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Brain and Behavior > 6.3.1 Ear Structure and Function > Flashcards

6.3.1 Ear Structure and Function Flashcards

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The Brain flashcards
1
Q

What makes up the kinetic labryinth and what is the function?

A
  • Semicircular Canals (three) and Crista Ampullaris
  • Detect changes in rotational acceleration
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2
Q

What is the sequence by which sound wave entering the ear result in 8th nerve activity?

A
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3
Q

What are the peripheral components of the auditory system?

A

-external, middle, and inner ear

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4
Q

What is the role of the vestibular system in regards to balance and movement?

A
  • Hair cells provide info about motion and gravity from the left and right sides
  • Brain compares the info from the two sides
  • Information does not reach the cortex, but does interact with the motor system
  • Other systems also provide info about position: Visual system and Proprioception (somatosensory)
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5
Q

What are the 3 components of the cochlea?

A
  • Inner: Scala Media filled with endolymph
  • Outers: Scala Vestibuli and Scala Tympani filled with perilymph
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6
Q

Both auditory and vestibular hair cells transduce energy via?

A

movement of their stereocilia

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7
Q

What are the transducers for both the auditory and vestibular system?

A

Hair cells

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8
Q

What is pressure equalization in regards to middle ear functions?

A
  • Eustachian tube connects the middle ear and the nasopharynx
  • Tensor veli palatini and salpingopharyngeous muscles open the Eustacian tube during swallow
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9
Q

Describe the movement of the basilar membrane, is it uniform throughout?

A
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10
Q

What is the role of the basilar membrane and how do hair cells affect this?

A
  • Basilar membrane: floppy membrane receiving different frequencies at specific regions
  • Hair cells sit atop of the basilar membrane within the scala media endolymph
  • Tectorial membrane sits atop of the stereocilia of the hair cells
  • As hair cells move, a shearing force is produced relative to the tectorial membrane
  • Causes changes in AP firing rate
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11
Q

What is the importance of the middle ear?

A

-filled with air; ossicles conduct vibrations from tympanic membrane to the oval window of the cochlea

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12
Q

What is the mechanism by which the saccule and utricle detect changes in linear acceleration (gravity)?

A
  • Stereocilia embedded in gelatinous glycoprotein matrix filled with otoliths
  • Otoliths (calcium carbonate crytsals) shift during linear acceleration
  • Results in bending of stereocilia
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13
Q

Damage to auditory or vestibular nerve results in?

A

Hearing loss or balance disorders

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14
Q

What is the importance of the inner ear?

A

-filled with fluid; where mechanical sound vibration or motion is transduced into neural activity

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15
Q

What is the function of the auditory system how is this achieved?

A

provides information about sound in the environment

  • Afferent info from CN VIII synapses on cochlear nuclei in brainstem
  • Auditory information reaches the cortex
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16
Q

How does the cochlea allow for transmission of sound?

A
  • Entry: from stapedal vibrations at oval window through scala vestibuli
  • Exit: at round window through scala tympani
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17
Q

What is the mechanism by which the ampullae (semicircular canals) detech angular acceleration?

A
  • Hair cells are located in ampullae on a ridge of tissue called the crista ampullaris
  • Stereocilia are embedded in the cupula, a tall glycoprotein matrix mass
  • Cupula is deflected by fluid flowing through the canal when the head turns
  • Results in bending of stereocilia
18
Q

Stereocilia have what at their tips and what is this importance?

A
  • Stereocilia have potassium channels at their tips
  • Bending causes either opening/closing of channels, influx of K+ causes opening of Ca++ channels, changing amount of NT released
  • Results in a change of AP frequency
19
Q

Describe the ionic composition of the endolymph vs the perilymph.

A
  • Endolymph: low Na, Cl; High K
  • Perilypmh: high Na, Cl; Low K
20
Q

The basilar membrane location that experiences the greatest displacement depends on?

