Cerebellum

Question 1

Answer 1

Question 2

Superior surface of the cerebellum

Answer 2

Lies beneath the dural tentorium cerebelli with the superior vermis raised, forming a midline ridge.

Question 3

Inferior vermis

Answer 3

Lies in a deep groove between the hemispheres.

Question 4

Folia

Answer 4

Folds of the surface of the cerebellum which are orientated approximately trasnveresely.

Between the folia lie fissures of varying depths, some of which can be used to divide the cerebellum anatomically into theree lobes

Question 5

Primary fissure

Answer 5

Separates anterior lobe from the much larger posterior lobe.

Question 6

Posterolateral fissure

Answer 6

Demarcates the location of the flocculus and the bermis, which together form the flocullonodular lobe

Question 7

Answer 7

Question 8

Answer 8

Question 9

Answer 9

Question 10

Answer 10

Question 11

Arrangement of the white matter of the cerebellum

Answer 11

Made up largely of afferent and efferent fibres that run to and from the cortex, towards which it extends characteristic irregular branch like projections, arborvitae.

Buried deep within the white matter are four bilaterally paired cerebellar nuclei.

Question 12

What are the four white matter nuclei of the cerebellum?

Answer 12

Dentate

Fastigial

Emobliform

Globose

Question 13

Answer 13

Question 14

Answer 14

Question 15

What is the histological arrangement of the cerebellar cortex?

Answer 15

3 layers

Molecular- fibre rich

Intermediate- Purkinje cell layer

Granular layer

Question 16

What are the principle afferent projections to the cerebellum

Answer 16

Spinocerebellar (from SC)

Olivocerebellar (inferior olivary nucleus)

Vestibulocerebellar (vestibular nuclei)

Pontocerebellar (pons)

Question 17

Passage of afferent fibres to the cerebellum

Answer 17

Mostly termiante in the cerbellar cortex, where they are excitatory tocortical neurones.

Fibres enter the cerebellum through one of the peduncles as eiether mossy fibres of climbing fibres depending on their origin.

Question 18

Afferents from the inferior olivary nuclei end up as ?

Answer 18

Climbing fibres

Question 19

All other afferent fibres end up as

Answer 19

Mossy fibres.

Question 20

What hapens to mossy fibres in the cerebellar cortex

Answer 20

Branch to supply several folia and end in the granular layer, in synaptic oncat with granule cells.

The axons of granule cells pass towards the surface ofr the cortex and enter the molecular layer.

Here they bifurcate to produce two parallel fibres that are originated along the axis of the folium

Question 21

Outline the Purkinje layer of the cerebellar cortex

Answer 21

A unicellular layer of the somata of Purkinje neurones.

Their profuse dendritic arborisations extend into the cortex, into the molecular layer.

The arborisations are flattened and orientated at right angles to the long axis of the folium. They are therefore traversed by numerous parallel fibres.

Inhibitory modulation of intracortical circuitry is provided by other neurones such as Golgi, basket and stellate cells.

most of these fibres do not leave the cerebellum and terminate in the deep cerebellar nuclei.

Question 22

Climbing fibres

Answer 22

Originate from the inferior olivary nucleus of the medulla.

Provide relatively discrete excitatory input to Purkinje cells.

Axon collaterals of climbing fibres ecite the nuroens of the deep cerebellar nuclei.

Purkinje cells are GABAergic, which means tat the output of the whole cerebellar cortex is mediated through inhibition of cells in the cerebellar nuclei

Question 23

Cerebellar nuclei from medial to lateral

FGED

Answer 23

Fastigial

Globose

Emboliform

Dentate

Question 24

Dentate nucleus

Answer 24

Thin layer of nerve cells reminiscent of a crinkled bag.

Question 25

Efferents of the cerebellar nuclei

Answer 25

Arise primarily from the cerebellar nuclei. Principal destinations are the reticular and vestibular nuclei of the medulla and ponse, red nucleus of the midnrain and the VLN of the thalamus

Question 26

What are the three cerebellar functional subdivisions?

Answer 26

Archicerebellum (flocculonodular lobe) Paleocerebellum (midline vermis and paravermis) Neocerebellum (hemispher)

Question 27

Archicerebellum

Answer 27

Primarily concerned with the maintenance of balance. Flocculonodular lobe and the associated fastigial nuclei It has extensive connections with the vestibular and reticular nuclei of the brainstem through the inferior cerebellar peduncles. Vestibular information is carried from the vestibular nuclei to the cortex of the ipsilateral flocculonodular loe. Cortical efferent fibres project to the fastigial nucleus which in turn projects back to the vestibular nuclei and to the reticular formation. A significant proportion of fastigial efferents cross to the contralateral side. This means that the influence of the archicerebellum is therefore bilateral and principally mediated by descending vestibulospinal and reticulospinal projections.

Question 28

Paleocerebellum

Answer 28

Influences muscle tone and posture Afferents consist principally of the dorsal and ventral spinocerebellar tract neurones that carry information from muscle, joint and cutaneous receptors and enter the cerebellum through the inferior and superior cerebellar peduncles. Fibres terminate largely in the cortex of the ipsilateral vermis and adjacent paravermis. Cerebellar efferents from these areas pass to the globose and emboliform nuclei and also to the fastigial nucleus. These project via the superior cerebellar peduncle to the contralateral midbrain where they influence the activity of cells giving rise to the descending rubrospinal tract.

Question 29

Neocerebellum

Answer 29

Concerned with muscular coordination. Principle afferent is the pontocerebellar fibres that arise in the pontine nuclei of the basal portion of the pons. These nuclei are influenced by widespread areas. Pontocerebellar fibres cross over to the opposite side of the brainstem entering the cerebellum through the middle cerebellar fibres terminating in the lateral part of the cerebellar hemisphere. Output from the neocerebellar cortex is via the dentate nucleus. It projects to the contralateral red nucleus and the ventral lateral nucleus of the thalamus via the superior cerebellar peduncle. Which decussates in the caudal midbrain.

Question 30

Midline cerebellar lesion

Answer 30

Loss of postural control.