Norepinephrine is a chemical in the body that acts as both a hormone and a neurotransmitter. It plays a crucial role in the body's "fight or flight" response, helping to prepare us for stressful situations. When we face danger, norepinephrine increases heart rate, blood pressure, and energy levels, allowing us to react quickly. In addition to its role in stress responses, norepinephrine is important for regulating mood and attention. Low levels of this chemical are often linked to conditions like depression and ADHD. Medications that affect norepinephrine levels can help improve symptoms in individuals with these disorders.