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AA Micro final exam theory > Cerebellar afferents and efferents > Flashcards

Cerebellar afferents and efferents Flashcards

1
Q

I. Basics
1. The connections of the cerebellum and other parts of the nervous system occur by 3 large pathways, called the
cerebellar peduncles
=> What are they?

A
  1. Superior cerebellar peduncle
  2. Middle cerebellar peduncle
  3. Inferior cerebellar peduncle
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2
Q

I. Basics
2. What is the role of Superior cerebellar peduncle pathway?

A

Superior cerebellar peduncle consists of almost entirely efferent pathway from deep cerebellar nuclei. Their axons project to the red nucleus and the thalamus

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3
Q

I. Basics
3. What is the role of Middle cerebellar peduncle pathway?

A

Middle cerebellar peduncle is an afferent
pathway to the cerebellum.
-> Gets input from the cerebral cortex through the pontine nuclei

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4
Q

I. Basics
4. What is the role of Inferior cerebellar peduncl

A

Inferior cerebellar peduncle consists of both
afferent and efferent pathways.
- Efferent pathways project to the vestibular nuclei and
reticular formation.
- The afferent pathways come from the vestibular nuclei, spinal cord and brainstem tegmentum

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5
Q

I. Basics
5. what are the 2 type of afferent fibers? What are their characteristics?

A
  • Mossy fibers end in rosette in cerebellar glomerulus and synapse with granular cells
  • Climbing fibers will run around the dendritic tree of a single Purkinje cell
  • Purkinje axons terminate in the nuclei of the cerebellum, but there are some fibers which go to the later vestibular nucleus (Deiters)
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6
Q

I. Afferent pathways
1. Where can you find Afferent pathways?

A
  1. From the vestibular system
  2. From the spinal cord
  3. From the brainstem
  4. From the cerebral cortex
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7
Q

I. Afferent pathways
2. What are the characteristics of Afferent pathways from the vestibular system?

A
  • Vestibulocerebellar tract originates from the vestibular ganglion and runs to the cerebellum without synapsing. Secondary fibers synapse in the vestibular nuclei
  • Nearly all fibers terminate in the nodulus, flocculus and fastigial nucleus
  • It is an ipsilateral pathway, so it does not cross
  • Runs through the inferior cerebellar peduncle
  • Ends in the flocculonodular lobe
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8
Q

I. Afferent pathways
3. What are the 2 tracts Afferent pathways from the spinal cord?

A
  1. Dorsal (posterior) spinocerebellar tract (Flechsig)
  2. Ventral (anterior) spinocerebellar tract (Gowers)
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9
Q

I. Afferent pathways - from the spinal cord
3B. What are the features of Ventral (anterior) spinocerebellar tract (Gowers)?

A

Crossed pathway in the superior cerebellar peduncle conveying information on motor orders to the lower body part to the cerebellum from premotor interneurons of the spinal cord

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10
Q

I. Afferent pathways - from the spinal cord
3B. What are the features of Dorsal/posterior spinocerebellar tract (Flechsig)

A

Uncrossed pathway in the inferior cerebellar peduncle originating in the nucleus dorsalis (Clarke nucleus) of the spinal cord to convey proprioceptive and epicritic sensibility from the lower body part to the cerebellum

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11
Q

I. Afferent pathways -
4. List 4 tracts with afferent pathways from the brainstem

A
  1. Nucleo-cerebellar tract (15, 16)
  2. Reticulo-cerebellar tract
  3. Olivocerebellar tract
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12
Q

I. Afferent pathways -
4A. What are the characteristics of Nucleo-cerebellar tract (15, 16)?

A
  • Transmits tactile impulses of the facial area (primarily of the trigeminal nuclei)
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13
Q

I. Afferent pathways -
4B. What are the characteristics of Reticulo-cerebellar tract?

A

Receives sensory fibers from the spinothalamic tract collaterals
=> Both these tracts run ipsilaterally to the inferior cerebellar peduncle, then to the spinocerebellum
=> Arcuate-cerebellar tract belongs here as well

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14
Q

I. Afferent pathways
4C. What are the characteristics of Olivocerebellar tract?

A
  • Originate from the inferior olive and runs contralaterally to the inferior cerebellar peduncle and terminate with climbing fibers to the entire cerebellar cortex
  • Olive and accessory nuclei receive ascending fibers from the spinal cord (spinoolivary tract) and fibers from the central tegmental tract
  • Central tegmental tract is the most important efferent pathway of the extrapyramidal motor system. Olive receives pallidoolivary, reticuloolivary and rubroolivary fibers.
  • Majority of the fibers of the central tegmental tract terminate in the olive, the rest terminate in the spinal cord
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15
Q

