The brainstem is the region of the brain that connects the cerebrum with the spinal cord. It consists of the midbrain, medulla oblongata, and the pons. Motor and sensory neurons travel through the brainstem allowing for the relay of signals between the brain and the spinal cord. Most cranial nerves are found in the brainstem.
The brainstem coordinates motor control signals sent from the brain to the body. This brain region also controls life supporting autonomic functions of the peripheral nervous system. The fourth cerebral ventricle is located in the brainstem, posterior to the pons and medulla oblongata. This cerebrospinal fluid-filled ventricle is continuous with the cerebral aqueduct and the central canal of the spinal cord.
In addition to linking the cerebrum and spinal cord, the brainstem also connects the cerebrum with the cerebellum. The cerebellum is important for regulating functions such as movement coordination, balance, equilibrium, and muscle tone. It is positioned above the brainstem and beneath the occipital lobes of the cerebral cortex. Nerve tracts traveling through the brainstem relay signals from the cerebellum to areas of the cerebral cortex that are involved in motor control. This allows for the coordination of fine motor movements needed for activities such as walking or playing video games.
The brainstem also controls several important functions of the body including:
- Blood pressure control
- Heart rate
- Other autonomic functions
- Relays information between the peripheral nerves and spinal cord to the upper parts of the brain
Directionally, the brainstem is located at the juncture of the cerebrum and the spinal column. It is anterior to the cerebellum.
The brainstem is composed of the midbrain and portions of the hindbrain, specifically the pons and medulla. A major function of the midbrain is to connect the three major brain divisions: forebrain, midbrain, and hindbrain.
Major structures of the midbrain include the tectum and cerebral peduncle. The tectum is composed of rounded bulges of brain matter that are involved in visual and auditory reflexes. The cerebral peduncle consists of large bundles of nerve fiber tracts that connect the forebrain to the hindbrain.
The hindbrain is composed of two subregions known as the metencephalon and myelencephalon. The metencephalon is composed of the pons and cerebellum. The pons assists in the regulation of breathing, as well as states of sleep and arousal. The cerebellum relays information between muscles and the brain. The myelencephalon consists of the medulla oblongata and functions to connect the spinal cord with higher brain regions. The medulla also helps to regulate autonomic functions, such as breathing and blood pressure.
Injury to the brainstem caused by trauma or stroke can lead to difficulties with mobility and movement coordination. Activities such as walking, writing, and eating become difficult and the individual may require life-long treatment. Stroke that occurs in the brainstem causes the destruction of brain tissue that is needed for the direction of vital body functions such as respiration, heart rhythm, and swallowing. A stroke occurs when blood flow to the brain is disrupted, most commonly by a blood clot. When the brainstem is damaged, signals between the brain and the rest of the body are disrupted. Brainstem stroke can cause problems with breathing, heart rate, hearing, and speech. It may also cause paralysis of the arms and legs, as well as numbness in the body or on one side of the body.
Murphy, Andrew. "Brainstem." Dr. Jeremy Jones, Radiopaedia, 2005.
Pietrangelo, Ann. "Brain Stem Stroke." Healthline, May 23, 2018.