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Neuro Quiz 3 > 35_Cerebellum_Jullet > Flashcards

35_Cerebellum_Jullet Flashcards

1
Q

Which side of the body does the cerebellum influence?

A

both ipsilateral and bilateral

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2
Q

The cerebellum receives CONTRAlateral projections from: (2)

A

cerebral cortex (via pontine nuclei) and inferior olive

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3
Q

The cerebellum receives IPSIlateral projections from: (3)

A

vestibular nuclei, spinal cord (dorsal spinocerebellar tract), and external cuneate nucleus

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4
Q

The cerebellum sends axons to: (4)

A

1) motor cortex (via superior cerebellar peduncle and VL of thalamus), 2) superior colliculus, 3) red nucleus, 4) brainstem (reticular formation, vestibular nuclei)

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5
Q

The superior cerebellar peduncle connects the cerebellum to this structure and it’s main function is:

A

midbrain; sends OUTPUT in the caudal midbrain

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6
Q

The middle cerebellar peduncle connects the cerebellum to this structure and it’s main function is:

A

pons; receives INPUT from cerebral cortex

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7
Q

The inferior cerebellar peduncle connects the cerebellum to this structure and it’s main function is:

A

medulla; receives INPUT from brainstem and spinal cord, and sends OUTPUT to brainstem nuclei

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8
Q

What are the functional subdivisions of the cerebellum? (3)

A

1) spinocerebellum, 2) vestibulocerebellum, 3) cerebrocerebellum

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9
Q

What is the anatomical relationship of the cerebellum?

A

1) inferior to occpital lobe, 2) dorsal to pons and medulla but separated via the 4th ventricle, 3) joined to brainstem via cerebellar peduncles

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10
Q

The 1˚ fissure separates these two lobes. The posterolateral fissure separates these two lobes.

A

1˚: anterior + posterior. Posterolateral fissure: posterior + flocculonodular lobes

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11
Q

What connects the two hemispheres of the cerebellum?

A

vermis

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12
Q

What is the tonsil? What can happen if the tonsils herniate?

A

it’s a cerebellar lobule that lies superior to the foramen magnum. With increased intercranial pressure, it can herniate through the foramen magnum and compresses the respiratory centers in the medulla.

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13
Q

What does the spinocerebellum consist of?

A

vermis + intermediate zone

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14
Q

What does the vestibulocerebellum consist of?

A

flocculus and nodulus

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15
Q

What is the input to the spinocerebellum?

A

spinal cord

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16
Q

What is the input to the vestibulocerebellum?

A

vestibular system

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17
Q

What is the input to the cerebrocerebellum?

A

cerebral cortex (via pontine nuclei + middle cerebral peduncle)

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18
Q

What is the function of the spinocerebellum?

A

regulate muscle tone and adjust movements by using sensory input (NOT cortical input) to adjust movements as they are being performed

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19
Q

What is the function of the vestibulocerebellum?

A

posture, balance, coordinated reflex eye movements to head movements (VOR)

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20
Q

What is the function of the cerebrocerebellum?

A

planning, initiating, and learning highly-skilled movements

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21
Q

What is the cellular organization of the cerebellum?

A

cerebellar cortex (outer layer of GM) + arbor vitae (inner core of WM)

22
Q

What is the cellular organization of the cerebellar cortex?

A

1) molecular layer (PC dendrites and GC axons), 2) Purkinje cell layer (PC cell bodies), 3) Granule cell layer (PC axons and GC cells). PC = purkinje cells. GC = granule cells. 4) inhibitory cells of PC (stellate, basket, golgi)

23
Q

What are the 3 cell types that inhibit Purkinje cells?

A

stellate, basket, golgi

24
Q

How is the cellular layer of the arbor vitae organized?

A

deep cerebellar nuclei (paired, integrates output information) and intersposed nuclei

25
Q

What nuclei comprises the deep cerebellar nuclei? Intersposed nuclei?

A

deep cerebellar nuclei: FASTIGIAL, INTERSPOSED, DENTATE. Intersposed nuclei: GLOBOSE, EMBOLIFORM

26
Q

What is the direct activation pathway of the cerebellar circuit?

A

Axons from the inferior olive of the medulla directly synapse onto purkinje cells

27
Q

What is the role of climbing fibers of the cerebellar circuit?

A

CLIMBING fibers relay messages of motor error from the inferior olive of the medulla directly to Purkinje cells and depress inappropriate signals from “Parallel fibers” via removal of AMPA-receptors at the PC-Parallel fiber junction. NOTE: appropriate synapses are not affected by the climbing fiber input and are enhanced to promote correct movement in future attempts

28
Q

What is the indirect activation pathway of the cerebellar circuit?

A

Axons from the pontine nuclei, vestibular nuclei, and spinal cord synpase onto GRANULE cells, which makes excitatory synapses onto Purkinje cell fibers, or INTERNEURONS, which makes inhibitory synapses onto Purkinje cells.

29
Q

What is the role of parallel fibers of the cerebellar circuit?

A

PARALLEL fibers synpase onto inhibitory interneurons that inhibit the Purkinje cells. These connections are plastic, which allows for short and long-term changes in cerebellar output

30
Q

What is the role of mossy fibers of the cerebellar circuit?

A

they are axons from the pontine nuclei, vestibular nuclei, and spinal cord synpase onto GRANULE cells

31
Q

What is the role of the cerebellar circuit? (2)

A

short-term error correction + long-term motor learning via LONG TERM DEPRESSION

32
Q

What is the inhibitory loop of the cerebellar circuit? What is the excitatory loop?

