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？单项选择题

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