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CNS > Unit 5 - Cerebellum (anatomy & physio lectures) > Flashcards

Unit 5 - Cerebellum (anatomy & physio lectures) Flashcards

1
Q

How much of the mass of the brain does it comprise

Proportion of the brain’s neurons in the cerebellum

A

10% mass of brain

50% of its neurons

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2
Q

Functions of cerebellum

A
  1. Maintenance of equilibrium (vestibular input // the vestibulocerebellum)
  2. Adjusting the postural muscles of the body (spinal output - spinocerebellum)
  3. Programming and fine tuning movements (cortical input - cerebrocerebellum)
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3
Q

vestibulocerebellum function

A

Maintenance of equilibrium

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4
Q

Spinocerebellum Function

A

Adjusting the postural muscles of the body

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5
Q

What can be seen on the superior surface of the cerebellum

A
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6
Q

Cerebrocerebellum function

A

Programming and fine tuning of movements

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7
Q

Name the dural folds related to the cerebellum

A

Falx cerebelli

Tentorium cerebelli

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8
Q

Name the 3 lobes of cerebellum

A

Anterior

Posterior

Flocculonodular

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9
Q

What lobes can be seen on the superior surface of the cerebellum

A

Anterior & posterior

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10
Q

What fissure separates the anterior lobe from the posterior/middle lobe

A

V-shaped primary fissure

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11
Q

What fissure separates the middle/posterior lobe from the flocculo-nodular lobe

A

Posterolateral fissure

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12
Q

What fissure does not mark the boundary between any lobes

A

Horizontal fissure

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13
Q

What structure is the roof of the 4th ventricle

A

Superior medullary velum

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14
Q

Name the structure found IN the 4th ventricle

A

Choroid plexus

(Surface can also be called the arbor vitae

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15
Q

What are intracerebellar nuclei

A

Masses of grey matter embedded in white matter of cerebellum on each side of the midline

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16
Q

Name the 3 intracerebellar nuclei

A

Fastigial (medial)

Dentate (lateral)

Interposed (= emboliform + globose)

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17
Q

Name the 2 nuclei that compose the interposed nucleus

A

Emboliform + globose

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18
Q

Describe the structure of the dentate nucleus

A

Crumpled bag shape with opening facing medially

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19
Q

Where do the white matter fibres of the dentate nucleus exit

A

Superior cerebellar peduncle

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20
Q

Name the 3 layers in the cerebellar cortex

A

Grey matter

White matter

Collection of nerve cells inside, from deep cerebellar nuclei

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21
Q

Distinguish between the outer, middle and inner layer of the cerebellar cortex

A

Outer - molecular layer (ML)

Middle - purkinje cell layer (P) - 1 cell thick

Inner - granular layer (GL)

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22
Q

What neurons & cells are present in the outer molecular layer

A

2 types of NEURONS:

Outer stellate cell

Inner basket cell

Also glial cells *

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23
Q

Describe the contents of the middle purkinje cell layer

A

Large Golgi type I neurons

Flask shaped

Arranged in a SINGLE layer

Dendrites branch profusely in molecular layer

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24
Q

Describe the synaptic relationship between the middle purkinje cell layer and the molecular layer

A

Branches of purkinje axons synapse with dendrites of basket cells and stellate cells in molecular layer

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25
Q

What is unique about middle purkinje cells

A

Form synaptic contact with parallel fibres from granule cell axons

They are the only cells that leave the cerebellum - the others remain in the molecular layer

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26
Q

Where do granule cell axons run

A

Run through the granule cell layer → white matter → synapses with cells in cerebellar nuclei

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27
Q

Contents of the inner granular layer

A

Small neurons with densely staining nuclei

Interneurons of the cerebellar cortex

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28
Q

Describe the path of the granule neuron

Where do the parallel fibres run

What cells are also present

A

Passes through the molecular layer → bifurcates at T junction → branches run parallel to long axons of folium → parallel fibres

