Supra-spinal Control 2 - Cerebellum & Basal Ganglia Flashcards
Name 3 other tracts (other than the corticospinal tract).
- Rubrospinal Tract
- Reticulospinal Tract
- Vestibulospinal Tract
How do the cerebellum & basal ganglia influence movement?
- Do not have their own tracts
- They exert influence on movements via other tracts especially corticospinal tracts
Give some facts about the cerebellum.
- Name
- Volume
- Percentage of Brain Neurones
- Location
- ‘Lesser Brain’
- 10% Total Brain Volume
- >50% of Total Brain Neurons
- Located Above the 4th Ventricle (above the medulla)
What are the majority of neurones of the cerebellum called?
- Granule Cells
Cerebellum function?
- Fine Motor Control during Movements
Requies high levels of computational power just to give fine motor control
What are the 3 parts of the cerebellum?
- Central Strip –> Vermis
- Laterally –> Hemispheres
- Between them –> Intermediate Area
Name the 4 nuclei of the cerebellum.
- Dentate
- Emboliform
- Globose
- Fastigial
Where is the dentate nucleus located?
- Most Lateral
Where is the fastigial nucleus found?
- Most Medial
What are the emboliform + globose nuclei called?
Where are they found?
- Interposed Pair
- Between dentate & fastigial nuclei
What processes information that comes into the cerebellum?
- Granule Cells
What neurone/cell projects out from the cortex to one of the subcortical grey matter structures (i.e. cerebellar deep nuclei)?
- Purkinje Cells
From where do purkinje cells project?
Where do they project to?
- From –> Lateral Hemispheres (largest part)
- Projected to –> Dentate Nucleus (lateral nucleus)
To where do fibres from the intermediate cerebellar cortex project to?
- Interposed Pair (intermediate nuclei)
To where do fibres from the cerebellar cortex midline project to?
- Fastigial (medial) nucleus
What is the source of the vestibulospinal tract?
- Vestibular Nucleus
What is the vestibular nucleus responsible for?
Balance
What does a small region of the cerebellar cortex do?
Small projection which bypasses the deep nuclei completely –> go to vestibular nuclei directly
Where does the fastigial nucleus also project?
- Vestibular Nuclei
- Important for Posture & Balance
Where do the interposed pair project to?
- Emboliform + Globose
Project forward & cross –> to the:
- Red Nucleus (mostly - source of rubrospinal system)
- Ventral-Lateral Nucleus Thalamus (main input for M1)
- Ventral-_Anterior_ Nucleus Thalamus (main input for premotor cortex)
How does the cerebellum influence voluntary actions?
- Influences motor & premotor cortex
- Via the Thalamus
Where does the cerebellar output go?
- Crosses (to contralateral side)
What are the 2 potential destinations of purkinje fibre outputs from the cerebellar cortex?
- Vestibular Nuclei
- Deep Cerebellar Nuclei
How are purkinje fibres in the cerebellar cortex layer arranged?
- Purkinke Fibre Cell Bodies –> sit in the Purkinje Cell Layer
- Dendrites –> stick up into the molecular layer
- Axons –> go down into the deep cerebellar nuclei
What is the nature of purkinje fibres?
- Inhibitory
What are the 2 types of cell input into the cerebellum?
- Mossy Fibres
- Climbing Fibres
Describe the path of the mossy fibres.
- Ascending Fibres –> terminating upon granule cells
- Their axons bifurcate & run along the cerebellar cortex which penetrates through dendritic trees of purkinje cells in the cortex
What is special about the purkinje cells?
- They are completely flat (fan-shaped)
- If you look at it from midline -> they are a thin line
- Parralel Fibres (granule cells) –> coming from the side –> will go through one small part of it (synapse)
Describe the path of the climbing fibres.
- Climb up the purkinke fibre
- Climb over the dendritic tree
- There is one climbing fibre per purkinje cell
- They have multiple synapses from the same fibre
Where do climbing fibres originally come from?
Inferior Olive (upper medulla)
Where do mossy fibres come from?
What modalities do they convey?
- Come from lots of places
- Convey all types of sensory modalities except olfaction & taste
- Provide lots of contextual information from around the body
How is motor instruction integrated?
- Copy of motor instruction –> sent out from motor cortex regarding desired movement
- This goes to the cerebellum to the dendritic tree
What is the function of the climbing fibre?
- Single Instruction
- Provides instruction to learn
- Causes modifications of synaptic weights in dendritic tree –> so that movements can be made better & more accurate
Name the 3 major transverse lobes (divisions).
- Anterior Lobe
- Posterior Lobe
- Flocculo-nodular lobe
Name the 2 deep transverse fissures which separate these lobes.
- Primary Fissure
- Posterolateral Fissure
How are these transverse divisions further divided?
- Each lobe is divided into several lobules containing individual folia
Where is the intermediate region found?
- Between vermis & hemispheres
What does the primary fissure divide?
- Anterior Lobe
- Posterior Lobe
(nothing to do with embryological origin)
What is the vermis & flocculo-nodular lobe?
- Vermis –> Vertical
- Flocculo-nodular lobe –> Transverse
What is the central part of the flocculo-nodular lobe called?
- Nodulus
What are the 3 major sagittal divisions?
- Medial Cerebellum (vermis)
- Intermediate Cerebellum (pars intermedia)
- Lateral Cerebellum (hemispheres)
What is the prefix for the subdivisions in the sagital plane?
- Begins with H
How are fibres distributed in the sagital plane?
- Right Cerebellum –> projects to the Right Cerebellar Nuclei
- Output from nuclei –> crosses
What does the superior cerebellar artery supply?
- Anterior Lobe
- (Part of the) Posterior Lobe
What does the posterior-inferior cerebellar/cerebral artery supply?
- Posterior Lobe
What does the anterior-inferior cerebellar/cerebral artery supply?
- Posterior Lobe
Which part of the cerebellum influences the vestibular function?
(Vestibulocerebellum)
- Flocculo-Nodular Lobe
- Vermis
What do the flocculo-nodular lobe & vermis control?
- Proximal Muscles
- Limb Extensors
Flocculo-nodular lobe.
- Input?
- Output?
- Input –> Vestibular Labyrinth
- Output –> directly to Vestibular Nuclei
Vermis.
- Input?
- Output?
- Input –> Neck & Trunk + Vestibular Labyrinth + Retinal & Extraocular Muscles
- Output –> focused on Ventro-Medial Descending System of Brainstem (i.e. reticulospinal & vestibulospinal) + cortex (corticospinal fibres)
Generally, what is the floccular-nodular lobe + vermis important for?
- Balance
- Posture
To where does the majority of ascending spinocerebellar tract take sensory information (including propioception) to in the cerebellum?
Which nuclei particularly?
(Spinocerebellum)
- Intermediate Parts of the Cerebellum
- Globolusform
- Fastigial Nucleus
What does the intermediate cerebellum receive information from?
What kind of information?
- Sensory Information from the Limbs
What does the intermediate cerebellum control?
Tracts?
- Dorso-Lateral Descending Systems
- Rubrospinal + Corticospinal Tracts
- Acting on the Ipsilateral Limb (double cross)
From where does the lateral cerebellum gets its input?
Tract called?
- Cortical input via pontine nucleus
- Pontocerebellum
What does the lateral cerebellum influence?
Via which nucleus?
- Motor & Premotor Cortex
- Via ventro-lateral nucleus of the thalamus
Where does the lateral cerebellum send its signals first before leaving the cerebellum?
- Dentate Nucleus (lateral)