The Hindbrain

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The hindbrain which surrounds the Fourth Ventricle consists of two major divisions the Metencephalon and the Myelencephalon.

Metencephalon

The Metencephalon consists of the Pones and the Cerebellum.

Cerebellum

The cerebellum (little brain) with its two hemispheres, resembles a miniature version of the cerebrum. It is covered by the cerebellar cortex and has a set of deep cerebellar nuclei.

These nuclei receive Projections from the cerebellar cortex and themselves send Projections out of the cerebellum to other parts of the brain. Each hemisphere of the cerebellum is attached to the dorsal surface of the pones by bundles of axons: the superior, middle, and inferior Cerebellar peduncles (little feet).

Damage to the cerebellum impairs standing, walking, of performance of coordinated movements. The cerebellum integrates this information and modifies the motor outflow, exerting a coordinating and smoothing effect on the movements.

Cerebellar damage results in Jerky, Poorly coordinated, exaggerated movements; extensive cerebellar damage makes it impossible even to stand.

Pones

The pones a large bulge in the brain stem, lies between the mesencephalon and Medulla Oblongata, immediately ventral to the cerebellum. Pones mean "bridge" but it does not really look like one. The pones contain in its core a portion of the reticular formation, including some nuclei that appear to be important in Sleep and Arousal. It also contains a large nucleus that relays information from the cerebral cortex to the cerebellum.

Myelencephalon

The Myelencephalon contains one major structure, the Medulla Oblongata (literally "oblong marrow"), just called the Medulla. This structure is the most caudal portion of the brain stem; its lower border is the rostral end of the Spinal Cord. The medulla contains part of the reticular formation; including nuclei that control vital functions such as Regulation of the Cardio-vascular system, Respiration and Skeletal muscle tonus.