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Advanced Neurosciences > The Cerebellum > Flashcards

The Cerebellum Flashcards

1
Q

Describe what the cerebellum does

A

It functions as a rapid corrective feedback loop smoothing and coordinating movements

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2
Q

Where does the cerebellum get its information?

A

Somatosensory areas
Visual
Auditory
Vestibular
Proprioceptive

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3
Q

Give a more detailed description of what the cerebellum does

A

Programmes ballistic movements - precise timing and appropriate patterns of skeletal muscle contraction
Compares intended and actual movements
Corrects ongoing movements
Activity occurs subconsciously
Motor learning pattern shift from conscious to unconscious

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4
Q

Where is the cerebellum found?

A

Situated in the posterior cranial fossa and covered superiorly by the tentorium cerebelli
Located dorsal to the pons and medulla
Accounts for 11% of the brains mass

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5
Q

Describe the structure of the cerebellum

A

Two hemispheres joined medially by the vermis
Internal white matter - arbor vitae
External grey matter (foila) - transversely arranged gyri

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6
Q

How in the cerebellum divided

A

By the primary and posterolateral fissures
Ant lobe
Post lobe
Flocculonodular lobe

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7
Q

What areas are the Ant and Post lobes further divided to?

A

Vermal zone - occupies the vermis
Intermediate (paravermal) zone - lies on each side of the vermis, medial regions of the cerebellar hemispheres
Lateral zone - lies lateral to the intermediate zone

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8
Q

What are cerebellar peduncles?

A

Paired fibre tracts that connect the cerebellum to the brainstem

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9
Q

Name the 3 cerebellar peduncles

A

Superior - cerebellum to midbrain
Middle - cerebellum to pons and the axis of the brainstem
Inferior - cerebellum to medulla

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10
Q

Describe the superior peduncles

A

Fibres originate from the neurons in the deep cerebellar nuclei and communicates with the motor cortex via the midbrain and the Diencephalon (thalamus)

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11
Q

Describe the middle peduncles

A

Cerebellum receives info advising it of voluntary motor activities initiated by the motor cortex

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12
Q

Describe the inferior or peduncles

A

Afferents conveying sensory info from muscle proprioceptors throughout the body and from the vestibular nuclei of the brainstem (medulla oblongata)

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13
Q

What are the functions divisions of the cerebellum?

A

Vestibulocerebellum- composed of the flocculonodular lobe
Spinocerebellum- composed of the vermis and paravermal zones
Cerebrocerebllum- composed of lateral zones

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14
Q

What does the vestibulocerebellum do?

A

Maintenance of balance and control of eye movement

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15
Q

What does the spinocerebllum do?

A

Regulation of muscle tone, coordination of skilled voluntary movement

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16
Q

What does the cerebrocerebellum do

A

Planning and initiation of voluntary activity

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17
Q

What are the spinocerebllar?

A

Post spinocerbellar tract
Ant spinocerebellar tract
Cuneocerebellar tract

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18
Q

Where does the Post spinocerebellar tract enter?

A

Enters the cerebellum via the inferior cerebellar peduncle

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19
Q

Where does the Ant spinocerebellar tract enter?

A

Enters the cerebellum via the superior cerebellar peduncle

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20
Q

Where does the cuneocerebellar tract enter?

A

Enters the cerebellum via the inferior cerebellar peduncle

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21
Q

Where does the inferior olivary nucleus receive info from?

A

Cutaneous afferents
Joint afferents
Muscle spindles
Then axons pass contrallaterally through the inferior peduncle
Also axons from the sensorimotor cortex directly and indirectly via the red nucleus

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22
Q

What is the deep pontine nuclei important for?

A

The primary route by which the cerebral cortex communicates with the cerebellum
(The basilar pons)

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23
Q

What does the reticular formation do?

A

Regulates spinal reflexes
Important for which reticular neurons regulate extensor motor tone at any given time

24
Q

Where does the reticular formation receive info from?

A

From the sensorimotor cortex which serves as a relay for cerebral cortical inputs to the cerebellum

25
Q

How does the tectum communicate with the cerebellum?

A

Through its superior and inferior colliculi
They provide visual and auditory info respectively
By projecting to the pontine nuclei which then go through the middle cerebellar peduncle to the cerebellar cortex

26
Q

What does the red nucleus do?

A

Serves as a relay from the sensorimotor cortex to the spinal cord via the rubrospinal tract
Sensorimotor cortex may also send signals through the red nucleus

27
Q

Describe the trigeminal system during cerebellar input

A

Secondary proprioceptive fibres associated with muscle spindle activity of the face and jaw reaching the cerebellum through the mesencephalic trigeminal nucleus

28
Q

How does the vestibular system influence cerebellar input?

