Cerebellum Flashcards
The cerebellum contains what percentage of all neurons in the brain?
50%
What percentage of brain volume does the cerebellum occupy?
10%
Does the cerebellum receive more inputs or outputs from axonal projections and to what degree?
40 times more inputs than outputs
What three tissue types is the cerebellum composed of?
Grey matter on the outside
White matter on the inside
Deep nuclei
What are the three major functional roles of the cerebellum?
Coordination of movement
Maintenance of equilibrium
Regulation of muscle tone
With which system does the cerebellum cooperate with to maintain equilibrium?
Vestibular system
How does the cerebellum modulate muscle activation to coordinate movement?
Via timing and pattern of muscle activation
What is the primary function of the cerebellum?
Ensure coordinated movement and detect the ‘error’ between intended and actual movement
How does the cerebellum influence movement via motor neurons?
Modifies activity patterns in upper motor neurons
The cerebellum project to the cortex via which brain structure/nucleus?
Thalamus - ventral lateral nucleus
What are the three lobes of the cerebellum?
Anterior
Posterior
Flocculonodular
What is the cerebellar cortex composed of in structure? How does it increase its surface area?
Surface grey matter with sulci and folia
Where is white matter found in the cerebellum?
Internally
Where are the cerebellar nuclei located?
Within the white matter
How many pairs of cerebellar nuclei are there?
3
What are the three pairs of cerebellar nuclei?
Fastigial
Interposed
Dentate
What are the three major regions of the cerebellar cortex?
Cerebrocerebellum
Spinocerebellum
Vestibulocerebellum
What are the 3 functional divisions of the cerebellum and their inputs?
Cerebrocerebellum - sensory and somatosensory inputs from spinal cord, control limb movements
Spinocerebellum - inputs from cortex, motor planning and coordination
Vestibulocerebellum - input from vestibular system, posture and balance
Which functional division is the only one to received direct input from spinal cord?
Spinocerebellum
What is the lateral part of the spinocerebellum important for in regards to movement?
Gross movement of distal muscles
What is the vermis aspect of the spinocerebellum important for?
Movement of proximal muscles
Where are topographic maps maintained in the cerebellum?
Spinocerebellum
Where do the inputs for the cerebrocerebellum originate?
Cerebral cortex
What is the cerebrocerebellum involved in, in regards to movement?
Motor planning and coordination, regulation of highly skilled movements
What group of animals has a highly developed cerebrocerebellum?
Primates
Which part of the cerebellum is the oldest, evolutionarily?
Vestibulocerebellum
Which part of the cerebellum houses the vestibulocerebellum?
Flocculonodular lobe
Where is the flocculonodular lobe/vestibulocerebellum found?
Caudal lobes of the cerebellum
Where do the inputs for the vestibulocerebellum originate?
Vestibular nuclei in the brainstem
What does the vestibulocerebellum regulate?
Movements underlying posture and equilibrium
How many cerebellar peduncles are there?
Three - superior, middle and inferior
Where do the efferent that leave the superior cerebellar peduncle project to?
Efferents to thalamus
What afferents arrive into the cerebellum via the middle cerebellar peduncle?
Corticopontocerebellar afferents
What afferents and efferents arrive/leave the cerebellum via the inferior cerebellar peduncle?
Spinocerebellar afferents/efferents
Where do cortical projections to the cerebellum mainly originate from?
Primary and association sensory cortices of parietal lobe
Motor and premotor cortices of the frontal lobe
Secondary visual regions
Inputs from frontal/parietal cortices arriving through the middle cerebellar peduncle are projected via which nuclei in the brain stem?
Pontine nuclei
Inputs from the frontal/parietal cortices that travel through the pontine nuclei will enter the cerebellum via which peduncle?
Middle cerebellar peduncle
The inputs from the frontal/parietal cortices that arrive through the inferior cerebellar peduncle are projected through which two nuclei?
Red nucleus and inferior olive
Frontal/parietal cortex projections into the cerebellum that pass through the red nucleus and inferior olive will enter the cerebellum via which peduncle?
Inferior cerebellar peduncle
Direct inputs from the spinal cord and vestibular nuclei enter via which cerebellar peduncle?
Inferior cerebellar peduncle
Which inputs arrive in the cerebellum directly via the inferior cerebellar peduncle (do not project through other nuclei)?
Spinal cord and vestibular nuclei
What are the two kinds of projections that occur FROM the cerebellum?
From cerebellar cortex to deep cerebellar nuclei
From deep cerebellar nuclei to upper motor neurons of cortex (via thalamus)
Where do the cerebellar outputs relay information to when sending signals from deep cerebellar nuclei to the upper motor neurons?
Thalamus
Where does the one direct projection from the vestibulocerebellum project to?
Vestibular nuclei
What are the 4 branches of cerebellar output?
Fastigial
Interposed
Dentate
Vestibular nuclei
What does the fastigial output project to?
