Cerebellum Flashcards
Where is the cerebellum located?
Sits under the cortex in the hindbrain near the brainstem.
How does the cerebellum represent areas of the body?
In a more random or jumbled way compared to the somatosensory cortex.
Why does the cerebellum represent areas of the body in a random/jumbled way?
It may enable the cerebellum to process and coordinate information from disparate parts of the body.
Name the three zones of the cerebellum.
Cerebrocerebellum.
Spinocerebellum.
Vestibulocerebellum.
What is the corresponding nucleus to the cerebrocerebellum?
Dentate nucleus.
What is the corresponding nuclei to the spinocerebellum?
Emboliform nucleus.
Globose nucleus.
What is the corresponding nuclei to the vestibulocerebellum?
Vestibular nucleus.
Fastigial nucleus.
Where does the cerebrocerebellum receive input from?
Cerebral cortex.
Inferior olivary nucleus of the medulla.
Where does the spinocerebellum receive input from?
Spinal cord.
Where does the vestibulocerebellum receive input from?
Vestibular nuclei of cranial nerve.
Superior colliculi and visual cortex.
What are the functions of the cerebrocerebellum?
Planning, coordination and execution of movements.
Cognition, language, learning and emotions.
What are the functions of the spinocerebellum?
Coordination of body and limb movement.
Maintenance of muscular tone.
What are the functions of the vestibulocerebellum?
Balance.
Ocular movements and gaze stability.
What are the folia?
Folds of the cerebellum.
What are the cerebellar peduncles?
They form the connection between the brainstem and the deep cerebellar nuclei.
Name the afferent pathways into the cerebellum.
Corticopontocerebellar tract.
Dorsal and ventral spinocerebellar tracts.
Vestibulocerebellar tract.
Describe the corticopontocerebellar tract.
Cerebral cortex –> pontine nuclei of the pons –> middle cerebellar peduncles –> deep cerebellar nuclei and cerebellar cortex.
Describe the dorsal spinocerebellar tract.
Posterior horn of the spinal cord –> inferior cerebellar peduncle –> cerebellum.
Describe the ventral spinocerebellar tract.
Posterior horn of the spinal cord –> medulla and superior cerebellar peduncle –> cerebellum.
Describe the vestibulocerebellar tract.
Vestibular nerve –> inferior cerebellar peduncle –> ipsilateral flocculonodular lobe.
What do all the afferent tracts have in common?
They are excitatory and travel to the cerebellum via mossy fibres and climbing fibres.
Where do the mossy fibres terminate onto?
Granule cells.
Where do the climbing fibres terminate onto?
Purkinje cells.
Name the two efferent pathways of the cerebellum.
Rubrospinal pathway.
Cerebellovestibular pathway.
Name the two tracts of the rubrospinal pathway.
Cerebellorubral tract.
Cerebellothalamic tract.
Name the two tracts of the cerebellovestibular pathway.
Vestibulospinal tract.
Cerebelloreticular tract.
Describe the rubrospinal pathway.
Travels mainly via the superior cerebellar peduncle and projects up to the thalamus and motor cortex.
Describe the cerebellorubral tract.
Globose and emboliform nuclei –> superior cerebellar peduncle via the red nucleus.
Describe the cerebellothalamic tract.
Dentate nucleus –> superior cerebellar peduncle –> thalamus and M1.
What is the role of the cerebellorubral tract?
Related to skeletal muscle tone.
What is the role of the cerebellothalamic tract?
Related to motor coordination.
Describe the cerebellovestibular pathway.
Fastigial nucleus –> inferior cerebellar peduncle –> spinal cord.
Describe the vestibulospinal tract.
Projects to the spinal cord via the vestibular nuclei.
What is the role of the vestibulospinal tract?
Related to coordination of balance and rapid eye movements.
Describe the cerebelloreticular tract.
Projects to motor neurons of the spinal cord via the reticular formation.
What is the role of the cerebelloreticular tract?
Related to stretch reflex and motor movements.
Describe the molecular layer.
Inhibitory.
Contains stellate cells.
Describe the Purkinje layer.
Inhibitory.
Contains Purkinje cells and basket cells.
Describe the granule cell layer.
Excitatory.
Contains granule cells and Golgi cells.
Which layer is the input layer?
Granule cell layer.
Which layer is the output layer?
Purkinje layer.
Describe Purkinje cells.
Large GABAergic neurons with broad dendritic fields.
Where does the Purkinje layer receive input from?
Internal input from granule cells via parallel fibres in the molecular layer.
External input from climbing fibres.
Describe how cerebellar circuitry is neuroplastic.
Since most cells in the cerebellum are inhibitory, higher excitatory inputs to these cells will result in overall inhibitory output.
This would inhibit descending motor systems in a refined way to enable coordinated smooth movement.
Modulation of the level of input to the Purkinje cells can reduce the inhibitory action of the Purkinje cells, and can lead to overall excitatory activity.
Describe climbing fibres.
Extend up from deep cerebellar nuclei.
Form excitatory synapses with the dendrites of Purkinje cells.
Each fibre can split to innervate several Purkinje cells.
A single action potential from a climbing fibre results in what?
A burst of action potentials (complex spike) in the Purkinje cell it is synapsed with.
What are the rosettes of a mossy fibre?
Each mossy fibre has up to 50 synaptic swellings called rosettes that form excitatory synapses onto the dendrites of several granule cells.
Describe parallel fibres.
Granule cell axons extend up into the molecular layer.
They divide to form parallel fibres at right angles to the dendritic spines of the Purkinje cells.
How do parallel fibres generate an action potential (simple spike) in a Purkinje cell?
Mossy fibres fire rapidly and simultaneously which causes the granule cells to fire together.
This activates many parallel fibres, which is sufficient to generate a simple spike.
Describe feedback inhibition.
Dendrites of Golgi cells in the molecular layer are excited by parallel fibres. This causes them to inhibit the mossy fibre > granule cell relay.
Describe feedforward inhibition.
Parallel fibres excite the dendrites of basket cells in the molecular layer. This inhibits Purkinje cells, resulting in balanced inhibition <> excitation.
How do basket cells interact with Purkinje cells?
They wrap around the cell bodies of the Purkinje cells.
What can damage to the cerebrocerebellum cause?
Abnormal coordination of voluntary movement.
Impaired ability to initiate and perform complex repetitive movements.
Scanning speech.
What is scanning speech?
Slow speech with lots of pauses between syllables and a large emphasis on certain syllables.
What can damage to the spincerebellum cause?
Ataxia of the body (difficulty sitting upright or standing without support).
What can damage to the vestibulocerebellum cause?
Subjective vertigo.
Objective vertigo.
Nystagmus.
What is subjective vertigo?
Individual feels as though they are rotating around in space.
What is objective vertigo?
Individual feels as though objects are rotating around them.
What is nystagmus?
Eyes make involuntary, rhythmic, oscillating movements.
The surface area of the cerebellum is equivalent to what?
80% of the cortex.
