vestibular and auditory Flashcards
what CN is involved in the vestibular and auditory system?
CN VIII - vestibulocochlear nerve
where does CN VIII (vestibulocochlear nerve) exit the skull?
internal acoustic meatus
what two nerves exit through the internal acoustic meatus?
CN VIII - vestibulocochlear nerve
CN VII - facial nerve
vestibular system detects (2)
head movement
position
vestibular system is essential for (3)
posture
stability
coordination
where is the vestibular system located?
inner ear within the petrous part of temporal bone
vestibular system is composed of
semicircular canals
utricle
saccule
semicircular canals detect
angular motion
utricle detects
horizontal acceleration
saccule detects
verticle acceleration
semicircular canals are at ____ angles to each other. how many bony canals?
right angles
3: anterior, lateral, posterior
what are the swellings at the bases of semicircular canals called?
ampullae
How many sensory receptors are in the vestibular system?
5:
ampullae (3)
utricle
saccule
ampullae detect
rotational movement
within each ampullae, there is a receptor organ called the
crista ampullaris
crista ampullaris
receptor organ within the ampullae
composed of hair cells and senses motion in the head
crista ampullaris senses
motion in the head
in the lateral semicircular canal, if the head turns to the right, the culpa
turns to the left
the culpa’s movement is ____ to the head movement
oppositive
semicircular canal movements:
lateral:
anterior:
posterior:
lateral: shake “no”
anterior: shake “yes”
posterior: side to side “maybe”
otoliths are like
crystals
where are otoliths located?
utricle and saccule
otoliths are displaced during
head acceleration
otoliths are displaced during acceleration and the ciliary bundles of the hair cells are deflected, then what?
sensory signal in CN VIII
benign paroxysmal positional vertigo
vestibular disorder caused by dislodges otoliths from the utricle into the semicircular canals
what are otoliths made of
calcium carbonate crystals
Free-floating otoliths in the semicircular canals disrupt normal fluid dynamics, sending false signals of motion to the brain
benign paroxysmal positional vertigo
symptoms of vertigo
Dizziness, nausea, and imbalance
where do signals from the vestibule travel to first?
vestibular nuclei in the brainstem
*junction of pons and medulla
the vestibular nuclei integrate input from what?
vestibular apparatus
visual system
proprioception
from the vestibular nuclei, where do signals get sent to? (4)
cerebellum
thalamus
spinal cord
oculomotor nuclei
function of processing regions after the signal gets sent from the vestibular nuclei
cerebellum:
thalamus:
spinal cord:
oculomotor nuclei:
cerebellum: balance and coordinates movement
thalamus: balance and spatial orientation
spinal cord: posture and balance (via vestibulospinal tracts)
oculomotor nuclei: eye movements to maintain a stable visual field during. movements *vestibulo-ocular reflex (medial longitudinal fasciculus (MLF))
cerebellum does what with signals from vestibular nuclei?
fine-tunes balance and coordinates movement
thalamus does what with signals from vestibular nuclei?
Relays vestibular information to the cortex for conscious awareness of balance and spatial orientation
spinal cord does what with signals from vestibular nuclei?
Influences motor neurons via the vestibulospinal tracts, maintaining posture and balance
oculomotor nuclei does what with signals from vestibular nuclei?
Via the medial longitudinal fasciculus (MLF), coordinates eye movements to maintain a stable visual field during head movements (vestibulo-ocular reflex)
vestibulo-ocular reflex via what?
medial longitudinal fasciculus (MLF)
coordinates eye movements to maintain a stable visual field during head movements
Cortical Processing
Signals reach the vestibular cortex, located in the parietal and insular regions of the brain, for conscious perception of motion and spatial orientation.
reflex pathways of the vestibular system
vestibulo-ocular reflex (VOR)
vestibulospinal reflex
vestibulo-ocular reflex (VOR)
Stabilize vision by coordinating eye movements with head movements
vestibulospinal reflex
Adjust body posture to maintain balance
if the head is turning to the right, causing the semicircular canals to move, what is activated?
