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Comd 3400 Anatomy Of The Ear > Section 3 > Flashcards

Section 3 Flashcards

0
Q

What part of the Inner ear is embedded within the petrous portion of the temporal bone?

A

The bony labyrinth (osseous portion of inner ear)

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1
Q

What portions of the ear does the temporal bone house?

A

Portions of the outer, middle and inner ear.

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2
Q

What is the main purpose of the bony labyrinth?

A

support and protections for the delicate portions of the inner ear.

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3
Q

Osseous Vestibule- where is it? What is superior, posterior and laterally?

A

Located central portion of the bony labyrinth.
posteriorly: Continuous with the semi-circular canals
Superior: continuous with the cochlea
Lateral wall: has the oval window and is the medial wall of the middle ear.
Part of the vestibular portion of the inner ear- not the hearing portion.

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4
Q

Vestibular Aqueduct- location, what does it house

A

Located on the medial portion of the middle ear and extends to the posterior surface of the temporal bone.
Houses the extension membranous Endolymphatic duct that terminates like a cul-de-sac within the cranal cavity.

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5
Q

What membraneous parts are located in the vestibule of the inner ear?

A

The Utricle and Saccule

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6
Q

What shape is the body/osseous vestibule?

A

Ovoid

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7
Q

How many osseous semi circular canals are there?

A

3

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8
Q

What are the names of the semicircular canals? What position are they in?

A

superior/anterior canal
Posterior
Lateral
Any two of the canals are perpendicular to each other.

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9
Q

How do the semicircular canals enter into the vestibule?

A

There are 5 orifaces that open into the vestibule. The medial side of the anterior and posterior canals share an opening. This shared opening is called the cruz camu or common cruz/canal

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10
Q

Ampulla

A

An enlarged portion near the opening to the vestibule. It is the sensory organ for balance within the semi circular canals.

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11
Q

Osseous Cochlea

A

snail shell-like boney formation of the middle ear. perhaps the hardest boney structure of the body.
Position: The apex of the cochlea points towards the cheekbone.

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12
Q

How many times does the cochlea wrap around?

A

2 5/8 times

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13
Q

Basal Turn of the Cochlea

A

Closest to the middle ear. Largest portion of the cochlea.

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14
Q

Mediolus of the cochlea location and function

A

perforated bony-central core of the cochlea that houses the 8th/auditory nerve and blood vessels. The medial end is continuous with the internal auditory meatus.

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15
Q

The Osseous cochlea is partially divided into and upper and lower duct- what are the names of these ducts?

A

Upper: scala vestibuli
Lower: scala tympani
Separated by a thin, bony shelf called the osseous spriral lamina.

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16
Q

Osseous Spiral Lamina- structure, function, houses,

A

Runs around the mediolas from the base of the cochlea to the apex. Composed of 2 thin, bony shelves that separates the upper and lower ducts. Between the shelves auditory nerve fibers pass from the hair cells in the cochlea to the spiral ganglion to form the auditory nerve.

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17
Q

Habenula perforata

A

Perforations in the osseous spiral lamina that accomodate nerve fibers.

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18
Q

What membranous structure completes the division of the cochlear ducts and attaches to the osseous spiral lamina?

A

cochlear duct or scala media

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19
Q

Hamulus

A

Near the apex, the spiral lamina terminates as a hook-like process. The hamulus assists in forming the boundry of the helictrema.

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20
Q

helictrema

A

The tiny opening in the apex of the cochlea. partially formed by the hamulus. This the only point in the cochlea where the scala vestibuli and the scala timpani communicate.

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21
Q

Three Openings of the cochlea

A

Round Window- opens into the tympanic cavity. Function: permits pressure to equalize between the scala vestbuli and the scala tympani. As the stapes/oval window moves inward, the round window buldges out. As the stapes/oval window moves outward the round window goes in.
Oval WIndow- interacts with the stapes of the middle ear and opens into the scala vestibuli
Cochlear aquaduct-very small opening not far form the round window that opens from the scala tympani into subaracnoid space of the cranal cavity.

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22
Q

Perilymph

A

the fluid that fills the cochlea, vestibule and semicircular canals. High in sodium content, similar to extracellular fluid. In the cochlea, perilymph fills the ducts but a different fluid fills the scala media.

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23
Q

paralymphatic spaces

A

The space between the bony and membraneous portions of the inner ear.

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24
Q

Internal auditory Meatus

A

bony canal that houses:
facial, auditory and vestiular nerves and portio of the basilar artery.
Carries these nerve bundles to the brainstem from the cochlea.

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25
Q

Quadrants of Internal Auditory Meatus

A

Anterior Top- house 7th/facial nerve (7up)
Anterior bottom- houses 8th/auditory nerve (coke)
Posterior Top- superior vestibular nerve
Posterior bottom- inferior vestibular nerve.

