The midbrain is a small part of the brain above the pons that integrates sensory information and relays it upward. The medulla and pons extend upward into the midbrain. The medulla, pons, and midbrain compose most of the brain stem, and the reticular activating system spans across all these structures. The reticular activating system serves to alert the rest of the brain to incoming signals and is involved in the sleep/wake cycle.

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