Cerebellum

Question 1

Where is the cerebellum located?

Answer 1

Sits under the cortex in the hindbrain near the brainstem.

Question 2

How does the cerebellum represent areas of the body?

Answer 2

In a more random or jumbled way compared to the somatosensory cortex.

Question 3

Why does the cerebellum represent areas of the body in a random/jumbled way?

Answer 3

It may enable the cerebellum to process and coordinate information from disparate parts of the body.

Question 4

Name the three zones of the cerebellum.

Answer 4

Cerebrocerebellum.
Spinocerebellum.
Vestibulocerebellum.

Question 5

What is the corresponding nucleus to the cerebrocerebellum?

Answer 5

Dentate nucleus.

Question 6

What is the corresponding nuclei to the spinocerebellum?

Answer 6

Emboliform nucleus.
Globose nucleus.

Question 7

What is the corresponding nuclei to the vestibulocerebellum?

Answer 7

Vestibular nucleus.
Fastigial nucleus.

Question 8

Where does the cerebrocerebellum receive input from?

Answer 8

Cerebral cortex.
Inferior olivary nucleus of the medulla.

Question 9

Where does the spinocerebellum receive input from?

Answer 9

Spinal cord.

Question 10

Where does the vestibulocerebellum receive input from?

Answer 10

Vestibular nuclei of cranial nerve.
Superior colliculi and visual cortex.

Question 11

What are the functions of the cerebrocerebellum?

Answer 11

Planning, coordination and execution of movements.
Cognition, language, learning and emotions.

Question 12

What are the functions of the spinocerebellum?

Answer 12

Coordination of body and limb movement.
Maintenance of muscular tone.

Question 13

What are the functions of the vestibulocerebellum?

Answer 13

Balance.
Ocular movements and gaze stability.

Question 14

What are the folia?

Answer 14

Folds of the cerebellum.

Question 15

What are the cerebellar peduncles?

Answer 15

They form the connection between the brainstem and the deep cerebellar nuclei.

Question 16

Name the afferent pathways into the cerebellum.

Answer 16

Corticopontocerebellar tract.
Dorsal and ventral spinocerebellar tracts.
Vestibulocerebellar tract.

Question 17

Describe the corticopontocerebellar tract.

Answer 17

Cerebral cortex –> pontine nuclei of the pons –> middle cerebellar peduncles –> deep cerebellar nuclei and cerebellar cortex.

Question 18

Describe the dorsal spinocerebellar tract.

Answer 18

Posterior horn of the spinal cord –> inferior cerebellar peduncle –> cerebellum.

Question 19

Describe the ventral spinocerebellar tract.

Answer 19

Posterior horn of the spinal cord –> medulla and superior cerebellar peduncle –> cerebellum.

Question 20

Describe the vestibulocerebellar tract.

Answer 20

Vestibular nerve –> inferior cerebellar peduncle –> ipsilateral flocculonodular lobe.

Question 21

What do all the afferent tracts have in common?

Answer 21

They are excitatory and travel to the cerebellum via mossy fibres and climbing fibres.

Question 22

Where do the mossy fibres terminate onto?

Answer 22

Granule cells.

Question 23

Where do the climbing fibres terminate onto?

Answer 23

Purkinje cells.

Question 24

Name the two efferent pathways of the cerebellum.

Answer 24

Rubrospinal pathway.
Cerebellovestibular pathway.

Question 25

Name the two tracts of the rubrospinal pathway.

Answer 25

Cerebellorubral tract. Cerebellothalamic tract.

Question 26

Name the two tracts of the cerebellovestibular pathway.

Answer 26

Vestibulospinal tract. Cerebelloreticular tract.

Question 27

Describe the rubrospinal pathway.

Answer 27

Travels mainly via the superior cerebellar peduncle and projects up to the thalamus and motor cortex.

Question 28

Describe the cerebellorubral tract.

Answer 28

Globose and emboliform nuclei --> superior cerebellar peduncle via the red nucleus.

Question 29

Describe the cerebellothalamic tract.

