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Y2 CONTROL & MOVEMENT > Cerebellum > Flashcards

Cerebellum Flashcards

1
Q

What are the 2 control centres that regulate the activity of descending pathways?

A

Basal ganglia:

  • involved in learned tasks and making decisions

cerebellum:

  • coordinates movement initiated by the precentral gyrus
  • allows movement to be precise
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2
Q

What are the 5 functions of the cerebellum?

A
  • Production of coordinated movements
  • maintain equilibrium, balance and posture
  • coordinates appropriate time, force and duration of muscle contraction (synergy)
  • may store instructions for patterns of movement
  • may have linguistic and cognitive functions
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3
Q

What is meant by synergy?

How is the cerebellum involved in synergy?

A

When 2 or more systems come together to produce a greater effect

the cerebellum receives information about intended movement from the precentral gyrus and from the limbs and muscles about their state

it then generates an adjusted coordinated outcome

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4
Q

On which side of the body does the cerebellum act?

A

The cerebellum acts ipsilaterally

it receives information from ipsilateral body parts and works on them

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5
Q

Where is the cerebellum found?

How is it attached to the rest of the brain?

A

It is found under the occipital lobes of the cerebral hemispheres

it is attached to the brainstem by three paired cerebellar peduncles

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6
Q

What do each of the cerebellar peduncles attach to?

A

Superior cerebellar peduncle attaches to the midbrain

middle cerebellar peduncle attaches to the pons

inferior cerebellar peduncle attaches to the medulla

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7
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A
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8
Q

What are the following structures of the cerebellum?

What is shown by numbers 2 and 3?

A

2 is the cerebral aqueduct

3 is the cerebral peduncles (crux cerebri)

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9
Q

What are the 3 lobes of the cerebellum?

A
  1. Anterior lobe
  2. posterior lobe
  3. flocculonodular lobe
  • the anterior and posterior lobes are separated by the primary fissure
  • the flocculonodular lobe is formed from the flocculus and nodule
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10
Q

What can happen to the tonsils if there is increased intracranial pressure?

A

Increased intracranial pressure (e.g. CSF) can lead to tonsillar herniation

the tonsils leave through the foramen magnum and compress the medulla

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11
Q

What are the 3 functional subdivisions of the cerebellum?

A

Vestibulocerebellum (Archicerebellum):

  • comprises flocculonodular lobe and most medial part of vermis

Spinocerebellum (paleocerebellum):

  • comprises most of the vermis and adjacent region of hemispheres

Cerebrocerebellum (neocerebellum):

  • comprises the lateral parts of the hemispheres
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12
Q

What are the following regions of the cerebellum?

A

Blue = vestibulocerebellum

purple = spinocerebellum

green = cerebrocerebellum

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13
Q

What is meant by the cerebellar homunculus?

A

The homunculus matches up to the function of specific subdivisions

the cerebellum is somatotopically organised

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14
Q

What is the function of the vestibulocerebellum?

A

It coordinates muscles involved in maintaining balance and constancy of visual fields

it receives input from the vestibular apparatus of the inner ear

the trunk and central muscles are involved in balance (blue)

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15
Q

what is the function of the spinocerebellum?

A

It coordinates muscles involved in posture and locomotion

these are the muscles such as thighs and hips (purple)

it controls gait - this is the way in which we walk

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16
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A
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17
Q

What is the function of the cerebrocerebellum?

A

It coordinates movements of the distal limbs (green)

it is particularly involved in fine, skilled and targeted movements of the hands

it is also involved in learning, linguistic and cognitive functions

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18
Q

What is the main function of the vestibulocerebellum?

A

It regulates balance and eye movements

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19
Q

Where does the vestibulocerebellum receive an input from?

A

It receives ipsilateral information about balance from the vestibular apparatus & nuclei in the inner ear

this area detects changes in balance as the fluid in the semicircular canals moves around

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20
Q

What happens when the vestibular apparatus detects changes in balance?

A

Information is sent to the vestibular nuclei in the medulla via the vestibular division of the vestibulocochlear nerve

Information is then sent to the vestibulocerebellum which generates a response

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21
Q

What are the efferent and afferent fibres travelling to and from the vestibular nucleus in the medulla?

A

Afferent fibres:

  • vestibulocerebellar fibres carry information about balance from the vestibular nucleus to the vestibulocerebellum

Efferent fibres:

  • cerebellovestibular fibres carry information about the response from the cerebellum to the vestibular nucleus
22
Q

How do the vestibulocerebellar afferents and cerebellovestibular efferent travel to and from the cerebellum?

A

Via the inferior cerebellar peduncle

this is connected to the medulla, where the vestibular nucleus is located

23
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A
24
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25
Q

What type of fibres do the efferent cerebellovestibular fibres synapse with?

A

They synapse within the vestibular nucleus

fibres travel to CN nuclei III, IV and VI via the medial longitudinal fasciculus

fibres travel to LMNs in the neck

fibres travel to LMNs via the vestibulospinal tract

26
Q

What is the role of the fibres travelling via the medial longitudinal fasciculus?

A

They travel to CN nuclei of III, IV and VI in the brainstem

they then travel to the muscles of the eyes

they control the movement of the eyes to keep the visual field focused at a certain point

27
Q

What is the role of fibres travelling in the vestibulospinal tract?

A

It coordinates actions in the muscles in response to changes in balance

it is an extrapyramidal descending pathway

28
Q

Where is the vestibular nucleus located?

A

In the pons and rostral medulla

it is part of the vestibulospinal pathway which controls posture

29
Q

What is the main role of the spinocerebellum?

