You know what it looks like… but what is it called?
TAKE THE QUIZ“activating system”
We have one entry that includes the term activating system.
reticular activating system
noun: a part of the reticular formation that extends from the brain stem to the midbrain and thalamus with connections distributed throughout the cerebral cortex and that controls the degree of activity of the central nervous system (as in maintaining sleep and wakefulness and in making transitions between the two states)
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Merriam-Webster unabridged