cerebellum

Question 1

describe the fibre types found in the cerebellum

Answer 1

no commissural fibres → cerebellum lacks structure corresponding to corpus callosum

no association fibres → cerebellum lacks structure corresponding to corona radiata

Question 2

where do the superior and inferior vela merge?

Answer 2

fastigium of the cerebellum

Question 3

when inter-cranial pressure becomes too high, what can happen to the cerebellum?

Answer 3

herniation of the cerebellar tonsils through the foramen magnum

although the tonsils have no distinct function, this herniation is lethal because it compresses the medulla → respiratory and cardiac control centres

Question 4

describe the blood supply to the cerebellum

Answer 4

blood supply separated into superior and inferior by horizontal fissure

SUPERIOR CEREBELLAR ARTERY:
• branches of basilar artery
• supplies superior half of cerebellum

ANTERIOR INFERIOR CEREBELLAR ARTERY:
• branches of basilar artery
• supplies anterior portion of inferior half of cerebellum

POSTERIOR INFERIOR CEREBELLAR ARTERY:
• branches of paired vertebral artery
• supplies posterior portion of inferior half of cerebellum

lots of variation between anterior/posterior inferior cerebellar arteries

Question 5

which fissure divides the cerebellum in half?

Answer 5

horizontal fissure

Question 6

which fissure separates the posterior and anterior cerebellar lobes?

Answer 6

primary fissure

Question 7

what does the posterolateral fissure separate?

Answer 7

posterior and flocculonodular lobes

Question 8

list the cerebellar peduncles and identify:
– where they connect to the midbrain
– how they connect to spinal cord

Answer 8

superior cerebellar peduncle (SCP) contains axons to/from the midbrain

middle cerebellar peduncle (MCP) contains axons from the pons

inferior cerebellar peduncle (ICP) contains axons to/from medulla

Question 9

which cerebellar peduncle is the largest?

Answer 9

middle cerebral peduncle

Question 10

vestibulocerebellar loop

Answer 10

unconscious functional loop (no involvement of cerebral cortex)

1) integration of sensory and motor information occurs at flocculonodular lobe
2) flocculonodular lobe and fastigial nuclei to vestibular nuclei of medulla via cerebellovestibular tract
3) vestibular nuclei travels ipsilaterally to spinal cord via vestibulospinal tract, then to skeletal muscle
4) feedback to flocculonodular lobe via vestibulocerebellar tract. afferent copy sent to fastigial nuclei

FUNCTIONS:
vestibulospinal reflex:
keeps the body in the centre of gravity (body equilibrium) by maintaining muscle tone and activating antigravity muscles (= function of lateral vestibulospinal tracts)

vestibulocervical reflex:
stabilizes position of the head (= function of medial vestibulospinal tracts)

vestibulo-ocular reflex:
stabilises gaze during head movement (= function of medial vestibular nucleus)

Question 11

spinocerebellar loop

Answer 11

1) cerebellar cortex to fastigial and interposed nuclei via purkinje cells
2) cerebellar nuclei to brainstem and on to extrapyramidal pathways (excluding tectospinal)
3) travels to spinal cord via these tracts and to skeletal muscle
4) feedback to cerebellar cortex via spinocerebellar tract

FUNCTION:
- modulates muscle tone, posture and body balance

Question 12

cerebrocerebellar loop

Answer 12

1) lateral hemispheres of cerebellum to dentate nuclei via purkinje cells
2) dentate nuclei to VA nuclei in ipsilateral thalamus via dentatothalamic tract
3) thalamus to ipsilateral primary motor cortex via thalamocortical tract
4) motor cortex to ipsilateral pontine nuclei via corticopontine tract
5) pontine nuclei back to lateral hemispheres via pontocerebellar tract. afferent copy sent to dentate nuclei

FUNCTION:
coordinates fast and alternating movement (e.g. speech) by planning motor actions

Question 13

what is the consequence of a lesion to the cerebrocerebellar loop?

Answer 13

limb ataxia as unable to plan movements