Lecture 29: Neuroanatomy of the Auditory and Vestibular Systems Flashcards

1
Q

What are the functions of the vestibular system

A

Transduce and interpret head movements, maintain position of visual axes when head is moving, send motor commands to the trunk and limb muscles in order to maintain balance

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1
Q

What is the vestibulo-ocular reflex

A

Maintain positioning of the visual axes when the head is moving

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2
Q

What is the function of the auditory system

A

Transduce and interpret vibrations due to sound

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3
Q

What structure receives information from the organs of balance on head movement and information on muscle firing from the cerebellum

A

Vestibular nuclei in the brain stem

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4
Q

What is the pathway of information on the head and body movement

A

Utricle, saccule and ampulla—> scarpa’s ganglion—> CN VIII—> nuclei in brainstem

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5
Q

What is responsible for sending motor to antigravity muscles to maintain upright posture

A

Vestibulospinal tracts

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6
Q

What is the pathway of motor to extraocular nuclei to coordinate eye movements

A

Medial longitudinal fasciculus—> oculomotor, trochlear and abducens nuclei

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7
Q

What brain structure is responsible for receiving input on body position and movement from cortex, spinal cord and vestibular movement. Coordinates motor output through the cortical and vestibular pathways. Coordinates timing of movement

A

Cerebellum

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8
Q

What could be the result of a lesion to CN VII or the vestibular nuclei

A

Disruptions in stance, head posture, and balance. Damage that includes the vestibular nuclei can also lead to loss of extensor muscle tone

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9
Q

What structures are encased within the bony labyrinth

A

Organs of balance and hearing, contained with the petrous portion of the temporal bone

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10
Q

What is the flow from the air filled outer and middle ear cavities to fluid filled ear cavities

A

Sound energy (outer)—> through tympanic membrane—> auditory ossicles (malleus-incus-stapes in middle ear)—-> oval window (inner ear)

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11
Q

What are the vestibular organs

A

Semicircular ducts, utricle, saccule and vestibular nerve

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12
Q

What are the cochlear organs

A

Cochlear duct and cochlear nerve

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13
Q

What region contains endolymph

A

Membranous labyrinth

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14
Q

What region contains perilymph

A

Region between the membranous ducts and the bony labyrinth

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15
Q

What type of receptors are located in the vestibular and cochlear apparatus and what do they depend on

A

Mechanoreceptors that depend on the mechanical displacement of receptors by fluid

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16
Q

What structures are responsible for sensing rotation of head

A

Semicircular ducts and ampulla

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17
Q

What structures are responsible for sensing linear head movement in a horizontal plane

A

Utricle and macula

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18
Q

What structures are responsible for sensing linear head movement in vertical plane

A

Saccule and macula

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19
Q

What is the vestibular ganglion

A

Scarpa’s ganglion

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20
Q

What vestibular organs and how many of each are located on each side of head

A

3 semicircular ducts with 1 ampulla
1 utricle with one macula
1 saccule with one macula
1 vestibular ganglion/scarpa’s ganglion

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21
Q
A
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22
Q
A
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23
Q

What is the function of the saccule

A

To monitor and activate in response to linear acceleration of vertical movements (up and down) relative to gravity vector

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23
Q

What is the function of the utricle

A

To monitor and activate response to linear acceleration of horizontal movements (side to side, front to back) relative to the gravity vector

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23
Q

What is the function of the three semicircular ducts

A

Function to monitor and respond to angular acceleration (rotation) of head in all planes

