Cerebellum

Question 1

Functional Divisions of Cerebellum

Answer 1

1. Cerebrocerebellum: plans complex motions and learning
2. Spinocerebellum: postural control (vermis), feedback control of ongoing motion + ballistic motion (lateral)
3. Vestibulocerebellum: balance and eye movements; receives info directly from vestibular receptors

Question 2

Dorsal Spinocerebellar Tract (DSCT)

Answer 2

Function: unconscious precise proprioceptive info from lower body
Origin: nucleus dorsalis (C8-L1)
Course: ipsilateral inferior cerebellar peduncle
Termination: anterior vermis of cerebellum

Question 3

Direct Arcuate Fibers/Cuneocerebellar Tract

Answer 3

Function: unconscious, precise proprioceptive info from upper body
Origin: accessory cuneate nucleus
Course: inferior cerebellar peduncle
Termination: vermis

Question 4

Trigeminocerebellar Tract

Answer 4

Function: unconscious precise sensory tract from face; general proprioceptive and exteroceptive info from head
Origin: subnuclei rostralis, interpolis of descending nucleus of V
Course: superior cerebellar peduncle (precise info); inferior cerebellar peduncle (general)
Termination: trigeminocerebellar fibers of anterior vermis

Question 5

Arcuocerebellar Fibers

Answer 5

Function: cerebro-cerebellar feedback loop; receive fibers from ipsilateral cerebral cortex
Origin: arcuate nuclei of upper medulla
Course: inferior cerebellar peduncle
Termination: contralateral cerebellar hemisphere via external arcuate fibers

Question 6

Reticulocerebellar Fibers

Answer 6

Function: convey general sensory modalities
Origin: lateral reticular nuclei
Course: inferior cerebellar peduncle
Termination: bilateral cerebellar hemispheres

Question 7

Olivocerebellar Fibers

Answer 7

Function: processing/relay center of sensory info from spinal cord and motor info from reticular formation and extrapyramidal system
Origin: inferior olivary nucleus
Course: inferior cerebellar peduncle
Temination: climbing fibers in contralateral cerebellar hemisphere

Question 8

Mossy Fibers

Answer 8

• from spinal cord, reticular formation, vestibular system, pontine nuclei
• input from spinal cord and brainstem reticular formation via inferior cerebellar peduncle
• input from pontine nuclei via middle cerebellar peduncle
• synapse with cerebellar granule cells and Golgi cell interneurons
• somatosensory arousal, equilibrium, and cerebral cortex motor info to the cerebellum

Question 9

Climbing Fibers

Answer 9

• originate in the contralateral inferior olive
• myelinated
• send axons to synapse directly on the Purkinje cells via the inferior cerebellar peduncle
• convey movement errors
• induce changes in cerebellar synapses = motor learning

Question 10

Deep Cerebellar Nuclei

Answer 10

from medial to lateral:

1. Fastigial N
2. Globose Nucleus
3. Emboliform Nucleus
4. Dentate Nucleus

Question 11

Fastigial Nucleus

Answer 11

• most medial nucleus
• vestibular functions and connections
• projects cerebellovestibular efferents to vestibular system with globose n

Question 12

Globose Nucleus

Answer 12

• projects cerebellovestibular efferents to vestibular system with fastigial n
• efferents from the lateral globose course with fibers from emboliform n and dentate n

Question 13

Emboliform Nucleus

Answer 13

-sends efferents fibers through superior cerebellar peduncle with fibers of dentate n and globose n

Question 14

Dentate Nucleus

Answer 14

-efferents with fibers of emboliform n and globose n
projects dentato-rubral and dentato-rubrothalamic fibers to:
-red nucleus
-ventral lateral nucleus of thalamus
-brainstem tegmentum
-reticular formation

Question 15

Tectocerebellar Fibers

Answer 15

Function: convey visual and auditory info
Origin: superior and inferior colliculi
Course: superior or middle cerebellar peduncles
Termination: cerebellar hemisphere

Question 16

Ventral Spinocerebellar Tract (VSCT)

Answer 16

I.
Function: unconscious, general proprioceptive info from lumbosacral levels
Origin: neurons in base of dorsal horn and intermediate grey matter > anterior white commissure > ascends in lateral funiculus
Course: superior cerebellar peduncle
Termination: ant vermis cerebellum

