This 2014 rodent study provided further information on the locus coeruleus segment of the brainstem:
“The brainstem nucleus locus coeruleus is the primary source of norepinephrine to the mammalian neocortex.
Neurons in the locus coeruleus maintain segregated connections to brain regions with distinctly different functions. Specifically, cells that communicate with the prefrontal cortex, a region involved in cognition and executive function, are characterized by properties that allow for independent and asynchronous modulation of operations in this area, compared with those that project to the motor cortex and regulate movement generation.”
http://www.pnas.org/content/111/18/6816.full “Heterogeneous organization of the locus coeruleus projections to prefrontal and motor cortices”