Brainstem

The brainstem sits beneath the cerebrum and cerebellum, where the base of the skull gives way to the spinal cord. Picture a stalk about as thick as your thumb. From top to bottom, it is divided into three parts: the midbrain, pons, and medulla oblongata. The medulla, at the very bottom, connects directly to the spinal cord.

It is small, but it has many jobs.

• The midbrain is involved in eye movements, pupil responses, and the body's startle response to loud sounds.
• The pons acts as a bridge between the cerebrum and cerebellum and contributes to facial sensation, chewing movements, and fine-tuning the breathing rhythm.
• The medulla contains centers that regulate breathing, heartbeat, and blood pressure. Reflexes such as coughing, vomiting, and swallowing also occur here.

Ten of the 12 pairs of cranial nerves (numbers 3 through 12) emerge from the brainstem. Most of the cranial nerves that move the eyes, produce facial expressions, enable swallowing, and regulate the activity of the heart and internal organs pass through this region. Among them, the vagus nerve is a long nerve that begins in the medulla and extends down into the chest and abdomen.

Inside the brainstem is the reticular formation, a network of interconnected nerve cells. It maintains wakefulness and helps shift between drowsiness and alertness. It is also partly responsible for the sudden alertness you feel when your body senses danger.

The brainstem is a kind of crossroads. Motor signals traveling from the cerebrum to the muscles pass through the brainstem on their way to the spinal cord. In the other direction, sensory information from the skin, muscles, and joints passes through the brainstem to reach the thalamus and cerebrum. One side of the brain controls the opposite side of the body because bundles of nerves cross from one side to the other along this route, mainly in the lower medulla.

The autonomic nervous system is also closely connected to the brainstem. Centers that adjust heart rate, breathing, and digestion to the body's condition are concentrated here, so the brainstem can be described as the place that sets the body's basic operating conditions.

Theoretical texts on Integrative Manual Therapy (IMT) describe the brainstem as an important center where sensory input converges. They explain that sensory information from receptors in the muscles, fascia, joints, and internal organs enters through the dorsal roots of the spinal cord and is transmitted to the cerebellum, cerebral cortex, brainstem, and various parts of the autonomic nervous system. This approach holds that sensory input from fascia and joints has a major influence on the central nervous system, so hands-on work with the body is considered to be linked to the nervous system's state of regulation. This is IMT's perspective on explaining the effects of manual therapy. The emphasis placed on work at the craniovertebral junction, where the neck meets the head, follows the same line of thinking.

Most of the brainstem's work happens without conscious awareness. Continuing to breathe while asleep, the airway automatically closing when you swallow, and blood pressure adjusting when you stand up suddenly are all part of its work. That is why you rarely notice its presence in everyday life.

Still, you may get a faint sense of its work at moments like these.

• When you feel tense, your breathing becomes shallow and your heart beats faster.
• When you breathe out slowly and deeply, you feel calmer.
• When the back of your neck has been stiff and aching for a long time, your head may feel foggy or your eyes may become tired.

You cannot work on the brainstem directly, but you can help the functions it regulates operate more comfortably.

• Breathe slowly: Breathing in for about 4 seconds and out for 6 seconds for just a few minutes may help you feel your body settle down.
• Loosen up your neck and shoulders: Sitting for a long time with your head jutting forward makes the back of your neck stiff. Once an hour, get up and gently move your head and shoulders.
• Get enough sleep: Your sleep schedule needs to be consistent for the system that shifts between alertness and drowsiness to function regularly.
• Be mindful of head and neck injuries: If your neck receives a major impact while driving or exercising, get it checked even if the symptoms seem mild.