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Basic anatomy of brainstem

Brainstem is located between the cerebrum and the spinal cord. It provides a pathway for tracts running between higher and lower neural centers
Brainstem is formed of 
1. Midbrain
2. Pons
3. Medulla

Connections of brainstem 
Brainstem is connected to the cerebral hemisphere by 2 cerebral peduncle and to the cerebellum on each side by the superior, middle and inferior cerebellar peduncle.

Components of the brainstem
Brain stem contains groups of nerve cells (gray matter) intermingled with several ascending and descending tracts (white matter).

Motor nucleus of cranial nerves are arranged in brain stem as follows
Cranial nerve 3 & 4 in midbrain 
Cranial nerve 5, 6 &7 in pons
Cranial nerve 9. 10, 11, 12 in medulla
Cranial nerve 1, 2 & 8 have no motor nucleus, they are sensory nerves concerned with special sensation perceived in special areas of cerebral cortex.