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Y3S1 NEURO > Cerebellum, balance and coordination > Flashcards

Cerebellum, balance and coordination Flashcards

1
Q

what are the names of the three pundcles that attach the cerebellum to the brain stem

A
  • Inferior Cerebellar Peduncle (ICP)
  • Middle Cerebellar Peduncle (MCP)
  • Superior Cerebellar Peduncle (SCP)
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2
Q

Which peduncles deal mainly with input

A
  • Middle Cerebellar Peduncle (MCP)

- Superior Cerebellar Peduncle (SCP)

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3
Q

Which peduncles deal mainly with output

A
  • Inferior Cerebellar Peduncle (ICP)
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4
Q

where does the superior Cerebellar Peduncle (SCP) connect to

A

the midbrain

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5
Q

where does the - Middle Cerebellar Peduncle (MCP) connect to

A

the pons and deals mainly with voluntary movements

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6
Q

what are the three lobes of the cerebellum

A

anterior
posterior
flocculonodular

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7
Q

• Vestibulocerebellum

A

this is at the very back of the cerebellum

– consists of flocculonodular lobes (white)
– input from vestibular & visual areas
– output to vestibular nucleus – controls equilibrium and eye movements

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8
Q

Spinocerebellum - middle strip

A

– consists of vermis of posterior and anterior cerebellum + adjacent
intermediate zones on both sides of vermis

– input from spinocerebellar & auditory, visual, vestibular systems & sensorimotor cortex

– output from vermis to fastigial nuclei to vestibular & reticular formation of pons and medulla

• Control antigravity muscles in posture and locomotion
– output from intermediate zone to interposed nuclei to red nucleus to thalamus then cortex
• Act on stretch reflexes & other somatosensory reflexes

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9
Q

Cerebrocerebellum - outer areas

A

– consists of lateral zones of the cerebellar hemispheres (pink/flesh)
– input from cerebral motor cortex & adjacent premotor & somatosensory cortices
– output to dentate nucleus to thalamus to motor and premotor cortices
– creates a feedback with the cortical sensorimotor system to plan sequential voluntary body and limb movements

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10
Q

what are the three layers of the cerebellum

A

molecular layer
purkinje cell layer
Granule cell layer

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11
Q

what are the two main input fibres

A
  • climbing fibres

- mossy fibres

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12
Q

mossy fibres

A

these indirectly stimulate purkunje fibres

inputs from pontine nuclei and other sources

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13
Q

climbing fibres

A

these directly stimulate purkunje fibres

inputs from inferior olivary nucleus

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14
Q

cerebellar output occurs via the deep nuclei, from lateral to medial what are they ?

A 
dentate nuclei 
emboliform nuclei 
globose nucleus 
fastigial nuclei 
vestibular nucelus
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15
Q

alcohol effects on the cerebellum

A

alcohol intoxication – depression of cerebellar circuits (truncal ataxia)

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16
Q

how does the cerebellum act as a comparator

A

– Cerebellum compares descending supraspinal motor signals with ascending afferent feedback
information
– Movement smoothly and accurately coordinated

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17
Q

how does the cerebellum act as a timing device

A

– Pontocerebellum – creates a sequence for motor activation
– Vestibulocerebellum – maintains balance
– Spinocerebellum – maintains posture

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18
Q

how does the cerebellum initiate and store movements

A

– Modifiable synapse (Purkinje cell)

– So can store motor information and update it

19
Q

• Primary role of cerebellum thought to be to

A

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

20
Q

how is the cerebellum informed of movement

A

by cortex before it occurs, then cerebellum processes sensory information to generate an error signal which is fed back to cortex and movement is adjusted

21
Q

• Hypotonia / Reduced muscle tone

A

Due to reduced input from Deep Cerebellar Nuclei neurone (DCNN) via descending
motor pathways to muscle spindle

22
Q

Incoordination / Ataxia

A

– Asynergy – inability to coordinate contraction of agonist and antagonist muscles
– Dysmetria – inability to terminate movements (intention tremor/past pointing)
– Dysdiadochokinesis – inability to perform rapidly alternating movements

23
Q

Dysarthria (scanning speech)

A

– Inability to articulate words (slurred and delivered slowly) due to incoordinated
oropharyngeal musculature

