The brainstem is the oldest, most primitive part of the brain. It connects the cerebellum with the spinal cord, acting as a highway for motor and sensory signals, while also controlling many vital life-sustaining functions. The brainstem regulates autonomic functions such as heart rate, breathing, blood pressure, and digestion; it controls basic reflexes such as swallowing, coughing, sneezing, and vomiting, it facilitates motor coordination and sensory processing; and it coordinates alertness, sleep, and consciousness.
The Midbrain (Mesencephalon) is located at the top portion of the brainstem, between the thalamus and pons. Its functions include processing visual and auditory reflexes (the superior colliculi visual tracking and eye movement, while the inferior colliculi auditory processing); contains crucial dopamanergic nuclei such as the substantial nigra, which is associated with motor control, and the ventral tegmental agree, which is associated with reward, motivation, and pleasure; it coordinates motor output and posture; and it helps regulate alertness and arousal.
The Pons, located in the middle part of the brainstem acts as a bridge between the cerebrum, cerebellum, and medulla. It coordinates voluntary movement by relaying sensory information from the contex to the cerebellum, it assists in controlling breathing rhythm, and it contains nuclei for several cranial nerves (which regulate facial sensations, hearing, balance, and eye movementent), and it plays a role in sleep and REM cycles.
The Medulla (AKA Medulla Oblongata) is the lowest part of the brainstem, continuous with the spinal cord. Its functions include regulating vital autonomic functions (heart rate, blood pressure, respiratory rate, digestion, swallowing and vomiting reflexes), and it contains decussation of pyramids (where motor fibers cross from one side of the brain to the opposite side of the body.
Brainstem
