Cerebellum Flashcards
Functional Divisions of Cerebellum
- Cerebrocerebellum: plans complex motions and learning
- Spinocerebellum: postural control (vermis), feedback control of ongoing motion + ballistic motion (lateral)
- Vestibulocerebellum: balance and eye movements; receives info directly from vestibular receptors
Dorsal Spinocerebellar Tract (DSCT)
Function: unconscious precise proprioceptive info from lower body
Origin: nucleus dorsalis (C8-L1)
Course: ipsilateral inferior cerebellar peduncle
Termination: anterior vermis of cerebellum
Direct Arcuate Fibers/Cuneocerebellar Tract
Function: unconscious, precise proprioceptive info from upper body
Origin: accessory cuneate nucleus
Course: inferior cerebellar peduncle
Termination: vermis
Trigeminocerebellar Tract
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
Arcuocerebellar Fibers
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
Reticulocerebellar Fibers
Function: convey general sensory modalities
Origin: lateral reticular nuclei
Course: inferior cerebellar peduncle
Termination: bilateral cerebellar hemispheres
Olivocerebellar Fibers
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
Mossy Fibers
- 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
Climbing Fibers
- 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
Deep Cerebellar Nuclei
from medial to lateral:
- Fastigial N
- Globose Nucleus
- Emboliform Nucleus
- Dentate Nucleus
Fastigial Nucleus
- most medial nucleus
- vestibular functions and connections
- projects cerebellovestibular efferents to vestibular system with globose n
Globose Nucleus
- projects cerebellovestibular efferents to vestibular system with fastigial n
- efferents from the lateral globose course with fibers from emboliform n and dentate n
Emboliform Nucleus
-sends efferents fibers through superior cerebellar peduncle with fibers of dentate n and globose n
Dentate Nucleus
-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
Tectocerebellar Fibers
Function: convey visual and auditory info
Origin: superior and inferior colliculi
Course: superior or middle cerebellar peduncles
Termination: cerebellar hemisphere
Ventral Spinocerebellar Tract (VSCT)
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
Central Tegmental Fasciculus
- link between extrapyramidal system and cerebellum
- originates in red nucleus, periaqueductal grey, and midbrain tegmentum
- olivocerebellar fibers
- inferior cerbellar peduncle
ICP Tracts
primary afferent pathways from spinal cord
- DSCT
- Direct Arcuate Fibers/Cuneocerebellar
- Trigemino cerebellar
- Arcuocerebellar
- Reticulocerebellar
- Olivocerebellar
SCP Tracts
- major efferent route from globose, emboliform, and dentate nuclei
- also afferent fibers from VSCT
1. VSCT
2. Trigemino cerebellar
3. Tectocerebellar
MCP Tracts
- largest peduncle
- afferent fibers from pontine nuclei relayed to cortex
Cerebellar Ataxia
lack of muscle control of coordination of voluntary motion
Midline Ataxia
- vestibulocerebellum or spinocerebellum lesion
- truncal instability
- titubation (nodding)
- Gait ataxia: wide base, irregular steps (lateral veering if only 1 side affected)
Appendicular Ataxia
- speech ataxia (scanning dysarthria)
- hypotonia (decreased muscle tone)
- decomposition of movement
- dysmetria - inability to accurately move intended distance
- dysdiadochokinesia - difficulty with rapid alternating movements
Cerebellar vs Sensory Ataxia
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
Nystagmus
rapid involuntary eye motions
Dysdiadochokinesia
inability to perform rapid alternating movements in controlled, coordinated fashion
Dysmetria
disturbance of trajectory or placement of body part during a movement, both in range and direction
Action Tremor
occurs with voluntary movements of muscle
Dysarthria
difficult or unclear articulation of speech that is otherwise linguistically normal
Decomposition of Movement
difficulty of movement in which gestures are broken up into individual segments instead of being executed smoothly
Cerebrocerebellum (lateral hemispheres)
- 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
Spinocerebellum (vermis and intermediate zone)
- 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
Vestibulocerebellum (flocculonodular lobe)
- 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