I. Afferent pathways
5A. Which tract with afferent pathway From the cerebral cortex?

A

Pontocerebellar tract

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16
Q

I. Afferent pathways
5B. What are the characteristics of Pontocerebellar tract?

A
  • Pathways from the cerebellar cortex of the frontal and temporal lobes extends to the pons
  • Together with the pyramidal tract, they form the cerebral peduncles.
  • In the peduncles they occupy the lateral and medial segments
  • Laterally lies the temporo-occipito-pontine tract (Türck) (2) and medially the fronto-pontine tract (Arnold) (3)
  • Fibers of the 1st neuron terminate in the pontine nuclei
  • Fibers of the 2nd neuron cross to the opposite side and form, as the pontocerebellar tract, the middle cerebellar peduncle
  • Fibers terminate as mossy fibers in the contralateral cerebellar hemisphere (neocerebellum)
17
Q

II. What are the characteristics of somatotopic representation?

A
  • The inputs to the cerebellum are topographical organized – the same of the body may be represented in more than one area of the cerebellum
  • Somatosensory information is present in 2 regions of the spinocerebellum.
    1. In the anterior lobe it is found in both the vermal and paravermal regions.
    2. In the posterior lobe it is found only in the paravermal area.
  • Auditory and visual afferents project to the central portion of the vermis, both caudal and rostral to the horizontal fissure
18
Q

III. What are the characteristics of afferent monoaminergic pathways?

A

The monoaminergic projections to the cerebellum originate from raphe nuclei, locus ceruleus and hypothalamus
- Raphe nuclei are responsible for serotonergic projections
- Locus ceruleus is the source of noradrenergic projections
- Hypothalamus is the source of histaminergic projections
=> All these go to all 3 layers of the cerebellar cortex
=> Projections probably modulate the overall level of cerebellar activity, but the mechanisms are not precisely understood

19
Q

IV. Efferent pathways
1. What are the 2 types of efferent pathway we have?

A

We have both crossed and uncrossed pathways, which originate from the cerebellar nuclei.

20
Q

IV. Efferent pathways
2. What are the Projections from the cerebellar cortex?

A
  1. Cerebrocerebellum, mainly projects to the dentate nucleus
  2. Spinocerebellum to the interposed nuclei (x2)
  3. Vestibulocerebellum to the fastigial nucleus.
21
Q

IV. Efferent pathways
3A. Which tracts with uncrossed efferent pathways can we find?

A

Here we find the cerebelloreticular and cerebellovestibular tracts

22
Q

IV. Efferent pathways
3A1. What are the characteristics of Cerebellovestibular tract?

A

Vestibulocerebellum sends efferents via the fastigial nucleus (6), and directly via Purkinje cells to the vestibular nuclei (4) and

23
Q

IV. Efferent pathways
3A2. What are the characteristics of Cerebelloreticular tract?

A

Vestibulocerebellum sends efferents to the nuclei of brain stem reticular formation

24
Q

IV. Efferent pathways
3A3. What is the role of Uncrossed efferent pathways?

A
  • the cerebelloreticular and cerebellovestibular tracts
  • These cerebellar efferents modulate the descending vestibulospinal and reticulospinal systems. Systems which constantly maintain and adjust body posture (balance)
25
Q

IV. Efferent pathways
3B1. Which tracts with crossed efferent pathways can we find?

A
  1. Cerebellothalamic tract
  2. Cerebellorubral tract
26
Q

IV. Efferent pathways
3B2. What are the characteristics of Cerebellothalamic tract?

A
  • Signals from cerebral cortical areas are processed in the cerebrocerebellum and exit the cerebellum through the dentate nucleus (10). Then they go to VA/VL of the thalamus and motor cortical areas
  • This pathway needs to cross as each cerebellar hemisphere is concerned with the ipsilateral side of the body. Since the fibers of the cerebral cortex cross before entering the cerebellum, they need to cross again to gain information from the appropriate cerebellum
  • The dentate axons exits the cerebellum through the superior peduncle and decussate at the cauda of the midbrain before going to the thalamus
  • The cerebellar excitation of the motor cortical areas results in the onset of the motor event via the descending corticospinal system
  • Individuals with damage to cerebrocerebellar structures have problems initiating and terminating motor actions
27
Q

IV. Efferent pathways
3B3. What are the characteristics of Cerebellorubral tract?

A
  • Spinocerebellum send axons to the globose and emboliform nuclei. From here the cerebellorubral tract starts
  • This pathway ends in the red nucleus
  • This pathway modulates the motor activity once it is
    initiated - leading to a smooth coordinated execution of the
    motor task
  • Individuals with damage to the spinocerebellum have poor
    motor coordination. Movements are jerky and tremors are evident
28
Q

V. Important Extra
2. What is the role of Cerebrocerebellum

A
  • Cerebrocerebellum is involved in the planning and initiation of the motor action
29
Q

V. Important Extra
3. What is the role of Spinocerebellum

A
  • Spinocerebellum oversees the execution and coordination of the motor event
30
Q

V. Important Extra
4. What is the role of Vestibulocerebellum?

A
  • Vestibulocerebellum functions during the execution of motor activities to maintain and adjust body posture
31
Q

V. Important Extra
5. What is the role of Olivocerebellar tract?

A

Olivocerebellar tract with climbing fibers is involved in learning complex motor tasks and motor plasticity (adaptable to change). Involved in muscle memory

AA Micro final exam theory (21 decks)

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