Question

Choose among the following spinal nerves of sacral region that form the part of cranio sacral division.

• A. I, III & V
• B. I, II & III
• C. II, III & IV
• D. II, IV & V

Hint:

Always associate the parasympathetic system with "craniosacral" outflow ($S_2, S_3, S_4$, i.e., II, III, IV sacral nerves).
Associate the sympathetic system with "thoracolumbar" outflow ($T_1 - L_2$).

Answer 1

The Correct Option is C

Step 1: Recall the two outflows of the autonomic system.
The sympathetic system exits from thoracic and lumbar segments, while the parasympathetic system exits from the brain through cranial nerves and from the sacral spinal segments, together called the craniosacral outflow.
Step 2: Zoom into the sacral part.
Not every sacral spinal nerve carries parasympathetic fibres, only a specific middle stretch of the sacral segments contributes to this outflow.
Step 3: Identify the exact segments.
The parasympathetic fibres in the sacral region arise from the second, third and fourth sacral nerves, the first and fifth sacral segments are not part of this outflow.
Final answer: Option 3, spinal nerves II, III and IV.