of corti?
Membrane that inner and outer hair cells are mounted on
Do the outer or inner hair cells contact the tectorial membrane?
Outer
Where does the organ of corti sit?
On top of the basilar membrane within the scala media
How are inner hair cells arranged?
Straight line
What type of synapse do the inner hair cells have?
Afferent
What type of synapse do the outer hair cells have?
Efferent
How are the outer hair cells arranged?
Bundles of arches
What does an influx of positive ions do to the outer hair cells?
Causes them to contract
What happens when the outer hair cells contract?
Causes the basilar and tectoral membranes get closer to one another, causing the inner hair cell to move
By how much does the cochlea amplify sound by?
50dB
Are loud sounds amplified in the cochlea?
No
What drives cochlear cells?
High potassium concentration of the endolymph of the scala media
