Cerebellum

Question 1

How much of the brain’s neurons does it make up?

How many inputs does it have compared to outputs?

What does it receive and give off?

What is it needed for?

Which structure does the cerebellum work with to perform its role?

Which 2 comparator systems does it use?

Answer 1

• > 50%
• Inputs > outputs; most outputs project to motor area, but not to spinal cord
• Receives cortical inputs and projects to the Motor Cortex
• Regulate planning + execution of voluntary movement; Needed for smooth movement and posture
• Basal ganglia
• o Feed-back comparator via sensory receptor input; Slower, suitable for Motor learning
  o Feed-forward comparator via inputs from cerebral cortex; On-line control

Question 2

What are the 3 functional domains of the cerebellum? What does each domain do?

What are the 4 cell types found in the cerebellum?

What excitatory inputs do the Purkinje cells receive?

What is the most abundant cell type in the cerebellum?

Answer 2

• • Spino-cerebellum; Modulates brainstem descending motor systems for muscle tone, movement coordination
  • Vestibulo-cerebellum; Regulates balance and eye movement
  • Cerebro-cerebellum; Planning of movement, regulation of cortical motor programs
• • Cerebellar matrix; highly regular structure, basic circuit
  • Purkinje cells; Large neurons, GABAnergic (INHIBITORY)
  • Granule cells
  • Local inhibitory interneurons; Basket, Stellate, Golgi cells
• o From Olivary nucleus via Climbing fibres
  o From Pons/Brainstem nuclei via Parallel fibres from Granule cells
• GRANULE CELLS

Question 3

What are the 3 symptoms of a Cerebellar Lesion?

Answer 3

• HYPOTONIA; Low muscle tone, uncoordinated muscle contraction
• POSTURAL ATAXIA; Unstable posture
• INTENTION TREMOR; Overshooting, Oscillation of voluntary movement

Question 4

What are the Subacute, Acute, and Chronic causes of cerebellar disorders?

What can a SOL in the cerebellum cause?

What are the clinical features of cerebellar disease?

Answer 4

• • Subacute - Tumour, Infection, Inflammatory (MS), Drugs (e.g. Antiepileptics, Lithium)
  • Acute - Acute Alcohol intoxication, Vascular, Infection
  • Chronic - Inherited, Chronic Alcohol abuse, Hypothyroidism, Coeliac disease
• Compress the 4th Ventricle = OBSTRUCTIVE HYDROCEPHALUS
• • Dysdiadochokinesia; unable to do rapid, alternating movements
  • Ataxia; of gait, limb, trunk
  • Nystagmus; involuntary eye movements
  • Intention Tremor
  • Dysmetria; lack of coordinated movement e.g. finger-nose test
  • Scanning Dysarthria; voice goes high and low, slow speech, clumsy sounding
  • Hypotonia
  • Overshoot; with arms out, push down and their arm will shoot upwards