Auditory and Vestibular System Flashcards
3 main divisions of the ear
Outer/External:
- Earlobe
- auditory canal through the external auditory meatus
Middle ear:
- Tympanic membrane/eardrum
- tympanic cavity
- ear ossicles,
- auditory/eustchian tube
Inner ear:
- Osseous/bony labyrinth: Cochlea, vestibule (utricle and saccule) and semicircular canals
- Membraneous labyrinth: Perilymph and endolymph
Other words for amplitude
Intensity, volume, loudness
what is amplitude/intensity and what is it measured in?
Difference in pressure between compressed and rarefied patches of air.
Measured in decibels (dB)
Amplitude in decibels
- Minimum detectable
- Whisper
- Normal voice
- Pain threshold
- 0 dB
- 30 dB
- 70 dB
- 125 dB
cycle
Distance between successive compressed patches/ amplitudes
Sound frequency/pitch
Number of cycles per second expressed in Hz
Human range of Hz
Most sensitive range of Hz
20-20,000Hz
1,000-4,000 Hz
Timbre
Mixture of multiple soundwaves/frequencies. Lots of sounds
External acoustic meatus. The outer 1/3 canal wall is ____ and the inner 2/3 wall (tympanic portion) is ___
Cartilage
Temporal bone
Wax secreting glands are called what and where are they found in the ear
They are called cerumen glands, found in the external acoustic meatus
The middle ear is located where in the skull
Within the petrous portion of the temporal bone
What is the importance of the auditory/eustachian/pharyngotympanic tube?
This tube connects the middle ear to the nasopharynx. It is usually closed, to protect the middle ear from pressure fluctuations and loud sounds.
When it is open, it facilitates in equalizing air pressure on both sides of the tympanic membrane. Opening the tube equalizes air pressure. Also allows mucous to flow from the middle ear to the nasopharynx, preventing an infection to travel into the inner ear.
The middle ear is slow to change pressure, causing distention of the ear drum, causing pain. Why you yawn/chew gum on airplanes to open up that tube and allow pressure to equalize.
Which tube connects the middle ear to the nasopharynx?
The auditory/eustachian/pharyngotympanic tube
Where are mastoid air cells located
In the mastoid process. Though to protect the ear and regulate pressure.
Do not want infection to travel here.
Characteristics of the tympanic membrane
Thin, fibrous CT with elastic fibers.
Concave external surface.
Center of the membrane is attached to the malleus.
Role of the ear ossicles
Transmit and enhances sound waves to the inner ear (cochlea) via the oval window
- Malleus (outer, attached to the tympanic membrane
- Inces
- Stapes attached to the oval window of the cochlea
Muscles of the ear ossicles
- Tensor tympani innervated by CN V3 (trigeminal -mandibular) is attached to the malleus
- Stapedius muscle innervated by CN VII (Facial) is attached to the stapes. Stapedius is the smallest muscle in the body.
They act to dampen propagation of sound waves once sound waves are no longer necessary to hear.
The chorda tympani of CN ___ passes through the middle ear on its way to innervate _____ and ____ glands.
CN VII passes through inner ear to synapse at the submandibular ganglion and innervate submandibular and sublingual salivary glands.
In the brain, the hearing (cochlea) part of the ear is located ____ and the balance (semicircular) part is located ____
Hearing is more anterior medial
Balance is more posterior lateral
The bony labyrinth of the inner ear contains
The cochlea (auditory), vestibule (balance) and semicircular canals (balance)
The vestibule contains
The utricle and saccule
The inner ear/cochlea is wound how many times to form a spiral structure?
It is wound about 3 times
Which 3 ducts are founds within the cochlea spiral?
- Scala vestibule. Communicates with the oval window and contains perilymph.
- Cochlear duct. Contains spiral organ/organ of corti that has hair cells that elicit an electrical impulse when basilar membrane is displaced. Contains endolymph.
- Scala tympani. Continuous with the scala vestibule at the center/apex of the spiral, called the helicotrema. Terminates at the round window. Contains perilymph.
Where is the helicotrema located and what does it connect
Located at the apex/center of the cochlea spiral. Allows for communication between the scala vestibule and the scala tympani.
