The remaining lateral area of each cerebellar hemisphere provides the planning of sequential movements of the entire body along with involvement in the conscious assessment of movement errors.
Control of the distal extremity muscles is by the intermediate zone of the cerebellar hemispheres, located adjacent to the vermis. įunction: The cortex of the vermis coordinates the movements of the trunk, including the neck, shoulders, thorax, abdomen, and hips. Each mossy fiber may stimulate thousands of Purkinje cells via multiple branching. The mossy fibers are the terminal branches of all other cerebellar afferent tracts. They represent the terminal ending of the olivocerebellar tracts. The climbing fibers are named so because they travel in the cortex like vine branches on a tree. Mossy fibers use glutamate, while the climbing fibers use aspartate as their main excitatory neurotransmitter to provide excitatory signals to the Purkinje cells. Climbing and mossy fibers provide the primary input to the cerebellar cortex. Their collateral branches make synaptic contacts with the basket and stellate cells of the granular layer. The axons are long, pass through the granular layer, enter the white matter, acquire a myelin sheath, and terminate in the intracerebellar nuclei. Their dendrites reach the molecular layer and have multiple branches. The Purkinje layer consists of Purkinje cells, which are large Golgi type I neurons. The molecular layer contains two types of neurons: the outer stellate cell and the inner basket cell. The gray matter of the cortex divides into three layers: an external - the molecular layer a middle - the Purkinje cell layer and an internal - the granular layer. Each fold is composed of an inner white matter core that is covered by gray matter. The cerebellar cortex is a sheet-like structure, made of a single sheet less than 1mm thick, and accordion-like folds fused at the midline (Essen 2018).
The cerebellum is neuron-rich, containing 80% of the brain’s neurons organized in a dense cellular layer. A deep horizontal fissure found within the posterior lobe separates the superior and inferior surfaces of the cerebellum. The V-shaped primary fissure separates the anterior and posterior lobe, while the posterolateral fissure separates the posterior and flocculonodular lobes. It is composed of two hemispheres joined by the vermis and is sub-divided into three lobes – anterior, posterior, and flocculonodular, which are separated by two transverse fissures. Tentorium cerebelli, an extension of the dura matter, separates the cerebellum from the cerebrum. The cerebellum, which is the largest part of the hindbrain, is located in the posterior cranial fossa, behind the fourth ventricle, the pons, and the medulla oblongata.
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