A molecular model of epinephrine (a.k.a. adrenaline), a neurotransmitter responsible for processes in the sympathetic nervous system, such as the "fight or flight" response. Epinephrine regulates physiological functions such as heart rate, vasodilation/vasoconstriction, and metabolic rates. Atoms are colored dark gray (carbon), light gray (hydrogen), blue (Nitrogen) and red (oxygen).