Parallel fibres are at right angles to dendritic processes of purkinje cells

Glial cells are also present

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29
Q

Name the 2 cerebellar cortical mechanisms

What are they closely related to

A

Climbing fibres

Mossy fibres

Excitatory to PURKINJE cells

30
Q

Origin & path of climbing fibres

A

Inferior olivary nucleus

Pass through granular layer

Number of synpases with dendrites of single Purkinje cell

Side branches synapse with stellate and basket cells

31
Q

How do mossy fibres differ from climbing fibres

Where do they terminate

Stimulation produced by mossy fibres

Where do the fibres arise from (3)

A
  • More diffuse excitatory effect
  • Terminate in granular layer (NOT molecular) and synapse with granule cells
  • Single fibre stimulates 1000s of purkinje cells through granule cells
  • Fibres arise from vestibular, spinal, reticular, cerebral/pontine sources
32
Q

Where do the efferent fibres of the purkinje cells end up

A

In deep cerebellar nuclei

33
Q

Overview of cells in cerebellum

A
34
Q

Describe the intrinsic fibres (white matter) of the cerebellum

A

They do not leave the cerebellum

Connect different regions of the cerebellum

35
Q

Describe the afferent fibres (white matter) of the cerebellum

A

Form greater part of WM → proceed to cerebellar cortex → mainly enter through middle and inferior cerebellar peduncles

36
Q

Where do the afferent fibres enter the cerebellar cortex

A

Through the middle and inferior cerebellar peduncles

37
Q

Describe the path of the efferent fibres

A

Purkinje cell axons → cerebellar nuclei → superior cerebellar peduncle

Some fibres don’t synapse in nuclei

38
Q

Name the 3 grps of white matter fibres

A

Intrinsic

Afferent

Efferent

39
Q

Superior cerebellar peduncle links

A

Cerebellum with nuclei in midbrain

40
Q

Middle cerebellar peduncle links

A

Cerebellum with pons

41
Q

Inferior cerebellar peduncle links

A

Cerebellum with medulla

42
Q

What passes through the inferior cerebellar peduncle

A

Largely afferent fibres passing to cerebellum

e.g. posterior spinocerebellar tract

43
Q

What passes through the middle cerebellar peduncle (largest)

A

Transverse fibres of pons from pontocerebellar pathway

44
Q

What passes through the superior cerebellar peduncle

A

Majority are efferent fibres from cerebellar nuclei

45
Q

Role of the cerebellum

A

It continuously receives convergent input from various sensory pathways and from motor pathways

When the cerebellum detects a disparity between the intended and actual movement, it may generate an error-correcting signal

This signal is transmitted to the premotor and primary motor cortices via the thalamus and brainstem

46
Q

Cerebellar pathway - voluntary movement

A

The primary motor cortex and the basal nuclei in the forebrain send impulses through the nuclei of the pons to the cerebellum

BLUE

47
Q

Cerebellar pathway - assessment of voluntary movements

A

Proprioceptors in skeletal muscles and joints report degree of movement in the cerebellum

PURPLE

48
Q

Cerebellar pathway - integration & analysis

A

The cerebellum compares the planned movements (motor signals) against the result of the actual movements (sensory signals)

ORANGE

49
Q

Cerebellar pathway - corrective feedback

A

The cerebellum sends impulses through the thalamus to the primary motor cortex and to motor nuclei in the brainstem

ORANGE

50
Q

FLOCCULONODULAR LOBE

  1. Anatomically
  2. Phylogenetically
  3. Functionally
A
  1. Oldest portion of cerebellum
  2. Archicerebellum
  3. Vestibulocerebellum - associated with vestibular system
51
Q

ANTERIOR LOBE, UVULA, PYRAMID

  1. Phylogenetically
  2. Functionally
A
  1. Paleocerebellum
  2. Spinocerebellum - gross movements of head and body
52
Q

POSTERIOR LOBE (EXCEPT UVULA & PYRAMID)

