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4 Neuroscience > L4 Audio System > Flashcards

L4 Audio System Flashcards

1
Q

Sound transduction steps

A
  1. Sounds start as a pressure wave in the air
  2. External ear focuses sound waves onto the tympanic membrane
  3. Vibration of the tympanic membrane causes vibration of the bones of the middle ear
  4. Vibration is transferred to the oval window at the inner ear
  5. Oval window vibrates fluid within the cochlea
  6. Vibration of fluid is turned into electrical impulses via mechanoelectrical transduction
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2
Q

The cochlea…

A

converts sound into electrical signals

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3
Q

Cochlea makeup

A

spiral structure with basal and apical ends. basilar membrane splits it.

basal = oval and round window

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4
Q

Basilar membrane

A

divides the cochlea into half
has specialized epithelial cells called cochlear hair cells

cochlear hair cells have projections called stereocilia

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5
Q

Tectorial membrane

A

sits above the stereocilia
moves the stereocilia as vibrations travel through the cochlea

the movement of the stereocilia will cause the release of NT, causing an AP

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6
Q

Cochlear hair cells

A

found in the basilar membrane
contains bundles of stereocilia and one kinocilium

has one row of inner hair cells, three rows of outer hair cells

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7
Q

Stereocilia

A

causes the release of NT, which makes an AP

made up of actin, arranged shortest to tallest

attached to other stereocilia via tip links

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8
Q

What happens to stereocilia with sound vibrations?

A

bend, can either be towards or away from the direction of the tallest stereocilia

TOWARDS: causes tip links to stretch and open transduction channels, causing influx of ions into hair cell

AWAY: hair cells releases less NT

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9
Q

Inner hair cells

A

sensory receptors
95% of fibers of auditory nerve come from these

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10
Q

Outer hair cells

A

receive efferent axons that arise from cells in the superior olivary complex

help modulate movement of the basilar membrane

cochlear amplifier

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11
Q

Sound localization

A

Created through tonotopy and coincidence detection neurons in the MSO

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12
Q

Tonotopy

A

cochlea is organized topographically, lower pitched sounds will travel farther along the basilar membrane towards apex

different pitched sounds interact with the cochlea differently

apex = low frequency
baislar = high frequency

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13
Q

Coincidence detection neurons

A

located in the medial superior olive

set of neurons that respond more strongly when input arrives from separate pre-synaptic neurons,

detects interaural time differences; whatever side the sound is closer to will alert the neurons to sound

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14
Q

Medial geniculate complex

A

receives convergent frequency and temporal information from ascending pathways

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15
Q

DCN pathway

A

Spiral Ganglion
DCN
Decussates in trapezoid body in pons
Inferior colliculus
Medial geniculate complex
A1

Purposes: Localization of sound, auditory filtering, integration of multisensory information

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16
Q

VCN Pathway

A

Decussates in the trapezoid body, also splits in the pons, creating two pathways to the A1

Purposes: Auditory signal transmission, pitch perception, tonal discrimination

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17
Q

Labyrinth

A

consists of 2 otolith organs–utricle and saccule and 3 semicircular canals

filled with endolymph, also has a perilymph which is between osseous labyrinth and membranous lanyrinth

18
Q

Otoconia

A

each otolith organ contains a membrane which is covered in calcium carbonate crystals (otoconia)

19
Q

Otolithic membrane

A

located in the macula (uricle and saccule), horizontal and vertical movements

covered in otoconia
vestibular hair cells project into the membrane, rooted in the macula

thick, gelatinous sustance that can be displaced by forces

20
Q

Movement of vestibular stereocilia

A

TOWARDS kinocilium (tallest) = increased NT release

AWAY kinocilium = decreased NT release

21
Q

Utricle

A

oriented horizontally
responds to horizontal translational movements, sideways head tilts

22
Q

Saccule

A

responds to vertical translational movements of the head, upward or downward head tilts

