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MD4001 Physiology > Cerebellum, balance and coordination > Flashcards

Cerebellum, balance and coordination Flashcards

1
Q

What does the vestibular apparatus do?

A

Sensory system that is responsible for providing our brain with information about motion, head position, and spatial orientation; it also is involved with motor functions that allow us to keep our balance, stabilize our head and body during movement, and maintain posture

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2
Q

What is the cerebellum shaped like?

A

A curled up woodlouse

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3
Q

What are peduncles?

A

Connections between cerebellum and brainstem

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4
Q

What do inferior peduncles connect?

A

Cerebellum to medulla

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5
Q

WHat info do inferior peduncles carry?

A

Sensory info from muscle proprioceptors

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6
Q

What do middle peduncles connect?

A

Cerebellum to pons

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7
Q

What fibres do middle peduncles carry?

A

Voluntary motor activities by motor cortex

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8
Q

What fibres to superior peduncles connect?

A

Neurons in deep cerebelar nuclei and communication with motor cortex via thalamus

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9
Q

Whta do the superior peduncles connect?

A

Cerebellum to midbrain

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10
Q

What tract along with the cerebellum allow for movement to be modified?

A

Rubrospinal

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11
Q

What is the cerebellum essentially?

A

Sensory integrating system

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12
Q

What does the molecular layer contain?

A

Lots of paralel fibres axons, sensory information

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13
Q

What does the purkinje cell layers contain?

A

Purkinje cells - all straight line

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14
Q

What does the granular cell layer contain?

A

Granular cells - also inputs from other cells i.e golgi cells

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15
Q

Where do climbing fibres synapse?

A

With paralel fibres in cortical regions

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16
Q

What do mossy fibres synapse with?

A

Paralel fibres in cortex and integrating sensory information

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17
Q

Are mossy and climbing fibres excitatory or inhibitory?

A

Excitatory

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18
Q

What cells produce inhibitory signals?

A

Golgi cells and purkinje cells

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19
Q

What are the cell layers of the cerebellum?

A
  • Molecular layer
  • Purkinje cell layer
  • Granule cell layer
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20
Q

What do granular cells do?

A

Interperts different inhibitory and positive signals.

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21
Q

What are the single output from the cerebellum?

A

Deep cerebellar nuclei (will send signals to red nuclei and then to thalamus )

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22
Q

What fibres are cerebellar inputs?

A

Mossy fibres and climbing fibres

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23
Q

What are the deep nuclei from lateral to medial?

A
  • Dentate nucleus
  • Emboliform nucleus (interposed nucleus)
  • Globose nucleus (interposed nucleus)
  • Fastigial nucleus
    Dont Eat Greasy Food
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24
Q

What are the functions of the cerebellum?

A
  • Act as a comparator
  • Acts as a timing device
  • Initiating and storing movements
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25
Q

How does the cerebellum act as a comparator?

A
  • Cerebellum compares descending supraspinal motor signals with ascending afferent feedback information
  • Movement smoothly and acuurately coordinated
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26
Q

What part of the cerebellum creates a sequence for motor activation?

A

Pontocerebellum

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27
Q

What part of the cerebellum maintains balance?

A

Vestibulocerebellum

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28
Q

What part of the cerebellum maintains posture?

A

Spinocerebellum

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29
Q

What allows for initiating and storing movements in the cerebellum?

A 
Modifiable synapses (purkinje cells)
- So can store information and update it
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30
Q

What does alcohol cause?

A

Depression of cerebellar circuits

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31
Q

What does the cerebellum integrate in order to modulate motor output?

A
  • Activity in the pre-motor and motor areas as well as spinal motor circuits (information about potential motor output)
  • Sensory feedback from vestibular system, visual system, and ascending proprioceptive info (about real motor output)
  • Modulation by the cerebellum is effected at the motor cortex and brainstem
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32
Q

Where has most of our understanding of the cerebellum’s control of movement come from?

A

Effects of lesions

33
Q

What is the primary role of the cerebellum?

A

Thought to be to supplement and correlate activities of other motor areas e.g. correction of rapid muscular movement initiated by cortex (typing, musical instrument)

34
Q

What types of neurons help to maintain posture?

A

Golgi tendon organs and muscle spindle

35
Q

What do the golgi tendon organs and muscle spindles reach the cerebellum via?

A
  • Nucleus dorsalis of Clarke
  • Post. spinocerebellar tract
  • Inf. cerebellar peduncle (restiform body)
  • Cerebellum
36
Q

What are the clinical features of cerebellar damage?

A
  • Hypotonia
  • Incoordination / ataxia
  • Dysarthria (scanning speech), inability to articulate words
  • Nystagmus
  • Palatal tremor / myoclonus
37
Q

How can cerebellar damage cause hypotonia?

A

Reduced inout from Deep Nuclei neurone (DCNN) via descending motor pathways to muscle spindle

38
Q

What is asynergy?

A

Inability to coordinate contraction of agonist and antagonist muscles

39
Q

What is dysmetria?

A

Inability to terminate movements (intention tremor/ past pointing

40
Q

What is Dysdiadochokinesis?

