The stalklike part of the brain which connects the forebrain (diencephalon and cerebrum) with the spinal cord is called the brainstem. From below upward, it consists of the medulla oblongata, pons and midbrain.

It is composed of nerve fibres and nerve cells. The nerve cells like spinal cord don’t create one central mass of grey matter; instead majority of them are aggregated to create well defined nuclei. Majority of the fibres in the brainstem are arranged longitudinally in the creation of tracts as in the spinal cord.

The brainstem nuclei have the following 2 types:

  • Nuclei of last 10 cranial nerves (i.e., 3rd-12th cranial nerves).
  • Other termed nuclei like red nucleus, substantia nigra, pontine nuclei, olivary nuclei, etc

The brainstem includes the diffuse system of cells and fibres named reticular formation along with well-defined tracts and nuclei. A number of the cells of reticular formation create essential centers, viz. cardiac, respiratory, vasomotor etc. They’re of Great Physiological Relevance, in spite of the fact that these centers aren’t anatomically demonstrable.