Test 4 Review Flashcards
1
Q
What is the pinna?
A
Everything on the outside that attaches to your ear.
2
Q
What is the external auditory canal?
A
Everything inside, starting from the little hole and going further back into the eardrum.
3
Q
What is the pinna made out of?
A
The whole thing is made out of cartilage EXCEPT for the earlobe, which is made of fat and vascularization.
4
Q
What is the function of the concha?
A
The concha helps with localization of sound in that in helps funnel the sound into the ear. The bulk of the sound increasing in collection id done in the concha.
5
Q
What is the function of the helix and antihelix?
A
They help with pinna cues in timing and localization.
6
Q
How many cranial nerves innervate the ear?
A
Five; Greater auricular, auriculotemporal, facial, auricular branch of vagus, and the lesser occipital
7
Q
What does the greater auricular innervate?
A
Sensory innervation to parts of the outer ear [tragus, anterior wall, external auditory meatus]
8
Q
What does the auriculotemporal innervate?
A
Parts of the outer ear (helix and antihelix)
9
Q
What does the facial nerve innervate?
A
The stapedius muscle
10
Q
What does the auricular branch of the vagus innervate?
A
The ear canal and tympanic membrane
11
Q
What does the lesser occipital innervate?
A
Helix of ear
12
Q
What artery supplies the pinna and ear canal and what are the branches?
A
The external carotid artery.
1. Superficial temporal artery: anterior portion of pinna, tragus, anterior helix, earlobe, and ear canal.
2. Posterior auricular artery: posterior portion of pinna and ear canal
3. Maxillary artery: Ear canal
13
Q
What are the functions of the outer ear?
A
Captures sound
Acts like a pre-amplifier [sound boost]
Changes the timing of sounds
Helps locate objects
14
Q
True or False: Different parts of the pinna add different amounts of gain to the total sound collected.
A
True
15
Q
What is microtia?
A
A condition where the external ear is underdeveloped or malformed at birth.
16
Q
What is anotia?
A
A completely undeveloped ear
17
Q
What clinical signs would you expect to see with a person who has microtia/anotia?
A
Preauricular pit, peanut ear, complete absence of ear
18
Q
How is microtia/anotia treated?
A
If the ear canal is there and the ear just closed up:
1. Drill out the entrance
2. Install a prosthetic
19
Q
What is an auricular hematoma?
A
Swelling of fluid and pooling of blood.
Boxers’ ear [also called cauliflower ear]
Results from blunt force trauma. Vesicles open, ear floods with blood and fluids. If not treated, it hardens.
20
Q
What is basal cell carcinoma?
A
Cancer that first shows as a red flaky spot on the antihelix. Scabs over: Open leaky sore. The longer it sits-more it will spread to the rest of the body.
21
Q
Sunburning of the ear:
A
Overabundance of radiation that destroys outer skin cells. When this occurs frequently, it is the cause of starting the cancer cycle (with apoptosis).
22
Q
What is perichondritis?
A
Bacterial infection for the cartilage/connective tissue. Results from trauma, punctures, piercings, and surgeries. Lose epidermal protective layering. Treated with strong antibiotics.
23
Q
What is otitis externa?
A
Infection of the outer ear.
Red flakiness, tenderness, super oily ear, oozing earwax, also called swimmers’ ear. Treated with over the counter ear drops.
24
Q
External auditory canal:
A
General S shape. No 2 ear canals are the same. 1/3 cartilage, intermedial 2/3 skin on bone. Osteocartilaginous junction: 1/3 cartilaginous, 2/3 bony
25
Lateral 1/3 of external auditory canal:
Passes through cartilage
Contains sebaceous glands, which secrete sebum for earwax production
Contains hair follicles
26
Earwax:
Combination of oil from the sebaceous glands and wax from the ceruminous glands. Mixing them together creates cerumen.
Biggest factor: Race but also very person specific. Slightly acidic (antifungal), serves as water repellent. Function: Lubricates, cleanses, and protects the ear.
27
What is excessive/impacted cerumen caused by?
Q-tips, Insert earphones, and earplugs
Can result in: Dizziness, hearing impairment, ringing in the ear, plugged sensation, soreness, and itching in the ear.
