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: Understanding the Question:
The question asks to identify the specific sacral spinal nerves that belong to the craniosacral division of the autonomic nervous system.

Step 2: Key Concept and Approach:
The autonomic nervous system has two major divisions:
1. Sympathetic division (thoracolumbar outflow from $T_1$ to $L_2$).
2. Parasympathetic division (craniosacral outflow).
The "sacral" part of the craniosacral outflow originates from the grey matter of specific sacral segments of the spinal cord.

Step 3: Detailed Explanation:

• Craniosacral Outflow: The parasympathetic preganglionic fibers emerge from the brainstem via cranial nerves (III, VII, IX, X) and from the sacral region of the spinal cord.

• Sacral Segments: The sacral parasympathetic fibers arise specifically from the second, third, and fourth sacral spinal cord segments ($S_2, S_3, S_4$).

• these preganglionic fibers travel through the pelvic splanchnic nerves to synapse in ganglia close to or within pelvic organs.

• In terms of sacral spinal nerves (represented as Roman numerals I to V corresponding to $S_1$ to $S_5$), these are the II, III, and IV nerves.


Step 4: Final Answer:
The spinal nerves of the sacral region involved in the craniosacral division are II, III, and IV.