Cerebellum

Where is the cerebellum?

It sits against the back of the brain stem, centered on the pons, in the posterior cranial fossa behind the fourth ventricle, the pons and the medulla oblongata. (OpenStax A&P 2e, 16.5; StatPearls, Cerebellum)

A tent-like shelf of dura, the tentorium cerebelli, separates it from the occipital lobes of the cerebrum above. (OpenStax A&P 2e, 13.3; StatPearls, Cerebellum)

What are the parts of the cerebellum?

Two hemispheres join at the midline vermis. The primary fissure separates the anterior and posterior lobes, and the posterolateral fissure separates the posterior and flocculonodular lobes. (StatPearls, Cerebellum)

A folded gray matter cortex covers a branched core of white matter, the arbor vitae, which surrounds three pairs of deep nuclei: from medial to lateral, the fastigial, interposed and dentate nuclei. (StatPearls, Cerebellum)

StatPearls puts 80% of the brain’s neurons in it, packed in a dense cell layer. (StatPearls, Cerebellum)

By function it divides into three zones. The spinocerebellum, the vermis and the paravermis beside it, takes body-sense input from the face and body; the vestibulocerebellum, the flocculonodular lobe, takes input from the vestibular nuclei; and the cerebrocerebellum, the rest of each hemisphere, takes input from the motor cortex through the pons. (OpenStax A&P 2e, 16.5; StatPearls, Cerebellar Dysfunction)

What does the cerebellum do?

It coordinates movement and keeps posture and balance. Its lateral hemispheres plan sequences of movement and take part in judging movement errors. (OpenStax A&P 2e, 13.2; StatPearls, Cerebellar Dysfunction and Cerebellum)

The midline regions keep balance and coordinate gait. The vermis coordinates the trunk, and the lateral hemispheres plan sequences of movement of the whole body. (OpenStax A&P 2e, 16.5; StatPearls, Cerebellum)

It also takes part in motor learning, how you learn and keep skilled movements. (OpenStax A&P 2e, 16.5; OpenStax Psychology 2e, 3.4; StatPearls, Cerebellar Dysfunction and Cerebellum)

Alcohol poisoning is the most common cause of cerebellar dysfunction. The resulting movement disorder, ataxia, shows as a wide, staggering gait and trouble walking heel to toe. (OpenStax A&P 2e, 14.3 and 16.5; StatPearls, Cerebellum and Cerebellar Dysfunction)

How does the cerebellum connect to the brain stem?

Three peduncles attach it: the superior to the midbrain, the middle to the pons, and the inferior to the medulla. (OpenStax A&P 2e, 16.5; StatPearls, Cerebellar Dysfunction, Cerebellum and Brainstem)

The largest of these links, the middle peduncle, joins it to the pons, and the pons and the cerebellum both develop from the metencephalon. (OpenStax A&P 2e, 13.1; StatPearls, Brainstem and Pons)

Where the sources differ

The sources disagree on whether the cerebellum starts movement. OpenStax A&P 2e says it is primarily responsible for initiating movements on the basis of equilibrium information; StatPearls says it cannot initiate muscle contraction. (OpenStax A&P 2e, 14.2; StatPearls, Cerebellum)