US High School Psychology Complete Practice Exam 2026

The reticular activating system (RAS) is the correct answer because it plays a crucial role in regulating arousal, alertness, and the transition between sleep and wakefulness. This system is a network of neurons located in the brain stem that send signals to various parts of the brain, including the thalamus, which serves as a relay station for sensory information. By doing so, the RAS is essential for maintaining consciousness and behavioral arousal. When the RAS is activated, it enhances alertness and attention, while its inactivity can lead to sleep or a state of reduced arousal.

In contrast, the cerebellum primarily focuses on the coordination of voluntary movements and balance, the limbic system is more involved in emotional responses and memory, and the cerebral cortex is responsible for higher-level processing like decision-making and reasoning. While these other structures contribute to various functions in the brain, they do not specifically determine arousal like the reticular activating system does.