brainstem

https://doi.org/10.1351/goldbook.11651
Unpaired subdivision of the brain, continuous with the spinal cord, that includes the thalamus, hypothalamus, pons, medulla oblongata, and the mesencephalon.
Source:
PAC, 2015, 87, 841. (IUPAC Glossary of terms used in neurotoxicology (IUPAC Recommendations 2015)) on page 854 [Terms] [Paper]