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Brain and Behaviour Year 2 > Cerebellum > Flashcards

Cerebellum Flashcards

1
Q

What cranial fossa is the cerebellum found in

A
  • posterior cranial fossa
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2
Q

what does the cerebellum do that the cortex does not

A
  • Cerebellum crosses the midline unlike the cortex
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3
Q

what does the midline of the cerebellum show

A

he midline of the cerebellum shows folia which are like oak leaves

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4
Q

what is the middle part of the cerebellum called

A
  • called the vermis
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5
Q

describe the folia

A
  • they go mediolaterally
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6
Q

describe the structure of the cerebellum

A

made out of 3 lobes

  • anterior
  • posterior
  • flocculonodular
  • vermis forms the midline - the posterior lobe is below that
  • the cerebellum has many narrow gyri which mostly run mediolaterally
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7
Q

what are the lobes of the cerebellum

A

made out of 3 lobes

  • anterior
  • posterior
  • flocculonodular
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8
Q

describe the structure of the flocculonodular lobe

A
  • has a nodulus in the middle

- and flocculus on either side

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9
Q

what does the primary fissure separate

A
  • it separates the anterior and posterior lobe of the cerebellum
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10
Q

what is the pons

A

The pons is a bridge of fibres that connect the cerebellum into the midbrain

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11
Q

what forms part of the roof of the 4th ventricle

A

-the nodulus from the flocculonodular lobe

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12
Q

what three pair of arteries supply the cerebellum

A
  • Superior cerebellar artery
  • Anterior inferior cerebellar artery
  • Posterior inferior cerebellar artery
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13
Q

what is the most common site of infarct in the posterior circulation

A
  • PICA is the most common site of an infarct in the posterior circulation
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14
Q

describe the microanatomy of the cerebellum

A

1, outer molecular layer – this is pale mostly axons and only a few cells
2, middle layer – has a single row or purkinje cells
3, inner layer – is granule layer, it is thick and contains vast numbers of granule cells

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15
Q

what are the input and outputs to the cerebellum

A

Inputs and outputs to the cerebellum are via the cerebellar peduncles

  • superior cerebellar peduncle
  • middle cerebellar peduncle
  • inferior cerebellar peduncle
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16
Q

describe wether the superior, middle and inferior cerebellar peduncle are inputs or outputs to the cerebellum

A
  • 1 – superior cerebellar peduncle – output fibres only
  • 2 - middle cerebellar peduncle (largest) input fibres from contralateral cerebral cortex and cranial nerves
  • 3 – inferior cerebellar peduncle – input fibres form the spinal cord
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17
Q

describe the dorsal posterior spincerebellar tract

  • ipsilateral or contralateral
  • where it passes
  • what information it carries
  • what lamina it is found in
A
  • Ipsilateral
  • It passes up into the brainstem and enters cerebellum in inferior cerebellar peduncle on the same side
  • It carries information from proprioceptors (joints, muscle spindles etc)
  • Mostly found in lamina VII
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18
Q

describe the ventral anterior spinocerebellar tract

  • ipsilateral or contralateral
  • what information it carries
  • what lamina it is in
A
  • Is contralateral
  • Carries information about state of reflexes in spinal cord
  • Also has cell bodies in lamina VII but crosses over to the other side of the spinal cord
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19
Q

describe the trajectory of the ventral atnerior spnocerebellar tract

A
  • Ventral (anterior) spinocerebellar is contralateral in spinal cord but then RECROSSES in brain stem to end up on same side it enters cord. Information from the body is passed to the same side in the cerebellum
  • Cerebellar signs are always on the same side as the lesion.
20
Q

cerebellar signs are …..

A

Cerebellar signs are always on the same side as the lesion.

