Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Neuroscience and Mental Health > 11. Vestibular system > Flashcards

11. Vestibular system Flashcards

1
Q

Which 3 systems maintain balance?

A
  • Proprioception
  • Vision
  • Inner ear
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the only thing the balance system can detect?

A

• Only acceleration

  • angle acceleration (turning)
  • linear acceleration (forward/backward)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is angular acceleration governed by?

A

3 semi-circular canals (head motion)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is linear acceleration governed by?

A

2 otolith organs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the normal functions of the vestibular system?

A
  • Subserve perception of movement in space and tilt with respect to gravity
  • Provide reflex balance reactions to sudden instability of gait or posture (vestibulo-spinal reflexes)
  • Stabilise the eyes on earth fixed targets - preserving visual acuity during head movements (vestibulo-ocular reflexes)
  • Assist control of blood pressure and heart rate during rapid up-down tilts
  • Assist synchronisation of respiration with body reorientations
  • Provokes motion sickness
  • Provide a reference of absolute motion in space - spatial orientation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the disorder relating to a false perception of movement in space?

A

Vertigo

vestibulo-cortical

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the disorder relating to instability of gait and posture?

A

Vestibular ataxia

vestibulo-spinal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the 2 disorders relating to the inability to stabilise the eyes?

A
  • Vestibular nystagmus - unilateral lesions
  • Oscillopsia - during head movement in bilateral vestibular lesions

(vestibulo-ocular)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What problems can arise in the acute phase of vestibular loss, and unilateral vestibular loss, respectively?

A
  • Slight impairment of orthostatic control

* Severe nausea and vomiting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What can a disorder of the vestibular system lead to, relating to orientation and motion?

A

Loss of co-ordination on:
• directional reorientation
• motion intolerance
• oversensitivity to visual motion in the environment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Which vestibular projection is related to nausea?

A

Vestibulo-autonomic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are the 2 main parts of the vestibular labyrinth?

A

• Bony labyrinth - bounded by petrous temporal bone filled with perilymph
• Membranous labyrinth
- filled with endolymph containing the receptor cells
- located within the utricle, saccule and semicircular canals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Where are the epithelial hair cells (sensory receptors) located in the vestibular labyrinth?

A
  • Macula - utricle and saccule

* Crista ampullaris (swelling of semicircular canals)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Where are the primary afferent neurones located in relation to the vestibular labyrinth?

A
  • Cell bodies in vestibular ganglion
  • Peripheral processes end in macula and ampulla
  • Central process synapse in brainstem vestibular nuclei
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What causes the deflection of the hair cells in the canals and which nerve do they signal to?

A
  • Head movement
  • Acceleration causes endolymph movement => deflection of macula (where all the hair cells are)
  • When you stop, this occurs in the opposite direction
  • Signals to the auditory nerve (cochlear nerve - one of 2 parts of CN VIII)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are hair cell cilia embedded in?

A
  • Otoconia

* Gelatinous matrix containing calcium carbonate crystals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How are the sensory hair cilia arranged?

A
  • Stereocilia - arranged in rows of varying heights

* Kinocilium - tallest one, for morphogenesis and mechotransduction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are the different nerve endings on hair cells?

A
  • Type I - chalice-like endings forming ribbon synapses

* Type II - simple nerve terminals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Describe the transduction mechanisms of the hair cells (hair cell receptor potential + ganglion cell discharge)

A

Hair cell receptor potential
• towards the kinocilium = depolarisation
• away from the kinocilium => hyperpolarisation

Ganglion cell discharge
• towards to kinocilium => increased frequency
• away from the kinocilium => decreased frequency

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the striola?

A
  • Dividing ridge that runs through the middle of the macula
  • Divides hair cells into populations with opposing hair bundle polarities
  • Kinocilia are oriented towards from it in the utricle, and away from it in the saccule
  • Tilt of the head to one side has opposite effects on corresponding hair cells of the other side
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Describe the orientation of the Otolith organs

A

Saccule
• Approximately vertical plane
• Hair cells with their overlaying layer of otoconia project normal to the plane with directional sensitivities:
- all combinations of vertical and antero-posterior directions

Utricle
• Approximately horizontal plane
• Hair cells project vertically with directional sensitivities:
- all combinations of lateral and antero-posterior directions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What force stimulates the Otolith hair cells and what give the complete signal?

