Cerebellum Flashcards
What is the cerebellum a component of?
Motor system
What are the major functions of the cerebellum
• Major functions – coordination of movement, motor planning, motor learning
How does the Cerebellum influence motor system?
Does not directly influence LMNs
Rather, indirectly influences UMN groups
• Damage results in movement disorders – problems with co-ordination of movement → ataxia
Damage on one side - eg. unilateral damage (stroke or tumour) would case ?
Unilateral damage (eg stroke, tumour) to cerebellum causes ipsilateral symptoms
The left cortex talks to the right cerebellum; But left cortex → right side of body
Compared to the basal ganglia in which unilateral damage will cause contralateral motor symptoms
There are also degenerative disorders of the cerebellum (slowly progressive, bilateral symptoms)
How does the cerebellum influence LMNS? Explain the pathway
Cerebellum -> thalamus -> cortex -> UMN (CST) -> LMN
OR cerebellum -> UMN - > LMN
Describe the principal cerebellar inputs (4)
- Cerebral cortex via pons (pontocerebellar fibers cross)
- Spinocerebellar (uncrossed or crossed twice) – proprioception from limbs
- Vestibulocerebellar (uncrossed, some crossed) – eyes, balance
- Inferior olivary nucleus (crossed)
What do the principal outputs allow the cerebellum to do?
Allows cerebellum to compare the motor plan (what we intent to do) with what the body is doing, makes adjustments (ongoing & repetitive movements)
Right side of cerebellum receives input concerned with the right side of the body
Cerebellum gets information on ongoing movement from the same side of the body
What are the major cerebellar outputs? (5)
- CC via the thalamus (crossed)
- Red nucleus (crossed) – to rubrospinal tract, —> upper limb flexors
- Reticular nuclei (bilateral) – control of voluntary movement
- Vestibular nuclei (bilateral) - CN III, IV & VI, vestibular nuclei
- Inferior olivary nucleus (crossed) - if lesion in inferior olivary nucleus it would seem like you have destroyed the cerebellum
- ie. GENERALLY right cerebellum sends outputs to parts of the brain associated with control of the right side of the body
What does the reticular nuclei control?
- Reticular nuclei (bilateral) – control of voluntary movement
What does the Red nucleus control?
- Red nucleus (crossed) – to rubrospinal tract, —> upper limb flexors
What does the vestibular nuclei control?
- Vestibular nuclei (bilateral) - CN III, IV & VI, vestibular nuclei
What does the inferior olivary nucleus control?
life?
What is the anatomy of the cerebellum?
It is located in the posterior cranial fossa
What separates the cerebellum from the occipital and temporal lobes?
TENTORIUM CEREBELLI
What does the cerebellum form the roof of?
the fourth ventricle
What are the lobes of the cerebellum?
ANT
PoST
FLOCULONODULAR
Where is the tonsil located? What would happen if there was an expanding mass inthe cerebellum?
xpanding mash in cerebellum will push tonsil towards medulla & s/c
Tonsilar herniation through foramen magnum
This would compress the junction between the medulla & spinal cord
Interferes with CV & respiratory centres – can be fatal
What part of the body does the vermiz/medial zone deal with?
• Vermis/medial zone (trunk) → Deals with the medial part of the body
Wht does the paravermis deal with?
PARAVERMIS = LIMBS
What does the lateral hemisphere/vermis/lateral zone control?
MOTOR PLANNING
What is the blood supply to the cerebellum?
All from a main artery- what?
VERTEBROBASILAR SYSTEM
- superior cerebellar aa
- AICA
- PICA
What inputs/outputs run through the SUPERIOR CEREBELLAR PEDUNCLE?
Midbrain, thalamus
What inputs/outputs run through the MIDDLE CEREBELLAR PEDUNCLE?
Pons
What inputs/outputs run through the INFERIOR CEREBELLAR PEDUNCLE?
