Auditory and vestibular system Flashcards
What are the two divisions of CN VIII?
Cochlear = sound Vestibular = head positions and movement.
Auditory & vestibular receptors are both innervated by _____.
CN VIII
The _______ is the outer most layer of the cochlea, vestibule and Semicircular canals.
Bony labyrinth
What lines the inside of the bony Labyrinth?
The membranous labyrinth = tube suspended in bony labyrinth.
- creates duct in each semicircular canal
- creates cochlear duct in cochlea
- 2 enlargements in the vestibule (Utricle & Saccule)
The _____ is the enlargement of the vestibule that is attached to the semicircular ducts.
Utricle
The _______ is the enlargement of the vestibule that is connected to the cochlear duct and utricle.
Saccule
Perilymph is found in the ______ and is similar to ______ in composition.
Bony labyrinth
CSF
Endolymph is found in the________ and is similar to ______ in composition.
Fills membranous Labyrinth
Similar to intracellular fluid
What produces endolymph?
Specialized cells of the Cochlea
*Resorbed in Endolymphatic sac
Meneires disease cause and symptoms?
- Obstruction of flow of endolymph in membranous labyrinth.
- transient attacks of vertigo, nausea, hearing loss and tinnitus.
______ are Auditory and vestibular receptor cells.
hair cells
_________ hair cells lack Kinocilium.
Cochlear
Hair cells have microvilli known as ________ arranged in graduated rows with ______ towards one side.
- Stereo cilia
- Tallest
Where does the Kinoculium reside?
near the tallest stereo cilia
- in the semicircular ducts, utricle & saccule *Not cochlear
How is receptor potential transduced?
gelatinous material at tips of kinocilium and stereo cilia. movement of G material causes deflection of stereo cilia.
Deflection toward the tallest stereo cilia causes what?
Depolarization of hair cell
Deflection away from tallest stereo cilia causes what?
Hyper polarization of hair cell
Deflection in perpendicular plane causes what?
Nothing!
________ moves perilymph.
Stapes
_______ & ______ convey airborne sound to fluid-filled inner ear.
Outer & middle ear
Tympanic membrane is _____ the size of the stapes footplate. What does this mean?
15x
= stapes vibrations have more force/unit area.
_______ pulls stapes away from oval window of the Cochlea, stiffening the Ossicular chain. What does this do?
Stapedius muscle (Innervated by VII) = Blocks sounds of own voice (Spasm can cause clicking sound in ear when speaking.)
_______ pulls the malleus in toward the middle ear, stiffening the ossicular chain. What does this do?
Tensor Tympani muscle (innervated by V)
= Blocks chewing sound; can anticipate loud sounds and cans spasm, causing tinnitus at low frequency.
What are the 3 structures of the Cochlea?
Scala Vestibuli (Sup.) Scala media (Med) Scala tympani (Inf)
________ is a perilymphatic space, continuous with vestibule.
Scala Vestibuli
(structure of cochlea)______ contains endolymph.
Scala media
_____ is a perilymphatic space, ends blindly at round window.
Scala tympani
What is the Organ of Corti?
A strip of cells (Made of two groups) that rests on basilar membrane.
Describe the 2 groups of cells that make up the Organ of corti.
- Inner hair cells = not attached to gelatinous tectorial membrane,instead its stimulated by endolymph movement across stereo cilia.
- Outer hair cells = Stereo cilia insert into tectorial membrane. (Vibrations in basilar membrane causes oscillations in membrane potential of hair cells.
Starting at stapes, describe transduction of sound/wave….
- stapes movement causes pulse in scala vestibuli that leads to a traveling wave of deformation in basilar membrane.
- Mechanical properties differ along the length of basilar membrane so location of peak amplitude deteremines of frequency of it.
- “Mechanical tuning” of basilar membrane is the beginning of tonotopic organization of auditory system.
- Particular frequencies are mapped to specific regions of relay nuclei and cortex.
How does a cochlear implant work?
takes advantage of the tonotopic organization cochlea.
