És, az üzenetküldögetés: idegek és mirigyek - és ez a kettő = egy !

... Except for this anatomical difference, the chemical signaling in the neural and endocrine systems is remarkably similar in mechanism. Even some of the chemical messengers are common to both systems. Epinephrine and norepinephrine, for example, serve as neurotransmitters in certain synapses of the brain and smooth muscle and also as hormones regulating fuel metabolism in the liver and in muscle. Although the neural and endocrine systems were traditionally treated as separate entities, it has become clear that in the regulation of metabolism they merge into a single neuroendocrine system.

Lehninger-Nelson-Cox: Principles of Biochemistry, 746.o.