Forbes: Cerebellum

Front 1

What does the cerebellum do?

Back 1

Motor Control: synergy of muscle action, muscle tone, equilibrium

Front 2

From where does the cerebellum receive sensory input?

Back 2

From muscles and joints (proprioception); from vestibular apparatus (makes adjustments).

Front 3

What are the 4 pair of deep cerebellar nuclei?

Back 3

Dentate - emboliform - globose - fastigial
(located in cerebellar medullary center)
(E&G = interposed nucleus)

Front 4

What types of cells are in the molecular layer in the cerebellum?

Back 4

Stellate and basket cells

Front 5

What types of cells are in the granule layer in the cerebellum?

Back 5

Granule and Golgi cells

Front 6

What are the 3 layers of the cerebellar cortex?

Back 6

1. Molecular
2. Purkinje
3. Granular

Front 7

From which fibers do granule cells receive input?

Back 7

Mossy fibers

Front 8

What is the NT of granule cells?

Back 8

Glutamate (excitatory)

Front 9

From which fibers do Purkinje cells receive input?

Back 9

Parallel and climbing fibers

Front 10

Where do the myelinated axons of Purkinje cells terminate?

Back 10

In the deep nuclei (almost exclusively)
REMEMBER:
Purkinje cell axons carry the sole output of cerebellar cortex.

Front 11

What is the NT associated with Purkinje cells?

Back 11

GABA (often with peptide co-transmitter)

Front 12

What are basket/Golgi/stellate cells?
What is the NT involved?

Back 12

Inhibitory interneurons
GABA

Front 13

What is the NT of mossy fibers?

Back 13

ACh (excitatory to both Purk cells and deep nuclei)

Front 14

Where do climbing fibers exclusively originate?

Back 14

contralateral inferior olivary complex
(= olivocerebellar fibers)

Front 15

What is the NT of climbing fibers?

Back 15

Aspartate (excitatory)

Front 16

What is the bottom line of cerebellar circuitry? (see slide 8)

Back 16

Excitatory afferents drive both cerebellar cortex and the deep nuclei. The complex circuitry in cortex refines or modulates the excitatory output of the deep nuclei, which then indirectly influences LMNs via the motor thalamus (VL), motor cerebral cortex, reticular formation, vestibular nuclei and red nucleus.

Front 17

What are the only excitatory neurons in the cerebellar cortex?

Back 17

Granule cells

Front 18

Where are afferents to the deep nuclei from?

Back 18

1. Extra-cerebellar source: Collateral branches of mossy and climbing fibers (excitatory)
2. Purkinje cells: "neurons in specific cerebellar areas project to specific deep nuclei" (inhibitory)

Front 19

Where do the vermal areas and flocculus project?

Back 19

Fatigial nucleus

Front 20

Where do paravermal areas (intermediate zone) project?

Back 20

Globose and Emboliform nuclei

Front 21

Where do lateral hemispheres project?

Back 21

To dentate nucleus

Front 22

Where is the most cerebellar output form?
What is the exception?

Back 22

Deep cerebellar nuclei
Flocculonodular lobe + cortex of uvula

Front 23

Describe the MCP:

Back 23

Entirely afferent
Only pontocerebellar

Front 24

Describe the ICP:

Back 24

Primarily afferent

Front 25

What are the afferents in the ICP?

Back 25

Dorsal spinocerebellar
Cuneocerebellar
Olivocerebellar
Vestibulocerebellar Trigeminocerebellar
Reticulocerebellar

Front 26

What are the efferents in the ICP?
Where do they go?

Back 26

Fastigial nuclei
Flocculonodular Lobe
Vermal areas of cortex
* Go to vestibular nuclei and reticular formation

Front 27

Describe the SCP:

Back 27

Primarily efferent.
Carries output of dentate/globose/emboliform nuclei to red nucleus and thalamus.
Afferent component: VSCT

Front 28

Which structures make up the vestibulocerebellum?

Back 28

Flocculonodular lobe and uvula

Front 29

What is the input and output to the vestibulocerebellum?

Back 29

In: from vest nerve/nuclei
Out: vestibulocerebellar cortex influences LMNs indirectly (via RF, vest nuc, fastigial nuclei)

Front 30

What is the function of the vestibulocerebellum?

