Auditory Anatomy and Physiology Flashcards
The concha has a resonance of _____ Hz.
5000 Hz
The acoustic property of the concha ___________________________.
Adds a peak of energy to the incoming message.
The external auditory canal has a resonance of _____ Hz.
2500
The acoustic property of the external auditory canal ______________________.
Adds a second boost of energy to the incoming message.
The acoustic properties of the outer ear _______ from person to person. (Stay the same/change)
Change from person to person
The first half to two-thirds of the canal is ___________.
cartilaginous - lined with glands that produce cerumen; lined with cilia
The second 1/3 of the canal is _______.
bone - it forms the first layer of skin that comprises the TM
The length of the external canal in adults is:
29-30 mm; 2.9-3.0 cm
The length of the external canal in infants is:
~14mm (grows to 21 mm by age 2)
The outer ear (pinna and ear canal) assists us in ________________
sound localization
The pinna and ear canal serve as a _________
resonator
The pinna and ear canal act as a ________ for the temporal bone (the hardest bone in the body)
cushion
What are the three ossicular bones?
malleus, incus, stapes
The tympanic membrane sits in a groove called the ______________
tympanic sulcus
What are the three layers of the tympanic membrane?
- Cutaneous: outer layer (skin)
- Fibrous: provides most of the structure and compliance. Density is greatest at center. Gives integrity to the very thin structure.
- Internal: mucous membrane; helps keep membrane healthy
Which layer of the tympanic membrane provides most of the structure and compliance?
The Fibrous layer
In the fibrous layer, density is greatest at the _______ and gives _______ to the very thin structure.
center; integrity
Which layer of the tympanic membrane is the outer layer (the skin)?
The Cutaneous layer
Which layer of the tympanic membrane is the mucous membrane that helps to keep the membrane healthy?
The Internal layer
The ossicular chain is held in place by what four things?
- TM
- 4 ligaments attached to the malleus and 1 ligament attached to the incus
- Tendon of the Tensor Tympani muscle and tendon of the Stapedius muscle.
- Annular ligament around Stapes footplate in the oval window.
Which two tendons help hold the ossicular chain in place?
The Tensor Tympani and Stapedius muscle
Which tendon contracts when presented with a loud sound?
Stapedius muscle
Which tendon protects the inner ear from damage?
Stapedius
The tendon of the Tensor Tympani and the Stapedius muscle are ________ elastic than in other places in the body.
much more elastic
The tendon of the Tensor Tympani and the Stapedius muscle make muscle contractions occur ________
more slowly - no sudden contractions
The Tensor Tympani muscle is a _____ muscle with a ____ effect.
large muscle; small effect
The Stapedius muscle is a _____ muscle with a _____ effect.
Small muscle; large effect on the transmission of sound through the ear
Middle ear muscles (2):
Tensor Tympani
Stapedius
The stapedius and tensor tympani contract in _______ directions to prevent primary rotation of the ossicular chain
opposite directions
Why do the stapedius and tensor tympani contract in opposite directions?
keeps them in their correct plane
The stapedius is completed encased in ____, only ___ enter the tympanic activity.
bone; tendons
(T/F) The stapedius is a protective mechanism.
True
The function of the middle ear muscles are to _____________________________.
Modify the vibration of the ossicular chain
The _______ contracts with loud sounds and just before speaking.
Stapedius
The _______ contracts during swallowing, chewing and some other facial movements.
Tensor Tympani
What are the two muscles of the eustachian tube?
Tensor veli palatine (TVP)
Levator veli palatin (LVP)
Can the ear drums repair themselves?
If they are healthy, they can repair minor issues
What is the function of the Eustachian tube?
To equalize the air pressure in the middle ear
To allow fluids trapped in the middle ear to be drained
Whose function is to modify the vibration of the ossicular chain?
The middle ear muscles: the tensor tympani and stapedius
What is the function of the middle ear?
To create an impedance match
There is an impedance mismatch between the ____ and the ____
outer ear; inner ear
Impedance
the sum of all the energy that opposes the transmission of sound
Equalizes the air pressure in the middle ear; allows fluid trapped in the middle ear to be drained
Eustachian Tube
(T/F) It takes an equal amount of energy to produce a wave in the fluid of the inner ear than in the atmosphere where sounds are generated.
FALSE. It takes MORE energy to produce a wave in the fluid of the inner ear than in the atmosphere where sounds are generated.
