Week 4 - Study Guide - Hearing Flashcards
Three parts of the ear
External
Middle
Internal ear (labyrinth)
Where is the pinna (auricle)?
Ear flaps
Where is cerumen produced?
Auditory canal
What function does earwax serve?
Deters insects
waterproofing
help prevent ear infections
Where is the external acoustic meatus?
Hole through the skull
canal through the skull to middle ear and inner ear
Middle ear is for
hearing
Air and bones to amplify sound
Tympanic cavity
Tympanic Membrane
at the border between the external and middle ear
eardrum
AKA
Tympanic membrane
Middle ear is filled with
Air
an air-filled tympanic cavity
The connection between the middle and inner ear is
the Oval and Round window
Oval window is a membrane associated with
vestibular canal
where the sound wave enters
Round window is a membrane associated with
tympanic canal - an inner component
where the sound waves leave
Oval window is where
on the stapes
Round window is where
round window is below the stapes
Middle ear has a connection from the ear to throat - what is it?
3 names
1. Auditory tube
2. Pharyngotympanic (auditory) tube
3. Eustachian tube
The auditory tube is open to ?
Open to the pharynx
What is the function of the auditory tube?
to equalize pressure of middle ear and the atmosphere
Feature in the middle ear
Epitympanic recess
is the dead-end cavity
Epitympanic recess may what?
detect very low wavelength sound
Name the three auditor ossicles from lateral to medial
- Malleus = hammer
- Incus = anvil
- Stapes = stirrup
Malleus is physically associated with…
with the tympanic membrane (eardrum)
What bone is closely associated with the oval window?
Stapes
3 auditory ossicles working –
- when the tympanic membrane vibrates
- ossicles pick up the vibration
- and they MAGNIFY it 20X
How much do the ossicle bones amplify sound?
20x
Internal Ear is about
Hearing & Balance
senses Rotation of head and Linear movement of head
What is the open space within the cavity of the skull called?
Bony Labyrinth
Where do you find the structures:
Vestibule
Semicircular canals
cochlea
Bony Labyrinth
Details about the bony labyrinth:
- Membrane lined
- filled with perilymph fluid
- located in the temporal lobe
What is the hollow tube within the bony labyrinth?
Membranous Labyrinth
Inner membrane that has more fluid
What type of fluid is in the membranous labyrinth?
endolymph fluid
What two things are in the Membranous Labyrinth?
- Endolymph fluid
- Receptors
Associated with either Balance & equilibrium or Hearing
Equilibrium sensors of the inner ear…
Contain Hair cells-
- Vestibular sensors - including the utricle and saccule
- Semicircular Canals
Vestibular Sensors are really good at general awareness of…
- influenced by gravity
- head position - whether you are right side up, upside down, off at an angle
- linear accel/decel - walking, running, walking sideways, up and down an elevator
All linear positions of motion where your head is moving on a straight trajectory
Semicircular Canals are all about…
angular accel/decel
rotation of the head including acceleration and deceleration.
If your head is rotating in space- the semicircular canals will sense it
The structure within the cochlear called
the Organ of Corti
What is the function of the Organ of Corti?
It responds to vibration
- that are picked up from the tympanic membrane and the ossicles picking up the vibration from the oval window
- interpret based on the sensors that get stimulated
- And what kind of action potentials are sent to the brain
The Cochlea has three regions -
- Vestibular canal (scala vestibuli)
- Cochlear Duct (scala media)
- Tympanic canal (scala tympani)
The cochlea has two membranes
- vestibular
- basilar
helicotrema
Feature that is the dividing line between the (top region) vestibular canal (scala vestibule) (where canal narrows)
And the (bottom region) Tympanic canal (scala tympani) begins
Sound waves enter this window and exit this window
enter the oval window
exit the round window
What bone is associated with the oval window?
stapes
What is inferior to oval window?
round window
Round window connects to
round window is the membrane that connects up to the middle ear again
Order from top to bottom the three regions of the cochlea
- vestibular canal (scala vestibuli)
- cochlear duct (scala media)
- Tympanic canal (scala tympani)
Name the two canals in the cochlea
- Vestibular canal (upper)
- Tympanic canal (lower)
What is located between the two canals in the cochlea?
Cochlear duct (scala media)
What fluid fills the upper and lower canal
(scala vestibuli and scala tympani)
perilymph fluid
What fluid fills the cochlear duct (scala media)?
endolymph fluid
What is the sensory structure in the cochlea?
Organ of Corti
Organization in the organ of corti?
top layer - tectorial membrane
middle - hair cells attached to the tectorial membrane
Bottom - Basilar membrane
WHICH MEMBRANE OF THE ORGAN OF CORTI VIBRATES?
the Basilar membrane
What happens in the organ of corti
- Basilar membrane vibrates
- hair cells bend and hit the tectorial membrane
- causing hyper or depolarization
High and low pitch is distinguished by
where in the cochlea hair cells hit
Detection of sound (perception of sound)
movement of the basilar membrane bends the haor cells in the Organ of Corti
Generates an AP
Stereocilia is associated with
the outer hair cells - in the inner hair cells
What is foundational in getting the APs from inner ear to the brain for both basilar membrane system and stereocilia system
Mechanical gates
Hair cells connect to gates creating one of two things -
- Hyperpolarization
- Depolarization
Pressure wave =
Sound
high pressure
low pressure
We will perceive the sound (pressure wave) …
- based on pitch
- frequency
- amplitude of the sound (loudness)
High Frequency =
High Pitch
Travels faster
Low Frequency =
Low pitch
(low pitch takes longer to travel)
Amplitude =
loudness
The Ossicles pick up the vibrations and amplify them by
20x
Why does it matter that the ossicles amplify by 20x?
because to have enough signal strength to move from air-filled to liquid-filled
What part of the ear amplifies sound?
ossicles
by 20x
Low frequency
causes vibrations where
distal portion of the membrane
furthest away from the oval window
High frequency causes vibrations where
proximal portion of the membrane
closest to the oval window
What are the two functions of the ossicles?