28
What is exostosis (osteoma)?
A benign growth of bone on top of existing bone (Surfer's ear)
Can cause: Decreased hearing, more frequent earwax impaction, and discomfort in rare cases. Extreme cases: Drill out and reopen the ear canal
29
What is the tympanic membrane?
The eardrum; it marks the border between the outer and middle ears.
Concave shape
3 layers:
1. Outer layer-same as EAC
2. Middle Layer: Tough fibrous connective tissue
3. Inner layer: Mucous membane
30
What are the landmarks of the tympanic membrane?
Malleus: Largest bone of the middle ear
Umbo: Tip of malleus that terminates near the middle of TM
Annulus: Ring of tissue that holds the TM in position at the end of the EAC
Pars Tensa: Taut area of TM (largest position)
Pars Flaccida: Area of loose tissue above the malleus
Cone of light: Light reflections observed in the anterior-inferior quadrant (otoscopy)
31
What is the purpose of the tympanic membrane?
To connect sound from the outer to the middle ear
To protect and separate the outer ear from the middle ear.
32
What is a perforation?
When the tympanic membrane has a hole, tear, or break in it.
It can heal on its own over time, or be "patched" with a surgery
33
What is tympanosclerosis?
White scarring of the tympanic membrane caused by calcium phosphate deposits in the middle and interior layers of the tympanic membrane.
Can be caused by frequent otitis media or repeated perforations.
34
The Middle Ear:
Air Filled Space.
Transmits sound-induced mechanical vibrations to fluid-filled cochlea. Eardrum and ossicles are the interface through which airborne vibration is converted to fluid vibration. Encased int he temporal bone. Normally closed but opens during swallowing and yawning.
35
What comprises the ossicular chain?
Malleus, incus, stapes
36
What are the middle ear muscles?
Tensor tympani and stapedius muscle
37
What is the purpose of the ossicles?
Transfer sound from the tympanic membrane to the cochlea
Amplify sound
Pressure applied to the TM is concentrated onto the much smaller stapes through a series of lever connections.
38
Lever Action Mechanism of the ossicles?
1. The ossicles rock back and forth on an axis, and the action of the stapes in the oval window is like that of a pivot.
2. Through leverage, the force received at the stapes footplate is greater than that applied at the malleus.
3. The ratio of TM displacement to oval window displacement is increased by 1:3:1.
39
What is the purpose of the middle ear muscles?
During the acoustic reflex, loud sounds make the stapedius muscle contract; this makes the middle ear system stiffen.
1. Tensor tympani pulls on malleus
2. Stapedius pulls on stapes.
40
When presented with a loud sound stimulus:
1. The stapedius and tensor tympani muscles of the ossicles contract.
2. The stapedius stiffens the ossicular chain by pulling the stapes of the middle ear away from the oval window and the tensor tymapni stiffens the ossicular chain by loading the tympanic membrane when it pulls the malleus in toward the middle ear.
3. Decreases transmission of vibrational energy-> electrical impulses sent to brain
41
Eustachian tube:
Only opening of the middle ear space is through the ET. It opens during swallowing and yawning.
42
Tensor Veli palatini vs Levator veli palatini:
Tensor Veli Palatini: Tenses soft palate
Levator Veli Palatini: Elevates soft palate.
Together: Tense, elevate, and close the passage between the nasopharynx and the oropharynx. Prevents food from entering nasopharynx while swallowing.
43
What happens when the tensor veli palatini and levator palatini muscles contract?
The Eustachian tube is forced open. Allows air pressure to equalize between the middle ear cavity and outside air. Equalization is essential for preventing damage to the TM and maintaining hearing acuity.
44
What cranial nerves innervate the middle ear?
Trigeminal, Vagus, glossopharyngeal, and facial
45
What does the maxillary artery supply?
The external surface of the tympanic membrane.
46
Negative middle ear pressure:
Air trapped within the middle ear becomes absorbed by the middle ear tissues without normal replenishmentthrough the ET.
47
What is Eustachian tube dysfunction:
A condition where the tubes that conenct the middle ear to the throat become blocked [ET gets blocked]
Common causes:
Edema of the ET secondary to infection/allergy
Blockage of the ET opening by hypertrophied adenoids
Structural abnormalities in the mechanism involved in opening ET.
