Arousal System

The arousal system activates the body for action, ranging from increased heartrate to emotional responses, and is essential for maintaining wakefulness. It primarily functions through the autonomic nervous system (ANS) and the central nervous system (CNS) to regulate alertness, wakefulness, and physiological responses. It involves the brainstem, thalamus, and cortex to modulate states of consciousness, reactivity, and stress responses. Key components of the arousal system include:

• Ascending reticular activating system (ARAS), in the brainstem, regulates wakefulness and alerts the cortex.
• Autonomic nervous system (ANS) controls involuntary physiological arousal, such as heartrate and blood pressure, through the sympathetic (fight or flight) and parasympathetic branches.
• Neurotransmitter systems — locus coeruleus-norepinephrine (LC-NE) system and other neurotransmitters (serotonin, dopamine, acetylcholine) — modulate physiological arousal.