How does the middle ear help to resolve the mismatch between the outer and inner ears?
There is a difference in the surface area of the TM relative to the area of the stapes footplate
This difference contributes about 25 dB of improved sound transmission by focusing the vibratory area onto the smaller footplate.
There is a leverage created by the geometric configuration of the ossicles contributing approximately another 12-13dB of amplification
The impedance mismatch between the outer and inner ears contributes about _______ of improved sound transmission by focusing on the vibratory area onto the smaller footplate.
25 dB
The sum of all the energy that opposes the transmission of sound
Impedance
The leverage created by the geometric configuration of the ossicles contributing approximately another ______ of amplification in the impedance mismatch between the outer and inner ears.
12-13 dB
The three semicircular canals are also called _______ canals
balance
What are the two windows of the inner ear?
Oval Window
Round Window
The oval window is located at the ______________
stapes footplate
The oval window is:
flexible (moveable)
The oval window opens into the ______________
scala vestibuli
The round window is at the base of the ___________
Scala Tympani
The round window equalizes:
pressure when the stapes moves in and out
When the stapes moves ___ at the ___ window, the ___ window moves ____.
moves in at the oval window, the round window moves out
The oval and round windows always move in _______.
opposition
The vibrations created by the oval and round windows are _____ for high frequency sounds and ____ for low frequency sounds.
faster; slower
What are the three ducts?
Endolymphatic duct
Scala vestibuli
Scala tympani
The boney labyrinth is made up of: (2 things)
scala tympani
scala media
The boney labyrinth is filled with the fluid called ______.
perilymph
Perilymph is similar to _________
…cerebrospinal fluid
…the ionic composition of extracellular fluid
Perilymph fills the:
scala vestibuli, scala tympani, vestibule, vestibular system
The vestibule is:
the connection between the cochlea and the semi-circular canals)
(a duct within a duct)
The vestibule contains:
the utricle and saccule of the membranous labyrinth
The membranous labyrinth houses:
sensory cells
What are the three parts of the membranous labyrinth?
Vestibular (2 parts): semicircular canals; utricle and saccule Cochlear duct (1 part): scala media
What are the three layers of the cochlea?
Scala vestibuli (top) Scala media (middle) Scala tympani (bottom)
Where do neurons go after they leave the cochlea?
The auditory pathway extends from the cochlea to the cerebral cortex via five orders of neurons
The _____ set of neurons extends from the inner ear cells to the cochlear nucleus.
first-order neurons
The utricle and saccule provide information about the movement of the ______
head
How many ampulla are there?
3: present at the end of each semicircular canal
The cochlea is where the actual transduction of _________ to ________ energy takes place
mechanical –> electrical
The movement of the fluid causes a deflection of the tiny hair cells (mechanical) of the inner ear which in turn sets off what?
An electrical signal that is then transferred to the brain for interpretation
Higher frequencies cause the ________ to move more than the _____.
base; apex
When the OHC’s are pushed by the basilar membrane into the tectorial membrane, the stereocilia are bent ______ the _____
towards; kinocilium
Shearing opens ______________ near the tips of the sterocolia allowing electrically charged ions to flow into the hair cell.
Ion channels
Which hair cells die/damage first?
High frequencies probably due to the scrubbing or shearing motion.
For noise induced hearing loss, the continual ‘pounding’ of the stapes into the basal ed of the cochlea
The stapes is embedded in the:
base of the cochlea
Action potential
Electrical Transduction
The endolymphatic sac is involved in ____________
fluid exchange
What are the boundaries of the membranous labyrinth (3)
Reissner’s Membrane
Spiral Ligament
Basilar Membrane
Separates the scala vestibuli from the scala media
Reissner’s membrane
Separates the scala tympani from the scala media as well as houses the sensory cells
Basilar membrane
holds the membranes in place
Spiral ligament
The membraneous labyrinth is suspended within the bony canal by:
The spiral ligament (stretches to the outside wall; suspends the Basilar membrane)
Osseous Spiral Lamina (thin shelf of bone)
What fluid is within the membranous labyrinth (scala media)
Endolymph
The ________ energy at the stapes footplate transmits its vibration into the fluids of the cochlea
Mechanical energy
The basilar membrane is located at the _____________.
base of the cochlear duct (scala media)
The (base/apex) of the basilar membrane is wider, has more mass, and is more flaccid.