A
  • Inertial resistance of the otoconial mass to linear head acceleration
  • Vector sum of utricular and saccular stimulation patterns give a signal of linear acceleration in all 3D directions
23
Q

How does the vestibular labyrinth convey information of a static upright body (head) position and a head tilt?

A
  • Vestibular ganglion neurones that innervate the saccule have tonic discharge
  • Due to constant hair displacement imposed by gravity
  • Input continues to produce action potentials over the duration of this stimulus
24
Q

What is the ampullary cupula and how are the hair cells related to it?

A
  • Structure providing the sense of spatial orientation
  • Located within the ampullae of each of the three semicircular canals
  • Gelatinous component of the crista ampullaris that extends from the crista to the roof of the ampullae
  • Cilia of the hair cells are embedded in this, and are stimulated by the differential movement of the endolymph and crista
25
Q

Which canal does rotation to the right stimulate?

A

Right canal

26
Q

Which canal does stopping a rightward rotation (deceleration to the right) stimulate?

A

Left canal

27
Q

What are the (4) different vestibular nuclei and how are they organised?

A 
Somatotopic organisation
• Kinetic labyrinth (SCCs)
- superior
- medial
• Static labyrinth (otoliths)
- lateral
- inferior
28
Q

What 4 main targets do the vestibular nuclei project to?

A
  • Spinal cord
  • Nuclei of the extraocular muscles
  • Cerebellum
  • Centres for cardiovascular + respiratory control
29
Q

What does the vestibular pathway from the static labyrinth (otoliths) influence?

A
  • Vestibulospinal tract
  • Antigravity muscles that contribute to upright posture and equilibrium
  • Blood pressure
30
Q

What does the vestibular pathway from the kinetic labyrinth (SCC) influence?

A
  • Medial longitudinal fasciculus
  • Eye movements that ensure that the retinal image is kept stationary when the head moves
  • Postural adjustments
  • Cardiovascular + respiratory function
31
Q

Describe the pathway of the lateral vestibulo-spinal tract

A

• Descends ipsilaterally in the ventral funiculus of the spinal cord
• Axons terminate in the lateral part of the ventral horn
- influence motor neurones to the limb muscles (especially extensor antigravity muscles)

32
Q

Describe the pathway of the medial vestibulo-spinal tract

A

• Descends bilaterally in the medial longitudinal fasciculus (MLF) to the cervical and upper thoracic spinal cord
• Axons terminate in the medial part of the ventral horn
- influence motor neurones to the neck and back muscles

33
Q

What is the vestibular-ocular reflex?

A
  • Reflex that functions to stabilise images during head movement
  • Done by producing eye movements in the direction opposite to head movement
  • This preserves the image on the centre of the visual field
  • With continuing head rotation frequent, saccades reposition the eyes more centrally to form an overall pattern of normal or ‘physiological vestibular nystagmus’
  • Nystagmus = involuntary eye movement
34
Q

How is the vestibular-ocular reflex carried out?

A

• Axons of the medial vestibular nucleus cross the midline and project to the contralateral abducens (VI) nucleus
- abducts the eye (in the opposite direction to head rotation
• Axons from the VI cross and ascend in the MLF and excite the contralateral oculomotor (III) nucleus
- adducts the other eye (in the opposite direction to head rotation)

35
Q

Which neurones project to the motor nuclei supplying extraocular muscles?

A

Superior and medial vestibular neurones

36
Q

How can you test the vestibulo-ocular reflex?

A

• Horizontal v.o. reflex can be elicited by warming or cooling the endolymph in the SCC
• Warm caloric test applied to the right ear (warm water pumped into the ear)
• Should produce a slow drift of the eyes away from the stimulated side
• Followed by a fast saccade towards the stimulated side
- direction of nystagmus named in accordance to this fast saccadic phase

37
Q

Describe the vestibulo-cerebellar pathways?

A
  • Afferents from the vestibular ganglion and nuclei
  • They go to the cerebellar cortex of the flocculonodular lobe
  • Cerebellar efferents from fastigial nucleus (deep) to all vestibular nuclei
  • Role in postural regulation (via vestibulo-spinal tracts) and eye movements (via MLF)
38
Q

Describe the vestibular pathways to the thalamus and cortex

A
  • All vestibular nuclei project to ventral posterior and ventral lateral nuclei of the thalamus
  • Thalamic nuclei project to 2 cortical areas (2V and 3a) - part of the ‘head region’ of the primary somatosensory cortex
  • Projection also to the superior parietal cortex: ‘vestibular cortex’ - spatial orientation
  • Cortical projections may account for feeling of dizziness (vertigo) during certain kinds of vestibular stimulation
39
Q

What are peripheral vestibular disorders caused by and give some examples?

