Norepinephrine, also known as noradrenaline, is a neurotransmitter and hormone that plays a key role in the body’s fight or flight response. It is primarily involved in states of arousal and alertness, increasing heart rate, blood pressure, and blood sugar levels to prepare the body for rapid action. In the brain, norepinephrine affects attention, perception, and motivation, contributing to heightened awareness and readiness. It is produced in both the brain and the adrenal glands and is closely related to dopamine, sharing many pathways and functions. Disruptions in norepinephrine levels are associated with several medical conditions, including depression, anxiety, and post-traumatic stress disorder (PTSD).