Cranial nerves (autonomic fibers) ONLY carry ___ fibers.

Cranial nerves (autonomic fibers) ONLY carry ___ fibers.

• A. Parasympathetic
• B. Sympathetic
• C. Both
• D. Somatic

Answer: (A)

Parasympathetic fibers are what travel with certain cranial nerves. In the head, the autonomic output that uses cranial nerves comes from preganglionic parasympathetic neurons in nerves III, VII, IX, and X. They synapse in nearby ganglia (like the ciliary, pterygopalatine, submandibular, otic, and intramural ganglia) to control glands and smooth muscles, such as pupil constriction, tearing, salivation, and slow heart rate. Sympathetic fibers to the head do not ride inside these cranial nerves; they originate from the thoracic spinal cord and reach the head via the carotid plexus and other periarterial routes. So cranial nerves carrying autonomic fibers are exclusively parasympathetic in this context.

Parasympathetic fibers are what travel with certain cranial nerves. In the head, the autonomic output that uses cranial nerves comes from preganglionic parasympathetic neurons in nerves III, VII, IX, and X. They synapse in nearby ganglia (like the ciliary, pterygopalatine, submandibular, otic, and intramural ganglia) to control glands and smooth muscles, such as pupil constriction, tearing, salivation, and slow heart rate.

Sympathetic fibers to the head do not ride inside these cranial nerves; they originate from the thoracic spinal cord and reach the head via the carotid plexus and other periarterial routes. So cranial nerves carrying autonomic fibers are exclusively parasympathetic in this context.