Exam 5 - Hearing Flashcards
Three Parts of Ears
- Outer
- Middle
- Inner
These parts of ears involved with hearing
outer + middle ear
These part(s) associated in both hearing and equilibrium
Inner ear
Receptors for hearing and balance Respond to separate/the same stimuli
Separate
Receptors for hearing and balance are activated dependently/independently
Independently
The ___ (pinna) is composed of the Helix (rim) and the Lobule (earlobe)
Aurical
The ___ ___ ___ leads to the middle ear
external acoustic meatus
Short, curved tube filled with ceruminous glands; secretes earwax
External acoustic meatus
Medial border is the ___ ___ (eardrum), which serves as the boundary between the outer and middle ears
Tympanic Membrane
Thin connective tissue membrane that vibrates in response to sound waves
Tympanic Membrane
Transfer sound energy to the middle ear ossicles
Tympanic Membrane
Region of ear where medial boundary is oval window, lateral border is tympanic membrane
Middle ear
Small, air-filled mucosa-lined cavity
Middle Ear = Tympanic Cavity
connects the middle ear to the nasopharynx
Eustachian (auditory) tube
mid ear
Equalizes pressure in the middle ear cavity with the external air pressure
Eustachian (auditory) tube
mid ear
Swallowing and yawning open this tube, allows equalization
Eustachian (auditory) tube
mid ear
Cold/ear infection; can’t equalize pressure, the tympanic membrane bulges
More difficult in babies/toddlers since this tube is more parallel
Occlusion of Eustachian tube
middle ear
Three small bones in the middle ear
Ossicles
= malleus, incus, and stapes
middle ear
Suspended by ligaments and joined by synovial membranes
Ossicles
= malleus, incus, and stapes
middle ear
Transmit vibratory motion of the eardrum to the oval window (vestibule of inner ear)
Ossicles
= malleus, incus, and stapes
middle ear
mucles contract reflexively (CN VIII & inferior colliculi) in response to loud sounds to prevent damage to the hearing receptors of the cochlea
Tensor tympani and stapedius mucles
Middle Ear
Bony labyrinth which contains twisting channels which work their way through the temporal
bone (petrous region) and filled with perilymph
Inner Ear
Auditory ossicles transmit the vibratory motion of the eardrum to the ___ ___ of the ____ (stapes)
oval window of the vestibule
Ossicles are suspended by ___ and joined by ____ membrane
ligaments; synovial membrane
Recall: Cranial Nerve ___, listed as an “S” actually has a very small motor component; motor component is reflex loop to inferior colliculi and back to the muscles
VIII
Bony labyrinth which contains twisting channels which work their way through the temporal
bone (petrous region)
Inner Ear
filled with perilymph
Inner Ear
Contains the vestibule (entrance), the semicircular canals, and the cochlea
Inner Ear
Bony labyrinth contains a matching membranous labyrinth) filled with
Endolymph
Inner Ear
The central egg-shaped cavity of the bony labyrinth
Vestibule
Inner Ear
Suspended in its perilymph are two membranous sacs
Vestibule
Inner Ear
Membranous sacs that extends into the semicircular canals
Utricle
Membranous sacs in Vestible that extends into the Cochlear duct
Saccule
Utricle and Saccule house equilibrium receptors regions called
Maculae
Maculae respond to
gravity and changes in the position of the head
Maculae also maintain static equilibrium, or
make adjustments to keep balance in the new position
Maculae sensory information is transmitted to the brain via the Vestibular branch of
CN VIII
Three canals that each define two-thirds of a circle and lie in the three planes of space
Semicircular Canals
Continuous with the utricle; each canal lined with membranous semicircular ducts
Semicircular Canals
The ___ is the swollen end of each canal and it houses an equilibrium receptor
known as the the___
ampulla; crista ampullaris
Responds to the angular dynamic movements of the head (rotation)
Crista Ampullaris
Makes adjustments to keep balance during dynamic rotation; maintains ___ equilibrium
Dynamic Equilibrium
Crista Ampullaris
Sensory information is transmitted to the brain via the Vestibular branch of ___ nerve
CN VIII
A bony 3-layered, conical, snail-shell spiral chamber that extends from the vestibule
Cochlea
A bony 3-layered, conical, snail-shell spiral chamber that extends from the vestibule; looks like a snail shell
Cochlea (Hearing)
Three chambers of the cochlear cavity
1) Scala vestibuli
2) Scala media
3) Scala tympani
Abuts the oval window, contains perilymph
Scala vestibuli
Contains endolymph
Scala media = cochlear duct
Terminates at the round window; contains perilymph
Scala tympani
These are continuous at the cochlear apex
Scala Tympani and Scala Vestibuli
houses the spiral organ of Corti
Scala media
hearing receptor with cell hairs = ?
