| The brain stem, shown here in colored cross section, is the lowest part of the brain. It serves as the path for messages traveling between the upper brain and spinal cord but is also the seat of basic and vital functions such as breathing, blood pressure, and heart rate, as well as reflexes like eye movement and vomiting. The brain stem has three main parts: the medulla, pons, and midbrain. A canal runs longitudinally through these structures carrying cerebrospinal fluid. Also distributed along its length is a network of cells, referred to as the reticular formation, that governs the state of alertness. |
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