Cerebellum
The cerebellum , metencephalon, is the small caudal portion of the brain. It is a roughly globular mass placed above the pons and medulla. The median part of the cerebellum is the vermis, and the lateral portions are known as the cerebellar hemispheres. The cerebellum is attached to the brainstem by 3 cerebellar peduncles on each side – rostral, middle and caudal. The grey matter of the cerebellum is arranged as the outer cortex which encloses the white matter of the inner medulla. The medulla radiates throughout the cerebellum and gives the impression of a tree; for this reason and because of an ancient belief that it is the seat of the soul, it is known as the arbor vitae or ‘Tree of Life’.
The functions of the cerebellum are concerned with balance and coordination of postural and locomotor activities.
Brainstem
The Medulla Oblongata (Myelencephalon)
The medulla oblongata is continuous with the upper spinal cord and forms the inferior part of the brainstem. It extends cranially from the foramen magnum to the inferior border of the pons. The medulla contains white and gray matter as well as the fibres of CN VI through XII. White matter: contains all the sensory tracts and motor tracts that extend between the spinal cord and other parts of the brain. On the ventral medulla, bulges of white matter form called Pyramids . These pyramids are formed by large motor tracts. Decussation of Pyramids : 90% of the axons from the left pyramid cross to the right side and 90% of the axons from the right pyramid cross to the left. This area is located just superior to the level of the spinal cord/medulla junction. This is the reason that each side of the brain controls movements on the opposite side of the body. Gray Matter: contains several nuclei that control vital body functions such as Cardiovascular Centre which regulates the rate and force of the heartbeat and the diameter of the blood vessels; the Medullary Rhythmicity Area of the Respiratory Centre which adjusts the basic rhythm of breathing; reflexes for swallowing, sneezing, coughing, hiccupping; Deglutition Centre which promotes swallowing after food has moved into the throat (pharynx).
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