Pathway from oval window to round window
Stapes pushes on the oval window- pushes perilymph into scala vestibuli- helicotrema- scala tympani- round window bulges out
The basilar membrane separates the cochlear duct from the
Scala tympani
The organ of corti is located where
Located in the cochlear duct, within the cochlea of the inner ear
When there is a change in fluid pressure from the scala tympani, the basilar membrane moves. This causes the ____ to move in a specific direction to initiate electrical response.
The stereocilia/hair cells
What initiates a depolarization in the ear?
K+ influx causes depolarization, resulting in a calcium influx and then release of glutamate
The main NT for audition and balance
Glutamate
Stereocilia are usually arranged in groups of ___
3 from short to tall
How to the hair cells bend when there is an excitatory or inhibitory response?
Excitatory- bend towards the tallest hair cell
Inhibitory- bend towards the shortest hair cell, away from the tall hair cell.
Which one moves and which one stays stationary? The basilar membrane and the tectorial membrane
The basilar membrane is moveable and the tectorial membrane is stationary. The tectorial membrane is what detects the hair cell movement.
High frequency sound waves are detected where along the cochlea?
At the base (up to 20,000 Hz)
Low frequency sound waves are detected where along the cochlea?
At the apex/center (200 Hz)
Primary auditory area of the brain
Area 41 and 42 in the superior temporal gyrus of the temporal lobe.
41 and 42 send projection fibers to the higher processing areas in the parietal and frontal lobes.
Where is Wernicke’s area and what does it play a role in
Located near 41 and 42 and in the temporal lobe.
Plays a role in understanding spoken language and interpreting sound.
Where are receptors located in the semicircular canals
Located in the ampulla, embedded in a gelatinous structure called the cupula
Cupula
Gelatinous structure that the hair cells of the semicircular canals are embedded in.
Head turns to the right. How does this affect the hair cells within the semicircular canals?
Excitation of R lateral semi-circular canal
Inhibition of L lateral semi-circular canal
Semi-circular canals detect which kind of movement?
Angular movement along the X, Y and Z axis.
- Horizontal, vertical, and transverse.
The vestibule or otolith organs contains which two structures
The utricle and saccule
The utricle and saccule of the vestibule contain hair cells that are oriented
Upright and perpendicular. 90 degrees apart
Which chamber within the utricle and saccule contain the hair cells?
The macula. Each structure has a macula. Composed of hair cells that are in contact with otoliths- jelly fluid containing calcium carbonate crystals.
Otoliths
Jelly like fluid within the utricle and saccule that contains calcium carbonate crystals.
Found within the macula of the vestibule structures.
The vestibule structures detect which kind of movement?
Movement associated with gravity. Linear acceleration. Head it stationary, body is moving.
Organ of static equilibrium
The macula of the vestibular (utricle and saccule)
Sensory impulse from the vestibular system travels where before reaching the cerebellum for interpretation?
Sensory impulse travels on the vestibular branch of the vestibulocochlear nerve to the pons and then cerebellum.
Which portions of the vestibular system detects angular movement? which portion detects linear movement?
Angular- semi circular canals
Linear- Vestibular. Utricle and saccular.
Where does the vestibular system project to? (Semicircular and vestibular)
Projects to the thalamus, EOM’s, cerebellum, and limbs
Two main types of hearing loss
Conductive- due to damage to a structure. Ex: the tympanic membrane or ossicles. Or too much ear wax prevents conduction. Or age related hearing loss. usually can be fixed. use hearing aids.
Sensorineural- damage to the nerves. Use cochlear impacts.
Tests to use to determine hearing loss:
Weber test and Rinne Test.
Sensorineural hearing loss could be due to:
Age, exposure to high frequency noise, trauma, toxicity from medications such as ahminoglycosides, viral infection, autoimmune disease (lupus)
Tinnitus
person perceives noises that aren’t actually there.
May indicate sensory hearing loss.
High pitch ringing
Vertigo
Person perceives motion that isn’t actually there
Which two aspects are the key to diagnosing vertigo?
Duration of episodes and association with hearing loss
Peripheral vertigo symptoms
- Onset is sudden
- Associated with tinnitus (ringing), hearing loss, and horizontal nystagmus
Example of peripheral vertigo disease
Menieres. Over active depolarization due to too much potassium (K+) in the cochlear endolymph.
Central vertigo symptoms
Usually due to a systemic disease, tumor, or autoimmune.
Onset is gradual with no associated auditory symptoms.
Usually more disabling.