right vestibular apparatus
once the fluid in the semicircular canal excited the hair cells, the signal is sent through the ____ to the ____
vestibular nerve to the vestibular nucleus
after the signal is sent to the vestibular nucleus, it travels to the (2)
abducens nucleus (pons)
oculomotor nucleus (midbrain)
*via medial longitudinal fasciculus (MLF)
From the vestibular nucleus, signals travel to the abducens nucleus (pons) and the oculomotor nucleus(midbrain) via the ___
medial longitudinal fasciculus (MLF)
the lateral rectus muscle is activated via the
abducens nerve (CN VI)t
The medial rectus muscle is activated by the
oculomotor nerve (CN III)
lateral rectus muscle is activated by the —–>
medial rectus muscle is activated by the —–>
lateral rectus muscle is activated by the —–> abducens nerve CN VI
medial rectus muscle is activated by the —–> oculomotor nerve CN III
auditory system
detects sound waves and converts them into electrical signals for processing by the brain
the auditory system is essential for
hearing, communication, and environmental awareness
three parts of the auditory system
external ear
middle ear
inner ear
external ear functions
collect and funnel sound waves
protect tympanic membrane
*external acoustic meatus
eardrum is the
tympanic membrane
auricle aka
pinna
middle ear functions
amplify and convert sounds into mechanical energy
provide pressure release
where is the middle ear located?
in petrous part of temporal bone
What is the middle ear continuous with?
Continuous with nasopharynx via auditory tub (aka pharyngotympanic tube, Eustachian tube)
auditory ossicles are what?
extremely dense bones covered in mucous membrane (not periosteum)
synovial joints
what do auditory ossicles do?
conducts vibrations from tympanic membrane to fluid-filled chamber of cochlea, via oval window
what type of joint are the auditory ossicles?
synovial joints
what are the three auditory ossicles?
malleus
incus
stapes
Manubrium of the malleus is
embedded in tympanic membrane
what is the smallest and lightest bone in the human body?
stapes
Change in size between tympanic membrane and footplate means vibration increases ___ in pathway through the ossicles
10x
middle ear infection that causes inflammation and fluid build-up
acute otitis media
acute otitis media can cause blockage of
pharyngotympanic tube
acute otitus media child vs adult
in children: Eustachian tubes are smaller and more horizontal, which makes it more difficult for fluid to drain out of the ear.
inner ear functions
Receive mechanical energy and convert into fluid wave
Respond to fluid waves for proprioception of sound
inner ear is located
in otic capsule in petrous part of temporal bone
sensory organs of inner ear
cochlea
vestibular apparatus
cochlea:
vestibular apparatus:
cochlea: hearing
vestibular apparatus: balance
path of sound
pinna (auricle)
external acoustic meatus
tympanic membrane
malleus
incus
stapes
oval window
fluid inside cochlea
When sound waves cause the stapes to move, they generate ___ waves in
the perilymph of the scala vestibuli
pressure
When sound waves cause the stapes to
move, they generate pressure waves in
the
perilymph of the scala vestibuli
Pressure waves initiated in the scala vestibuli pass through the ___ ___ and into the scala tympani
cochlear duct
Pressure waves initiated in the scala vestibuli pass through the cochlear duct and into the ___ ___
scala tympani
pressure waves end in the scala tympani where they are eventually relieved at the
round window
Vestibular membrane
Separates the scala vestibuli from the cochlear duct
barrier to maintain the distinct ionic composition of the endolymph in the cochlear duct
Basilar membrane
Separates the scala tympani from the
cochlear duct
structural support for the organ of Corti and is crucial for translating sound waves into neural signals
tympanic membrane separates:
basilar membrane separates:
tympanic membrane separates: scala vestibuli from cochlear duct
basilar membrane separates: scala tympani from the cochlear duct
Tectorial membrane
Facilitate the deflection of hair cell stereocilia by creating a shearing force during cochlear vibrations. This motion opens ion channels in the hair cells
Organ of Corti
Houses inner and outer hair cells, supporting cells, and the tectorial membrane, functioning as the primary site for sound wave transduction into neural impulses
Hair cells in the cochlea
Sensory cells in the cochlea that convertmechanical vibrations into electrical signals and amplify vibrations to enhance hearing sensitivity and clarity
cochlea pitch locations
base: high pitch
apex: low pitch
human hearing range is generally between
20-20K Hz
hertz
“Hz” (hertz) measures the frequency of a sound, which determines its pitch (how high or low it sounds)
decible
“Decibel” (dB) measures the intensity of a sound, indicating its loudness
electrical signals from the hair cells of the cochlea are transmitted via the
cochlear nerve
cochlear nerve is a branch of the
vestibulocochlear nerve CN VIII
the cochlear nerve transmits signals to where first?
