thus , the largest brain na system , which emanates from locus coeruleus and innervates vast regions of the neuroaxis , is largely activated in the same situations and by the same mechanisms ( e.g . blood-volume and chemoreceptors ) as the sympathetic system , and may provide part of the central machinery for the anxiety reaction associated with hypercapnia as well as the withdrawal reactions after clonidine or morphine .
C0006104
brain
C0023951
locus