Which region of your midbrain plays a role in arousing you to a state of alertness when, for example, in the dark of your apartment you accidentally stumble over your roommate who has passed out on the floor?

The brainstem reticular formation (BRF) is not a different structure in the brain but is distributed throughout the core of the brainstem.

It is dessipiated from medulla into the midbrain. It plays a major role in the arousal and consciousness of the brain.

It also keep the body alert in conditions such as moving in dark, moving on stairs.

It also controls the movements and sensation and visceral functions.