Epinephrine HCl, a compound functioning as a hormone, neurotransmitter, and medication, is synthesized by adrenal glands and some neurons. It is essential in the fight-or-flight response, enhancing blood flow to muscles, heart output, pupil dilation, and blood sugar levels through its interaction with alpha and beta receptors. Epinephrine HCl is present in various animals and some unicellular organisms.