anatomy > Semester 1 > Flashcards

Semester 1 Flashcards

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1
Q

What is contained inside the temporal bone?

A

Organs of hearing and balance and entire peripheral auditory system
Internal carotid artery (branch off from the common carotid artery)
Internal jugular (Vein carries blood from brain from the face back to the hear off from the common carotid artery)
Facial Nerve (VII) Facial expression, Taste from front 2/3 of tongue

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2
Q

What four parts constitute the temporal bone?

A

Made up of four parts.

Squamous, Petrous bone, mastoid bone, tympanic bone

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3
Q

What are the characteristics of the four different parts of the temporal bone and where are they located?

A

Squamous - Thin, transluscent, extends from the zygomatic arch
Petrous bone - dense, thick, houses organs of hearing and vestibular system. Extends medially
Mastoid bone: Thick, small bulb behind pinna, numerous air filled spaces
Tympanic bone - Inferior to squamous, only viewed on medial aspect, house TM and EAM

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4
Q

What constitutes the OE?

A

Outer Ear - EAM and Pinna

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5
Q

Label the parts of the pinna…from inner to outer

A

Tragus, antitragus, lobule, Helix, triangular fossa, antihelix, crus of helix, cymba concha, cavum concha, EAM

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6
Q

What is the function of the EAM?

Located?

A

Protects, amplifies, localises.
Outer 1/3: Cartilagenous. Physical barrier, hairs, protects from foreign objects cerumen glands (produces cerumen) sebaceous glands (sebum) for moisture.
Inner 2/3 Bone, much thinner skin, no wax glands

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7
Q

Name the two materials that make up the cochlea

A

Osseous (bony) labyrinth:
Membranous labyrinth: Filled with endolymph
Drilling through cochlea: Osseous labyrinth, Perilymphatic space, membranous labyrinth

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8
Q

Where is the endolymphatic sac located?

A

ocated border of brain and temporal bone

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9
Q

What does endolymph contain?

A

High concentration of potassium (K+) - positively charged

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10
Q

Where is the oval window located?

A

At the base of the Scali Vestibuli

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11
Q

How does the scali media differ from the scali vestibuli and the scali tympani?

A

Scali media is located between the scali vestibuli and scali tympani, it condtains endolymph, and the organ of corti.

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12
Q

Where is the Reissner’s membrane located?

A

It is the membrane between the scali vestibuli and scali media

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13
Q

What is the function of the round window?

A

Give and take system, located at the other side of the scali tympani.

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14
Q

What is the function of the hair cells?

A

There are inner and outer hair cells. Hair cells convert mechanical energy (hydro-dynamic energy) into electrical energy transmitted down the auditory nerve all the way to auditory cortex*

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15
Q

Describe the anatomy of the organ of corti

A

Located within the membraneous part of the cochlea, almost on the basilar membrane. 4 hair cells (3 OHCs, 1 IHC). IHC is located closer to the auditory nerve. The tectorial membrane (gelatinous structure) is located above the hair cells. The stereocilia of the OUTER hair cells, are embedded in the tectorial membrane, bathed in endolymph.
There are also surrounding cells, which are supporting cells

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16
Q

Name other cells within the organ of corti and their function, other than the HCs

A

Pillar cells - between outer and inner cells
Ganglion cells - Cell bodies of afferent fibres that innervate inner and outer hair cells (within Rosenthal’s Canal).
Claudius cells, Dieter Cells, Basilar Cells, Hensen cells

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17
Q

What is the stria vascularis?

Where is it located?

A

Contains numerous blood vessels, involved in maintaining high concentration of K+ in endolymph. Contains the Reisnner’s membrane, lateral wall and side of scali vestibuli?
Outer layer, exterior to scali media

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18
Q

Describe the location and function of the tectorial membrane?

A

OHCs embedded in tectorial membrane, hence bathed in endolymph. Attaches to spiral limbus.