21
Q

describe the input and outputs to the cerebellar cortex

A
  • These are routed through the deep cerebellar nuceli which lie in the white matter below the cortex ( these are roughly equivalent to the thalamus for the cerebral cortex).
  • From medial to lateral these are; Fastigial n. Globose n. Emboliform n. Dentate n.
  • Different parts of the cortex are connected to different deep nuclei.
22
Q

what is the large cerebellar nuclei

A
  • Dentate is the large nuclei
23
Q

describe what part of the cerebellum are connected to what nuclei

A

1) Hemispheres connect to dentate nuclei
2) Anterior lobe connects to globose and emboliform ( interposed) nuclei
3) Vermis connects to fastigial nucleus
4) Flocculo-nodular lobe lconnects to lateral vestibular nuclei of the pons (this nucleus serves the same function for the F/N lobe as the deep nuclei do for the other cerebellar zones).

24
Q

what does the cerebellum do

A
  • its role is to help the motor cortex produce accurate and smooth movements by modulating and refining the motor cortex commands using feedback from proprioceptors and other sensory organs
25
Q

what does cerebellar damage do

A
  • produces overall clumsiness, abnormal fatigue and instability of movement
  • . Extraocular eye muscles are particularly affected.
  • The cerebellar cortex exhibits neuronal plasticity, so partial recovery of function after injury is possible.
  • Damage to the deep nuclei causes persisting disability.
26
Q

name the functional three zones in the cerebellum and what they comprise of

A
  • Vestibulocerebellum comprises Flocculonodular lobe connected to lateral vestibular nucleus (in pons)
  • Spinocerebellum comprises Anterior lobe and vermis connected to fastigial, globose & emboliform nuclei – connected to the spinal cord
  • Cerebrocerebellum comprises Posterior lobe (cerebellar hemisphere) connected to dentate nucleus – connected to the cerebrum
27
Q

where does the vestibulocerebellum nerve operautes

A

1) The Vestibulocerebellum operates via the flocculo-nodular lobe

28
Q

what does the vestibulocerebelum do

A
  • coordinates head and eye movement to ensure the stability of gaze
  • controls balance of the head on the body via the medial vestibulospinal tract
  • control the balance of the body on the ground via the lateral vestibulospinal tract
29
Q

describe how vestibulocerebellum carires out waht it does

A
  • Information from the vestibular apparatus about the movements of the head is sent to the vestibular nuclei in the pons & medulla.
  • This information is combined with information coming from the extra-ocular eye muscles and from muscles in the neck about head movements.
  • The vestibular nuclei compute the necessary muscle actions to keep the eyes balanced in the head, the head balanced on the body, and the body balanced on the ground
30
Q

What do motor commands from the neck and eye muslces go from
- what do motor commands from the legs go via

A
  • Motor commands to the neck and eye muscles are sent via the medial longitudinal fasciculus and its caudal extension the medial vestibulospinal tract MVST.
  • Motor commands to the legs go via the lateral vestibulospinal tract.
31
Q

where are motor commands stored

A
  • The ‘motor programs’ for these tasks are stored in the cortex of the flocculo-nodular lobe
32
Q

what does the spinocerebellum do

A

2) The Spinocerebellum (anterior lobe and vermis) controls locomotion and limb co-ordination:
- it sends motor commands down the reticulospinal tracts to co-ordinate postural and locomotor movements

33
Q

what does the cerebrocerebllum

A
  • Co-ordinates movement initiated by motor cortex.

- This includes speech, voluntary movements of hands and arms, and hand-eye co-ordination.

34
Q

name the parts of the neocerebellum

  • cortex
  • deep nuclei
  • input
  • output
A
  • Cortex: cerebellar hemispheres
  • Deep Nuclei: dentate
  • Input: From cerebral cortex via middle cerebral peduncle
  • Output: To motor (VL) thalamus via superior cerebral penduncle
35
Q

name the three major distinguishable cerebellar syndromes

A
  1. Flocculonodular syndrome
  2. Anterior lobe syndrome
  3. Neocerebellar syndrome
36
Q

describe flocculonodular syndrome

A
  1. Little control of axial muscles
  2. Wide-based ‘ataxic’ gait, reeling and swaying
  3. Tendency to fall to side of lesion
  4. Nystagmus
  5. Severe cases cannot sit or stand without falling
37
Q

What can cause flocculonodular syndrome

A
  1. Most common in young children with medulloblastoma in 4th ventricle
38
Q

describe the medulloblastoma

A

It is the most common malignant central nervous system tumor in children.
- It accounts for 15 to 20 percent of all paediatric brain tumors.