Sterocilia
This is the hearing receptor with sterocilia
Spiral Organ of Corti
The “floor” of the cochlear duct is composed of the ___, which supports the organ of Corti
basilar membrane
The “roof” of the organ of Corti is covered with the stiff gel-like ___; ends of stereocilia are embedded (trapped) in this covering
tectorial membrane
The ___ (filled with perilymph) sits below the scala media and terminates at the membrane covered, flexible round window
scala tympani
The signals are transmitted along the cochlear branch of Cranial Nerve ___
VIII
alternating areas of high and low pressure originating from a vibrating object
Sound
radiate outward in all directions; illustrated by a sine wave
Sound waves
the number of waves that pass a given point in a given time (Hz)
Frequency
intensity of a sound measured in decibels (dB)
Amplitude
The distance between two consecutive crests
Wavelength
subjective interpretation of amplitude
Loudness
Normal range is 0-120 dB (damage at prolonged 100dB +)
Loudness
perception of different frequencies
Pitch
Normal human range is from 20–20,000 Hz
Pitch
The higher the frequency, the ___ the pitch
higher
Sound waves vibrate the ___, thus pushing / vibrating the ___ and
subsequently amplifying the pressure
tympanic membrane, ossicles
The stapes pushes against the ___, creating fluid waves in the ___
oval window, scala vestibuli
The flexible round window bulges outward, allowing fluid to move in ___
waves
Sounds in the hearing range pass through the ___, vibrating the ___.
This movement sets up shearing forces that deflect the embedded stereocilia
cochlear duct, basilar membrane
Moving hair cells create___potentials which lead to ___Ps
graded, action
Sound waves of low/high frequency (> or < 20 Hz; inaudible) do not affect the cochlear duct
-Travel around the apex and therefore do not excite hair cells
low, less than
Audible sound waves will/will not vibrate the basilar membrane
-Excite specific hair cells located according to the frequency of the sound
will
Higher frequency waves deflect the short and stiff basilar membrane fibers near/far from the
oval window
near
Mid and low frequency waves deflect longer basilar membrane fibers further down/up
the cochlea, closer to the apex
further down
Age-related stiffening of the joints of the ossicles, so can’t vibrate as fast;
subsequent loss of high frequency hearing
Otosclerosis
Bending of the stereocilia embedded in the gel-like tectorial membrane
Excitation of Hair Cells in the Organ of Corti (Spiral Organ)
Bending stereocilia:
1) Opens ____ gated ion channels
1) Mechanically
Bending sterocilia:
2) Causes a ___ potential (with subsequent release of the neurotransmitter glutamate)
graded
Bending stereocilia:
3) ___ travel along the cochlear nerve afferent fibers (at the base of the hair cells)
AP’s
Transmission of Sound in Ear: Overview
1. Sound waves vibrate ___ membrane
Tympanic
- Auditory ossicles vibrate. Pressure is ___
amplified
- Pressure waves created by the ___ pushing on the oval ___ move through the perilymph in the scala ____.
stapes
window
vestibuli
- Sounds in the hearing range go through the cochlear duct, vibrating the basilar membrane and deflecting hairs on inner hair cells. The moving hair cells stimulate transduce to graded potentials that will ultimately send APs along the ___ nerve.
cochlear
audible sound waves
20-20,000 Hz
stereocilia are embedded in gel-like
tectorial membrane
5) Impulses from the choclea pass via the spiral ganglion to the ___ nuclei of the medulla.