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19
Q

Outer Hair cells

A

Cylindrical shape. “Amplifiers”
Receive mostly efferent innervation directly onto the OHC,. Receive 10% afferent fibre innervation
Divergent, one sing;e afferent fibre innervating many OHCs

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20
Q

Differences btw OHCs and IHCs

A

OHC vs IHC
Amplifiers vs Receptors (mechanoelectrical trasnduction)
Cylindrical vs Piriform shape
Divergent innervation vs Convergent innervation
Type II afferents vs Type I afferents
w like configuration vs toothbrush
Large efferent terminal vs efferent synapses on afferent terminal

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21
Q

Purpose of Tip Links

A

Joins all stereocilia of one HC together. Allow them to move together.
Act like trap doors - mechanically pull and open ion channels at tip of stereocilia. As stereocilia are displaced laterally by tectorial membrane, and shearing force tip link pulls on ion channel, causing it to open resulting in endolymphatic fluid flowing into stereocilia. Therefore, influx of K+ causing depolarisation of hair cell.

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22
Q

What type of frequencies does the apex of the cochlea respond maximally to?
Why?

A

Low frequencies
Basilar membrane is ‘tuned’ to different frequencies.
“Place-coding” filters complex speech frequencies into constituent components

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23
Q

Explain the travelling wave…

A

Pressure wave stimulated at the Scali Vestibuli results in displacement of Basilar Membrane in upward direction. Basilar membrane pushed up, shearing force working on stereocilia.

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24
Q

What are primary afferent neurons

A

Consist of type 1 (95% onto IHCs) and type 2 carry electrical signals from the IHCs to the brain via VIII (auditory, cochlear and vestibular nerves)

