Brain stem: Definition, Function, Location, Structure and Associated Injuries

It is the region of the brain that connects it to the spinal cord. It consists of the mesencephalon, the medulla oblongata and the protuberance.

The motor and sensory neurons travel through the brainstem allowing the relay of signals between the brain and the spinal cord . Most cranial nerves are found in the brainstem .

The brainstem manages vital functions such as breathing, circulation, sleep, digestion and swallowing.

These are the involuntary functions controlled by the autonomic nervous system. The brainstem also controls the reflexes and coordinates the motor control signals sent from the brain to the body.

This region of the brain also controls the autonomous life support functions of the peripheral nervous system. The fourth cerebral ventricle is located in the brainstem, posterior to the pons and the medulla oblongata.

This ventricle filled with cerebrospinal fluid is continuous with the cerebral aqueduct and the central canal of the spinal cord.


The brainstem controls several important functions of the body, including:

  • Excitement.
  • Breathing.
  • Blood pressure control.
  • Digestion.
  • Heart rate.

Other autonomous functions:

It transmits information between the peripheral nerves and the spinal cord to the upper parts of the brain

In addition to linking the brain and the spinal cord, the brainstem also connects the brain to the cerebellum . The cerebellum is important to regulate functions such as coordination of movement, balance and muscle tone.

It is located above the trunk of the brain and below the occipital lobes of the cerebral cortex.

The nerve tracts that travel through the brainstem transmit signals from the cerebellum to areas of the cerebral cortex that are involved in motor control. This allows the coordination of the fine motor movements necessary for activities such as walking or playing video games.


Directionally, the brainstem is at the junction of the brain and the spine. It is anterior to the cerebellum.


The brainstem consists of the mesencephalon and parts of the hindbrain, specifically the pons and marrow. A main function of the mesencephalon is to connect the three main brain divisions: forebrain, mesencephalon, and rhombencephalon.

The main mesencephalon structures include the tectum and the cerebral peduncle. The tectum is composed of rounded protuberances of brain matter that are involved in visual and auditory reflexes.

The cerebral peduncle consists of large bundles of nerve fibers that connect the anterior brain with the posterior brain.

The rhombencephalon is composed of two subregions known as metencephalon and myelencephalon. The metencephalon is composed of the protuberance and the cerebellum.

The protuberance helps in the regulation of breathing, as well as in the states of sleep and arousal. The cerebellum transmits information between the muscles and the brain.

The myelencephalon consists of the medulla oblongata and functions to connect the spinal cord with superior brain regions. The cord also helps regulate autonomic functions, such as breathing and blood pressure.

Brainstem injuries

Brainstem injuries caused by trauma or stroke can cause difficulties with mobility and coordination of movement. Activities such as walking, writing and eating become difficult and the individual may require lifelong treatment.

The stroke that occurs in the brainstem causes the destruction of brain tissue that is needed to direct the body’s vital functions, such as breathing, heart rate and swallowing.

stroke occurs when the blood flow to the brain is interrupted, most commonly by a blood clot.

When the brainstem is damaged, signals between the brain and the rest of the body are interrupted. Stroke can cause breathing problems, heart rate, hearing and speech. It can also cause paralysis of the arms and legs, as well as numbness in the body or on one side of the body.

Cerebral strokes are often caused by mechanical blockage of the blood vessels, which can occur during a high-speed chiropractic manipulation of the neck, or some other event that causes a very forceful neck movement, such as after a roller coaster.

The vertigo (rotation) is a common symptom of early stroke.

A large blow to the upper brain stem can cut the connections between the brain and the body. In such a case, a person can retain consciousness and intelligent thinking, but be completely paralyzed except for eye movements. This is called blocking syndrome.