What is the functional importance of the brain stem?
The brain stem is a small, narrow region connecting the spinal cord with the diencephalon and cerebrum.
It lies ventral to the cerebellum, which it links via the cerebellar peduncles. Its functions are critical to survival.
The brain stem is densely packed with many vital structures such as long ascending and descending pathways that carry sensory and motor information to and from higher brain regions.
It contains the nuclei of cranial nerves III through XII and their intramedullary fibers.
It also possesses groups of neurons that are the major source of noradrenergic, dopaminergic, and serotonergic inputs to most parts of the brain. In addition, other specific nuclear groups, such as the reticular formation, olivary bodies, and red nucleus, lie within the brain stem.
In short, it is a complicated but highly organized structure that controls motor and sensory activities, respiration, cardiovascular functions, and mechanisms related to sleep and consciousness.
Consequently, a small lesion in the brain stem can affect contiguous structures and cause disastrous neurologic deficits.