- transferring the vibration from the middle ear to the inner ear
- Amplification (20x)
What light conditions are we in if… (Light or Dark)
Rod pigment is in 11-cis retinal form
Dark
What light conditions are we in if… (Light or Dark)
cGMP is bound to the gate on the rod membrane
Dark
What light conditions are we in if… (Light or Dark)
cGMP is being converted to GMP
low light
talking about rods
What light conditions are we in if… (Light or Dark)
PDE is being activated by transducin
low light
rods again
photobleaching
What light conditions are we in if… (Light or Dark)
Rod is inhibited & bipolar cell begins to depolarize
light
Difference between sensorineural and conductive
- Conductive hearing loss is impeded (ear wax example) through the external or middle ear or both
- sensorineural hearing loss is problem in the cochlea or neural pathway to the auditory cortex
otitis media
infection in the middle ear that causes inflammation and build-up of fluid behind the eardrum
otosclerosis
can happen when abnormal bone growth in your middle or inner ear interferes with sound’s ability to travel
causing progressive hearing loss
Meniere’s disease
a disorder caused by build of fluid in the chambers in the inner ear
affecting balance and hearing - vertigo bouts
tinnitus
Ringing in the ears
Vestibulocochlear nerve decussates in
crosses over in the medulla
BUT some fibers cross back
Brain is processing sound from both ears
Loudness affects …
Tympanic membrane - it will move more or less depending of the sound was loud or soft
Which frequency is harder to pinpoint the location?
low frequency
Localization of sound by
- timing - closer ear detects first
- loudness - move tympanic membrane more or less
- high pitch sounds perceived as loudest in ear nearest the source
- Low-pitch sound perceived as equally intense - harder to figure out where it is happening
Hair cells are attached to the cranial nerves of the vestibular or cochlear named what kind of nerve?
vestibulocochlear nerve
Location of the Utricle & Saccule sensors
- against the walls of the inner ear
- between the semicircular canals and the cochlea
Utricle and Saccule sense…
- linear translation
or (static) - Equilibrium sense related to gravity
The name of the receptor structure within the utricle and saccule
Macula
Macula is made up of
- Hair cells with stereocilia
- embedded in a gelatinous matrix
- covered with CaCO3 crystals = otoliths
additional weights on top on the gelatinous mixture
JELLO THEORY with fruit
Why do we have otoliths on top of the macula within the utricle and the saccule?
- to be most sensitive to small linear motions
they allow for improved sensitivity
Think of the semicircular canals as 3 loopdy loops on a roller coaster…
- the motion in each of these 3 canals is in a different orientation
- Allowing us to be sensitive to how our head is rotating in space
- in various directions
Semicircular canals can sense
Angular Rotation
Hair bundle in the semicircular canals
Kinocillium and nerves - sterocilia
When you shake the fluid in the semicircular canals it causes the fluid to move…
- Causing cupulla to bend hair cells
- Crista ampullaris
Bend one way causes inhibition
other way causes excitation
Name of the fluid in the semicircular canals
Endolymph
Name of the hair cells in the semicircular canals
Crista ampullaris
sensory hair cells
Enlargement in the semicircular canals is called
Ampulla
an open space where the hair sensors are located
Name of the Open space where the hair sensors are located (in the semicircular canals)
Ampulla
Name of the sensory hair cells in the semicircular canals
Crista ampullaris
What is the gelatinous mass that is embedding in the hair cells of the semicircular canals?
Cupula
The sensors in the semicircular canals sense
- Acceleration
- Deceleration
BUT not steady speeds
responds to changes in a rotation causing an AP to be sent
Where in the Cochlea is perilymph located?
Scala vestibuli & Tympani vestibuli
Where in the Cochlea is endolymph located?
scala media
Name the two membranes of the Cochlea
- tectorial membrane
- Basilar
Explain how sound waves (pressure) travel to the labyrinth & cause perception of auditory signals (high versus low frequencies???)
- Air–>Bones–>Fluid with amplification,
- basilar membrane vibrates
- hair cells deflect against the tectorial membrane
Two types of eye movements
- Slow
Smooth pursuit - Fast
Saccade
Smooth pursuit
SLow eye motion
eyes move opposite to head
-You can watch car drive by as it moves L to R or vice versa
- a smooth tracking motion
Saccade
Fast eye motion
Eye moves same as head
Extreme L to R
Not tracking anything
Moving eyes quickly to a new target in visual space
Optokinetic nystagmus - elicited
Making quick eye movements
track
head does not move but eyes move
Nystagmus - clinical
twitching - general motion
Pattern of motion due to lack of eye control
