Norepinephrine:

Norepinephrine, also known as noradrenaline, is a chemical with two functions. As a neurotransmitter, it sends signals across nerve endings to other nerve, muscle, or gland cells. As a hormone, it’s released by adrenal glands in response to stress and low-blood pressure. It’s essential to regulate arousal, attention, cognitive function, and stress reactions; increases alertness, mood, memory; and affects the sleep-wake cycle. Norepinephrine keeps steady in blood flow to skeletal muscles/contraction and glucose levels in the bloodstream. It affects the eyes, kidneys, pancreas, lymphoid organs, and intestines. Exercise and cold temperatures increase norepinephrine turnover. Also see Epinephrine