Norepinephrine: Fight or Flight
Norepinephrine is also a neurotransmitter made from the amino acid tyrosine. Norepinephrine is found in both the peripheral nervous system and in the brain. In the peripheral nervous system, it is involved in the sympathetic nervous system, which energizes the body for high levels of energy expenditure during our "fight or flight" response to stress. About half of all the norepinephrine in the brain is found in the locus coeruleus in the hindbrain, where it is involved in waking us up (arousal).