Why are hormones and neurotransmitters different from each other?
A hormone, by definition, is a compound produced by an endocrine gland and released into the bloodstream where it can find it's target cells at some distance from it's actual site of release. A neurotransmitter on the other hand is a compound released from a nerve terminal. When an electrical impulse travels to the end of a nerve cell, it stimulates the terminal of this cell to secrete a chemical signalling molecule at a special junction between nerve cells called a synapse. These nerve terminals are in direct apposition with their target cells to ensure rapid and specific delivery of the signal. This mode of transmission is in general much faster than the endocrine transmission I mentioned above. Both target cells possess receptors for the signalling molecule and may produce identical biochemical responses, it's just a question of the release mechanism that determines whether or not a given molecule is a neurotransmitter or a hormone. So, in the case of adrenaline, it's a hormone when the adrenal gland releases it into the bloodstream and it goes to the heart or the lungs OR it's a neurotransmitter when it is released from a stimulated presynaptic nerve cell and acts on it's neighbouring postsynaptic cell. Source: http://www.madsci.org/posts/archives/2000-04/956588883.Ns.r.html you cannot make a neurotrans, mitter but you can make a hor mone