24
Q

Nystagmus

A

– Rapid jerky eye movements – disruption between vestibular nucleus and oculomotor nuclei

25
Q

• Palatal Tremor / Myoclonus

A

– Rare condition

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

26
Q

which system generates our sense pf balance

A

vestibular

27
Q

the role of the pinna

A

collected and focuses sound waves

28
Q

Middle ear is

A

air filled chamber, bounded by tympanic membrane on one side and oval window on the other

29
Q

Eustachian tube

A

connects middle ear to nasophyarynx, allows pressure equalisation

30
Q

Membranous Labyrinth

A
  • Labyrinth filled with endolymph and encased in temporal bone
  • Auditory part is cochlea
31
Q

vestibular part of the ear contains 2 structures known collectively as the otolith organs

A
  • utricle

- saccule

32
Q

in the saccule there are hairs

A
  • Mechanoreceptors that respond to minute movement changes
  • Consists of one large kinocilium and 50 -150 stereocilia
  • Hair cells of cochlea lose there kinocilium with age; vestibular hair cells do not
33
Q

what is the role of the otolith organs

A

• Detect changes in linear acceleration (i.e. that experienced as a car starts or stops) and head angle

34
Q

Macula is orientated what way in the saccule and in the utricle when the head is upright

A

vertically = saccule

horizontally = utricle

35
Q

each individual hair cells synapses on an axon of what nerve

A

vestibular nerve (part of cranial nerve VIII)

36
Q

Otoliths are

A

particles of calcium carbonate; they are denser than the endolymph

They are pulled by gravity and mock gelatinous cap in the same direction; cilia of hair cells are deflected

37
Q

Mechanotransduction in Hair Cells

A
  • Hair cells, project hairs into an otolithic (ear stone) containing gelatinous structure.
  • Cilia + kinocilium – provide directional information
  • Movement of otolithic membrane (from tilting or translational movement) bends the cilia/kinocilium in a very direction specific way
  • A 0.5-micron movement of the kinocilium opens/closes the hair cell cation channels
38
Q

Semicircular canals (Ampulla)

A

Sensitive to angular acceleration (head rotation movements)
• Hair cells clustered in sensory epithelium, crista ampullaris
• Hair cells project into gelatinous cupula, all hair cells orientated in same direction
• As head rotates canal moves but endolymph stays put, this bends the hair cells and they either excite or suppress transmitter release depending on direction of movement

39
Q

Vestibular Nervous pathway

A
  • Vestibular axons from CN VIII make direct connections to vestibular nucleus & cerebellum
  • Axons from otolith organs project to lateral vestibular nucleus, which project via vestibulospinal tract to spinal motor neurons – posture
  • Axons from semicircular canals project to medial vestibular nucleus, which project via medial longitudinal fasiculus to motor nerves of trunk and neck muscles – keeps head straight as body moves
40
Q

Semicircular canals control eye movements – Vestibulo-ocular Reflex

A
  • Direct stimulation of ampullary nerves elicits specific eye movements
  • Stimulation of afferents from left horizontal canal causes eyes to turn right (vestibulo-ocular reflexes)
  • Specific adaption to allow gaze to remain steady during head movement
  • Lateral recti – cranial nerve VI (abducens nucleus)
  • Medial recti – cranial nerve III (oculomotor nucleus)
41
Q

Ménière’s Disease

A

Clinical symptoms - vertigo, nausea, tinnitus and hearing loss

  • The vestibular apparatus is bathed in endolymph
  • Normally drains to venous sinus
  • Meniere’s cause is unknown, but there is an excessive accumulation of endolymph and damage to hair cells
  • Accumulation of endolymph is probably due to poor drainage
42
Q

Why does increased pressure in the endolymph cause both tinnitus/hearing loss and dizziness?

A

because there is damage to the hair cell sin the vestibular apparatus so they are stimulated when they shouldn’t be causing dizziness, this causes an increase in endolymph in the cochlea and therefore hearing loss/tinnitus

43
Q

Vertigo

A
  • Sensation of turning or rotation in space in absence of actual rotation
  • Clinical symptoms - nausea, vomiting and gait ataxia
  • Caused by 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

Y3S1 NEURO (44 decks)

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