Medulla, spinal cord
Inferior Cerebellar peduncle has inputs from the SPINAL CORD and MEDULLA - expand major INPUTS
- Vestibular ganglia, nuclei (right next to it (above)) - movement
- Posterior spinocerebellar tract & cuneocerebellar tract, sensory nuclei of V (proprioceptive upper & lower limb etc)
- Inferior olivary nucleus (sends axons across the midline to ICP)
- Reticular formation- regulation of sleep wake cycles
Inferior Cerebellar peduncle has inputs from the SPINAL CORD and MEDULLA - expand major OUTPUTS
o Vestibular nuclei (UMN of VST)
o Reticular nuclei (UMN to reticulospinal tracts)
o Inferior olivary nucleus
The MIDDLE CEREBELLAR PEDUNCLE has only INPUT from PONS- expand
‘movement’
Inputs from pontine nuclei (pontocerebellar fibers), which receive input from cerebral cortex (corticopontine fibers)
Motor, premotor, supplementary motor area, and somatosensory cortex
Also association cortex, limbic cortex, other areas
Superiior Cerebellar Peduncle gets info from MIDBRAIN AND THALAMUS- what are some o th INPUTS?
o Anterior spinocerebellar tract (crosses twice)
o Tectum
Superiior Cerebellar Peduncle gets info from MIDBRAIN AND THALAMUS- what are some o th OUTPUTs?
Outputs
- Red nucleus – UMN (and loop amongst red nucleus, inferior olivary nucleus, back to cerebellum)
- VA/VL thalamus (same nuclei processing info from the basal ganglia), then to the cerebral cortex (motor areas including UMNs & elsewhere)
- Superior cerebellar peduncle decussates in caudal midbrain
What are the layers of the cerebellar cortex?
Highly folded, three layers:
- Molecular basket, stellate- few neuro
- Purkinje
- Granular
Where do the purkinje fibres project?
project to deep nuclei, only output neurons from cerebellar cortex
What are the fibre types in the cerebellum?
CLIMBING from inferior olive, direct to purkinje. Climb directly up purkinje neurons/dendritic tree. Purkinje does main processing of info within the cerebellum
MOSSY all other input, to granule cells, which project to Purkinje neurons via parallel fibers
What are the deep cerebellar nuclei? (3 kinds)
Dentate
Interposed - Emboliform &Globose
Fastigial
Inputs into cerebellum go-
- Inputs to cerebellar cortex & collateral fibers to deep nuclei
- Purkinje neurons of cerebellar cortex project to deep cerebellar nuclei
- Deep nuclei then project directly or indirectly to UMN systems
eg. give me an example of input from the vestibular trunk (pathway)
Vestibular trunk —-> inferior cerebellar peduncle –> either FLOCCULONODULAR node or VERMIS –> FASTIGIAL -> ICP -> Vestibular & reticular nuclei
eg. give me an example of input from the LIMB (pathway)
Limb -> ICP -> Medial hemispheres (paravermis) -> interposal nuclei - > RED NUCLUS (motor coordinaiton)
eg. give me an example of input from the PONS from. cerebral cortex(pathway)
Pons -> MCP -> lateral hemisphere ->dentate nucleus -> SCP -> V/A VL thalamus -> cerenra; cortex
What is within the VERMIS ?
What does the VERMIS do?
fastigial deep nucleus
Compares sensory input (spinocerebellar = proprioception; vestibular) with motor plan (cortico-ponto-cerebellar output)
Makes adjustments to UMN activity to smooth, co-ordinate ongoing & repetitive movements of trunk & proximal limbs
What would damage to the vermis do?
affects trunk (axial) & proximal limb muscles
Problems with equilibrium/balance → truncal ataxia - stance & gait uncoordinated, wide-based gait, frequent falls
Hyporeflexia & hypotonia – don’t know why – but normal strength
Which parts of the cerebellum are involved with movements of the eye?
Flocculonodular lobe
- Smooth pursuit (tracking) eye movements
- Cancelling or changing of the vestibuloocular reflex
- So from flocculonodular lobe → vestibular nuclei → not only to vestibulospinal tracts, but they also hook into CN III, IV & VI nuclei for the control of eye movements
Part of vermis
- Coordination of saccades
What is the ‘intermediate’ cerebellum?
Paravermis (medial hemisphere) – interposed deep nuclei
- Compare sensory input with motor plan
- Makes adjustments to UMN activity to smooth, coordinate ongoing & repetitive movements of limbs
What would damage to the paravermis cause?
Damage – affects distal limb muscles, leading to appendicular ataxia
o Intension (action) tremor
o Dysmetria (inaccurate reaching), overshoot
o Decomposition of movement – poor timing & coordination of complex movements involving numerous muscles
o Dysdiadochokinesia – difficulty performing rapidly alternating movements (flipping hands)
What is the Lateral Cerebellum- functions and damage?
• Lateral hemisphere, dentate deep nuclei
o Planning movements
o Improves performance on subsequent repeated movements, encodes programs of learned skilled movements
o Cognitive functions (connections with association cortex)
What would damage to the lateral cerebellum cause?
o Delays in initiating movements (planning of movements)
o Problems with motor learning (procedural memory)