48
Tympanic membrane retraction:
Can interfere with the normal vibration of TM and may produce a slight conductive hearing loss
49
What is otitis media:
Infection of the mucous membrane lining of the ME space.
Serous otitis media with effusion: Fluid in the middle ear
Suppurative otitis media: Fluid buildup in the middle ear with pus formation (purulent organisms. [seen in 70% of children before age 2]
Risk Factors: ETD, barotrauma, anatomical deformities, age, immune system integrity, exp. to tobacco smoke, winter season, SES
50
What is otosclerosis?
Formation of new growth of spongy bone, usually over the stapedial footplate of one or both ears. The footplate becomes partially fixed in the oval window, stiffening the ossicular chain.
Common cause of hearing loss in adults that is often hereditary (70%)
Observed in Caucasians, 2x as common in women
Progressive; onset mid childhood to late middle adulthood
51
What is the treatment for otosclerosis?
Surgery can be anything from a simple shaving down of the bone to a full removal of the stapes and replacement with a prosthesis
52
What is the inner ear composed of?
The cochlea (hearing)
The semicircular canals (balance, rotation)
The vestibule (balance, linear motion)
53
The Cochlea:
Houses the organ of hearing
The name comes from its snail-like shape
Embedded in the temporal bone
In humans the cochlea has 2.5 turns
54
Membranous Labyrinth:
Filled with endolymph
55
Osseous (Bony) Labyrinth:
Filled with perilymph
56
What are the two portions of the inner ear?
Vestibule/semi circular canals
Cochlea
57
Scala Media:
Contains the Organ of corti
This structure converts mechanical energy to the neural code of hearing
Note the location of the cochlear nerve
58
Organ of Corti:
The organ of corti is transduction site
Contains specialized cells that convert mechanical energy to neural signaling
59
Basilar Membrane:
The spiraled canal of the cochlea is ~35mm long
Organ of Corti rests on the basilar membrane
60
Frequency map of the basilar membrane:
The base of the basilar membrane is stiff and narrow
The apex is thinner and more flexible
61
Inner and outer hair cells:
In a healthy ear OHC and IHC work together
OHC provide increased input to IHC
IHC transmit nearly all of the auditory input
62
Inner Hair Cells:
The human ear has approximately 3,500 Inner Hair Cells
The cell body is “pear” shaped
The top of the IHC is populated by projections known as stereocilia
63
Innervation of IHC:
IHC are heavily innervated by type-I myelinated auditory nerve fibers
Each IHC can be innervated with as many as 10-15 fibers
Note fibers ONLY connect to one IHC
64
Outer Hair Cells:
Outer hair cells are sensory receptors with a motor protein (prestin)
There are approximately 12,000 OHC in the human ear arranged in 3-4 rows
In response to basilar membrane motion, OHC are activated and expand and contract thereby enhancing basilar membrane motion
This electromotility is presumed to be the force-generating mechanism for cochlear amplification
65
OHC Innervation:
OHC are innervated by 5-10% of afferent auditory nerve fibers (type II)
Note that the pattern of innervation where type-II fibers make connections with many OHC
66
Inner Hair Cell Sterocilia:
Three rows of stereocilia are arranged in a sweeping curve or “u” shape
Note that there are three rows of stereocilia
67
Outer Hair Cell Sterocilia:
Three rows of stereocilia arranged in a “W” formation
Note the three rows of stereocilia
68
Vestibular System:
Sensory system
Motion
Head position
Spatial orientation
Responsible for balance
69
Semicircular canals vs otolith organs:
Semi circular Canlas
Nodding
Side to side
Tilting left to right
Otolith Organs
Horizontal plane
Vertical plane
70
Semicircular canals:
Fluid flows from canals to ampulla
Hair cell bundles move in response to fluid
Neuro transmitters are released
Information about movement is sent to the brain
71
Otolith organs:
Utricle
Horizontal plane
Saccule
Vertical plane
Movement in otoconia shifts fluid above hair bundles
Response is sent to the brain
72
Functional role of the Cochlea:
Transduction- Converting acoustical-mechanical energy into electro-chemical energy (inner hair cells)
Frequency Analysis-Breaking sound up into its component frequencies (outer hair cells, basilar membrane and excitation pattern)
73
Transduction:
Inner Hair Cells are the sensory transducers, converting motion of stereocilia into neurotransmitter release.
