My main confusion is what differentiates the action of a transmitter substance as a neurotransmitter and as a hormone. For example, when norepinephrine is being talked about as transmitter substance that modulates brain responsiveness and information processing, it's a neurotransmitter. But when norepinephrine is involved in the functions of the autonomic nervous system (ANS), does it work as a hormone or a neurotransmitter?
Quoting from Physiology of Behavior, by N. Carlson, 2013 edition:
"Neurons in the central nervous system contain a1- and a2-adrenergic receptors and b1- and b2-adrenergic receptors. All four kinds of receptors are also found in various organs of the body besides the brain and are responsible for the effects of epinephrine and norepinephrine when they act as hormones outside the central nervous system."
So does that mean that whenever norepinephrine works outside the CNS, it works as a hormone?