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25
What are the differences of Type 1 and Typer 2 afferent fibres?
Type 1 = myelinated, convergent, many Type 1 fibres innervate 1 IHC. Type II fibres will branch off and innervate numerous OHCs
26
What is the Transition Zone?
AKA Cerebellar Pontine Angle. Space between the organ of corti (IAM) and the brainstem. Called TZ bc where PNS meets CNS. Shift from oligo-dendrite cells within PNS to glial cells within CNS
27
What causes an Acoustic Neuroma?
Arise from Schwann cells that produce myelin. These type of tumours typically grow in transition zone/CP angle or in Internal Auditory Canal. *Generally only occur unilaterally, high frequency unilateral HL
28
What mode of innervation is the medial ollivarycochlea bundle associated with? Where is it located?
Efferent innervation to the OHCs, directly. Superior ollivary complex (within the brainstem)
29
What does the Lateral olivocochlear bundle do?
Innervates onto afferent fibres innervating IHCs. Located in the superior ollivary complex (in brainstem). Unmyelinated.
30
What are the three parameters that contribute to pitch perception?
1. Place of stimulation (place code) 2. OHC Contribution Amplifiers, and ability to code frequencies and their resolution 3. Temporal Code (phase locking)
31
List structural features of the Basilar Membrane which dictate the place of stimulation of frequencies?
``` Width of BM (wider at apex) Tensile properties (at apex it is floppy) Weight + Shape (of organ of corti and hair cells etc) (at apex heavier, bigger - hair cells are longer) ```
32
What is tonotopic organisation? And How does it impact sound transmission?
Show that you get maximal displacement of specific frequencies in a tonotopic manner - this pattern continues all the way to the brainstem.
33
Where is prestin found? What is it?
In OHCs - a protein
34
How does prestin impact the travelling wave?
Provide contractile properties of hair cells (shorten and lengthen), provides boost/energy to the movement of the BM so the IHCs can be embedded into tectorial membrane, thus in endolymph leading to larger APs and maximal displacement at those regions. The mechanical changes in the length of the hair cell amplify the displacement of the basilar membrane and creates a more vigorous electrical response to the stimulus
35
What are the resting potentials of: - Scala Media - IHC - OHC
+80mV - 45mV - 70mV
36
Which Hair Cells have the greater potential difference?
Outer hair cells
37
How would you measure the electrical potential of hair cells?
Insert an electrode through the TM, close to the promontory, to record the response of the IHCs or OHCs and determine firing of the afferent and efferent fibres
38
Compound action nerve potential (CAP) (gross evoked potentials)
Provides info about depolarisation of hair cells and early portion of afferent fibres,
39
Auditory brainstem evoked potentials (ABRs)
Provide info about synaptic terminals further along the brainstem. Ax can tell us more about the pathologies affecting transmission of Aps up the auditory cortex. Each peak corresponds to sites along the brainstem
40
Otoacoustic emission (OAEs)
Allow us to assess the state of OHCs. Soft sound, stimulates Prestin activity, which in turn produces a sound which can be recorded by the very sensitive microphone placed in
41
Why is there a greater latency of APs for lower frequency sounds?
afferent fibres that respond to higher frequency sounds, are stimulated earlier bc the fluid pressure wave doesn't have to travel as far in the cochlea partition
42
Different frequencies receive different amplification by the OE, True or False
True - Higher frequencies, higher amplification
43
What plane is affected by ITD and IID locational factors????
Horizontal ITD interaural timing differences, more useful for localising low-frequency sounds (hearing sound from L ear before RE) Interaural Intensity differences, more important in localising high frequencies
44
Label what is the tight part of the TM, functions a little like the skin of a drum. Vibrates in response to acoustic stimulus.
Pars tensa
45
What is the umbo?
Centre-ish of the TM, region that is most concave (towards the cochlea). Site that malleus attaches to
46
What is the function of the pars flaccida? How many layers does it have?
Loose and flaccid, maintain pressure in Middle Ear. | 2
47
Name the ligaments of the TM? (5)
``` Anterior Ligament of Malleus: Superior Ligament of Malleus: Lateral Ligament of Malleus Superior Ligament of Incus Posterior ligament of incus: ```
48
Name the muscles of the TM | What is their purpose
Tensor tympani muscle - Protection, reduce vibrations running through the ossicles. Also innervates TVP. Attaches to handle of malleus. Contraction: Pulls malleus in antero-medial direction('inward') to stiffen TM. Stapedius muscle - innervated by the facial nerve (VII). protection, reduces the vibrations happening at the footplate Contraction of the muscles pulls the stapes posteriorly (sideways). Reduces low frequency middle ear gain
49
Describe the chorda tympani nerve
Located and weaves through the ossicles, runs along lateral wall btw TM layers into the jaw. associated with tongue sensation and tase - branch of VII
50
What is the function of the Eustachian Tube?
Pressure equilibrium. Innervated by Trigeminal nerve (v). Activated by tensor veli palatini muscle
51
List 3 functions of the ET
