Plan
► Structural and functional organization of medulla oblongata.
► Structural and functional organization of pons Varolii.
► Structural and functional organization of mesencephalon (midbrain).
► Structural and functional organization of diencephalon.
► Structural and functional organization of cerebellum.
► Function of reticular formation of brainstem.
The brainstem is a part of the brain consisting of the medulla oblongata, the pons Varolii, and the mesencephalon (midbrain). All formations of the brainstem perform three basic functions: reflex, conducting and regulatory functions. Most of the brainstem formations lose segmental structure inherent to the spinal cord. Only in the caudal sections of the medulla oblongata bordering on the spinal cord, some signs of segmental structure are preserved which is reflected in the topography of nuclei of the cranial nerves.
Structural and Functional Organization of Medulla Oblongata
The medulla oblongata is the most caudal part of the brainstem located between the pons and the spinal cord. The medulla contains nuclei of IX-XII cranial nerves separated by the conducting pathways ascending and descending through the medulla.
The nuclei of IX cranial nerve (glossopharyngeal nerve, or n. glossopharyn-geus) supply muscles and mucosa of the oral cavity. They participate in different food reflexes (chewing, swallowing, salivary reflexes).
The nuclei of X cranial nerve (n. vagus) supply most of the internal organs (the heart, lungs, gastrointestinal organs, etc.). Vagus is the most potent parasympathetic nerve of the ANS.
The nucleus of XI cranial nerve (accessory nerve, or n. accessorius) is a motor nucleus. It supplies skeletal muscles - sternocleidomastoid and trapezius muscles. Participates in motor actions, such as rotating and tilting the head, raising shoulder girdle and adduction of scapulars toward the spine.