From which levels do parasympathetic preganglionic neurons exit the brainstem or spinal cord?

From which levels do parasympathetic preganglionic neurons exit the brainstem or spinal cord?

• A. C1-C4
• B. S2-S4
• C. L1-L2
• D. T1-T4

Answer: (B)

Parasympathetic preganglionic neurons come from a craniosacral outflow, meaning their cell bodies reside in brainstem nuclei and in the sacral spinal cord. The spinal component exits the CNS at the sacral levels S2 through S4, traveling with the pelvic splanchnic nerves to innervate pelvic organs and the distal gut. The brainstem portion exits via the cranial nerves III, VII, IX, and X. The other options reflect sympathetic outflow (thoracic and upper lumbar) or non-parasympathetic origins, so they don’t fit.

Parasympathetic preganglionic neurons come from a craniosacral outflow, meaning their cell bodies reside in brainstem nuclei and in the sacral spinal cord. The spinal component exits the CNS at the sacral levels S2 through S4, traveling with the pelvic splanchnic nerves to innervate pelvic organs and the distal gut. The brainstem portion exits via the cranial nerves III, VII, IX, and X. The other options reflect sympathetic outflow (thoracic and upper lumbar) or non-parasympathetic origins, so they don’t fit.