Cerebellum Function and Divisions

The cerebellum is divided into three functional regions: spinocerebellum, cerebrocerebellum, and flocculonodular lobe.

The spinocerebellum controls limb and trunk movements, as well as muscle tone.

The cerebrocerebellum is responsible for coordination and planning of movements.

The flocculonodular lobe regulates balance and eye movements.

Mossy fibers are excitatory fibers carrying information from the spinal cord and brainstem to the cerebellum.

The largest part of the cerebellum, responsible for planning and coordinating complex movements, and receiving input from the cerebral cortex.

A part of the cerebellum involved in motor learning, coordination, and balance, receiving input from the spinal cord.

The oldest part of the cerebellum, responsible for maintaining balance and eye movements, receiving input from the vestibular system.

A layer in the cerebellar cortex that contains Purkinje cells, responsible for output signals of the cerebellum.

A deep cerebellar nucleus that receives input from the cerebrocerebellum and sends output to thalamus and ultimately the cerebral cortex.

Purkinje cells are inhibitory neurons in the cerebellar cortex that receive input from climbing and mossy fibers.

Deep cerebellar nuclei are collections of neurons located deep within the cerebellum. These nuclei integrate information from the cerebellar cortex and relay it to other brain structures.

When Purkinje cells are damaged, they can no longer inhibit the deep cerebellar nuclei. This leads to overactivity in the deep nuclei, resulting in increased muscle tone (hypertonia).

Climbing fibers are excitatory fibers that originate in the inferior olive and synapse directly on Purkinje cells. They play a key role in motor learning and error correction.

The cerebellum's role in coordinating movement involves modulating the activity of motor neurons (both alpha and gamma) in the spinal cord. This fine-tunes movement and smooths out motor commands.

The vestibulocerebellum, also known as the flocculonodular lobe, is responsible for balance and eye movements. It receives input from the vestibular system and projects to the vestibular nuclei in the brainstem.

A lesion in the cerebellar cortex or deep cerebellar nuclei can lead to a decrease in muscle tone (hypotonia). This is because the inhibitory signal from Purkinje cells is disrupted, resulting in less control over motor function.

The flocculonodular lobe is a part of the cerebellum, responsible for maintaining balance and coordinating eye movements.

Vestibular nuclei receive input from balance-sensing organs (the labyrinth) in the inner ear. These nuclei project to the vestibulospinal tracts, controlling axial muscle movements.

The cerebellum influences muscle tone through the spinocerebellum and its deep nuclei. Purkinje cells in the cerebellar cortex inhibit the deep nuclei, while climbing and mossy fibers excite them. This interplay regulates muscle contraction.

Damage to the cerebellar cortex leads to hypertonia (increased muscle tone) because the inhibitory function of the Purkinje cells is lost. Damage to the white matter results in hypotonia (decreased muscle tone) because the signal pathways are disrupted.

The cerebrocerebellum, the largest part of the cerebellum, plays a crucial role in coordinating voluntary movements. It receives motor plans from the motor cortex and sensory feedback from the spinal cord, comparing intended and actual movements to refine motor control.

The cerebrocerebellum receives input from the motor cortex (intended movement), the spinal cord (actual movement), and proprioceptors (feedback on muscle position). This information is used to correct errors in movement, ensuring smooth and accurate execution.

Dysdiadochokinesia is a condition where a person struggles to perform rapid, alternating movements, such as patting their knee with one hand and the back of the other hand in a rhythmic sequence. It is often a sign of cerebellar dysfunction.

Dysmetria is the inability to accurately judge the distance and range of movement. It is a common symptom of cerebellar dysfunction, leading to movements that overshoot or undershoot the target, causing clumsiness.