The gut as a neurological organ

We refer to the gut as a neurological organ to emphasize the particular imp ortance of the nervous system in the regulation of digestive functions, giv en that the gastrointestinal tract is innervated by five different classes of neurons: intrinsic enteric neurons, vagal afferents, spinal afferents, p arasympathetic efferents and sympathetic efferents. Virtually each aspect o f digestive activity is under the regulatory influence of neurons, among wh ich the enteric nervous system (ENS) plays the most important part. The ENS acts like a brain in the gut that functions independently of the central n ervous system, contains programmes for a variety of gastrointestinal behavi ours and governs the activity of all gastrointestinal effector systems acco rding to need. Intrinsic sensory neurons supply the ENS with the kind of in formation that this system requires for its autonomic control of digestion, whereas extrinsic afferents notify the brain about any data that are relev ant to energy and fluid homeostasis and the sensation of discomfort and pai n. Many diseases of the gut, particularly the functional bowel disorders, s eem to be related to dysfunction of the ENS and other components of the gas trointestinal innervation. The ENS and extrinsic afferents are hence prime targets for the therapeutic management of gut diseases and for the relief o f the pain and discomfort associated with these disorders.