Figure 4.

Nervous control of the gastrointestinal tract: the neural control of the gastrointestinal tract depends on the extrinsic nerves of the autonomic nervous system and the intrinsic neural networks, also known as the Enteric Nervous System (ENS). The extrinsic nerves are nerve fibers that originate outside the gastrointestinal tract and innervate its organs under the control of the autonomic (sympathetic and parasympathetic) nervous system, while regulating the activities of the neurons of the ENS. However, the ENS also functions autonomously, independently assisting the motor and secretory activities of the gastrointestinal tract. It is characteristic that even if the intestinal nerves of the autonomic system are injured or sectioned, many secretory and motor functions of the intestine are kept under the control of the ENS. Previously, the prevailing theory was that the ENS was an extension of the parasympathetic autonomic nervous system, whereas, today, there is the understanding that it constitutes an autonomic neural plexus involved in reflex and other activities of the gastrointestinal tract independently of exogenous nerve stimuli [74]. Credits: Original figure by I.A. Charitos.