cochlear nuclei
the ventral and dorsal cochlear nuclei are located in the
rostral medulla
cochlear nerves synapse in the
the ventral and dorsal cochlear nuclei
Dorsal acoustic stria:
Carries signals directly to higher auditory centers
Intermediate acoustic stria:
Part of the processing route from the dorsal cochlear nucleus.
what are the two pathways following the synapse in the cochlear nuclei?
dorsal acoustic stria
intermediate acoustic stria
dorsal acoustic stria
carries signals directly to higher auditory centers
intermediate acoustic stria
part of the processing route from the dorsal cochlear nucleus
dorsal acoustic stria vs intermediate acoustic stria
Dorsal acoustic stria: Carries signals directly to higher auditory centers.
Intermediate acoustic stria: Part of the processing route from the dorsal cochlear nucleus.
some fibers from the ventral cochlear nucleus project to the ___ ____ ____ via the trapezoid body
superior olivary complex
Some fibers from the ventral cochlear nucleus project to the superior olivary complex via the
trapezoid body
where does sound localization begin? (determining direction of sound)
from the ventral cochlear nucleus project to the superior olivary complex via the trapezoid body
superior olivary complex is critical for _____ hearing (processing inputs from both ears)
binaural
how do signals travel after the superior olivary complex?
via lateral lemniscus
*a fiber tract that transmits auditory information to the midbrain.
the lateral lemniscus is a fiber tract that transmits
auditory information to the midbrain
the lateral lemniscus transmits auditory info from the ___ to the ___
superior olivary complex to the midbrain
what connects the superior olivary complex to the midbrain (tract)?
lateral lemniscus
what nucleus is responsible for refining timing and amplitude data?
nucleus of the lateral lemniscus
all auditory fibers converge at the ___ in the mid-brain
inferior colliculus
where is the inferior colliculus located?
midbrain
what does the inferior colliculus do?
integrates spatial and spectral sound info and coordinates auditory reflexes
*where all auditory fibers converge in the midbrain
from the inferior colliculus, signals go to what? and where is it located?
medial geniculate nucleus (MGN)
in the thalamus
the medial geniculate nucleus acts as a ____ station
relay
where does refining of the auditory signals AND preparing for higher-order processing occur?
at the medial geniculate nucleus
what is the final destination of auditory signals?
primary auditory cortex in the temporal lobe
where does sound perception occur (including recognizing pitch, tone, and location)?
primary auditory cortex
auditory pathway locations (10)
- Cochlear hair cells
- Bipolar Cells of Cochlear Ganglion
- Cochlear Nerve (branch of CN VIII)
- Cochlear Nuclei
- Trapezoid Body
- Superior Olivary Nuclei
- Lateral Lemnisci
- . Inferior Colliculi
- Medial Geniculate Bodies
- Primary Auditory Cortex
The utricle and saccule in the vestibular system primarily detect which type of movement?
Vertical and horizontal linear acceleration
Damage to one lateral lemniscus does not result in complete hearing loss. Which feature of the auditory pathway prevents total loss of hearing in this case?
Crossed and uncrossed projections in the cochlear nuclei
A patient reports dizziness and hearing loss on the left side. Examination reveals a drooping left eyelid and reduced taste sensation on the left anterior tongue. Imaging shows a mass compressing cranial nerves VII and VIII. Which structure is most likely affected?
Internal acoustic meatus
A malfunction in which vestibular structure would impair detecting vertical motion, such as ascending or descending in an elevator?
saccule
Which part of the cochlear basilar membrane is most sensitive to high-frequency sounds?
the base, which is narrow and stiff
A tennis player struggles to track the ball during a fast rally, reporting dizziness and blurred vision with side-to-side head movements. Which vestibular structure is most likely affected?
horizontal (lateral) semicircular canal
A child presents with muffled hearing and a sensation of fullness in the ears after a cold. Examination reveals a bulging tympanic membrane without perforation. Dysfunction of which structure most likely contributed to this condition?
eustachian tube
A runner notices increased unsteadiness when running downhill. Testing reveals impaired detection of linear acceleration. Which vestibular structure is most likely damaged?
utricle
The vestibulo-ocular reflex is essential for which function?
stabilizing vision during head motion
A 45-year-old woman experiences episodic vertigo and hearing loss. Examination reveals diminished taste sensation on the anterior two thirds of her tongue and difficulty closing her right eye. Which structure is most likely affected?
internal acoustic meatus