  1. Phylogenetically
  2. Functionally
A
  1. Neocerebellum
  2. Cerebral cerebellum (pontocerebellum) - fine voluntary movements
53
Q

Overview of archicerebellum, paleocerebellum and neocerebellum

A
54
Q

Midline lesion - flocculonodular lobe (vestibulocerebellum)

A

Responsible for co-ordination of the paraxial muscles associated with equilibrium

Truncal ataxia

Tumours in children

55
Q

Anterior lobe syndrome (spinocerebellum)

A

Chiefly maintain co-ordination of limb movements

Chronic alcoholics (also Vit B deficiency)

Damage to Purkinje neurons

Gait ataxia

56
Q

Posterior lobe syndrome (cerebrocerebellum)

A

Learning and storage of all of the sequential components of skilled movements

CVA, tumour, trauma, degenerative diseases

Loss of co-ordination of voluntary movement (appendicular ataxia), intention tremor, decreased muscle tone

57
Q

Functions of cerebellum

What side of the body does it influence

What does damage result in

A
  • Indirectly regulates movement and posture by adjusting motor fibre output
  • Improves accuracy of movement
  • Motor learning - motor adjustments
  • Ipsilateral side
  • Damage disrupts co-ordination of movement, motor learning, balance, causes flaccidity and active tremors
58
Q

Where does input to cerebellum come from (w/ regard to cortex)

A

Mainly from cerebral cortex

  • Primary motor and premotor
  • Sensory cortices and visual areas
  • Also spinal cord and brainstem
59
Q

Where does input to cerebellum come from (w/ regard to nuclei)

A

Input mainly via nuclei of pons and medulla

  • Pontine nuclei - vestibular nuclei
  • Inferior olive - receives info from descending spinal circuits
  • External cuneate/dorsal nucleus of Clarke - motor & sensory input
60
Q

Name the cells of the granule cell layer

A

Granule cells

Golgi cells

61
Q

Where do mossy fibres receive inputs from

Where do they originate

Where do they synapse

A

Receive inputs from sensory and motor pathways

Axons of cell bodies from BRAINSTEM nuclei (mostly pontine)

Synapse onto granule cells which then synapse onto purkinje cells

62
Q

Where do climbing fibres originate

Where do they receive inputs from

Where do they synapse

A

Originate in inferior olivary nucleus

Receive inputs from RED nucleus, cerebral cortex & spinal cord

Climbing fibres synapse directly onto purkinje cells

63
Q

Afferents of cerebellar cortex

A
64
Q

What do interneurons influence

A

The firing of the purkinje fibres

65
Q

CEREBROCEREBELLUM

What is the input output particular with

What is its function

Consequence of lesions

A
  • Input-output particular with premotor cortex
  • Motor planning (motor cortex), timing of sequential movements
  • Lesions result in delays in initiation of movement, disturbances in coordination and sequence of muscle movements, slurring of speech
66
Q

SPINOCEREBELLUM

Receives input from

What is it responsible for

Consequences of damage to the area

A
  • Input from spinal cord & motor areas - output to motor cortex and brainstem motor pathways
  • Motor execution and controls muscle tone - compares sensory signals with ingoing movement & corrects for deviation in movement
  • Danage results in ACTIVE TREMOR particularly arms, past pointing, reduced muscle tone
67
Q
A
68
Q

VESTIBULOCEREBELLUM

What is the input-output related to

Function

What does damage result in

A
  • Main input-output with vestibular nuclei in medulla
  • Balance, motor execution (medial descending tracts), facial (eye) movements
  • Damage results in balance problems, slow speech, ataxia in legs
69
Q

Deep cerebellar nuclei

A
70
Q

Overview of cerebellar circuits

A
71
Q

What do lesions in the cerebellum cause

A

A movement incoordination syndrome

→ ATAXIA

72
Q

Other than movement, what else does the cerebellum influence

A

Involved in cognition and executive control - impact on pathologies like dyslexia and autism

Autonomic control via hypothalamus regulation

CNS (36 decks)

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