Ventilation - equilibrium Clearance - drainage of excess secretions in ME Protection - reflux, i.e. vomiting
52
How does the ME overcome impedance mismatch?
Acting as a mechanical transformer: 1. Area ratio 2. Lever action
53
What is meant by area ratio?
Any vibrations of TM (55m2)are concentrated on smaller area at Oval Window (3.2mm2 ) Larger area/Lower Pressure (@ TM) >>>. Smaller area/Higher Pressure (@ OW) i.e. thumb tack onto a wall
54
What is meant by lever action?
Basically malleus and incus act as fulcrum in the lever system -
55
There is no loss of energy in the ME system during sound transmission T or F? How/Why?
False. "buckling" ossicles do not just vibrate back and forth, "slippage" bc they are not rigid. Force required to commence movement of the ligaments, muscles and bones (inertia)
56
Approximately how much does the OE amplify sound energy?
10dB
57
The stapedius muscle tenses in response to loud sounds T or F?
True - Protects by contracting, causing greater stiffness thus increasing impedance
58
What is the mechanism of the stapedius muscle tensing called?
Acoustic reflex
59
Is the acoustic reflex full proof?
No, it is effective for loud sounds, however not for higher frequencies, due to the latency. Fatigues over time (50% efficiency after 2-3 seconds)
60
Describe the acoustic reflex in terms of brainstem response
Afferent (bringing sensations towards the CNS): - Acoustic stimulus L ear > cochlear > converted to electrical signal > Carried into brainstem via Auditory Nerve which runs into the Internal Auditory Canal and runs as part of Vestibulocochlear Nerve (VIII) > arrives at brainstem at "cochlear nucleus" which are the first group of neurons for the central auditory processing/start of sound processing > Signal sent to both R and L Superior Ollivary Complex (group of neurons in brainstem) This is the reason why there is bilateral activation and relays stimulation to both muscles. Efferent (bringing stimuli away from the CNS): Once signal has arrived at Superior Ollivary Complex , sent to facial nucleus in the brainstem > transferred down VII > Stapedius branch > contracts stapedius
61
What is the natural frequency of the concha?
Natural (resonant) frequency of concha is ~5,000Hz Vs EAM ~2,500Hz (varying b/w ppl) The resonance of each cavity is such that each structure increases the sound pressure at its resonant frequency by about 10-12dB.
62
Who is responsible for discovering the passive process?
Vonbeckashay
63
Who is responsible for discovering the passive process?
Von Bechashay's
64
What occurs at rest in the hair cells?
Receive some leakage of mechanically gated ion channels - they are not full proof.. Some K+ from endolymph into cell... hence small passive APs occur. - SPONTANEOUS activity of the basal part of the cell, sometimes leading to NT release
65
What occurs at rest in the hair cells?
Receive some leakage of mechanically gated ion channels - they are not full proof.. Some K+ from endolymph into cell... hence small passive APs occur, in absence of BM movement, - SPONTANEOUS activity of the basal part of the cell, sometimes leading to NT release
66
Leakage of K+ ions into the HCs is less at rest than at medial deflection T or F? Why?
False | Allows for cell to repolarise
67
What happens instead of the phasic response for high-frequency sounds?
Hair cells can't keep up at high freqs thus just get a large shift in potential over time while sound is on Direct current response rather than alternating current response *remember acts like a battery system
68
List the three neural parameters of (intensity) loudness perception?
1. Rate of neural firing 2. Threshold of neurons firing 3. Number of neurons firing
69
What are the differences btw low spontaneous fibres and high spontaneous fibres?
High spont = Low threshold activation, therefore softer sounds, low DR 10-40dB Low spont = Lazier, louder sound to be activated, greater DR - more and more fibres activating. Kick in when high spontaneous fibres saturate.
70
Where are low and high spontaneous fibres located?
``` Low = Modeollar of IHC, closer to aud nerve, High = pillar cell side, lateral ```
71
List the three parameters of (frequency) pitch perception?
1. Place of stimulation (place code) 2. OHC contribution 3. Temporal code (phase locking)
72
What are the functions of theGlial cells?
Two types of glial cells - located in the PNS and CNS Oligodendrocytes - responsible for the production of myelin in the CNS Schwann cells - responsible for the production of myelin in the PNS
73
Where is the cuticular plate located and what is its purpose?
At the top of the hair cells anchoring the stereocilia to the hair cell at the base
74
Maintaining eye gaze stability is an important function of the... a. Otolithic cells b. Vestibular Spinal Reflex c. Saccade system d. Vestibular Ocular Reflex e. Spiral Ganglion cells
d. Vestibular Ocular Reflex
75
Nystagmus cannot be generated by... a. movement of the visual field b. binocular vision c. Sudden rotational acceleration d. peripheral vestibular pathology e. alcohol intoxication
b. binocular vision
76
The pendulum model of SCC function suggests that... a. smooth pursuit eye movements require a moving target b. Cupula displacement is proportional to head velocity c. gravity affects endolymph flow d. eye movement control is often inaccurate e. hair cells only respond to movement in one direction
b. Cupula displacement is proportional to head velocity
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