Myelencephalon (Medulla oblongata)

The medulla oblongata is the most caudal part of the brain.

Forming the junc. of the brain w/ the spinal cord.

Ant. the medulla lies against the basilar portion of the occipital bone.

Pos. it abuts the ventral surface of the cerebellum.

Desc. pyramidal (motor) tracts and asc. spinothalamic tracts (pain and T° sensation) decussate as they pass via medulla.

CN nuclei located in the medulla:

• • Inf. portions of CN V (trigeminal)

  • CN VIII (vestibulocochlear).

  • CN IX (glossopharyngeal)

  • CN X (vagus)

  • CN XI (accessory)

  • CN XII (hypoglossal).

The medulla also contains the nuclei for a variety of modulatory asc. and desc. pathways:

• • Serotonergic tracts

  • adrenocorticotropic

  • endorphin

  • melanocyte stimulating hormone

  • adrenergic fibers.

These sys are involved in modulating asc. and desc. tracts, and also provide input into the reticular activating sys. more rostrally.