Which of the following statements about the sympathetic nervous system is correct?
关于交感神经系统，下列哪项陈述是正确的？

Question

BlackTom AI · Accepted Answer

Preganglionic sympathetic neurons characteristically diverge, so a single preganglionic fiber branches and synapses on many postganglionic (sympathetic ganglion) neurons. This divergence is a fundamental organizational principle that produces coordinated, widespread sympathetic effects.

Relevant knowledge points:
- Sympathetic outflow is "thoracolumbar": preganglionic neuron cell bodies lie in the intermediolateral cell column of the spinal cord from T1 to L2 (not only thoracic).
- Preganglionic fibers travel to paravertebral (sympathetic chain) or prevertebral ganglia and can branch extensively, producing a high divergence ratio (classically on the order of 1:20 or more; in some tissues much higher).
- The enteric nervous system provides local control of the gut but receives modulatory sympathetic and parasympathetic input; the gastrointestinal tract is not devoid of sympathetic innervation.
- Not every histologic tissue is innervated (for example, cartilage and some epithelial layers lack direct autonomic innervation), so “every tissue” is not strictly true.

Step-by-step reasoning:
1. Identify where sympathetic preganglionic neurons reside: T1–L2 spinal segments (thoracolumbar), so option claiming “all are in thoracic spinal cord” is incorrect.
2. Track a preganglionic axon: it enters the sympathetic chain and sends collaterals to multiple ganglia and postganglionic cells; this anatomical branching explains how one preganglionic neuron can influence many postganglionic neurons.
3. Consider functional consequence: divergence allows a single central signal to activate multiple effectors (e.g., sweat glands, blood vessels, heart), producing a coordinated fight-or-flight response.
4. Compare alternatives: (2) “Every tissue” is too absolute and false; (3) wrong anatomical location; (4) false because the GI tract receives sympathetic modulation in addition to intrinsic enteric control.

Therefore the correct statement is: “A single sympathetic preganglionic neuron regulates the function of many sympathetic ganglion neurons,” which matches the provided answer.

Which of the following statements about the sympathetic nervous system is correct? 关于交感神经系统，下列哪项陈述是正确的？Single choice

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