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Cerebellum

Last updated: March 4, 2021

Summarytoggle arrow icon

The cerebellum is the part of the hindbrain that lies within the posterior cranial fossa, inferior to the occipital lobes and dorsal to the brainstem. It consists of three lobes (the anterior, posterior, and flocculonodular lobe). Functionally, it is divided into three zones. These are the cerebrocerebellum (the lateral zones), which receives sensory information from the cerebral cortex and is responsible for the planning of movements that are just about to occur (motor planning); the spinocerebellum (the vermis and intermediate zones), which receives proprioceptive information from the dorsal columns of the spinal cord and is responsible for the coordination of movements (motor execution); and the vestibulocerebellum (the flocculonodular lobe), which receives information from the vestibular nuclei and visual cortex and is responsible for balance and ocular movements. The cerebellar cortex transmits the information received from the three afferents (i.e., the cerebrum, spinal cord, and vestibular nuclei) to the four cerebellar nuclei (dentate, emboliform, globose, and fastigial) within the inner white matter. The cerebellar nuclei send efferent impulses to the thalamus, red nucleus, and reticular formation to execute cerebellar functions. The cerebellar tracts travel through the cerebellar peduncles.

Overview [1]

Structure [2][3]

  • The 2 hemispheres of cerebellum are separated in the midline by the cerebellar vermis.
  • The cerebellar tonsil is an ovoid lobule located on the inferomedial aspect of each cerebellar hemisphere, above the foramen magnum
  • Sulci and fissures further divide the cerebellum into lobes (see “Lobes and fissures” below)

Cerebellar tonsil herniation through the foramen magnum can occur due to a Chiari malformation or an increase in intracranial pressure, resulting in brainstem compression and cardiopulmonary arrest.

Lobes and fissures

Cerebellar peduncles

Peduncle Characteristics Tracts
Superior cerebellar peduncles (SCP)
  • Connects the cerebellum to the midbrain
  • Major efferent pathway
Middle cerebellar peduncles (MCP)
  • Connects the cerebellum to the pons
  • Largest peduncle
  • Major afferent pathway
  • Afferent tracts from the contralateral cortex (pontocerebellar mossy fiber pathway)
Inferior cerebellar peduncles (ICP)
  • Connects the cerebellum to the medulla and spinal cord
  • Afferent and efferent pathways
  • Afferent tracts carrying ipsilateral proprioceptive information from the spinal cord
  • Efferent tract composed primarily of Purkinje cell axons


Cerebellar lesions cause neurological deficits on the ipsilateral side!

Vasculature of the cerebellum [2]

Zones of cerebellum

Cerebrocerebellum

Spinocerebellum

Vestibulocerebellum

Corresponding cortex
  • Vermis and intermediate zones
Corresponding nuclei
Input
Function
  • Planning and execution of movements
  • Coordination of complex and sequential motor movements
  • Nonmotor functions: cognition, language, learning, and emotions
  • Coordination of body and limb movement
    • Vermis: central body (trunk, head, and proximal limbs)
    • Intermediate zones: distal limbs (hands, fingers, feet, toes)
  • Maintenance of muscular tone
  • Balance
  • Ocular movements and gaze stability
Effect of lesions

For further information on the effects of cerebellar lesions, see “Clinical features” in cerebellar syndromes.

A tip to remember the symptoms of cerebellar lesions: lesions of the medial part of cerebellum (i.e., vermis, flocculonodular lobe, and corresponding deep nuclei) affect medial structures (i.e., axial and proximal limb musculature), resulting in symptoms including truncal ataxia and nystagmus. Lesions of the lateral parts of cerebellum (i.e., the hemispheres) affect lateral structures (distal limb musculature), resulting in symptoms such as ipsilateral limb ataxia.

References:[4][5]

The cerebellum is composed of the outer gray matter (cerebellar cortex) and inner white matter (cerebellar medulla).

Cerebellar cortex [5]

  • Receives afferent inputs from the cerebrum, spinal cord, and vestibular nuclei
  • Sends neural impulses to the cerebellar nuclei
  • Composed of 5 types of neuronal cells, densely packed and arranged in 3 layers
  • The cortex is primarily an inhibitory structure; all cerebellar cells except granule cells are inhibitory.
Layer Cell types Function

Molecular layer

(outermost layer)

  • Receives excitatory input from parallel fibers
  • Sends inhibitory impulses to Purkinje cells

Purkinje cell layer

(middle layer or ganglionic layer)

  • Receive excitatory input from climbing fibers and granule cells
  • Send inhibitory impulses to the deep cerebellar nuclei and thereby control the output of all motor coordination of the cerebellum

Granular layer of the cerebellum

(inner layer)

  • Golgi cells: located in the upper portion of the granular layer
  • Granule cells (excitatory): small, densely packed neurons that secrete glutamate
    • Most abundant cell type in the cerebellum

Cerebellar medulla

Glutamate is the neurotransmitter of granule cells, which are the only excitatory cerebellar cells. GABA is the inhibitory neurotransmitter of all other cerebellar cells.

Purkinje cells provide the only efferent effect from the cerebellar cortex to the cerebellar nuclei, and, thus, play an essential role in the regulation of cerebellar output!

Purkinje cells are inhibitory!

References:[4][5][6][7][8][9]

Afferent cerebellar tracts (input) [4][10]

Afferent cerebellar tracts
Source Tracts Course Function
Cerebral cortex
  • Corticopontocerebellar tract
  • Motor planning, motor learning, and cognition
  • Cortico-olivocerebellar tract
  • Corticoreticulocerebellar tract

Spinal cord

  • Spinocerebellar tract
  • Dorsal spinocerebellar tract
  • Ventral spinocerebellar tract
  • Cuneocerebellar tract
  • Rostral spinocerebellar tract

Vestibular nerve

  • Vestibulocerebellar tract



Excitatory input to the cerebellar cortex travels through mossy fibers and climbing fibers!

Mossy fibers terminate on granule cells. Climbing fibers terminate on Purkinje cells.

Efferent cerebellar tracts [10]

Tract Nucleus Course Function
Rubrospinal tract
  • Dentate nucleus
  • Emboliform nucleus
  • Globose nucleus
Cerebellovestibular tract
  • Fastigial nucleus
  • Coordination of balance and saccadic ocular movements
  • Stretch reflex and motor movements

Deep cerebellar nuclei (from lateral to medial): "Don't Eat Greasy Food" (Dentate, Emboliform, Globose, Fastigial).

The deep nuclei are the only output from the cerebellum.

References:[1][11][12][13][14][15][16][17][18][19]

The cerebellum derives from the hindbrain (rhombencephalon) and metencephalon.

For more information on the embryology of the nervous system, see “Embryology” in “The cerebral cortex, meninges, basal ganglia, and ventricular system.”

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  15. Superior Cerebellar Artery. https://radiopaedia.org/articles/superior-cerebellar-artery. Updated: January 1, 2019. Accessed: January 6, 2019.
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