text: The reason we don't fall off the bed while sleeping is due to a knob-like structure, called the pons, located at the base of the brainstem. \n\nThe pons assists in arousal, control of autonomic functions (breathing, heart rate), relays sensory information between the cerebrum and cerebellum, and finally, sleep.\n\nWhen we sleep, the pons virtually paralyzes the main motor muscles of the body and therefore stops us from possibly rolling off the bed. \n\nIn sleep-walkers, the pons does not function properly, allowing the body to function and move normally, even though the person's brain is very much asleep.