The neuroendocrine system of the gastrointestinal tract.

The use of increasingly refined techniques in endocrinologic research resulted in a challenge to the classical concept of hormones. The regulatory activity of the highly complicated neuroendocrine system is mediated not only by hormones but by neurotransmitters, paracrine substances, and possibly by substances secreted into the gastrointestinal lumen as well. The system is divided into the central and peripheral nervous system and the endocrine system. The latter consists of the endocrine glands and the disseminated endocrine system. Research into the activities of the system will result in important advances in the fields of physiology, pathophysiology and pathology.