Brainstem

The brainstem is the part of the brain that connects the diencephalon and other higher brain regions with the spinal cord. It lies in front of the cerebellum and consists of three major regions: the midbrain, pons, and medulla oblongata. It contains gray matter, including numerous groups of neurons called nuclei, as well as white-matter pathways carrying information between the spinal cord, cerebellum, and higher regions of the brain .¹

The brainstem participates in many fundamental physiological functions. Neural circuits within it contribute to the regulation of breathing, heart rate, blood pressure, swallowing, sleep and wakefulness, and arousal. It also contains nuclei associated with most cranial nerves, supporting functions such as eye movements, facial sensation and movement, hearing, balance, and swallowing .^1,2

Many major sensory and motor pathways pass through the brainstem between the spinal cord and higher brain regions. The brainstem is therefore both a communication route and an active processing center. It also communicates extensively with the cerebellum and contains networks that integrate sensory, motor, autonomic, and behavioral responses .¹

The brainstem is distinct from both the spinal cord and higher brain structures such as the cerebral cortex. The spinal cord connects the brain with much of the peripheral body and contains its own sensory, motor, and reflex circuits. The brainstem lies above it and contains additional nuclei and networks involved in cranial, autonomic, motor, and arousal-related functions .^1,2