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26
Q

Membranous Labyrinth

A

Parallels the bony labyrinth. Filled with endolymph. Has 3 divisions-
the semi circular canals
utricle and the saccule-
cochlear duct/scala media-

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27
Q

Endolymph

A

fluid that runs through the membranous labyrinth.
similar to perilymph (fills the spaces around membraneous portions) but has an ionic composition similar to intracellular fluid.
- high in potassium
-same fluid runs through the cochlea, sense organs and semi-c canals

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28
Q

Cochlear Duct/scala media- what does it comprise (generally)

A

The system for hearing

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29
Q

3 Semicircular ducts- location

A

housed in the corresponding semicircular canals of the bony labyrinth. Same names: superior/anterior, horizontal/lateral and posterior ducts. Right angles to each other.
5 openings all enter the Utricle located in the vestibule.

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30
Q

Which ducts are also known as the vertical ducts?

A

The superior/anterior and posterior

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31
Q

Membranous ampulle

A

correspond with location of osseous ampulla. Each ampulla contains receptors called Crista Ampularis.

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32
Q

Crista Ampularis: location, function, and comprised of-

A

Found within the ampulla. This is a receptor organ for movement within the semicircular canals. detects rotational or angular movements.
Each one contains:
sensory hair cells
Supporting cells (These tow things are also called stereocilia)
Cupula- gelatinous mass that sits on top of the receptor/sensory hair cells

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33
Q

Saccule and Utricle contain what sensory organ?

A

Macula.

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34
Q

Macula

A

Similar to composition of crista ampullaris in the semi-cirular canals.
Made up of:
1. supporting membrane (epithelial cells)
2. sensory hair cells- stereocilia
3. Otolithic membrane- gelatinous portion overlaying the stereocilia. DIFFERS FROM SSC, contains Otoconia or otoliths.

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35
Q

Otoconia or otoliths

A

Calcium Carbonate crystals that provide mass to the otolithic membrane and make it responsive to gravity.

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36
Q

What type of equilibrium does macula detect?

A

static equalibrium

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37
Q

What type of fluid is in the saccule and the utricle?

A

endolymph

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38
Q

what is static equilibrium?

A

The movements of the body relative to the forces of gravity.

-linear movements (linear acceleration and deceleration)

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39
Q

What is the gelatinous portion of the semi-circular canals called? in the crista ampullaris

A

cupula

40
Q

What is the gelatinous portion in the vestibule called? in the macula

A

otolithic membrane

41
Q

What do both the ampulla and macula have in common regarding their sensory hair cells?

A

The hair cells have one single longest stereocilia. referred to as the kinocilium

42
Q

What is the single longest hair in the sensory hair cells called?

A

kinocilium

43
Q

How many membraneous ducts are there in the cochlea?

A

3.
scala vestibuli or vestibule- superior
Scala media (cochlear duct)- located in the middle
Scala Tympani- the most inferior of the three.

44
Q

Ductus Reuniens

A

Membraneous duct that communicates from the basal region of the cochlea with the saccule of the vestibule- its a membraneous communication duct.

45
Q

Endolymphatic duct

A

membraneous duct housed within the osseous vestibular aqueduct

  • courses from the vestibule to the endolymphatic sac (posterior surface of temporal bone).
  • filled with endolyph
  • thought to help regulate endolymphatic pressure.
46
Q

Scala Media

A

aka cochlear duct Found in between the scala vestibili and scala tympani. Connects to the osseous spiral lamina (bony shelf that divides the ducts partially. Division is completed by the cochlear duct/scala media.

47
Q

What are the 2 membranes within the scala media/cochlear duct that separate the scalae?

A

Floor: basilar membrane
Roof: reissner’s membrane

48
Q

Basilar membrane

A

forms the floor of the scala media. extends from the osseous spiral membrane to the outer sidewall of the cochlea (attaches to a thickened spiral ligament along this sidewall.

49
Q

Reissner’s membrane

A

Form the roof of the scala media/cochlear duct and floor of scala vestibuli. The end is continuous with the stria vacularis on the outer wall of the cochlea and medially with the spiral limbus.

50
Q

Stria vascularis

A

a highly vascularized tissue that is firmly attached to the spiral ligament on the outer wall of the cochlea and attaches to Reissners membrane. Supplies blood and nutrients to the cochlea and may manufacture endolymph.

51
Q

Helicorema

A

The space at the apex of the cochlea that allows the scala timpani and scala vestibuli to communicate. At this point the scala media isnt present.

52
Q

True or false- the osseous spriral lamina gets larger toward the apex of the cochlea.