cochlear
6) Axons will project to and synapse at
a. Superior olivary nucleus (pons/medulla)
- involved with directional hearing
6)) Axons will project to and synapse at
Inferior colliculus
auditory reflex center
7) From there, impulses pass to the ___ cortex via the thalamus
Auditory Cortex
Look at p 51 of the powerpoint on hearing
okay
Part of brain that
- provides conscious awareness of sound, including loudness, pitch and direction
Auditory Cortex
Part of brain that
- Some (but not all) auditory pathways decussate so that both cortices receive input from both ears
- this is how we “localize” the source of the soundn
Auditory Cortex
Part of brain that:
-Stores memories of sounds
Auditory Association Cortex
Multiple ___ regions, including Wernicke’s, involved with language ___
cortex; comprehension
something hampers sound conduction to the fluids of the inner ear
(e.g. impacted cerumen, perforated eardrum, otitis media [middle ear infection], otosclerosis)
Conduction deafness
results from damage to the neural structures at any point from
the cochlear hair cells to the auditory cortical cells
Sensorineural deafness
provides a sense of hearing for someone who is profoundly deaf but
has a functioning auditory nerve
Cochlear Implants
ringing or clicking sound in the ears in the absence of auditory stimuli
Tinnitus
Due to
-cochlear nerve degeneration,
-inflammation of middle or internal ears,
-side effects of aspirin (and many other ototoxic drugs),
-exposure to loud sounds over extended
period of time (concerts, earbud-style headphones with volume too high)
Tinnitus
equilibrium receptors in the vestibule and semicircular canals
Vestibular Apparatus
(maculae in vestibule) monitor static equilibrium
Vestibular receptors
(cristae ampulares) monitor dynamic equilibrium
Semicircular Canal Receptors
___ macula in each saccule wall and ___ macula in each utricle wall
One; One
Static Equilibrium
Monitor the static position of the head in space, necessary for the control of posture
Maculae and Static Equilibrium
Will also respond to linear acceleration forces, but not rotation
-Example: speeding up in a car on the road, traveling in a straight line
Maculae and Static Equilibrium
Contain supporting cells and hair cells
Maculae and Static Equilibrium
Each hair cell bundle has ___ stereocilia and a single ___ embedded in the ___ membrane
many sterocilia; single kinocilium; otholithic membrane
Gel-like mass studded with tiny CaCO3 stones called otoliths
otolithic membrane
tiny CaCO3 stones
otoliths
add weight to the gel membrane so that it shifts along the surface of
the hair cells with position changes
Otoliths
Dendrites of ___ nerve fibers encircle the base of the hair cells
vestibular
Macula in the utricle responds to ___ movement
horizontal
Macula in the saccule responds to ___ movement
vertical
Otolithic membrane movement which bends the hair cells (within a hair bundle) in the direction of the ___
kinocilium
Activating the Macula
Hair cells trasduce signal which ___ vestibular nerve fibers
depolarizes
Thus, ___ the frequency of action potentials generated in the ___ nerves
increases; vestibular
Movement in the opposite direction (hair cells bend ___ from the kinocilium)
- Hyperpolarizes vestibular nerve fibers
- Reduces the rate of impulse propagation
away
From the increase/decrease in impulse frequency, the brain is informed of the changing position of the head
truth.
- Nerve impulses generated in the ___ fiber
vestibular
- When hairs bend toward the kinocilium, the hair cell depolarizes, exciting the nerve fiber, which generates ___ frequent action potentials.
more
- When hairs bend away from the kinocilium, the hair cells hyperpolarizes, inhibiting the nerve fiber, and ___ the action potential frequency
decreasing
One ___ in the ampulla of each semicircular canal
Crista
Respond to rotational/angular movements
Crista Ampullares of Semicircular canals
Contain supporting cells and hair cells
Crista Ampullares of Semicircular canals
Each ___ has support cells and hair cells
crista
Each hair cell bundle has ___ stereocilia and a single ___ embedded in gel-like mass called CUPULA.
many
Kinocilium
Dendrites of ___ nerve fibers encircle the base of the hair cells
Vestibular
Cristae respond to changes in _____ of the head
Velocity of rotatory movements
Activating the Crista Ampullaris
When rotating/spinning, endolymph flows in the ___ direction of the spin
opposite
Reminder: each plane of rotation is represented by a
different semicircular canal
Endolymph flow over the cupula bends the embedded ___ in the cristae, Causes ___, and a ___ frequency of impulses
hairs
depolarization
high
Once the spinning stops, the ___changes direction over the cupula
- Hair cells bend in the opposite direction
- Causes ___ and ___ frequency of impulses
endolymph
hyperpolarization
lower
The result is that the brain is informed of ___ movements of the head
rotational
Equilibrium pathways are coplex and ___ traced
incompletely
Impulses travel directly to the reflex centers of the ___ in the brain stem and/or the ___
- both receive simultaneous inputs from the visual receptors and proprioceptors (eyes, muscles, and joints)
vestibular nuclei
cerebellum
Fast input which permits a Fast reflexive response
- doesn’t proceed to thalamus/cerebral cortex
- Permits our body to respond reflexively and quickly
Equilibrium Pathways
Reflex Output
Extrinsic Eye Muslce Control for eye movement
Cranial Nerves
III, IV, V
Reflex Output
___ nerve and ___ tract control for neck movements to change the position of the head in space
Accessory nerve
Vestibulospinal tract
Labyrinth disorder that affects both the cochlea and the semicircular
canals, causing vertigo, nausea, and vomiting (and usually severe tinnitus)
Meniere’s Syndrome
The rapid beating of the eyes following rapid & repeated rotatory movements
Nystagmus
Vestibular system interprets your head as “spinning” but your visual inputs show your
head has stopped spinning
Nystagmus
Benign Paroxysmal Positional Vertigo
BPPV
Loose otoliths enter the semicircular canal
BPPV (Benign Paroxysmal Positional Vertigo)