A

Mechanical properties of the membrane and frequency of sound

21
Q

What are the characteristics of the Macular organs?

A
  • Saccule and Utricle
  • Detect changes in linear acceleration (gravity)
22
Q

What is the Stria Vascularis?

A

lining of the scala media, secretes K+ ions to maintain potential

23
Q

What is the importance of the external ear?

A

-amplifies sound reaching the tympanic membrane

24
Q

What is the function of the vestibular system how is this achieved?

A
  • provides information about motion and gravity
  • Afferent info from CN VIII synapses on vestibular nuclei in brainstem
  • Information does NOT reach the cortex
25
Q

What are the properties of the inner hair cells of the cochlea?

A
  • Primarily responsible for sending info to the CNS via CN VIII afferents
  • Organized in a single row
  • Sensory transducers
  • Single CN VIII afferent contacts a single inner hair cell; one IHC receives several contacts
26
Q

Hair cells within the cochlea sit on what?

A

They sit in a specific orientation on a structure called the basilar membrane.

27
Q

Describe the central auditory pathway.

A
28
Q

What are the peripheral components of the vestibular system?

A

Inner ear

29
Q

Shearing force against stereocilia with basilar membrane movement does what?

A

change in hair cell membrane potential causes release of neurotransmitter at the base.

30
Q

What are the characteristics of outer hair cells?

A

-Change the stiffness of the basilar membrane

-Damage changes thresholds and

  • Organized in three rows
  • Modulate sensory transduction by IHCs
  • Synapse with efferent fibers from the brain
  • Originating in superior olivary nucleus
  • Amplify the transduction of quiet sounds and attenuate the transduction of loud sounds
  • Can create otoacoustic emissions
31
Q

Describe the wave displacement of the basilar membrane at the base and apex. Relate this to stiffness and frequency.

A
  • Wave produced by stapes at oval window moves from base to apex of the basilar membrane
  • Stiffness of the membrane differs along its length
  • -Base: narrow and stiff
  • -Apex: wide and flexible

-Amplitude of displacement at a given location of the membrane depends on the frequncy

  • -Base: high frequencies (stiff membrane ⇒ requires more energy to displace)
  • -Apex: low frequencies (flexible membrane ⇒ requires less energy to displace)
32
Q

How do the basilar membrane and cochlea act in tonotopic organization?

A
33
Q

How does the middle ear gain control of vibrations reaching the inner ear?

A
  • Tensor tympani and stapedius muscles can change the stiffness of the tympanic membrane
  • Used to dampen the movement of the stapes
  • Increases the dynamic range of the inner ear and protects cochlear hair cells from loudness
34
Q

What are the two membranes of the cochlea?

A
  • Vestibular: separates scala vestibuli from scala media
  • Basilar: separates scala media from scala tympani
35
Q

Describe the membrance potentials between the endolymph and the hair cell membrane and what the importance of this is.

A
  • Endolymph: +80mV
  • Hair Cell Membrane: -40mV
  • 120mV membrane potential difference drives K+ ions from the endolymph into the hair cells
36
Q

How is sound information organized in the auditory system?

A

Auditory - frequency

37
Q

What is impedence matching in regards to middle ear functions?

A

-Ossicular chain and the size difference between the tympanic membrane and oval window prevent loss of pressure at the oval window

38
Q

Outer hair cells are innervated by?

A
39
Q

What does the cochlea do?

A

Produces nerve impulses in response to sound and vibration

40
Q

What are the two types of organs in the vestibular system?

A

Static Labyrinth (macular organs)

Kinetic Labyrinth

41
Q

How does hair cell bending in regards to kinocilium alter the function of nerve conduction?

A
  • Deflection of hair bundle toward kinocilium (tall side): depolarization and excitation
  • Deflection of hair bundle away from kinocilium (tall side): hyperpolarization and inhibition

Brain and Behavior (89 decks)

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