A

Inability to perform rapidly alternating movements

41
Q

How can cerebellar damage cause dysarthria?

A

Incoordinated oropharyngeal musculature

42
Q

What is nystagmus?

A

Rapid jerky eye movements

43
Q

How does cerebellar damage cause nystagmus?

A

Disruption between vestibular nucleus and oculomotor nuclei

44
Q

What is a palatal tremor / myoclonus?

A

Hypertrophy of inferior olive which causes damage to dentate nucleus of cerebellum and red nucleus in midbrain

45
Q

What system generates our sense of balance?

A

Vestibular system

46
Q

What can the ear be divided into?

A

Outer, middle and inner ear

47
Q

What structure collects and focuses sound waves?

A

Pinna

48
Q

What is the middle ear bound by?

A

Air filled chamber bounded by tympatic membrane on one side and oval window on the other

49
Q

What does the eustachian tube connect?

A

Middle ear to nasopharynx, allows pressure equalisation

50
Q

What do semi-circular canals give us information about?

A

Move,ent of the head

51
Q

What do sacular organs give info about?

A

Accelaration

52
Q

What bone is the labyrinth elcased in?

A

Temporal bone

53
Q

What is the labyrinth filled with?

A

Endolymph

54
Q

What is the auditory part of the labyrinth?

A

Cochlea

55
Q

What are the 2 structures contained in the vestibular part of the membranous labyrinth?

A
  • Otolith organs (detect gravity and head tilt)

- Semicircular canals (detect head rotation)

56
Q

What are the hair cells of the saccule?

A
  • Mechanoreceptors that respond to minute movement changes

- Consist of one large kinocillium and 50-150 sterocilia

57
Q

What hair cells lose there kinocillium with age?

A

Coclea

58
Q

What are the hair cells contained in?

A

Gelatinous cap

59
Q

What sits on top of the gelatinous cap?

A

Otoliths (particles of calcium carbonate, denser than the endolymph cause hair cells to move in same direction))

60
Q

What are the otolithic organs?

A

Saccule and utricle

61
Q

What do the otolithic organs detect?

A

Changes in linear acceleration

62
Q

What way are the macula orientated?

A

Vertically in saccule and horizontally in utricle when head is upright

63
Q

Where do the hair cells synapse?

A

Axon of vestibular nerve (CN VIII)

64
Q

What provide directional information?

A

Cilia and kinocilium

65
Q

What opens/closes the hair cell cation channels?

A

0.5-micron movement of the kinocilium

66
Q

What causes K+ channels to open in the stereocilia?

A

Mechanical deformation towards the kinocilium

  • Ca2+ enters the cell, allowing vesicle fusion and the release of transmitter
  • Away causes K+ channels to close
67
Q

Where are hair cells clustered?

A

In sensory epithelium - crista ampullaris

68
Q

What are semicircular canals sensitive to?

A

Angular acceleartion (head rotation movements)

69
Q

What happens to the semicircular canals when the head rotates?

A

Canal moves but endolymph stays put, this bends the hair cells and they either excite or suppress transmitter releases depending on direction of movement

70
Q

Describe the vestibular nervous pathway?

A
  • Vestibular axons from CN VIII make direct connections to vestibular nucleus and cerebellum
  • Axons from otolith organs project to lateral vestibular nucleus, which project via vestibulospinal tract to spinal motor neurons - posture
  • Axons from semicircular cnanals project to medial vestibular nucleus, which project via medial longitudinal fasiculus to motor nerves of trunk and neck muscles - keeops head straight as body moves
71
Q

What is the semicircular canals which control eye movements reflex called?

A

Vestibulo-ocular reflex

72
Q

Direct stimulation of what nerve elicits specific eye movements?

A

Ampullary nerves

73
Q

Stimulation of afferents from left horizontal canal causes eyes to turn in wht direction?

A

Right (vestibulo-ocular reflex)

74
Q

What does the vestibulo-ocular reflex allow for?

A

Allows gaze to remain steady during head moveemnt s

75
Q

What nerve stimulates the lateral recti?

A

Cranial nerve VI - Abducens via abducens nucleus

76
Q

What nerve stimulates the medial recti?

A

Cranial nerve 3 - oculomotor via oculomotor nucleus

77
Q

What is menieres disease?

A
  • Vestibular appartus bathed in endolymph - excessive accumulation of endolymph and damage to hair cells due to poor draniage (probably)
  • Normally drains to venous sinus
  • Excessive stimulation
  • Symptoms of vertigo, nausea, tinnitus and hearing loss
78
Q

What is vertigo?

A
  • Sensation of turning or raotation in space in absence of actual rotation
  • Nausea, vomitting and gait ataxia
79
Q

What can vertigo be caused by?

A
  • Debris from otolithic membrane adhering to cupula in ampulla of posterior semicircular canal
  • Can be due to lesions of vestibular aspect of CNVIII or central lesions affecting brainstem vestibular nuclei
  • Inappropriate activation of hair cells

MD4001 Physiology (22 decks)

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