A

Via the ICP to the flocculonodular lobe

29
Q

What are the deep cerebellar nuclei?

A

Don’t Eat Greasy Food
Dentate nucleus
Emboliform nucleus
Globose nucleus
Fastigal nucleus

30
Q

Describe the Dentate nuclei

A

Project contralaterally through the superior cerebellar peduncle to neurones in the contralateral thalamus and thalamus to motor cortex

31
Q

What is the function of the Dentate nucleus?

A

To influence planning and initiation of voluntary movement

32
Q

Describe the emboliform nucleus

A

Project mainly to the contralteral red nuclei and small group is projected to the motor cortex

33
Q

What is the function of the emboliform nucleus?

A

Red nuclei to rubrospinal tract control of proximal muscles

34
Q

Describe the fastigial nuclei

A

Project to the vestibular nuclei and to the pontine and meduallary reticular formation

35
Q

What is the function of the fastigial nuclei?

A

The vestibulospinal tracts
Recticulospinal tracts

36
Q

What is another name for the posterior lobe of the cerebellar hemispheres?

A

The neocerebellum

37
Q

What are the three layers to the cortex of the cerebellum?

A

Molecular layer - Parallel fibres from granule cells
Purkinje cell layer - Single cell thick
Granule cell layer - granule cell bodies

38
Q

What cells are found in the granular cortex level of the cerebellum?

A

Abundant with granule cells
But also have Golgi cells - their processes radiate to all other cell layers
(Inhibitory GABA-ergic interneurons - cell bodies found close to the purkinje layer

39
Q

What is the structure / pathway if the granular cell layer?

A

3-5 dendrites arranged in a claw like appearance
Receive mossy fibre afferents
Axons travel to the molecular level where they branch in a T junction to form parallel fibres
Golgi and granule cells synapse with mossy fibres

40
Q

What cells are found in the molecular layer of the cortex of the cerebellum?

A

Dendrites if purkinje cells
Parallel fibres (granule axons)
Basket cells
Stellate cells

41
Q

What are basket and stellate cells?

A

Inhibitory GABA-ergic cells that synapse with perkinjes
Receive input from parallel and climbing fibres

42
Q

Describe the purkinje cell layer of the cerebellum

A

It is one cell thick and contains the perkinje cell (largest cell of the cerebellar cortex)
Dendrites emerge from its neck and thick dendritic trees are directed into the molecular layer

43
Q

What input does the purkinje cell layer receive?

A

Receive excitatory input from granule cells via parallel and climbing fibres

44
Q

Where do purkinje cell axons terminate?

A

Terminate in one of the feel cerebellar nuclei

45
Q

What do purkinje cells do?

A

Vermal zone - project to the fastigial nucleus
Hemispheres - project to the Dentate nucleus
Paravermal region - project to interposed nuclei
Purkinje cells are inhibitory

46
Q

What are mossy fibres?

A

Are cerebellar afferents originating from all sources except the inferior olivary nuclear complex

47
Q

What do mossy do?

A

Synapse with Golgi and granule cell dendrites
They are excitatory fibres that utilise glutamate as the neurotransmitter

48
Q

List some of the places mossy fibre afferents come from

A

Spinal cord
Post column nuclei
Trigeminal system
Pontine and vestibular nuclei

49
Q

What are climbing fibres?

A

They are excitatory fibres that use aspartate as their neurotransmitter
Arise from the inferior olivary nucleus and ascend through the granular and Purkinje layers to reach the molecular layers

50
Q

What is the synapse ratio of climbing fibres to Purkinje cells?

A

Each individual climbing fibre forms an excitatory synapse with one purkinje cell
This one to one ration is key in motor learning

51
Q

What are the only output cells of the cerebellar cortex?

A

Purkinje fibres
So although mossy and climbing fibres are excitatory, purkinjes are inhibitory so the only output of the cerebellar cortex is inhibitory
The excitement level of the mossy/ climbing fibres will determine the level of inhibition

52
Q

What is tonic inhibition?

A

It’s how purkinje cells function
All excitatory inputs will be converted to inhibitory
Removing the excitatory influence of the cerebellar inputs

53
Q

How can the overall output of the cerebellum be excitatory if the only output from the cerebellar cortex is inhibitory?

A

Climbing and mossy fibres send collaterals to the deep cerebellar nuclei which results in immediate activation of the cerebellar nuclei

54
Q

Describe the process of inhibition

A

Collateral excitation if the deep cerebellar nuclei is followed inhibition mediated by purkinje cells, which are activated by Golgi and parallel fibres
When purkinje inhibition ceases there can be an increase in deep nuclei excitation

55
Q

What is the basic explanation of cerebellar output?

A

Initial activation
Inhibition
Disinhibition

Advanced Neurosciences (20 decks)

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