Norepinephrine acts as both a hormone and what?

Norepinephrine acts as both a hormone and a neurotransmitter, which is essential for understanding its role in the body. As a neurotransmitter, norepinephrine is released by nerve endings in the central and peripheral nervous systems, where it plays a crucial role in transmitting signals between neurons. This influences various functions, such as mood regulation, alertness, and response to stress.

In addition to its neurotransmitter role, norepinephrine is released from the adrenal medulla during stress responses, functioning as a hormone that impacts various organs and systems throughout the body. This dual function allows norepinephrine to effectively modulate physiological responses, making it integral to functions such as the fight-or-flight response.

The other options do not accurately describe the role of norepinephrine. For instance, it is not a neurotransmitter inhibitor, nor does it act as a muscle stimulant or an amino acid. Understanding its dual nature helps in grasping the broader implications of how neurotransmitters and hormones interact within the body.