A

INHIBITORY loop: purkinje cells inhibit the deep cerebellar nuclei. EXCITATORY loop: axons from the inferior olive of the medulla, pontine nuclei, vestibular nuclei, and spinal cord forms excitatory connections directly with the deep cerebellar nuclei (instead of going through the Purkinje cells).

33
Q

Where does the deep cerebellar nuclei connect to?

A

output to 1) motor cortex, 2) brainstem nuclei, 3) vestibular nuclei

34
Q

What is the only output pathway of the cerebellum that does NOT project through the deep cerebellar nuclei?

A

vestibulocerebellum

35
Q

What is the input pathway of the vestibulocerebellum? Output?

A

INPUT: axons from the vestibular apparatus (internal ear, semi-circular ducts, otoliths) and vestibular nuclei of the brainstem synapse onto the granule cells of the FLOCCULONODULAR LOBE via the INFERIOR cerebellar peduncle. GC’s synpase onto purkinje cells (ipsilateral). OUTPUT: PCs send axons to the ipsilateral vestibular nuclei in the brainstem to influence the activity of upper motor neurons of the vestibulospinal tract (VST) and VOR (via oculomotor + abducens nucleus), which regulates postural movements to maintain body equilibrium and muscle tone.

36
Q

Where does the spinocerebellum receive input from?

A

propriocetive info from the IPSILATERAL side of the body

37
Q

Where does the vermis receive input from? (spinocerebellar pathway) Where does it send its output to?

A

INPUT: spinocerebellar + cuneocerebellar tracts (carry proprioceptive info from the ipsilateral side of the body/limb muscles) OUTPUT: Ipsilateral FASTIGIAL nuclei, which project bilaterally to the vestibular nuclei + reticular formation of the brainstem (via INFERIOR cerebellar peduncle) and contralaterally to the VL thalamus (via SUPERIOR cerebellar peduncle).

38
Q

Where does the vestibular nuclei + reticular formation project to? (spinocerebellar pathway)

A

axial muscles via spinal cord (specifically the vestibulospinal + reticulospinal tract)

39
Q

Where does the VL of the thalamus project to? (spinocerebellar pathway)

A

motor cortex (ventral corticospinal tract + corticobulbar tract) to control axial, facial, and tongue muscles

40
Q

Where does the intermediate zone receive input from? (spinocerebellar pathway) Where does it send its output to?

A

INPUT: spinocerebellar + cuneocerebellar tracts (carry proprioceptive info from the ipsilateral side of the body/limb muscles) OUTPUT: ipsilateral INTERSPOSED nuclei, which project contralaterally to the red nucleus of the midbrain and the motor cortex via VL thalamus. These then influence descending pathways that control limb muscles by way of the rubrospinal tract and lateral corticospinal tract.

41
Q

Where are the 2 decussations of the intermediate zone? (spinocerebellar pathway)

A

this is the pathway that modulate limb muscles. FIRST decussation: projections from the interposed nuclei (globose + emboliform) dcussate in the superior cerebellar peduncle (caudal midbrain). SECOND decussation: corticospinal + rubrospinal pathways decussate as they descend the spinal cord. END result: each side of the cerebellum regulates motor function on the IPSILATERAL side fo the body

42
Q

Where does the cerebrocerebellum pathway receive input from? Where does it send its output to?

A

INPUT: Cerebral cortex (sensory, motor, association cortices) project ipsilaterally to the pontine nuclei in the brainstem via corticopontine tract OUTPUT: PCs project to ipsilateral dentate nucleus, which cross over via the superior cerebellar peduncle and project to 1) motor cortex via VL thalamus, 2) red nucleus

43
Q

Where are the 2 decussations of the cerebrocerebellum pathway?

A

FIRST decussation: pontine nuclei -> purkinje cells. SECOND decussation: dentate nucleus -> 1˚ and premotor cortex (via VL thalamus) and red nucleus (in rostral midbrain)

44
Q

In the cerebrocerebellum pathway, what are the dentatothalamic fibers?

A

fibers of the dentate nucleus that project to the contralateral motor cortex via the VL thalamus

45
Q

In the cerebrocerebellum pathway, what are the dentatorubral fibers?

A

fibers of the dentate nucleus that project to the contralateral red nucleus (parvocellular division of the nucleus that does not give rise to the rubrospinal tract)

46
Q

What is the feedback loop of the cerebrocerebellum? What is the purpose of this loop?

A

LOOP: PCs (cerebrocerebellum, lateral hemisphere) => ipsilateral dentate nucleus => red nucleus => inferior olive => Purkinje cells (via climbing fibers + inferior cerebellar peduncle). PURPOSE: feedback loop that allows the cerebellum to modulate the activity of the PCs

47
Q

What is ataxia? What is this caused by?

A

loss of coordination of voluntary movements; can be due to input/output pathways of the cerebellum

48
Q

What are the 3 different types of ataxia?

A

gait (lower limbs), truncal (axial muscles), and limb (upper limbs)

49
Q

Unilateral lesions of the cerebellum generally result in:

A

ipsilateral symptoms (depending on where the lesion is). Note that if there are bilateral projections, a unilateral lesion would produce no symptoms!

50
Q

Damage to the vestibulocerebellum results in:

A

no equilibrium/coordination of head/eye movements

51
Q

What does a midline lesion to the spinocerebellum results in? Lateral lesion?

A

MIDLINE: truncal ataxia + dysarthria (slurring of speech). LATERAL: gait ataxia

52
Q

Damage to the cerebrocerebellum results in:

A

impairments of upper limb movements (affects highly skilled movements) and dysarthria if damage is bilateral

Neuro Quiz 3 (7 decks)

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