Answer 29

Dentate nucleus --> superior cerebellar peduncle --> thalamus and M1.

Question 30

What is the role of the cerebellorubral tract?

Answer 30

Related to skeletal muscle tone.

Question 31

What is the role of the cerebellothalamic tract?

Answer 31

Related to motor coordination.

Question 32

Describe the cerebellovestibular pathway.

Answer 32

Fastigial nucleus --> inferior cerebellar peduncle --> spinal cord.

Question 33

Describe the vestibulospinal tract.

Answer 33

Projects to the spinal cord via the vestibular nuclei.

Question 34

What is the role of the vestibulospinal tract?

Answer 34

Related to coordination of balance and rapid eye movements.

Question 35

Describe the cerebelloreticular tract.

Answer 35

Projects to motor neurons of the spinal cord via the reticular formation.

Question 36

What is the role of the cerebelloreticular tract?

Answer 36

Related to stretch reflex and motor movements.

Question 37

Describe the molecular layer.

Answer 37

Inhibitory. Contains stellate cells.

Question 38

Describe the Purkinje layer.

Answer 38

Inhibitory. Contains Purkinje cells and basket cells.

Question 39

Describe the granule cell layer.

Answer 39

Excitatory. Contains granule cells and Golgi cells.

Question 40

Which layer is the input layer?

Answer 40

Granule cell layer.

Question 41

Which layer is the output layer?

Answer 41

Purkinje layer.

Question 42

Describe Purkinje cells.

Answer 42

Large GABAergic neurons with broad dendritic fields.

Question 43

Where does the Purkinje layer receive input from?

Answer 43

Internal input from granule cells via parallel fibres in the molecular layer. External input from climbing fibres.

Question 44

Describe how cerebellar circuitry is neuroplastic.

Answer 44

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.

Question 45

Describe climbing fibres.

Answer 45

Extend up from deep cerebellar nuclei. Form excitatory synapses with the dendrites of Purkinje cells. Each fibre can split to innervate several Purkinje cells.

Question 46

A single action potential from a climbing fibre results in what?

Answer 46

A burst of action potentials (complex spike) in the Purkinje cell it is synapsed with.

Question 47

What are the rosettes of a mossy fibre?

Answer 47

Each mossy fibre has up to 50 synaptic swellings called rosettes that form excitatory synapses onto the dendrites of several granule cells.

Question 48

Describe parallel fibres.

Answer 48

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.

Question 49

How do parallel fibres generate an action potential (simple spike) in a Purkinje cell?

Answer 49

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.

Question 50

Describe feedback inhibition.

Answer 50

Dendrites of Golgi cells in the molecular layer are excited by parallel fibres. This causes them to inhibit the mossy fibre > granule cell relay.

Question 51

Describe feedforward inhibition.

Answer 51

Parallel fibres excite the dendrites of basket cells in the molecular layer. This inhibits Purkinje cells, resulting in balanced inhibition <> excitation.

Question 52

How do basket cells interact with Purkinje cells?

Answer 52

They wrap around the cell bodies of the Purkinje cells.

Question 53

What can damage to the cerebrocerebellum cause?

Answer 53

Abnormal coordination of voluntary movement. Impaired ability to initiate and perform complex repetitive movements. Scanning speech.

Question 54

What is scanning speech?

Answer 54

Slow speech with lots of pauses between syllables and a large emphasis on certain syllables.

Question 55

What can damage to the spincerebellum cause?

Answer 55

Ataxia of the body (difficulty sitting upright or standing without support).

Question 56

What can damage to the vestibulocerebellum cause?

Answer 56

Subjective vertigo. Objective vertigo. Nystagmus.

Question 57

What is subjective vertigo?

Answer 57

Individual feels as though they are rotating around in space.

Question 58

What is objective vertigo?

Answer 58

Individual feels as though objects are rotating around them.

Question 59

What is nystagmus?

Answer 59

Eyes make involuntary, rhythmic, oscillating movements.

Question 60

The surface area of the cerebellum is equivalent to what?

Answer 60

80% of the cortex.