II.
Function: gross postural adjustments and overall proprioception of lower limb
Origin: lumbosacral spinal cord > terminate on scattered cells in base of dorsal horn and intermediate grey > secondary axons crossover in ant commissure > ascend in contralateral ventral spinocerebellar tract
Course: superior cerebellar peduncle
Termination: cerebellar cortex of vermis

Question 17

Central Tegmental Fasciculus

Answer 17

• link between extrapyramidal system and cerebellum
• originates in red nucleus, periaqueductal grey, and midbrain tegmentum
• olivocerebellar fibers
• inferior cerbellar peduncle

Question 18

ICP Tracts

Answer 18

primary afferent pathways from spinal cord

1. DSCT
2. Direct Arcuate Fibers/Cuneocerebellar
3. Trigemino cerebellar
4. Arcuocerebellar
5. Reticulocerebellar
6. Olivocerebellar

Question 19

SCP Tracts

Answer 19

• major efferent route from globose, emboliform, and dentate nuclei
• also afferent fibers from VSCT
  1. VSCT
  2. Trigemino cerebellar
  3. Tectocerebellar

Question 20

MCP Tracts

Answer 20

• largest peduncle

- afferent fibers from pontine nuclei relayed to cortex

Question 21

Cerebellar Ataxia

Answer 21

lack of muscle control of coordination of voluntary motion

Question 22

Midline Ataxia

Answer 22

• vestibulocerebellum or spinocerebellum lesion
• truncal instability
• titubation (nodding)
• Gait ataxia: wide base, irregular steps (lateral veering if only 1 side affected)

Question 23

Appendicular Ataxia

Answer 23

• speech ataxia (scanning dysarthria)
• hypotonia (decreased muscle tone)
• decomposition of movement
• dysmetria - inability to accurately move intended distance
• dysdiadochokinesia - difficulty with rapid alternating movements

Question 24

Cerebellar vs Sensory Ataxia

Answer 24

Cerebellar:
-difficulty with narrow base regardless if eyes closed or open
-normal vibratory sense proprioception and ankle reflexes
Sensory:
-narrow base with eyes open but not closed
-abnormal vibratory sense, proprioceptiom, ank;e reflexes

Question 25

Nystagmus

Answer 25

rapid involuntary eye motions

Question 26

Dysdiadochokinesia

Answer 26

inability to perform rapid alternating movements in controlled, coordinated fashion

Question 27

Dysmetria

Answer 27

disturbance of trajectory or placement of body part during a movement, both in range and direction

Question 28

Action Tremor

Answer 28

occurs with voluntary movements of muscle

Question 29

Dysarthria

Answer 29

difficult or unclear articulation of speech that is otherwise linguistically normal

Question 30

Decomposition of Movement

Answer 30

difficulty of movement in which gestures are broken up into individual segments instead of being executed smoothly

Question 31

Cerebrocerebellum (lateral hemispheres)

Answer 31

- input: cerebral cortex, inferior olivary nucleus of medulla, pontine nuclei - output: thalamus red nucleus - function: planning and execution of movements, coordination of complex and sequential motor movements, cognition, language, learning, emotions - lesions: abnormal coordination of ipsilateral voluntary movements, fall toward side of lesion, dysmetria, intention tremor, dysdiadochokinesia, scanning speech/ataxic dysarthria

Question 32

Spinocerebellum (vermis and intermediate zone)

Answer 32

- input: spinal cord - vermis: input from trunk and proximal part of limbs - intermediate zones: input from distal part of limbs - Function: coordination of body and limb movement, maintenance of muscle tone, error correction, receives proprioceptive info - vermis function: central body (trunk, head, proximal limbs) - Intermediate zones: distal limbs (hands, fingers, feet) - lesions of vermis: trunk and proximal muscles affected, truncal ataxia, gait ataxia (wide-based), head tilting - lesions of intermediate zones: ipsilateral distal limbs affected, limb ataxia, hypotonia, dysmetria, intention tremor, dysdiadochokinesia

Question 33

Vestibulocerebellum (flocculonodular lobe)

Answer 33

- input: vestibular nuclei of CN VIII, superior colliculi and visual cortex - outputs: fastigial nucleus to vestibular nuclei - function: balance, ocular motion and gaze stability - lesions: vertigo, nystagmus