A

False! The osseous spiral lamina gets smaller while the basilar membrane gets larger. This means that the basilar lamina is more stiff at the base of the cochlea than it is at the apex.

53
Q

The osseous spiral lamina has two sides and houses the peripheral nerve fibers. What is the top layer of the OSL continuous with?

A

The spiral Limbus

54
Q

Spiral limbus

A

a thickening of of the periosteum (connective tissue around the bone. Continuous with the upper spiral lamina and reissner’s membrane.

55
Q

Tectorial membrane

A

continuous with the spiral limbus and reaches toward the outer wall. (if the spiral limbus was a turtle shell the tectoral membrane would be the head.Thought to connect with the supporting cells (hensen’s cells)

  • mass increases from base to apex.
  • covers the entire organ of corti
56
Q

What is firmly embedded into the tectorial membrane and what organ does it cover?

A

Outer hair cells are firmly attached to the underside of the TM (the stereocilia are embedded in it)
The tectorial membrane is situated immediately above the organ of corti and overs its length.

57
Q

Spiral ligament

A

Found along the outer wall of the cochlea. it is a thickening of the periosteum. Projects inward near the basilar membrane to form a shelf call the basilar crest.

58
Q

Where is the basilar crest located?

A

Shelf-like prominence created by the spiral ligament near the basilar membrane.

59
Q

Organ of Corti

A

Also known as the sensory organ of hearing. Basilar membrane serves as a footing for the organ of corti. Runs the entire length of the cochlear duct/scala media. Consists of: supporting structures, sensory cells and nerve fibers.

60
Q

Supporting cells that lie medial to the inner hair cells. What do they do?

A

Stalk separates the lateral sides of the inner hair cells.

61
Q

Inner and Outer pillar cells form:

A

Forms the tunnel of corti.Base of pillar cells sits on the basiar membrane. This base is broad, very supportive, 45 degree angle, lacated betweek outer and inner hair cells.

62
Q

Space of Nule (sp?)

A

Lateral to the outer pillar. space between outer pillar and outer hair cells. size varies.

63
Q

Deiter cells

A

Support the outer hair cells

64
Q

Reticular lamina

A

forms the ceiling of the sensory and supporting cells. separates the endolymph from the internal structures of the organ of corti. the fluid inside the organ of corti is a different fluid called cortilymph. cilia of hair cells penetrates the reticular lamina. RL also supports the hair cells

65
Q

Cortilymph

A

similar to perilymph. High in sodium, low in potassium fills around the organ of corti and base of hair cells.

66
Q

What fluid is the base of the hair cells in the cochlea in?

A

cortilymph. The tops of the hair cells is in endolymph.

67
Q

Cuticular plate

A

Tops of inner and outer hair cells are thickened to for the cuticular plate. joined with support cells and rods of corti, they for the reticular lamina.

68
Q

Inner and outer hair cells are similar- t of f

A

FALSE

They differ in nerve supply, shape, function and arrangement of cillia.

69
Q

Inner Hair cells

A
  • Humans ear has about 3500
  • arranged in a single row between supporting cells
  • tear drop/gourd shaped and stronger than outer hair cells. And contain more mitochodria
  • 50-70 sterocilia per cell formed in a U shape.
  • tallest cilia are distal/away from the center of the body
  • all cillia tend to move together when the tallest ones are bent/ cross links
  • these hair cells do not make contact with the tectorial membrane.
70
Q

Outer Hair cells

A

Cylindrical shape with rounded base
Each cell has 3 or more rows of hairs that form a V or W shape.
The longest of the stereocilia are embedded in the tectorial membrane.
also has cross links that help them move together.
Contain actin/protein that allows the hair cells to shorten or lengthen.
Cells are grouped 3-5 parallel rows throughout the cochlea.3-4-5ish from base to apex.

71
Q

How does the innervation of the inner hair cells work?

A

Each cell is connected to as many as 10 eighth nerve fibers “many-to-one”. these fibers are type 1 myelinated fibers that make up 95% of the auditory nerve.

72
Q

How are the outer hair cells innervated?

A

by type 2 fibers- small (myelinanted and unmyelinated)- one strand attaches to many OHC. they are afferent and efferant. IHC are only afferent.

73
Q

Who hypothesized that auditory processing takes place in the cochlea?

A

Gold in 1946

74
Q

Who discovered that acoustical energy emerges from the ear and what did they call it?

A

in the 1970s david kemp discovered that gold was on to something. This energy was first called Kemp’s echos and later termed otoacoustic emissions.

75
Q

Who won a nobel prize for describing mechanics of the traveling wave of the cochlea?

A

George von Bekesy- most popular/ accepted theory today.

76
Q

In what way is the BM displaced?

A

Some displacement occurs radially but the majority of the displacement is longitudinally. The BM is more rigid radially.