Mechanical Electro-chemical
Outer Hair Cells have both forward and reverse transduction--
Mechanical Electro-chemical
Mechanical Electro-chemical
74
Hair Cell Activation:
Displacement of the stereocilia causes the cation channels to open
potassium (K+) enters the hair cell, causing it to depolarize. At the same time, another cation, calcium (Ca2+), also enters the cell.
K+ channels close before the stereocilia return allowing rapid, successive, stimulation cycles to occur.
75
Ion Channels Are Opened Via Tip Links
Tip Links connect tip of shorter stereocilia to the side of a stereocilium in the next taller row
Bending toward taller rows pulls tip links
Bending toward shorter rows relaxes tip links
76
Tip Links
Note the mechanical displacement of the stereocilia
Mechanical action opens ion channels when movement towards the taller stereocilia occur
77
Stereocilia bent towards tallest row:
Potassium flows into cell
Calcium flows into cell
Voltage shifts to a less negative value
More neurotransmitter is released (glutamate?)
78
Active mechanism of basilar membrane function
Outer hair cells provide additional gain to incoming acoustic energy
Primarily the gain is provided at the frequency of the basilar membrane with the best response to the incoming stimulus
79
Prestin:
Motor protein that can contract and elongate
This protein is embedded on OHC providing the mechanism for electromotility
When the OHC membrane potential is altered, somatic shape changes of up to 5% occur
OHCs shorten when depolarized and lengthen when hyperpolarized
80
Tuning and Frequency Selectivity:
Basilar membrane movement and the active component result in a narrowly tuned response
This translates to frequency selectivity
Recordings from AN fibers show a sharp peak with a low threshold and a shallow low frequency tail
81
Loss of the active component:
When the active component (OHC) is removed we observe increased thresholds and a broadened response
82
Sensory Physiology:
The basic unit of the nervous system is the Neuron or nerve cell
Neurons undergo voltage changes-
SPONTANEOUSLY
IN RESPONSE TO STIMULATION
83
Neural activity:
Post-synaptic Potentials-- Local, Variable changes in voltage near synapse
Action Potentials-- Conducted through axon, “all or none,” “spike”
84
Ionic Changes:
Na+ channels open allowing a flood of sodium ions into the cell. This causes the membrane potential to become positive.
The K+ channels open allowing the potassium ions to flow out of the cell.
The Na+ channels close. This stops inflow of positive charge. But since the K+ channels are still open it allows the outflow of positive charge so that the membrane potential plunges.
When the membrane potential begins reaching its resting state the K+ channels close.
Now the sodium/potassium pump starts transporting sodium out of the cell, and potassium into the cell so that it is ready for the next action potential.
85
Threshold and dynamic range:
Neural fibers have a resting firing rate (spontaneous rate)
The minimum stimulus level that increases firing rates above the spontaneous rate is the threshold
The range between the threshold and maximal firing rate is the dynamic range
For AN fibers this is ~0-40 dB
Intensity coding is the result of both firing rate and population of synchronous firing among neurons
86
Damage to the ear:
Damage to any part of the ear can cause hearing loss
Damage to the inner ear results in hearing loss that cannot be reversed
Threshold is the lowest intensity needed to detect sound
87
Age related hearing loss
Presbycusis
Starts in the high frequency
Due to hair cell loss over time
Treated with use of hearing aids
88
Noise Induced Hearing Loss
Noise notch at 4000 Hz
Cause by exposure to loud sounds
Cause by outer hair cell loss/damage
89
Ototoxicity:
Steeply sloping
High frequency
Due to ototoxic medication
Hearing loss is usually monitored during treatment
90
Acoustic Neuroma:
Tumor on the auditory nerve
Unilateral hearing loss
High frequency
Tinnitus
91
Vestibular Schwannoma:
These space occupying tumors make up 10% of all intracranial tumors
