Anatomy and Function of the Cerebellum

The Cerebellum

• The cerebellum is a large, bilaterally symmetric "little brain" located in the posterior cranial fossa.
• It influences the timing and force of contractions of voluntary muscles, resulting in smooth, coordinated movements.

Anatomy of the Cerebellum

• The cerebellum is divided into three areas: sagittal (into three areas), and horizontal (into three lobes).
• It is connected to the brainstem by three pairs of peduncles (superior, middle, and inferior).
• The cerebellum has three layers of cortex, three nuclei, and three cerebellar syndromes can be identified.

Cerebellar Peduncles

• Three pairs of peduncles connect the cerebellum to the brainstem:
  • Superior cerebellar peduncle: connects the cerebellum to the midbrain, mainly output fibers (efferent).
  • Middle cerebellar peduncle: connects the basilar part of the pons to the cerebellum, entirely input fibers (afferent).
  • Inferior cerebellar peduncle: connects the medulla to the cerebellum, mainly input fibers (afferent) with some output fibers (efferent).

Function of the Cerebellum Peduncles

• Connect the brainstem to the cerebellum.
• Send in and out signals to and from the cerebellum.

Lobes of the Cerebellum

• The cerebellum is divided into three lobes:
  • Anterior lobe: receives input from the limbs via spinal connections.
  • Posterior lobe: receives input from the cerebral cortex, the largest part of the cerebellum.
  • Flocculonodular lobe: receives input from the vestibular apparatus, the most ancient part of the cerebellum.

Zones of the Cerebellum

• Three cerebellar zones:
  • Midline: vermis (intermediate zone).
  • Lateral: lateral hemispheres on either side.

Histology of the Cerebellum

• Grey matter: found on the surface of the cerebellum, forming the cerebellar cortex.
• White matter: found underneath the cerebellar cortex, containing cerebellar nuclei.

Cerebellar Cortex

• Receives information from many parts of the nervous system, both central and peripheral.
• Has 40 times as many afferent fibers as efferent fibers.
• The cerebellar cortex is dissimilar to the cerebral cortex in many ways, including:
  • None of its activity contributes directly to consciousness.
  • Its hemispheres possess ipsilateral representation of the body parts.

Cerebellar Output

• All output from the cerebellum originates from the cerebellar deep nuclei.
• A lesion to the cerebellar nuclei has the same effect as a complete lesion of the entire cerebellum.

Functions of the Cerebellum

• Integrates information from various sources to regulate movement and coordination.
• Plays a crucial role in motor learning and adaptation.

Syndromes of the Cerebellum

• Anterior lobe syndrome: characterized by gait ataxia, loss of coordination, and instability, particularly in the lower limbs.
• Posterior lobe syndrome: characterized by impaired coordination and learning, particularly in the upper limbs.