Apex
The (base/apex) of the basilar membrane is narrower and more stiff (under more tension).
Base
The scala media gets ________ base to apex.
Smaller
The basilar membrane gets _____ from base to apex.
Wider
Low frequencies cause a motion from the ______ to the _____ but more at the _____.
base; apex; apex
Are the outer and inner hair cells embedded in the basilar membrane?
Yes
Do the stereocilia of the outer hair cells touch the tectorial membrane?
YES
Do the outer hair cells touch the tectorial membrane?
NO: They stop just short of the tectorial membrane
The basilar membrane displacement causes ______ of the stereocilia.
Shearing
The tallest of the hair cells
Kinocilium
When the stapes moves ______, it pushes the basilar membrane up. Hair cells move into the tectorial membrane. Bend is ______ the tallest hair cells.
Out; toward
When the stapes moves ____, the basilar membrane extends downward, the stereocilia are bent _______ from the kinocilium.
Up; away from
The shearing movement of the hair cells is what transmits __________
The electrical energy
The shearing motion is due to :
several pivot points in the Organ of Corti - pivot points are attached to the spiral lamina and spiral ligament
How fast does the shearing motion occur?
If the tone is 1000 Hz, the BM moves at a rate of 1000 x/sec.
E.g., 4000 Hz = 4000 times/second
Does the whole BM move at 1000 x/second during the shearing motion?
No. Just the spot that responds best to 1000 Hz. Higher frequencies at the base, lower toward the apex.
What makes the IHC’s move back and forth?
Movement of fluid between the TM and the BM. Fluid washing over the stereocilia
The ion channels create a change of voltage from ________ to _____ and is what generates the firing of the nerve
Negative to positive
Some of the fluids and cells within the cochlea are positively charged and some are negatively charged
Resting potential
Has little/no electrical change (0-5mV)
Perilymph
Movement of the perilymph within the cochlea
Hydromechanical Transduction
traveling wave and shearing of the stereocilia
Mechanical (Step 3) Transduction
TM, ossicular, and stapes movement
Mechanical (Step 1) Transduction
Order of transduction:
Mechanical, hydromechanical, mechanical, electrochemical, electrical –> auditory nerve
change in the ionic composition within the hair cells that produces an action potential
Electrochemical transduction
Inner hair cells transduce sound waves into electrical impulses that reach the brain via the ______ nerve.
VIII
the signal is transduced a number of times:
Transduction
___________ motion of BM causes fluid to be pumped in and out of the internal spiral sulcus which bends ______.
Up and down; stereocilia
Current causes the cell to release ____________ which elicits responses in primary auditory neurons
a neurotransmitters
Reflects amplification provided by the cochlear amplifier. Low level sounds near center frequency are amplified
Active response
Because inner hair cells are not directly attached to the tectorial membrane, shearing occurs via _____________.
fluid movement
The cochlear amplifier improves: (2)
The sensitivity of the basilar membrane
Frequency selection
Reflects variation in stiffness of the Basilar Membrane
Passive response
Motility increases the ______ of the basilar membrane.
Displacement
Increase in input is called the:
Cochlear amplifier
OHC change in _________________
shape - they length and shorten
Motility generates:
force
(Force changes the motion of the traveling wave
Positive feedback loop
Increases the displacement of the basilar membrane)
Outside the cell, there is _________ charge.
Positive
Isolates the cell body from the stereocilia
Reticular lamina
The battery of the cell; pumps positively charged ions into the hair cell and then pumps them back out again into the endolymph.
Stria vascularis
Inside the cell, there is _________ charge.
Negative
Where do neurons go after they leave the cochlea?
The auditory pathway extends from the cochlea to the cerebral cortex via five orders of neurons
Has a high positive charge (80mV)
Endolymph
The intracellular potential (inside the hair cells) is highly ________
negative
Energy starts as acoustic energy and then once it hits the ear drum, becomes:
Mechanical energy
In the aging ear, we now believe that it is the aging of the __________ that is actually changing more rapidly than actual hair cell loss.
Stria vascularis
OHC’s are equal to the:
rate of the stimulus frequency
Forces changes the motion of the ______________
traveling wave
Outer hair cells ________ sound impulses
Amplify
at the top of each hair cell
Sterocilium
Kinocilium are the tallest of the outer/inner hair cells
Outer
forms the overlying portion of the tectorial membrane
internal spiral sulcus
pivotal points are found on the:
basilar membrane
