Brain stem

The brain stem is the part of a humanoid brain that controls all vital functions.

The psi-wave device used by the Prytt was connected directly to the brain stem. 

In late 2366, the Zalkonian known as "John Doe" damaged his brain stem when his ship crash-landed on a planet. 

In 2369, while performing an autopsy on Hon-Tihl, Dr. Julian Bashir noted that Hon-Tihl's membrane permeability in the columnar cells in his brain stem were off. 

In 2373, The Doctor's 'daughter' Belle's brain stem was compromised after she severely hit her head.