Rev Esp Enferm Dig
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The only non-general sensation that can be elicited from the gastrointestinal (GI) tract is that of pain, which can go from slight discomfort to severe pain. However, in certain parts of the intestine, such as the rectum and gastroesophagus, the sensation of pain can be preceded by a non-painful sensation of distension at low levels of stimulation. GI pain is often dull, poorly defined and difficult to pinpoint. ⋯ In any case, the number of afferent nociceptive fibers in the intestine is minimal, and this accounts for the fact that large areas of the GI tract appear to be insensitive or to require considerable stimulation before pain can be elicited. The few afferent nociceptive fibers contained in the sympathetic nerves can excite quite a few second order neurons in the medulla spinalis, which in turn generate an extensive divergence within the medulla spinalis and brain stem, including at times long supraspinal branches. This divergent input can activate different motor, autonomous and sensory systems, thus triggering the general reactions which characterize visceral nociception: diffuse pain which is difficult to pinpoint, referred at times to somatic areas, and autonomous and somatic reflexes resulting in prolonged motor activity.