Cerebellum

: The portion of the brain in the back of the head between the cerebrum and the brain stem.

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The large posterior brain mass lying dorsal to the pons and medulla and ventral to the tentorium cerebelli and posterior portion of the cerebrum; it consists of two lateral hemispheres united by a narrow middle portion, the vermis. [L. dim. of cerebrum, brain]

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cer·e·bel·lum .ser-ə-'bel-əm n, pl -bellums or -bel·la -'bel-ə a large dorsally projecting part of the brain concerned esp. with the coordination of muscles and the maintenance of bodily equilibrium, situated between the brain stem and the back of the cerebrum and formed in humans of two lateral lobes and a median lobe

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n.

the largest part of the hindbrain, bulging back behind the pons and the medulla oblongata and overhung by the occipital lobes of the cerebrum. Like the cerebrum, it has an outer grey cortex and a core of white matter. Three broad bands of nerve fibres - the inferior, middle, and superior cerebellar peduncles - connect it to the medulla, the pons, and the midbrain respectively. It has two hemispheres, one on each side of the central region (the vermis), and its surface is thrown into thin folds called folia. Within lie four pairs of nuclei.

The cerebellum is essential for the maintenance of muscle tone, balance, and the synchronization of activity in groups of muscles under voluntary control, converting muscular contractions into smooth coordinated movement. It does not, however, initiate movement and plays no part in the perception of conscious sensations or in intelligence.

• cerebellar adj.

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cer·e·bel·lum (ser″ə-belґəm) [L. dim. of cerebrum brain] [TA] the part of the metencephalon that occupies the posterior cranial fossa behind the brainstem and is concerned in the coordination of movements. It is a fissured mass consisting of a body, comprising a narrow middle strip (the vermis) and two lateral lobes (the hemispheres), connected with the brainstem by three pairs (inferior, middle, and superior) of peduncles. The cerebellum is subdivided into an anterior lobe, which is separated from the posterior lobe by the primary fissure, which is in turn separated from the flocculonodular lobe by the posterolateral fissure. The lobes are further subdivided into lobules; those of the vermis are denoted I–X, with the corresponding hemisphere portion of each lobule denoted HII–X (with no HI in humans). Each lobule consists of a series of individual folia divided by deep transverse fissures, the deeper fissures demarcating the divisions into lobules. cerebellar adj