Reference guide
Brainstem anatomy and function
Updated 04 October 2026 · An educational introduction
In this guide
The brainstem is the lower part of the brain. It sits in front of the cerebellum and continues downward into the spinal cord. Because it lies between the higher brain and the spinal cord, it provides an important route for messages travelling in both directions.
It is also involved in automatic functions that keep the body working, including breathing, heart rate, blood pressure regulation, swallowing, alertness, and protective reflexes. “Automatic” here means that these actions can happen without conscious planning.
Think of the brainstem as a busy junction: information from the body travels upward, instructions travel downward, and local networks help organise essential actions.
Anatomy of the brainstem
The brainstem is usually described from top to bottom as the midbrain, pons, and medulla oblongata. These regions are continuous with one another, but each has characteristic structures and connections.
The midbrain
The midbrain, also called the mesencephalon, is the uppermost part of the brainstem. It helps coordinate eye movements, visual and auditory responses, movement, alertness, and some sleep-related rhythms.
Important midbrain structures include the tegmentum, tectum, cerebral peduncles, and cerebral aqueduct. The tegmentum contains networks involved in movement and pain regulation. The tectum includes the superior and inferior colliculi, which help organise rapid responses to visual and sound information.
The pons
The pons lies between the midbrain and medulla. Its name means “bridge,” reflecting the many fibre pathways that connect the cerebrum, cerebellum, and lower brainstem.
Pontine networks contribute to movement coordination, facial sensation and movement, hearing, balance, sleep, and breathing patterns. The pons is not a single simple relay; it contains nuclei and pathways that help different parts of the nervous system exchange information.
The medulla oblongata
The medulla is the lowest part of the brainstem and continues into the spinal cord. It contains important centres and pathways involved in breathing, heart-rate regulation, blood-vessel tone, swallowing, coughing, sneezing, and vomiting.
Many signals between the brain and spinal cord pass through the medulla. It also contains nuclei associated with several cranial nerves and helps maintain stable internal conditions, a process called homeostasis.
The brainstem supports essential functions, but it does not work alone. Breathing, movement, sensation, and awareness depend on connected systems throughout the brain, spinal cord, and peripheral nerves.
Cranial nerves connected to the brainstem
Cranial nerves carry sensory information toward the brain and motor instructions away from it. Most cranial nerves are connected with brainstem nuclei, although the olfactory and optic nerves have different developmental and anatomical relationships.
Brainstem-related cranial nerves support functions including eye movement, facial sensation, hearing, balance, facial expression, swallowing, voice, tongue movement, and some internal organ control.
- Oculomotor and trochlear nerves: help control eye movement.
- Trigeminal nerve: carries much of the face’s sensation and supports chewing.
- Abducens nerve: helps move the eye outward.
- Facial nerve: supports facial expression, taste from part of the tongue, and some gland activity.
- Vestibulocochlear nerve: carries information related to hearing and balance.
- Glossopharyngeal and vagus nerves: contribute to swallowing, taste, voice, and internal organ regulation.
- Accessory and hypoglossal nerves: support neck, shoulder, and tongue movements.
General and special pathways
Cranial nerve fibres can be grouped by the kind of information they carry. General pathways handle broad sensory and motor functions, while special pathways are associated with senses such as hearing, balance, taste, and vision or with muscles that developed from particular embryonic structures.
Key points to remember
- The brainstem links the brain with the spinal cord.
- Its three main regions are the midbrain, pons, and medulla oblongata.
- It carries ascending sensory and descending motor pathways.
- It helps coordinate breathing, circulation, swallowing, sleep, and reflexes.
- Many cranial nerves connect with nuclei in the brainstem.
The brainstem is therefore both a passageway and an active control network. Learning its three major regions provides a useful foundation for exploring the spinal cord, cranial nerves, cerebellum, and wider nervous system.