77
Q

What frequencies does the basal and apex of the cochlea resonate at?

A

the base resonates at higher frequencies and the apex at lower frequencies. the more mass, the lower the frequency. the bm gets larger toward the apex.

78
Q

after maximum displacement, what happens to the traveling wave?

A

wave dampens quickly after maximum displacement.

79
Q

Are the pivot points for the tectorial membrane and basilar membrane in the same place?

A

no, they are displaced. Results in a sheering motion.

80
Q

Cross links and Tip links- what do they do? where are they?

A

Cross links hold the stereocilia together and tip links hold them together at the tip.

81
Q

The trap door theory: compression

A

Compression causes the stereocilia to bend towards the medilas (toward the shorter side of the hair). Results in hyperpolarization of the cell. This “closes” the trap door. There is little to no ion flow into the cells when this happens.

82
Q

Trap door theory:rarfaction

A

The stereocilium is pushed away from the medilas towards the longer hairs. Causes increased tension on the tip links. Opens the “trap door” to the cell and allows ion flow into the cells. This results in depolarization.

83
Q

Depolarization

A

The hair cells are negatively charged on the inside and positively charged on the outside.
The tip-links cause the ion channels to open rapidly when tightened. Allowing potassium(positive ions) into the hair cells.
This leads to the opening on calcium cells.
Neurotransmitter cells travel across the synapic cleft and are released from the hair cell to the receptors on the nerve cell.
Contact with the receptors transmits to the brain.

This happens when the BM is displaced towards the scala vestibuli (rarefaction)

84
Q

Hyperpolarization-inhibition

A

Hair cells are bent towards the shorter end- less firing from the cell. This is when the BM is desplaced towards the scala tympani (compression)

85
Q

Electromotility of Outer Hair Cells

A

The outer hair cells contract when the BM moves upward during rarefaction- causing depolarization.
The OHC expand with the BM moves downward during a compression wave.-hyperpolarization.

86
Q

Resting potentials- definition

A

voltage potential differences measured when the cochlea is at rest.

87
Q

Scala Media resting potential- what is it and what is it called? What to they think generates this charge?

A

Name: endocochlear potential-
constant positive potential
80mV (relative to scala tympani and scala vestibuli)
Thought to be generated by the stria vacularis

88
Q

Electrical potential found within the hair cells- what is it and what is it called?

A

Intracellular

-70mV (hair cells at rest)

89
Q

Stimulus/sound- evoked potentials

definition

A

potentials that arise when the cochlea receives a stimulus.

90
Q

Cochlear Microphonic

stimulus-evoked potential

A

Wever and Bray Discovered in 1930

Alternating current that mimics the frequency of the incoming signal. Is either generated by or in the presence of the OHC. Useful to test if OHC function.

91
Q

Summating potential

A

an accoustic stimuli evokes a direct current shift in the extracellular response making the scala media electrically negative with respect to the scala tympani. Occurs upon stimulation of the organ of corti.
Both IHC and OHC contribute but they this IHC are mostly responsible. The direct current shift is maintained as long as sound is present.

92
Q

Action Potential/ whole nerve potential

A

Arises directly from stimulation of a large number of hair cells simultaneously, eliciting nearly syncronous discharge of the 8th nerve.

  • all or nothing- it fires or doesn’t
  • large negative potential N1
  • second, lesser negative potential (N2)
93
Q

What are the 2 types of neurons of the 8th nerve?

A

Low spontaneous rate (high threshold)- high level of stimulation, respond to higher range of INTENSITY. Little or no random background firing noise.
High spontaneous rate (low threshold)- responds at low signal INTENSITIES- random firing.

94
Q

Post-Stimulus Time Histograms

A
  • used to look at rate of firing data over time. The intensity of the neuron firing is always the same the the rate differs.
  • When 8th nerve responds to a stimulation you get an initial burst of activity, followed by a decline back to a plateau while stimulus continues.
  • after stimulus is finished, the response fiber drops to below the baseline (recovery period) and then rises back up to the baseline.
95
Q

Characteristic frequency

A

Frequency specificity of the 8th nerve- the frequency to which it responds best.

96
Q

auditory nerve-what does it do?

A

carries electrical impulses from the cochlea to the brain stem.

97
Q

Where does the auditory nerve run from?

A

The terminal buttons on the hair cells–>
through the habenella perforate (small openings in the spiral lamina–>
to the rosenthals canal (an enlarged area that accommodates the spiral ganglion cells.—>
Comes together to form the trunk of the cochlear nerve. –>
through the internal auditory meatus–>to the brain stem

98
Q

Central Auditory Pathway

A

Responsible for comparison of sensations, processing and localizing sound.
Classical pathways

Comd 3400 Anatomy Of The Ear (3 decks)

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