A

Problems with the labyrinth and vestibulocochlear nerve
• vestibular neuritis (acute)
• BPPV (intermittent)
• Meniere’s disease (recurrent) bilateral, unilateral

40
Q

What are central vestibular disorders caused by and give some examples?

A 
Problems with the CNS (brainstem/cerebellum)
• Stroke
• MS (acute)
• Tumours
• Cerebellar degeneration (chronic)
41
Q

What is oscillopsia?

A
  • Marked loss of vestibular function
  • Impaired eye stabilisation during rapid head movement - vestibulo-ocular reflex is the only mechanism that can drive fast compensatory eye movements
  • Visual world will seem to oscillate or lag behind during active or passive head movements
42
Q

How can you test for oscillopsia?

A
  • Head shaking test
  • Focus on target
  • Normally eyes remain fixed
  • In oscillopsia, eyes will be taken off target, and multiple catch up saccades will be made to regain the target
  • May affect one side
43
Q

What are the different types of vestibular ataxia?

A

Bilateral vestibular disorder
• Mild gait ataxia
• Worse at speed, when negotiating rough ground or when vision is reduced

Unilateral vestibular disorder
• Tendency for the body and head to lean or fall to the lesioned side

44
Q

How does a loss of vestibular tone affect BP?

A
  • Provokes hypotensive episodes

* Patient feels faint as well as dizzy

45
Q

What is the likely cause of vestibular vertigo that lasts seconds or minutes?

A

Seconds
• Benign positional vertigo
• BPPV (due to debris in canals)

Minutes
• Vertebrobasilar insuffiency

46
Q

What is the likely cause of vestibular vertigo that lasts hours or days?

A

Hours
• Meniere’s syndrome
• Hearing disturbance

Days
• Vestibular neuritis
• Infarction of labyrinth

47
Q

What is Benign, Paroxysmal Positional vertigo (BPPV) caused by?

A
  • Normally there are little, dense crystals in the hair cells
  • If you bang your head, crystals fall off hair cells and fall into the fluid in the canals
  • Otoconial debris stimulate the ampulla causing false signals of head rotation
  • Results in short-lived dizziness with head movements
48
Q

What is Meniere’s syndrome caused by?

A
  • (Reissner’s/basilar) membrane between endolymph and perilymph
  • Membrane splits and the fluids mix => loss of balance function on affected side
  • Vicious attack of vertigo and hearing loss
  • Triad: vertigo, tinnitus, deafness
  • Very rare
49
Q

What is vestibular neuritis?

A
  • Sudden, unilateral vestibular loss
  • Hearing is spared
  • No CNS symptoms or findings
  • After URTI; mini-epidemics (viral related)
50
Q

What is a vestibular migraine?

A
  • Most common cause of recurrent spontaneous vertigo attacks
  • Migraine symptoms during attack
  • Hearing usually spared
  • Response to treatment
51
Q

How can you test for BPPV?

A
  • Dix-Hallpike manoeuvre
  • Positive test - patient reports of reproduction of vertigo and nystagmus is observed
  • Modified test is done with patient moved sideways, done due to anxiety or discomfort with conventional (supine) manoeuvre
52
Q

What is the manoeuvre is done to move debris out of the sensitive part of the SCCs?

A
  • Semont repositioning manoeuvre

* Patient is rapidly moved from lying on one side to another

53
Q

Where do the vestibular projections go to, involved in perception of motion in space, and how can a unilateral canal lesion affect this?

A

• Via thalamus to temporo-parietal ‘spatial’ cortex

  • The tonus of the intact canal gives a signal as if the head is rotating to the intact side
  • Patient may experience symptoms of intense spinning or feelings as if on a boat (vertigo)
  • Eyes are drive to the lesioned side because of this
  • Brainstem detects this and causes saccades to the intact side - seen in the acute phase of loss and minimised by visual suppression mechanisms

Neuroscience and Mental Health (17 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions