ENTERIC NERVOUS SYSTEM
The enteric nervous system (ENS) consists of plexuses within the wall of the digestive tract (see figure 16.2). The plexuses includesensory neurons that connect the digestive tract to the CNS;sympathetic and parasympathetic neurons that connect the CNS to the digestive tract; and (3) enteric neurons, located entirely within the enteric plexuses. A unique feature of enteric neurons isthat they are capable of monitoring and controlling the digestive tract independently of the CNS through local reflexes. For example, stretching of the digestive tract is detected by enteric sensory neurons, which stimulate enteric interneurons. The enteric inter-neurons stimulate enteric motor neurons, which stimulate glands to secrete. Although the ENS is capable of controlling the activities of the digestive tract completely independently of the CNS, normally the two systems work together. CNS control of parasympathetic branches of the vagus nerve and sympathetic nerves (primarily, the splanchnic nerves) can override the actions of enteric neurons. Hence, the ENS is an independent subdivision of the PNS that is integrated with the ANS.
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