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Neurosciences > Exam2Lec3Audition > Flashcards

Exam2Lec3Audition Flashcards

1
Q

What is sound?

A

Sound is pressure waves generated by vibrating air molecules

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2
Q

What are the 4 major features of sound?

A
  • Amplitude: perceives loudness (decibels)
  • Frequency: perceives pitch (Hertz)
  • Phase: relationship b/w 2 sine waves
  • Waveform
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3
Q

Perception of sound corresponds to what 2 things?

A

Loundess and pitch

amplitude and frequency

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4
Q

What are the limits to human hearing (amplitude and frequencies)?

A

most sensitive freq thereshold: 2000-5000 hz
uncomfortable loundess amplitude: 100 db SPL
feelling/pain amplitude: 120-140 db SPL

does not mean we cannnot pervice all frequency

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5
Q

What are the structures of the external ear?

A

Pinna, concha, and the auditory meatus

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6
Q

What are three fxn’s of the external ear?

A
  1. Protection
  2. Sound gathering providing a high frequency boost > 3K Hz
  3. Sound localization and elevation detection

the outer ear alters the effectice spectrum of sound in a manner dependent on the location (up or down) of the sound source in the vertical plane
BASICALLY -brings in sound from air and alter sound wave to perceive where it comes from

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7
Q

What structures are in the middle ear?

A

Tympanic membrane
Malleus
Incus
Stapes

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8
Q

What is the fxn of the stapes?

A

Stapes is the smallest bone and it pounds the oval window to send signal into inner ear

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9
Q

What is the function of the middle ear?

A

Impedance matching which is when air has a lower impedance (resistance to movement) than the fluid in the inner ear

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10
Q

With NO middle ear, what occurs to the db and why?

A

30db loss intensity

b/c no impedance matching

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11
Q

WITH a middle ear, what occurs db?

A

34 db gain to resolve impedance mismatch between air and fluid

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12
Q

What strutures are in the inner ear?

A

Scala vestibuli, scala tympani, scala media, basilar membrane, organ of corti, cochlea

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13
Q

As the stapes pounds on the oval window, where does the fluid move?

A

Fluid moves inside the cochlea

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14
Q

What is perilymph vs endolymph?

A

Perilymph is similar to other EC fluid (0 mv, low K+)
Endolymph in the scala media has higher K+, lower Na+ concentration (+80 mV)

scala tympani and scala vestibuli have perilymoh

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15
Q

For the tonotopic organization of the cochlea, the basilar membrane (BM) is stiffest and least stiff where?

A

Stiffest as the base, and least stiff at the apex

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16
Q

Gradient in stiffness of the BM changes location of maximum displacement depending on what? Where do detect high frequences? Where do we detect low frequencies?

A

Depends on the frequencey of the sound wave
* High frequences=base
* low frequencies= apex

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17
Q

Tonotopic mapping can be found all the way where?

A

All the way up to the higher order processing centers in the brain

the cochlea performs a “tonotopic mapping” of frequency to place along the BM. This is an impt feature

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18
Q

cochlea:organ of corti

What is the organ of corti comprised of?

A
  1. Basilar membrane
  2. 3 rows of outer hair cells
  3. 1 row of inner hair cells
  4. Supporting cells

inside scala media

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19
Q

What is the tectorial membrane?

A

Cover apical matrix of the organ of corti

not apart of organ of corti

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20
Q

How do hair cells gets excited generally?

A

When the basilar membrane moves in the upward direction, a “shear force” is generated.

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21
Q

Explain how hair cells gets excited step-by-step

A
  1. Stereocilia (connected by tip links) bend in the lateral direction which opens MET (mechanaelectric transducer) channels
  2. K+ curent depolarizes cell & opens voltage dependent Ca2+ channels leading to transmitter release
  3. Ca2+ dependent K+ channels open-repolarization
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22
Q

How are hair cells inhibited?

A
  • When the basilar membrane moves in the downward direction, the stereocilia bend in the **medial **direction
  • Medial bending closes the MET (mechanoelectric transducer) channels and repolarizes/inhibits the hair cells
23
Q

What are 4 characteristics of outer hair cells?

A
  • Known as “sound amplifiers”
  • 3 rows along length of cochlea
  • 12,000 OHCs total
  • Cylindrical in shape
24
Q

What are 4 characteristics of inner hair cells?

A
  • Known as “sound transducers”
  • 1 row along length of cochlea
  • 3,500 IHCs total
  • Flask shaped

Inner Hair Cells are what sends auditory signaling to the brain, whereas Outer Hair Cells do not.

25
Q

OHCs ____ the vibration of BM and serve to ____ hearing sensitivity

A

amplify, improve

26
Q

Activation/Inhibition of an OHC causes it to change in length by stretching what? what are the 2 phases?

A

Prestin Proteins in the cell body.
Excitatory phase: shortens cell (BM moves up)
Inhibitory phase: elongates cell (BM moves down)

27
Q

Explain the most common type of permanent hearing loss

A

Occurs when there is damage to OHCs and the cochlear amplifier is lost

28
Q

IHC ____ mechanical vibrations into neuronal signals

A

transduces

29
Q

Explain how IHC transduces mechaninal vibration into neural signals?