A

It regulates body and limb movements related to gait and locomotion

30
Q

What information does the spinocerebellum receive?

How does it respond to this?

A

It receives unconscious proprioception (status of the whole limb) from Golgi organs / muscle spindles

  • length of muscle (spindle)
  • speed of movement
  • level of tension (Golgi tendon)

it responds by adjusting muscle tone and execution of movements through modifying descending pathways

31
Q

What side of the body does the spinocerebellum control?

A

The right side of the cortex sends out signals for intended movement of the left side of the body

the left side of the body brings information to the cerebellum

the spinocerebellum acts on the ipsilateral side, so must exert an influence on the descending pathways from the right side of the cortex

32
Q

How does a muscle send information to the spinocerebellum?

A

Via spinocerebellar tracts (afferents)

it analyses sensory information and generates a response to adjust movement by modifying descending pathways

33
Q

What is the role of spinocerebellar tracts?

How do they enter the cerebellum?

A

Proprioception and other sensory information from the spinal cord passes into the cerebellum via the inferior cerebellar peduncle

this allows the cerebellum to know what muscles are doing

34
Q

What is the role of the cerebrocerebellum?

A

Control of fine motor skills and targeted movements of the limbs, particularly the hands

also involved in learning, linguistic and cognitive functions

35
Q

Where does the cerebrocerebellum receive information from?

A

It receives information on intended movements that are in progress from the cerebral cortex

it receives this information via corticopontine and olviocerebellar fibres

36
Q

What pathway must information take when travelling from the cortex to the cerebrocerebellum?

A
  • The left side of the body is controlled by the right side of the cortex
  • for information to reach the cerebellum, there must be crossing over at the midline
  • descending fibres stop in the pons and olives of the medulla and then descend to the cerebellum after crossing the midline
37
Q

What is the role of the cerebrocerebellum after receiving information about planned movement from the cerebral cortex?

A

It ensures a smooth and orderly sequence of muscle contractions with intended precision, force and direction

this is particularly important for upper limb activities

38
Q

How do the fibres from the cerebral cortex reach the cerebrocerebellum?

A

It receives input from motor cortex via:

  • pontine nuclei - fibres enter the cerebellum via the medial cerebellar peduncle
  • inferior olivary nucleus - fibres enter the cerebellum via the inferior cerebellar peduncle

the cerebellum knows about intended movements

39
Q

What must be remembered about the influence of the cerebellum?

A

The influence of the cerebellum is ipsilateral

the right side of the cerebellum coordinates action of muscles on the right side of the body and vice versa

40
Q

How do the spinocerebellum and cerebrocerebellum work together?

A

Spinocerebellum:

  • proprioception & other sensory information from the spinal cord passes into the cerebellum via ICP on ipsilateral side
  • Knows what muscles are doing

Cerebrocerebellum:

  • input from cortex via nuclei in the pons and inferior olivary nucleus
  • Knows about intended movements

Output:

  • output to motor cortex (via thalamus), reticular nuclei and red nucleus via SCP
  • ensures intended movements are coordinated and controlled
41
Q

What are the efferents sent from the spinocerebellum?

A

Cerebellothalamic and cerebellorubral efferents are sent to the thalamus and red nucleus

they travel via the superior cerebellar peduncle

42
Q

How does the spinocerebellum influence descending pathways?

A

It influences descending pathways to control muscle tone and execution of movements via rubrospinal and corticospinal tracts

43
Q

What afferents are received by the cerebrocerebellum?

A

It receives pontocerebellar afferents from the contralateral pontine nucleus via MCP

it receives olivocerebellar afferents from the contralateral inferior olivary nucleus via ICP

44
Q

What efferents are sent from the cerebrocerebellum?

A

Cerebellothalamic efferents are sent to the contralateral thalamus via SCP decussation

from the thalamus, these fibres project to the motor cortex

45
Q

What pathways does the cerebrocerebellum influence?

A

It influences descending pathways to ensure intended movements are precise via:

  • corticospinal tracts
  • corticorubral (rubrospinal) pathways
  • corticoreticular (reticulospinal) pathways
46
Q

What are the roles of the reticulospinal and rubrospinal pathways?

A

Reticulospinal pathway:

  • involved in voluntary movement, breathing & consciousness
  • runs from the reticular formation

Rubrospinal pathway:

  • controls muscle tone
  • runs from the red nucleus
47
Q

In general, what are the effects of cerebellar damage?

A

Depending on the subdivision of the cerebellum damaged, predictable deficits will be observed

leads to uncoordinated movements or ataxia (no order)

the person is still able to move as the cortex is initiating movements, but in a disordered manner

48
Q

What is truncal ataxia?

What type of lesion causes this?

A

An inability to stand or sit without falling over to one side

it is a midline lesion affecting vestibulocerebellum

it is most commonly due to medulloblastoma (an overgrowth in the medulla compressing the flocculonodular lobe)

49
Q

What is meant by gait ataxia?

Which region of the cerebellum is lesioned?

A

The lower limbs are most affected with staggering and wide-based gait

due to a lesion of the spinocerebellum

most common in chronic alcoholics due to degeneration of cerebellar neurones in paravermal areas

50
Q

What happens if there is a lesion of a cerebellar hemisphere?

A

This is a lesion of the cerebrocerebellum

in coordination of voluntary movement, particularly in the upper limb

there are many possible causes and patients show:

  • tremor of intent
  • past pointing or dysmetria (cannot estimate distance or force)
  • adiadochokinesia (unable to perform fast movements)
  • dysarthria (problems with speech)

Y2 CONTROL & MOVEMENT (69 decks)

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