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Vestibular system Flashcards

1
Q

What are the mechanical sensors of the vestibular system?

A

Canals and Otoliths

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2
Q

How do you generate output in the vestibular system?

A

Movement and Gravity act as input, CNS integrates information and cause ocular reflex and postural control

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3
Q

What are the otolith organs and where are they located?

A

Utricule and Saccule, located in vestibule (bony landmark) and connected by conduit

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4
Q

How many semicircular canals are there and what are they called?

A

3 - anterior, posterior, lateral

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5
Q

How are canals and otolith organs connected?

A

Semicircular canals have an ampulla, which connect to the utricle

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6
Q

What is the primitive mechanism of vestibular organs?

A

Statocyst - crystallised calcium ball moves freely across cells with hairs during movement which is transduced to an electrical signal

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7
Q

How do otolith organs detect movement?

A

Utricle and Saccule contain maculae (horizontal and vertical respectively). Hairs move in response to movement.

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8
Q

How does the arrangement of maculae affect the type of movement detected?

A

Vertical arrangement on saccule means hairs are horizontal, therefore detect up down movement and vice versa for utricle

S-accule , standing up
Utricle, sideways movement

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9
Q

What is the maculae

A

Unit containing hair cells, gelatinous matrix and otoliths (carbonate crystals for hair deflection)

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10
Q

What is detected by otoliths

A

Linear acceleration and tilt

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11
Q

What is the location of hair cells in the semicircular canal?

A

Hair cells are located in ampulla crista. Hair cells are surrounded by cupula which helps hair cell movement.
Rest of canal has endolymph, K+ rich

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12
Q

How do the hair cells move in the semicircular canal?

A

Fluid movements put pressure ampulla, cause movement of hair cells

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13
Q

What is the advantage of having three semicircular canals?

A

Angular acceleration - all planes of movement can be covered, anterior and posterior are 90°, lateral are horizontal

canals work in pairs, anterior and posterior of each ear work together as they are in the same plane

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14
Q

Vestibular hair cells name

A

kinocilium and stereocilia. move towards kino to depolarise membrane

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15
Q

Hair cell potentials

A

Hair cells have resting potential -> basal discharge on the nerve. Depolarisation increases nerve discharge, hyperpolarisation decreases nerve discharge

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16
Q

Describe the neuronal pathway of vestibular afferents

A

Vestibular ganglion primary afferents end in vestibular nuclei in pons, neurons go to abducens nuclei and oculomotor nuclei

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17
Q

What is the connection between the abducens and oculomotor nuclei?

A

Medial longitudinal fasciculus

18
Q

Vestibulospinal tract

A

Vestibular ganglion primary afferents synapse with vestibulospinal tract for postural control

19
Q

What are the functions of the vestibular system?

A

Detect and inform about head movements
Keep images fixed in retina during head movements
Ultimately for balance

20
Q

What is the vestibulo-ocular reflex?

A

Keeps images fixed in the retina, despite head movement.
Eye movement occurs in the opp direction to head movement but at the same velocity and amplitude

21
Q

What are the two factors used to categorise vestibular disorders?

A

Timing and Laterality

22
Q

What are the main complaints in acute and unilateral disorders?

A

Vertigo, Dizziness, Imbalance and Nausea

Eyes moving without body movement, seeing the world move.

23
Q

What are the main complaints in slow disorders with any laterality?

A

Imbalance and Nausea, NO vertigo

24
Q

What are the two types of location balance disorders, and which part of the brain is affected?

A

Peripheral vestibular disorders (vestibular organ and/or VIII nerve - Vestibulocochlear)

Central vestibular disorders (CNS - brainstem or cerebellum)

25
Q

What are three examples of peripheral vestibular disorders?

A

Vestibular Neuritis,
Benign Paroxysmal Positional Vertigo (BPPV - dislodged crystals),
Meniere’s disease (vertigo and tinnitus)

26
Q

What are three examples of central vestibular disorders?

A

Stroke, MS, Tumours

27
Q

BPPV
Benign Paroxysmal Positional Vertigo

A

Normal gelatinous matrix in maculae are dislodged.
Moves around in the canal despite no actual bodily movement. Abnormal signal.
Cause patient to experience the world as moving.

symptoms occur when the patient moves their head

28
Q

Vestibular Neuritis

A

Inflammation of semicircular canals

29
Q

Vestibular migraines

A

Can cause dizziness and vertigo

30
Q

What 3 body components do physicians assess in vestibular disorders?

A

Eyes, Ears, Legs

31
Q

What are 5 red flags to suspect vestibular disorders?

A

Headache,
Gait problems, difficulty walking
hyper-acute onset of disorder, usually vascular
hearing loss,
prolonged symptoms (>4 days)

32
Q

What is a clinical test for people who have one pupil in a central middle position and one pupil at the central but top of eye?

A

Cover the central eye, does the other pupil go back to a central middle position

33
Q

How can you classify balance disorders on timing?

A

Acute,
Intermittent,
Recurrent,
Progressive

34
Q

What are 2 examples of acute balance disorders?

A

Vestibular Neuritis,
Stroke

35
Q

What clinical exam can you do for acute balance disorders?

A

HINTS Exam -
Head Impulse (horizontal rotational VOR),
Nystagmus (sudden jerky eye movement - if a train goes past do there eyes keep jumping back after following a carriage),
Test of Skew deviation (vertical misalignment)

36
Q

What is an example of intermittent balance disorders?

A

Benign Paroxysmal Positional Vertigo

37
Q

What clinical exam can you do for intermittent balance disorders?

A

Dix-Hallpike Test (lie down, hang head off table at 45 degree angle, do they get vertigo by watching eyes)

38
Q

What is an example of a recurrent balance disorder and what is its main symptom?

A

Meniere’s Disease (migraine)

39
Q

What are two examples of progressive balance disorders?

A

Vestibular Schwannoma, MS

40
Q

What is the vestibulo-spinal reflex?

A

Body posture changes during slipping to gain balance

Neuro (12 decks)

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