Norepinephrine primarily acts as a neurotransmitter in the central nervous system, regulating mood and emotions.

Norepinephrine is a hormone produced by the adrenal cortex primarily involved in regulating blood pressure and heart rate.

Norepinephrine is a neurotransmitter released by postganglionic sympathetic neurons, exerting effects on target organs via adrenergic receptors.

Norepinephrine is a hormone secreted by the posterior pituitary gland, responsible for regulating water balance and blood pressure.