The sensory neurons of the ENS supply the mucosal epithelium. Some of the sensory neurons also function as chemoreceptors that are activated by the presence of certain chemicals in food located in the lumen of a GI organ. Other sensory neurons function as stretch receptors and are activated when food distends (stretches) the wall of a GI organ.
Autonomic Nervous System (ANS)
The ENS can function independently. However, it is subject to regulation by neurons of the ANS. The Vagus nerves (CNX) supply parasympathetic fibres to most of the GI tract with the exception of the last half of the large intestine which is supplied by parasympathetic fibres from the sacral spinal cord. In general, parasympathetic stimulation of the GI tract causes increased GI secretions and motility by increasing the activity of the ENS neurons. The parasympathetic nerves form neural connections with the ENS. Sympathetic nerves that supply the GI tract arise from the thoracic and upper lumbar regions of the spinal cord and like the parasympathetic nerves, they form neural connections with the ENS. In general, sympathetic nerves that supply the GI tract cause a decrease in GI secretions and motility by inhibiting the neurons of the ENS. Emotions such as anger, fear, and anxiety may slow digestion because they stimulate the sympathetics. Most ENS neurological activity happen by Gastrointestinal Reflex pathways feeding information to the CNS to activate or inhibit regions of the GI tract.
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