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23
Q

What organs of the vestibular membranous labyrinth Transduce acceleration

A

Utricle, saccule and semicircular ducts

24
Q

Where are the hair cells located within the semicircular ducts

A

Ampulla

25
Q

Ampullary crest hair cells embed in the ___

A

Crista

26
Q

Stereocilia embed in the ___

A

Gelatinous cupula

27
Q

Moving ____ bends the cupula which tilt the ___ towards ____

A

Endolymph, sterocilia and kinocilium

28
Q

Cilia are surrounded by ___

A

Endolymph

29
Q

What is the concentration of K+ and Na+ in the endolymph

A

K+ (high)= 150mM and Na+ (low)=1mM

30
Q

Cell bodies and dendrites of the hair cells are surrounded by ___

A

Perilymph

31
Q

What is the concentration of K+ and Na+ in perilymph

A

Low K+ and high Na+

32
Q

What happens when stereocilia move towards kinocilium

A

Hair cells depolarize and Ca2+ enters cell and increase firing rate

33
Q

What happens when sterocilia are deflected away from kinocilium

A

Hair cells hyperpolarize and decrease firing rate

34
Q

What makes up the internal structure of stereocilia and kinocilium

A

Actin

35
Q

What are the otolith organs

A

Utricle and saccule

36
Q

Otolith organs Transduce ___ acceleration

A

Linear acceleration
Utricle- detects horizontal displacement
Saccule- detects vertical displacement

37
Q

Moving of the head allows displacement of ___ which moves and tilts sterocilia toward kinocilium

A

Gelatinous cap

38
Q

Hair cells in macular organs have ___ orientation

A

Mirrored

39
Q

What does the reversal line indicate and what is the functionality

A

Indicates where hair cell orientation changes. Functionally some hair cells are depolarizing while others are hyperpolarizing

40
Q

What structure is responsible for summing the signal of the variation in stimulation from the reversal line

A

Vestibular nuclei

41
Q

Hair cells are ___ polarized on right and left sides

A

Oppositely polarized

42
Q

Hair cells will ___ on the side of the head toward which the person is turning meanwhile will ___ on the side from which the Person is turning

A

Depolarize (increase firing rate), hyperpolarize (decrease firing rate)

43
Q

Vestibular nuclei compare firing rates from each side, magnitudes should ___ in a healthy individual

A

Match

44
Q

What structure controls vestibuloocular relfex

A

Semicircular canals

45
Q

Ex: head rotates to the right but eyes stay forward. What organ monitors head rotation? What muscles receive motor commands to keep eyes centered

A

Vestibular organs monitor head rotation
Motor commands are sent to contract the LEFT lateral rectus and RIGHT medial rectus

46
Q

A lesion to CN VIII, vestibular apparatus or vestibular nuclei leads to an imbalance of ____ received by vestibular nuclei

A

Action potentials

47
Q

What is the result of imbalanced action potentials received by vestibular nuclei

A

Perception that the head is constantly moving when its not

48
Q

What structures provide mammals with an extended range of hearing compared to other vertebrates

A

The middle ear contains the malleus, incus, and stapes in mammalian anatomy whereas the anatomy in non-mammalian vertebrates only contains the stapes, therefore mammals have a greater ability to amplify sound

49
Q

What animal can hear at the highest frequency

A

Bottlenose dolphin

50
Q

What animal can hear at the lowest frequency

A

Elephant

51
Q

Where is the cochlea located in relation to the semicircular ducts

A

Rostromedially

52
Q

The footplate of the stapes transmits vibrations to the membrane of the ___ and ___ of the scala vestibuli

A

Oval window and perilymph

53
Q

The mechanoelectrical mechanism is embedded in

A

Scala media

54
Q

Fluid displacement from the oval window creates waves and displacements in membranes of the ____

A

Cochlea

55
Q

What fluid fills the cochlear duct

A

Endolymph

56
Q

What fluid fills the scala vestibuli and scala tympani

A

Perilymph

57
Q

Stereocilia hair cells along the basilar membrane are embedded into the ____ membrane

A

Gelatinous tectorial membrane`

58
Q

Displacements of the basilar membrane relative to the tectoral membrane displaces the stereocilia resulting in what

A

Causing mechanoelectrical transduction and depolarization

59
Q

What membrane helps encode frequency

A

Basilar membrane

60
Q

What frequency is best encoded closest to stapes and oval window

A

high frequencies

61
Q

What frequency is best encoded farthest away from stapes and oval window

A

Low frequencies

62
Q

How can animals determine where a sound came from

A

Interaural time/arrival difference and interaural level difference are used to compute location based on timing and sound level differences received between each side