A
  1. Activation of an IHC causes a chemical rxn in the cell
  2. This rxn causes neurotransmitter release at the base of the IHC
  3. Neurotransmitter activates the auditory neuron (CN VIII)
30
Q

What is the characteristic frequency (CF)?

A

The frequency of greatest sensitivity for the 8th nerve fiber

31
Q

Auditory nerve fibers (ANFS) from all parts of the cochlea come togeher in the modiulus to form what?

A

Cochlear portion of the 8th cranial nerve (auditory nerve)

32
Q

What are type I nerve fibers and what type of hair cell is it associated with?

A

Afferent from CNVIII (auditory nerve)
Associated with IHC

33
Q

What are type 2 nerve fibers and what type of hair cell is it associated with?

A

Efferent’s that can modify sound
Associated with OHC

34
Q

Explain the central auditory pathway

A
  1. Auditory nerve
  2. Cochlear nucleus (CN)
  3. Superior olivary complex (SOC)
  4. Inferior colliculus (IC)
  5. Medical geniculare body (MGB)
  6. Auditory cortex

NOTE: From the superior olive complex (SOC) and up, information from either ear (binaural) is traveling together.

35
Q

What is the 1st auditory nuclues?

A

Cochlear nucleus

36
Q

Cochlear nucleus
lxn?
Uniaural or Binaural?
Main fxns?

A

Lxn: medulla (brainstem)
Uniaural: receives input from 1 ear
Main fxns: relay signals to the SOC (w/o processing), analyzes complex signals and sends this info to the IC (inferior colliculus)

37
Q

Superior Olivary Complex (SOC)
lxn?
Uniaural or Biaural?
How many nuclei involved in sound localization?

A

Lxn: pons (brainstem)
Binaural: receives input from BOTH ears
2 nuclei involved in sound localization

38
Q

What are the two nuclei involved in sound localization in the SOC?

A

LATERAL superior olive (LSO) and MEDIAL superior olive (MSO)

39
Q

What is the LATERAL superior olive (LSO) localize and what does it use ?

A

Localization of HIGH frequency sounds
Using interaural sound level (loudness) differences

40
Q

What is the MEDIAL superior olive (MSO) localize and what does it use ?

A

Localization of LOW frequency sounds
Using interaural time differences

41
Q

Inferior colliculus
lxn?
Combines?
Coordinates?

A

Lxn: midbrain (brainstem)
Combines spatial info (from SOC) with info about complex sounds (from CN)
Coordinates auditory and visual responses in combination with the superior colliculus

42
Q

The inferior colliculus is involved in auditory reflexes including what?

A
  1. Auditoru startle reflex (loud sounds causes large scale muscle contraction)
  2. Head-turn response
43
Q

Medial geniculate Body (MGB)
lxn?
Receives what?

A

Lxn: thalamus (gateway to the cortex)
receives most inputs from IC and projects to auditory cortex

44
Q

The MGB is a ____ for info going up to (or down from) the auditory cortex

A

relay station

45
Q

What is the highest level of sound processing?

A

Auditory cortex

46
Q

What does the auditory cortex mediate?

A
  1. Auditory memory
  2. Use spatial info regarding the location of a sound source to mediate appropriate (non-reflexive) motor responses
  3. Formation of concepts about auditory stimuli
47
Q

What does the auditory cortex perform?

A
  1. Complex auditory discriminations, including speech discrimination
  2. Difficult auditroy tasks
48
Q

Central auditory pathway summary, 4 points

A
  1. Major pathways crossed
  2. SOC and higher lvl nuclei receive biaural input
  3. alll nuclei contain tonotopic maps (cells are arranges in order of best stimulus frequency)
  4. Nuclei involved in sound localization also contain maps of spatial location
49
Q

What does feedback control of the auditory system periphery?

A

reflexes from strong efferent pathways

50
Q

There are about how many efferent auditory nerve fibers in humans thought to modulate cochlear activity?

A

1,600

efferent auditory nerve fibers=type 2
modulate sound perception via efferent

51
Q

Part of the olivocochlear bundle descends from what?

A

From the superior olivary complex to the cochlea

52
Q

What are the 2 components of the olivocochlear bundle?

A
  1. UOCB (uncrossed olivocochlear bundle): LSO–> INNER hair cells on the SAME side
  2. COCB (crossed olivocochlear bundle): MSO–> OUTER hair cells on the OPPOSITE side
53
Q

What is the superior olivary complex sensitve to?

A

Sensiitive to sound pressure. Only 10-20 db above hearing threshold can evoke the reflex with cocb and uocb

54
Q

What is the reflex responsible reducing mid-high frequency sounds and is impt for hearing background noise?

A

COCB of the SOC neurons that target OHC and they dampens their amplifying action

Neurosciences (28 decks)

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