Medial descending systems
What does the interposed output project to?
Lateral descending systems
Which cerebellar output projects to medial descending systems?
Fastigial
Which cerebellar output projects to lateral descending systems?
Interposed
Which two cerebellar outputs control motor execution?
Interposed and fastigial
Where does the dentate cerebellar output project to?
Areas 4 and 6
What part of motor movement does the dentate output control?
Motor planning
What part of motor movement do the fastigial and interposed cerebellar outputs control?
Motor execution
What cerebellar output controls motor planning?
Dentate
Which part of motor movement does the vestibular nuclei control?
Balance and eye movements
Which cerebellar output controls balance and eye movement?
Vestibular nuclei
What are the three layers of the cerebellar cortex?
Molecular
Purkinje cell
Granule cell
Molecular, purkinje cell, and granule cell layers are layers of which cerebellar structure?
Cerebellar cortex
The molecular layer of the cerebellar cortex is primarily made up of what cellular structure?
Large dendritic trees
Which cerebellar cortex layer has large dendritic trees?
Molecular layer
Which cerebellar cortex layer houses neuron cell bodies?
Purkinje cell layer
What does the Purkinje cell layer of the cerebellar cortex house?
Purkinje neuron cell bodies
What does the granule cell layer of the cerebellar cortex contain?
Climbing fibers, mossy fibers, and granule cells
Which cerebellar cortex layer has climbing fibers, mossy fibers, and granule cells?
Granule cell layer
Which fibers provide excitatory input to granule cells?
Mossy fibers
Mossy fibers provide excitatory input to what cell type?
Granule cells
What do climbing fibers and granule cells create together?
Feed forward circuits
Are climbing fibres, mossy fibres, and granule cells excitatory or inhibitory?
Excitatory
Are Purkinje neurons excitatory or inhibitory?
Inhibitory
Where do mossy fibres originate from?
Pontine nuclei, spinal cord, vestibular system
Where do climbing fibers originate from?
Inferior olive
Where do Purkinje neurons send signals to?
Deep cerebellar nuclei
What do Purkinje neurons do in relation to movement?
Inhibit movement
What information regarding movement do mossy fibres transmit?
Sensory information
What information regarding movement do climbing fibres transmit?
Motor planning information
What neurotransmitter do Purkinje neurons release?
GABA
How many synaptic connections do climbing fibres make?
Multiple with Purkinje cell
How many synaptic contacts do Purkinje cells have?
One
What are three other cell types found in the cerebellar cortex?
Stellate
Basket
Golgi
Are stellate cells excitatory or inhibitory?
Inhibitory
Are basket cells excitatory or inhibitory?
Inhibitory
Are Golgi cells excitatory or inhibitory?
Inhibitory
What postsynaptic potential is generated in Purkinje cells due to climbing fibres?
Excitatory postsynaptic potentials
Are parallel fibres inhibitory or excitatory?
Excitatory
Which neurotransmitter do parallel fibres transmit?
Glutamate
Which neurotransmitter do climbing fibres transmit?
Aspartate
What cellular response follows parallel fibre synapse?
mGluR receptors activated increasing IP3 and DAG concentrations (leading to increased calcium)
What cellular response follows climbing fibre synapse?
Increase in calcium
Which two fibres in the cerebellar cortex activate at approximately the same time?
Parallel and climbing fibres
What effect does dual activation of parallel and climbing fibres have on Purkinje cells?
Long term depression
Increase in calcium activates PKC which internalises AMPA receptors, fewer AMPA receptors are available and smaller EPSPs are evoked, causing less Purkinje activation
Which fibre relays motor error to Purkinje cells?
Climbing fibres
How does long term depression assist in motor learning?
Climbing and parallel fibres synapse at the same time causing a long term depression due to the internalisation of AMPA receptors. Next time movement is performed, appropiate Purkinje cell output to deep cerebellar nuclei occurs
What is the potential role of Golgi cells?
May limit duration of granule cell input to Purkinje cells via modulation of climbing fibre input
What functional role do basket cells have?
Provide lateral inhibition that could focus on spatial distribution of Purkinje cell activity
What condition and symptoms can a lesion in the cerebellum cause?
Ataxia - uncoordinated and inaccurate movements
How does alcohol impact cerebellar circuits?
Increased GABAergic inhibition of granule cells causes excess GABA output - slows movement and makes you clumsy
What is Freidreich’s ataxia?
A rare hereditary neurodegenerative movement disorder that affects the cerebellum
What is the inheritance pattern for Freidreich’s ataxia?
Autosomal recessive
Which protein is mutated in Freidreich’s ataxia?
Frataxin
What is the cellular function of the protein frataxin?
It is a mitochondrial protein involved in iron metabolism - needed for respiratory chain function
What does mutated frataxin result in?
Oxidative stress and cerebellar atrophy