_________ is the primary ascending auditory pathway. Where are the fibers from?
lateral lemnisucs pathway *Constists mostly of fibers from dorsal cochlea nucleus)
Where the Primary auditory cortex located?
In the transverse temporal gyro of Heschl (Superior surface of temporal lobe)
_____ is important in sound localization.
Superior olivary nucleus
How and where does the Superior olivary nucleus receive fibers?
Receives fibers from bilateral cochlear nuclei, fiber cross midline they trapezoid body.
- two sub nuclei = medial (arrival time comparison) & lateral.
___________ detects linear and angular acceleration.
Vestibular divison of VIII
- Regulates posture, coordinates eye & head movements.
- Maintains orientation in response to movements.
Whats the main difference between the semicircular duct, utricle, saccule and the cochlea duct?
Semicircular ducts, saccule & utricle are suspended in bony labyrinth where as the cochlea duct is stretched.
Each ampulla of the semicircular ducts contain _______.
Crista.
What are the structures of the Semicircular ducts?
Crista = transversely oriented ridge with hair cells.
Seterocilia in gelatinous mass: cupula
Cupola of the semicircular ducts, covers ______ and extends across _______.
- crista
- ampulla
Deflection of the cupola in one direction leads to ________.
Increased firing in afferent fibers.
Describe how defection of the cupola occurs…
Rotation of semicircular ducts, as rotation begins endolymph lags behind. If movement continues it will catch up and sensation disappears until you stop, and your endolymph doesn’t……..
_____ & _______ receptors detect linear acceleration of the head.
Utricle and Saccule each contain a patch (Macula)
- Utricle = macula is horizontal when head is straight
- Saccule = macula is vertical when head is upright.
Utricle detects what specifically?
forward-backward & side to side.
Saccule detects what specifically?
Forward-backward & up and down
What is the Otolithic membrane?
Gelatinous membrane of the macula
- contains calcium carbonates crystals, otoconia, otoliths that makes this membrane DENSER than endolymph.
What is the primary afferent cell body of the vestibular system?
Vestibular (Sacrpas ganglion) internal auditory canal
What are the two types Projections of the vestibular system?
Peripheral process: Synaptic ending on hair cells
Central process: most to vestibuli nuclei of rostral medulla, caudal pons.
What are the Four vestibular input Nuceli? What is the relationship of the semicircular duct macula with these nuclei?
- Superior
- Inferior
- Medial
- Lateral
* Each SC duct and macula has its own pattern and termination pattern in these nuclei.
Besides the 4 vestibular nuclei, what else provides input to vestibular system?
Cerebellum (Flocculonodular lobe)
spinal cord
contralateral vestibular nuclei
Where does lateral Vestibulospinal fibers arise from?
The Lateral Nucleus down lateral funiculus
What is the function of the lateral Vestibule spinal tract?
Mediates postural changes to accomodate tilts in the body.
Where does Medal VS tract originate from?
Medial nucleus
Function of medal VS tract?
Stabilizes head movement as you walk
coordinates head and eye movement
What is the VOR and what does it do?
Vesctibuloocular relfex = works to prevent images from moving on the retina.
What is Nystagmus?
VOR can’t compensate for head movements, interrupted by very rapid eye movements in opposite direction (watching telephone poles out car window)
How does does alcohol make the cupola sensitive to gravity?
Normal cupula density = endolymph density
- as blood alcohol increase EtOH infiltrates cupola and density of cupola decrease relative to endolymph and nystagmus results.
What is position sense mediated by?
By vestibular, proprioceptive and visual systems all working together to produce sense of orientation and movement. ( if one is defective other two can compensate)
What is Romberg’s sign?
swaying or loosing balance when eyes are closed.
_______ is between Scala tympani & Scala Media.
Basilar membrane
__________ is between scala Tympani & Scala vestibuli.
Reissners membrane
_____ is spongy bone is surrounding the spiral ganglion..
Modiolus
Stimuli for organ of corti is…..
Sound
Stimuli for cristae is…..
angular acceleration
Stimuli for maculae is…
linear acceleration
