What is the brain stem?
The brain stem is the developmentally oldest part of the brain. Together with the diencephalon, sometimes also with the cerebellum and parts of the terminal brain, it is often referred to synonymously as the brain stem. However, this is not correct: the brain stem includes all parts of the brain that developed during embryonic development from the so-called second and third cerebral vesicles. The brain stem, on the other hand, includes all parts of the brain except the cerebrum.
The brainstem consists of the midbrain (mesencephalon), the bridge (pons) and the medulla oblongata (medulla oblongata, afterbrain or myelencephalon). The bridge and cerebellum are also called the metencephalon (hindbrain). Together with the myelencephalon (medulla oblongata), it forms the rhombic brain (rhombencephalon).
Midbrain
The midbrain (mesencephalon) is the smallest section of the brain. You can read more about it in the article Midbrain.
Bridge (brain)
The bridge (pons) in the brain is a strong white bulge at the base of the brain above the medulla oblongata. It is connected to the cerebellum by a cord called the cerebellar peduncle.
Medulla oblongata
The medulla oblongata forms the junction with the spinal cord. You can read more about this section of the brain in the article Medulla oblongata.
What is the function of the brainstem?
The brainstem is responsible for essential life functions such as controlling heart rate, blood pressure and breathing. It is also responsible for important reflexes such as the eyelid closure, swallowing and coughing reflex. Sleep and the various sleep and dream phases are also controlled here.
Within the bridge runs the pyramidal pathway – the connection between the motor cortex and the spinal cord, which is important for voluntary motor signals (i.e. voluntary movements). Through the pons, these signals, which come from the cerebral cortex, are transmitted to the cerebellum.
The brainstem is traversed by the formatio reticularis – a net-like structure of nerve cells and their processes. It is involved in various autonomic functions of the organism, such as the control of attention and the state of alertness. Circulation, breathing and vomiting are also controlled here.
Where is the brain stem located?
The brainstem is located in the lower part of the skull at the base of the skull, hidden by the cerebrum and cerebellum. Downward, it merges with the spinal cord with an ill-defined boundary – this area is called the medulla oblongata (medulla oblongata). In this area, the pyramidal junction, the nerve tracts coming from the brain cross to the opposite side.
What problems can the brainstem cause?
When nerve tracts leading within the brainstem to cranial nerve nuclei located further downstream are damaged on both sides, pseudobulbar paralysis develops. The main symptoms are speech and swallowing disorders, impaired tongue mobility, and hoarseness.
When the cerebrum is damaged alone, vital functions are maintained only by the brainstem. In what is known as a waking coma, the affected person is awake but does not gain consciousness and cannot make contact with their surroundings.
A brainstem infarct can affect those areas that are important for consciousness or breathing. In such a case, the lesion is life-threatening.
