Inhibitory presynaptic fibers to the gastrointestinal tract originate from which spinal segments?

Inhibitory presynaptic fibers to the gastrointestinal tract originate from which spinal segments?

• A. C3-C5
• B. T1-T4
• C. T5-T12
• D. T10-L1

Answer: (C)

Inhibitory control of the gastrointestinal tract is mediated by the sympathetic nervous system. The preganglionic sympathetic neurons that supply the abdomen lie in the intermediolateral cell column from about T5 through L2, and their fibers form the thoracic splanchnic nerves. These preganglionic fibers travel to prevertebral ganglia such as the celiac, superior mesenteric, or aorticorenal ganglia, where they synapse and then send postganglionic fibers to the GI organs. This pathway mainly covers the foregut through midgut and into the proximal hindgut, producing inhibition of motility and secretion and sphincter constriction. Therefore, the spinal segments giving rise to these inhibitory presynaptic fibers are in the T5–T12 range, making that option the best match.

Inhibitory control of the gastrointestinal tract is mediated by the sympathetic nervous system. The preganglionic sympathetic neurons that supply the abdomen lie in the intermediolateral cell column from about T5 through L2, and their fibers form the thoracic splanchnic nerves. These preganglionic fibers travel to prevertebral ganglia such as the celiac, superior mesenteric, or aorticorenal ganglia, where they synapse and then send postganglionic fibers to the GI organs. This pathway mainly covers the foregut through midgut and into the proximal hindgut, producing inhibition of motility and secretion and sphincter constriction. Therefore, the spinal segments giving rise to these inhibitory presynaptic fibers are in the T5–T12 range, making that option the best match.