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NE Exam 2 > 12. Vestibular system > Flashcards

12. Vestibular system Flashcards

1
Q

What are the 5 components of the vestibular system?

A
  1. peripheral receptor apparatus
  2. central vestibular nuclei
  3. vestibuloocular network
  4. vestibulospinal network
  5. vestibulothalamocortical network
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2
Q

The _______ ______ ________ is the inner ear and is responsible for transfusing head motion and position

A

Peripheral receptor apparatus

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3
Q

The ______ ______ ______ is involved in integrating and distributing information that controls motor activities and spatial orientation

A

Central vestibular nuclei

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4
Q

The ________ _______ is involved in the control of eye movement

A

vestibuloocular network

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5
Q

The _____ ______ coordinates head movements, axial musculature and postural reflexes

A

Vestibulospinal network

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6
Q

The _________ ______ is involved in conscious perception of movement and spatial orientation

A

vestibulothalamocrotical network

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7
Q

What are the receptor organs that are involved with rotational head movements?

A

Semicircular canals

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8
Q

What are the receptor organs that are involved with translational head movements and linear accelerations

A

otolith organs and the utricle and saccule

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9
Q

What are the receptor cells in the vestibular organs innervated by?

A

Primary afferent fibers of the vestibular organ

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10
Q

_______ is located between the membranous and the bony labyrinths and is similar in composition to CSF

A

Perilymph

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11
Q

_______ is in the membranous labyrinth and bathes the receptors of the auditory and vestibular systems

A

Endolymph

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12
Q

What is the cause of a vestibular disease?

A

The disturbance in volume or ionic concentration of the endolymph

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13
Q

Describe the blood supply to the vestibular system

A

Via the labyrinthine artery form the AICA that entires the temporal bone through the internal acoustic meatus

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14
Q

What is the function of the stylomastoid artery in the vestibular system?

A

Feeds the semicircular canals but is NOT the primary source

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15
Q

If there is a decrease or interruption in blood flow to the vestibular system, what happens?

A

Vertigo, nystagmus, and unstable gait

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16
Q

What is the cause of Meniere’s disease?

A

Disruption of the endolymph volume which results in an abnormal distension of the membranous labyrinth

When this happens, it leads to vertigo, vomiting, tinnitus, and make head movements difficult with association fluctuating hearing loss

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17
Q

What is the treatment of Meniere’s disease?

A

Diuretic and salt restricted diet to decrease the hydrops

small shunt into the endolymphatic sac

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18
Q

What is the purpose of hair cells?

A

To register positional changes of the head and respond by moving in a way that will depolarize or hyper polarize the cell; they are organized how they are going to move

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19
Q

If the hair cells move toward the kinocilium, what happens?

A

The cells are depolarized

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20
Q

If the hair cells move away from the kinocilium what happens?

A

The cells are hyper polarized

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21
Q

Differentiate between type 1 and type 2 hair cells

A

Type 1 hair cells are innervated by a nerve calyx which is like a cup like thing at the bottom of the cell

Type 2 hair cells are innervated by boutons

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22
Q

What is the ampullae?

A

semicircular ducts that have hair cells embedded in the cristae and extend into the cupula

Notices rotational acceleration

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23
Q

Describe how the ampullae are activated

A

rotational acceleration causes displacement of endolymph and causes the cupula to bend to one side or another and the stereo cilia are displaced

If the cilia move towards the kinocilium then an action potential will occur

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24
Q

What is the maculae?

A

Utricle and saccule are involved with otoconia involvement (ear stones)

Notices gravity/linear acceleration

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25
Q

Describe how the maculae are activated?

A

Gravity and linear accelerations displace the otoconia and bend the underlying hair cells stereo cilia

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26
Q

Describe the vestibular afferents

A

The primary afferents are from CN VIII from the semicircular duct or the otoliths enter at the pontomedullary junction and project to the vestibular nuclei

27
Q

_______ ______ are directionally selective and encode direction, speed of movement, and head position

A

Vestibular nuclei

28
Q

What do the secondary afferent neurons target?

A

CN III, IV, VI, vestibulocerebellum, SC, reticular formation, and thalamus

29
Q

________ _______ are reciprocal connections with analogous contralateral nucleus

If you turn your head to the right side, the right side is activated and the left side is inhibited so that you dont get dizzy

A

Vestibulovestibular fibers

30
Q

______ _____ arise from all SC levels to provide proprioceptive input

Head involved with posture

A

Spinovestibular fibers

31
Q

The _______ _______ is the only sensory organ body that sends direct fibers to the cerebellum

A

Vestibulocerebellar fibers

32
Q

These fibers course through the juxtarestiform body and part of the inferior cerebellar peduncle

A

Vestibulocerebellar fibers

33
Q

What do the primary vestibulocerebellar fibers target? Where do they terminate?

A

Target the dentate nucleus and terminate as the mossy fibers

34
Q

What do the secondary vestibulocerebellat fibers target?

A

Target the flocculonodular lobe and the fastigial and dentate nuclei

35
Q

What do the reciprocal cerebellovestibular fibers target?

