From the Guidelines
The parasympathetic cranial nerves are classified as General Visceral Efferent (GVE) rather than General Somatic Efferent (GSE) or Special Visceral Efferent (SVE). The parasympathetic cranial nerves include:
- Cranial nerve III (oculomotor)
- Cranial nerve VII (facial)
- Cranial nerve IX (glossopharyngeal)
- Cranial nerve X (vagus)
These nerves carry GVE fibers that innervate smooth muscles and glands, as mentioned in 1.
In contrast, GSE fibers are found in cranial nerves III, IV, VI, and XII, which control extraocular muscles and tongue muscles.
SVE fibers are found in cranial nerves V, VII, IX, X, and XI, which innervate muscles derived from the branchial arches, as seen in 1 and 1.
This classification system is based on embryological origin and function of the muscles being innervated.
Parasympathetic fibers specifically target visceral structures like glands, smooth muscle, and cardiac tissue, which is why they are classified as GVE rather than GSE or SVE.
The table below summarizes the classification of parasympathetic cranial nerves:
Cranial Nerve Classification III (oculomotor) GVE VII (facial) GVE IX (glossopharyngeal) GVE X (vagus) GVE
From the Research
Parasympathetic Cranial Nerves Classification
The parasympathetic cranial nerves can be classified into General Somatic Efferent (GSE) and Special Visceral Efferent (SVE) based on their functions.
- The glossopharyngeal nerve (IX) contains parasympathetic efferent fibers for the parotid gland 2, which can be classified as SVE.
- The vagus nerve (X) contains parasympathetic efferent fibers for intrathoracic and abdominal organs 2, which can also be classified as SVE.
- There is no evidence to suggest that any of the parasympathetic cranial nerves are classified as GSE, as GSE fibers are typically involved in the innervation of skeletal muscles, whereas parasympathetic fibers are involved in the innervation of smooth muscles and glands.
Summary of Parasympathetic Cranial Nerves
- Glossopharyngeal nerve (IX): SVE
- Vagus nerve (X): SVE
Note: The classification of parasympathetic cranial nerves as GSE or SVE is based on their functional roles, and the available evidence suggests that the glossopharyngeal and vagus nerves are involved in SVE functions 2, 3, 4.