23
Q

Striola

A

divides the utricle and saccule so that they can have separate actions

along the axis of striola = excite hair cells on one side and inhibit hair cells along the other

24
Q

Semicircular canal pairs

A

Right and Left horizontal canal
Right anterior canal and left posterior canal
Left anterior canal and right posterior canal

25
Q

Semicircular Canals Hair Cells

A

Ampulla = bulbous expansion at the base
Cupula = gelatinous mass in ampulla which contains hair cells
Endolymph = fluid fills each canal

26
Q

Cupula Movements

A

AWAY from head movement. Displaces the hair bundles in the cupula towards movement

they are all organized with kinocilia pointed in the same direction

27
Q

If the head turns to the left, what happens to the stereocilia in the left and right horizontal canals?

A

LEFT HC has stereocilia deflected towards kinocilium, cupula deflects right. Firing rate of L vestibular nerve increases

RIGHT HC has stereocilia deflected away from kinocilium, cupula deflects towards the right and firing rate of R vestibular nerve decreases

28
Q

Can you have negative firing rate in the vestibular system?

A

No
vestibular system is always active
firing rate increases or decreases from the baseline (which is not 0)

vestibular system has a high activity at rest

29
Q

What motions are the same in the otolithic membrane?

A

Backwards and Forward acceleration
Forward and Deceleration

30
Q

Static movements and vestibular

A

sitting in a static position changes the baseline firing rate

31
Q

Translational movements

A

transient increase or decrease of firing rate

32
Q

Forward head tilt causes

A

occurs within the saccule

top hair cells to deflects towards, increasing activity
bottom hair cells deflect away, decreased activity

33
Q

Left head tilts causes

A

occurs within the utricule

left hair cells deflect towards, increased activity
Right hair cells deflect away, decreased activity

34
Q

Semicircular Canals Static vs Movements

A

SCC only detect changes in angular or rotational acceleration

constant velocity will produce a baseline firing

35
Q

Vestibulo-ocular reflex

A

helps with producing eye movements that counter head movements, helping gaze to remain fixed on a particular point

plays a big role in vertical gaze stabilization in response to linear movements

36
Q

Pathway of VOR

A

vestibular input from scarpa’s ganglion signals change in vestibular state

info is transmitted to vestibular nuclei

medial vestibular nucleus communicates with abducens nucleus, causing inhibition of ipsilateral lateral rectus, excitation of medial rectus of ipsilateral and lateral recuts of contralateral eye

37
Q

How would turning your head to the right affect VOR?

A
  1. Turning head to the right increases firing rate of right vestibular nerve
  2. Right vestibular ganglion sends info to the right medial vestibular nucleus
  3. The medial vestibular nucleus sends excitatory fibers to the contralateral abducens nucleus
  4. The abducens nucleus has two outputs–> motor pathway that excites contralateral lateral rectus and an interneuron that excites the medial longitudinal fasiculus to oculomotor nucleus to excite ipsilateral medial rectus
  5. Oculmotor nucleus activates neurons that cause the medial rectus of the right eye to contract
38
Q

Summary of excitation of VOR

A

Excites ipisilateral medial rectus
Excites contralateral lateral rectus

Inhibits ipsilateral lateral rectus
Inhibits contralateral medial rectus

39
Q

Vestibulo cervical reflex

A

modulates head position with respect to what is happening in the SCC. Basically a reflex

Pathway: medial vestibular nucelus, MLF to upper cervical region

40
Q

Vestibulo-spinal reflex

A

excites extensor muscles and inhibits flexor muscles to promote upright posture

mediated by medial and lateral vestibulospinal tracts and reticulospinal tract

input comes from otolith organs

41
Q

Thalamocortical pathways

A

helps us to know where we are in space, whether an object is coming towards us or we are going towards an object

projects to many cortical areas

rostral fastigal nucleus helps with the distinguishing

4 Neuroscience (9 decks)

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