39
Q

where does a medulloblastoma originate from

A

It usually originates in the wall of the fourth ventricle.

40
Q

what family of tumour is the medulloblastoma originte from

A

cranial primitive neuroectodermal tumours (PNET).

41
Q

what are the symptoms of anterior lobe damage

A

Ataxia: ataxic gait (overlaps with flocculonodular syndrome) – widely spaced legs in order to keep balance

Hypotonia: generalised muscle weakness and fatigue,

Reflexes may be depressed or pendular (upper motor neurone lesions

42
Q

what is anterior lobe damage seen in

A

Often seen in alcoholics due to malnutrition and lack of B vitamins

43
Q

what symptoms are in neocerebellar syndrime

A

Loss of hand-eye co-ordination.

Dysmetria (inaccurate reaching with intention tremor

Dysdiadochokinesis is the irregular performance of rapid alternating movements of hands

Intention tremors occur on an attempt to touch an object. A kinetic tremor may be present in motion. The finger-to-nose and heel-to-knee tests are classic tests of anterior lobe cerebellar dysfunction. 0inability to flex and extend easily?

Loss of good speech articulation (slurred speech) due to loss of co-ordination of muscles involved in speech production.

There may be a loss of cognitive eye movement (active scanning) and other perceptual difficulties or motor difficulties involving skilled movements (eg playing a muscial instrument)

There may also be deficits in selective attention& perception due to failure of ‘eye movement programs”

44
Q

what are common causes of neocerebellar syndrome

A
  • stroke
  • trauma
  • tumor
  • degenerative diseases
45
Q

name the signs of the cerebellar stroke

A

1) Headache, Vertigo, Nausea, Vomiting

2) Eye Movement problems
- These symptoms typically affect only one eye and contribute to vertigo.
- Problems affecting the eyes include a rapid/slow movement or tremor of the eyeball (nystagmus), drooping eyelids (ptosis) and constricted pupils.

3) Dysarthria and Dysphagia
- Dysarthria is a motor disorder of speech weakening the muscles of the mouth, face and respiratory system.
- Speech may be slurred, slow, monotonous and hoarse.
- There may also be drooling and difficulty chewing or swallowing (dysphagia) due to incoordination or weakening of the throat and esophageal muscles.

4) Ataxia
- Ataxia is a loss of balance and coordination while walking, and is a common symptom in cerebellar strokes.
- Patients experiencing ataxia walk as if intoxicated; feet are set widely apart and patients wobble or lean to one side.
- Alcohol use during a cerebellar stroke further impedes cerebellar function and increases the intensity of symptoms.

5) Arm Weakness and
- Incoordination
Cerebellar stroke victims exhibit clumsiness, incoordination and weakness, usually in only one arm.
- Trembling hands and arms inhibit the ability to perform tasks, such as picking up and holding a cup.
- A primary test for stroke involves the patient raising both arms to determine if one is held dramatically lower than the other due to trembling, weakness and incoordination.

46
Q

alcohol intoxication ….

A

Alcohol intoxication mimics many features of cerebellar damage*;

  1. slurred speech,
  2. ataxic gait,
  3. double vision (diplopia)
  4. inco-ordination,
  5. intention tremor etc.
47
Q

why does alcohol intoxication mimic cerebellar damage

A

The cerebellum has many GABA-ergic interneurones which are especially sensitive to the effects of alcohol.

Brain and Behaviour Year 2 (36 decks)

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