Every second, your body performs essential tasks without requiring conscious attention. You breathe while you sleep, your heart keeps beating, your blood pressure adjusts as you stand up, and protective reflexes can make you cough or swallow before you have time to think about them.
Many of these processes depend on interconnected neural networks within and around the brainstem.
Located at the base of the brain, the brainstem connects the brain with the spinal cord and contains pathways and groups of nerve cells involved in movement, sensation, autonomic regulation, alertness, and important reflexes. It is made up of three main regions: the midbrain, pons, and medulla oblongata.
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The anatomical illustration accompanying this article highlights several of these structures, including the pons, medulla, spinal cord, sensory pathways, motor pathways, and the pyramidal decussation.
Understanding these structures helps explain how the nervous system coordinates communication between the brain and the rest of the body.
What Is the Brainstem?
The brainstem is the lower portion of the brain that forms a major connection between the brain, cerebellum, and spinal cord.
It consists of three regions:
Midbrain — the uppermost part of the brainstem
Pons — the middle portion
Medulla oblongata — the lowest portion, continuous with the spinal cord
The brainstem contains both gray matter, including groups of nerve-cell bodies called nuclei, and white-matter pathways, which carry signals between different parts of the nervous system. Ten of the 12 pairs of cranial nerves are associated with nuclei in the brainstem.
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Because so many pathways pass through this relatively compact region, the brainstem participates in a remarkably wide range of functions.
The Pons: More Than a “Bridge”
The word pons comes from Latin for “bridge,” an appropriate description for a structure that provides important connections between different parts of the nervous system.
The pons sits between the midbrain and medulla. It contains pathways connecting the cerebrum and spinal cord with the cerebellum, which plays an important role in coordinating movement and balance.
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The pons is also associated with several cranial nerves involved in functions involving the face, eyes, hearing, balance, and chewing.
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