A

Vestibular nuclei in the juxtarestifrom body

36
Q

________ is a nonspecific term that means spatial disorientation and may or may not involve feelings of movement, accompanied with nausea or instability, and may not be secondary to a vestibular issue

A

Dizziness

37
Q

______ is an illusion of body motion, spinning, turning sensation when it is not actually occurring

A

Vertigo

38
Q

Differentiate between subjective and objective vertigo

A

Subjective vertigo is when the patient experiences the sensation of spinning when things are not actually moving (I am spinning in the room)

Objective vertigo is the sensation of objects moving when the patient is not (the room is spinning)

39
Q

This is one of the most common vestibular disorders and is characterized by brief episodes of vertigo that coincide with changes in body position (getting out of bed, bending over, etc)

A

Benign paroxysmal positional vertigo

40
Q

This disorder can be secondary to the otoconial crystals from the utricle becoming dislodged and lodged into the cupula of the semicircular canal, which results in abnormal cupula deflections with head positional changes

A

Benign paroxysmal positional vertigo

41
Q

What is a vestibular schwannoma

A

Benign tumor of the schwann cells of the vestibular root that impinges on everything that is going through the internal acoustic meatus

CNVII CNVIII labyrinthine artery to the vestibular organ (from AICA)

42
Q

Where are vestibular schwannomas typically found? What are the sx?

A

in the cerebellopontine angle

hearing loss, gait abnormalities, and tinnitus

43
Q

If a patient presents with severe vertigo, nausea, vomiting, but no hearing loss, including a recent viral infection what is the possible diagnosis?

A

Vestibular neuritis

involves edema of the vestibular system and the vestibular nerve

44
Q

What is the treatment for vestibular neuritis

A

Antiemetics, vestibular suppressants, corticosteroids, and antiviral agents

45
Q

the ______ ________ ______ arises from the lateral and inferior vestibular nuclei and project to the ipsilateral SC

This is a powerful control of extensors for maintenance of posture

A

Lateral Vestibulospinal tract

46
Q

The _____ ______ _____ has fibers that descend bilaterally through the MLF and terminate on the cervical SC stabilizing the neck flexor and extensor musculature

A

Medial vestibulospinal tract

critical in the vestibulocolic reflex that stabilizes the head via activation of the neck musculature

47
Q

What are the cortical areas that are targeted by the thalamocortical pathways?

A

Primary somatosensory cortex

Parietoinsular vestibular cortex

Posterior parietal cortex

48
Q

What will lesions in the parietoinsular vestibular cortex result in?

A

vertigo, unsteadiness, and loss of visual vertical

49
Q

What will lesions in the posterior parietal cortex result in?

A

Confusion and spatial awareness

50
Q

Describe the vestibuloocular reflex

A

Stabilizes retinal images during head movements through vestibular input

helps you to be able to read things while walking, and adjust to head movements with eye movements to accompany so that you are able to focus

51
Q

Describe the eye position during the VOR

A

saw tooth position with a slow phase and a fast phase

If you rotate your head to the right, then the ocular muscles are activated to move the eyes to the left in the slow phase, activating the right vestibular apparatus and the left lateral rectus and right medial rectus

The quick phase takes the eyes back to the right with the head, to offset the slow phase

52
Q

______ is the combo of a slow phase punctuated by fast return phase

A

Nystagmus

53
Q

How is nystagmus named?

A

For the direction of the fast phase

54
Q

Describe what happens when you move your head to the right

A

The fluid in the semicircular duct moves and causes an activation of the right afferent fibers

This alerts the right vestibular nuclei and the left CN VI nucleus and the right CN III nucleus

The left lateral rectus is linked with the right medial rectus

55
Q

Describe what happens with the VOR with a rightward rotation of the head

A

Right vestibular afferents are activated

Eyes rotate slowly to the left

Abrupt shift back to the right (right beating nystagmus)

decreased activity of the left vestibular afferents

Right lateral rectus and left medial rectus relax

56
Q

Describe spontaneous nystagmus

A

Unilateral damage to the vestibular system

The output of the damaged side is silenced causing differences in the firing rates of CN VIII which can cause nystagmus

57
Q

What can peripheral damage lead to?

A

Vestibular labyrinth and/or CN VIII

imbalance between left and right vestibular input causes nystagmus

Does not affect voluntary saccades and smooth pursuit

58
Q

What does central damage of the brainstem or cerebellum lead to?

A

Nystagmus with impaired voluntary saccades

Involvement of multiple pathways

59
Q

Describe the caloric test

A

Tests the vestibular labyrinth system and the VOR without moving the head

water is used to alter the convection currents in the endolymph which alters the CN VIII firing rate

60
Q

When warm water is used in the caloric test, what happens?

A

Currents are generated that mimic the head turning to the irrigated side; nystagmus will beat toward the irrigated ear

61
Q

When cold water is used in the caloric test, what happens?

A

Currents are generated toward the opposite side; nystagmus does the same

62
Q

What is the oculocephalic reflex?

A

Rotating the head back and forth horizontally induces eye movements that are dependent on the visual and vestibular function

The reflex occurs when the patients eyes move in the opposite direction of the head movements

63
Q

When is the oculocephalic reflex tested?

A

in a comatose patient; to assess brainstem function; if it is intact, then the brainstem is fine and vice versa

NE Exam 2 (24 decks)

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