Cerebellum

Question 1

What is the cerebellum?

Answer 1

Cerebellum
 ‘little brain’ with cortex and white matter
 11% of brain mass but more neurones than rest of brain put together!
 Works below the level of consciousness
 Receives inputs from cerebral cortex, brain stem nuclei and sensory
receptors
 coordinates voluntary motor movement, balance and equilibrium, and
muscle tone

Question 2

Describe basic anatomy

Answer 2

Consists of midline body and two lateral lobes
 Lobes separated by deep cleft into which projects the falx cerebelli
 Occupies most of the posterior cranial fossa
 Rests on floor of posterior cranial fossa
 Separated from occipital lobe by transverse fissure and tentorium cerebelli
 Pons and medulla lie anteriorly, with IV ventricle in-between

Question 3

Describe the layers of the cerebellum

Answer 3

Cortex
 Three layers
 Molecular (outermost)
 Purkinje (monolayer of large cells)
 Granule (many small cells)

Question 4

What are the inputs and outputs of the cerebellum?

Answer 4

 Two inputs
 Mossy fibres (middle peduncle)
 Climbing fibres (inferior peduncle)
 One output
 Purkinje-cell axons (most to dentate nucleus)

Question 5

What do the 3 cerebellum peduncles communicate with?

Answer 5

• Superior peduncle – ventral spinocerebellar (contralateral, sensory)
• Middle peduncle – cortico-ponto-cerebellar motor cortex
• inferior peduncle – vestibule-cerebellar tract, dorsal spinocerebellar (ipsilateral, sensory)

Question 6

What can cerebellum damage lead to?

Answer 6

Damage to the cerebellum can lead to:
1) loss of coordination of motor movement (asynergia),
2) the inability to judge distance and when to stop (dysmetria)
3) the inability to perform rapid alternating movements
(adiadochokinesia)
4) movement tremors (intention tremor)
5) staggering, wide based walking (ataxic gait)
6) tendency toward falling
7) weak muscles (hypotonia)
8) slurred speech (ataxic dysarthria)
9) abnormal eye movements (nystagmus)

DDK - probelms rapid alternating movements
Ataxia - lack of voluntary control
Nystagmus - slow(towards damage), rapid (away, determines)
Intention tremor
Speech impairment
Hypotonia

Question 7

2 outputs? -which penducle and what do they control

Answer 7

-Mossy fibres/Motor control/Middle peduncle (connects pons)
-Climbing fibres/proprioception, vestibular inputs/inferior/olivocerebellar nuclei
(connects medulla )

Question 8

Output?

Answer 8

Purkinje fibres - synapses with parallel

-their output is inhibitory

Question 9

Role of granule cells?

Answer 9

• input (mossy or climbing) to granule to purkinje

- they are excitatory