Back 30

Maintains balance/equil (by adjusting muscle tone in axial and neck muscles & controlling eye mov't) in response to vestibular stimulation.

Front 31

What makes up the spinocerebellum?

Back 31

Medial cerebellum
Most of vermis + paravermal (medial hemisphere zone)

Front 32

What is the input / output to spinocerebellum?

Back 32

In: from SC tracts (DSCT, VSCT, CCT)
Out: from spinocerebellar cortex --> fastigial nuclei (from vermal areas) OR globose and emboliform nuclei (from paravermal areas)

Front 33

How does the spinocerebellum indirectly influence LMNs?

Back 33

(see page 6)

Front 34

What is the function of the spinocerebellum?

Back 34

Influences muscle tone and synergy of movements (especially of limbs) during stereotyped activities such as walking and during changes in posture. Impact primarily on axial and proximal limb muscles.

Front 35

What makes up the neocerebellum?

Back 35

Lateral portions of hemispheres

Front 36

Describe input/output of neocerebellum:

Back 36

In: indirectly from cerebral cortex via pontocerebellar or olivocrebellar tracts.
Out: to dentate nuclei, influences LMNs indirectly via thalamus --> motor cortex (via CST and CBT) OR Red nuclei (via RST)

Front 37

What is the function of the neocerebellum?

Back 37

Planning/programming of complex movements and adjustments in muscle tone (required for non-stereotyped/learned/skilled mov't). Impact = on limb muscles (especially distally)

Front 38

What's the bottom line of how cerebellum works with other CNS structures to achieve motor control?

Back 38

Cerebellum acts as a comparator: It compares what the motor cortex is telling the muscles to do with what they are actually doing. In response, the cerebellum makes the appropriate adjustments via its connections with motor cortex (via thalamus) and with brain stem nuclei (vestibular and reticular formation) which give rise to tracts that will influence lower motor neurons.

Front 39

What do cerebellar lesions produce?

Back 39

Motor disturbances w/o voluntary paralysis.

Front 40

How does midline cerebellar damage occur?

Back 40

From damage to vermis, sometimes extending into spinocerebellum or flocculonodular lobe (vest.C)
Ex. Medulloblastoma, chronic alcoholism

Front 41

What are S/S of midline damage?

Back 41

Bilateral!
Dysequilbrium, ataxic (wide) gait, swaying side-side, positional nystagmus, obstructed CSF flow

Front 42

How does neocerebellar syndrome occur?

Back 42

Damage to cerebellar hemispheres or its connections (cerebellar cortex, deep nuclei, med center, peduncles).

Front 43

When is neocerebellar syndrome most severe?

Back 43

When deep nuclei or SCP are involved.
(If spared, most deficits are compensated for w/time by intact regions)

Front 44

What are the S/S of neocerebellar syndrome?

Back 44

Deficits superimposed on basically intact volitional mov't - usually involving fine control (ex. force, range, rate, direction of mov't)
* Abn mov't greatest when muscles are being used (ex. intention tremor)
* Unilateral lesion? Deficits ipsilateral.

Front 45

Ataxia

Back 45

Intermittent or jerky movements due to errors in rate, force and direction; often used in reference to gait. Look for associated signs to differentiate from ataxia due to lesions elsewhere.

Front 46

Nystagmus

Back 46

Ataxia of ocular muscles

Front 47

Hypotonia/Hyporeflexia

Back 47

Pendular knee jerks: damping of the reflex is slowed, so there is more than the usual number of swings.

Front 48

Asthenia

Back 48

Weakness; tire easily d/t hypotonia

Front 49

Asynergy/dyssynergy

Back 49

Decomposition of movement; complex movements are broken down into their basic components. Lack of cooperation between closely related muscle groups; heel-to-shin test.

Front 50

Dysarthria/scanning speech

Back 50

Asynergy in muscles used for speech; thick and monotonous; irregular volume and rhythm.

Front 51

Dysmetria

Back 51

Past-pointing; abnormal range of movement; finger-to-nose test.

Front 52

Dysdiadochokinesia or adiadochokinesia

Back 52

Abnormality in rapidly alternating movements; combination of asthenia, dysergia and dysmetria.

Front 53

Intention tremor

Back 53

Occurs during mov't

Front 54

Rebound

Back 54

Delay in stopping the mov't