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12 cranial nerves

Learning objectives

This study unit will help you to:

  1. Learn the definition and types of cranial nerves. 
  2. Identify each of the 12 cranial nerves.
  3. Name the origin and function of each cranial nerve.

Watch videos

The cranial nerves are a group of 12 nerves that originate directly from the brain or the brainstem. Each cranial nerve can be denoted by a name (e.g. olfactory nerve) or a number (i.e. Roman numerals: I-XII). The number of each nerve is based on its origin, when the brain and brainstem are observed from rostal to caudal. All 12 nerves are bilateral and collectively function to relay information to/from various parts of the body and brain.

Watch our first video that covers the basics of cranial nerves. The second video will help you in memorizing the cranial nerves and their types with a couple of very useful mnemonics.

According to the type of nuclei and subsequently the type of nervous fibers that constitute the nerve, we can classify them into seven modalities.

Key points about cranial nerve modalities
Nerve fiber terminology Efferent (motor)
Carries information from the brain to the periphery
Afferent (sensory)

Carries information from the periphery to the brain
Mixed

Carries information both ways
Special

Carries information from/to the special senses (vision, smell, taste, hearing and balance)
General

Carries information from/to any other part of the body, except the special senses
Somatic

Carries information to/from the skin or skeletal muscles
Visceral

Carries information to/from internal organs
Nerve fiber types/modalities General somatic afferent (GSA)
Conveys general sensation from skin
(a.k.a. [general] somatic sensory)
General visceral afferent (GVA)

Conveys general sensation from viscera
(a.k.a. [general] visceral sensory)
Special somatic afferent (SSA)

Conveys senses derived from ectoderm (e.g. sight, sound, balance)
(a.k.a. special somatic sensory)
Special visceral sensory (SVA)
 
Conveys senses derived from endoderm (e.g. taste, smell)
(a.k.a. special visceral sensory)
General somatic efferent (GSE) 
Conveys motor innervation for skeletal muscles
(a.k.a. [general] somatic motor)
General visceral efferent (GVE)

Conveys motor innervation for smooth muscle, cardiac muscle and glands
(a.k.a. [general] visceral motor)
Special visceral efferent (SVE)

Conveys motor innervation for muscles derived from pharyngeal arches
(a.k.a. special visceral motor, branchial motor)

Take a quiz

Now that you have watched the videos about the cranial nerves, solidify your knowledge by taking our quiz.

If you want to get a broader overview and choose the topics you’ll get quizzed on, try out our customizable quiz.

Download the following PDF worksheets and identify the 12 cranial nerves.

BLANK WORKSHEET (PDF)LABELED WORKSHEET (PDF)

Browse atlas

Now you can observe each nerve in more detail with our image gallery:

Summary

Key points about the cranial nerves
Definition A set of 12 peripheral nerves emerging from the brain that innervate the structures of the head, neck, thorax and abdomen
12 cranial nerves Olfactory nerve (CN I): Afferent/sensory (SVA)
Optic nerve (CN II): 
Afferent/sensory (SSA)
Oculomotor nerve (CN III):
Efferent/motor (GSE & GVE)
Trochlear nerve (CN IV): 
Efferent/motor (GSE)
Trigeminal nerve (CN V): 
Mixed
Ophthalmic nerve (V1): Afferent/sensory (GSA)
Maxillary nerve (V2): Afferent/sensory (GSA)
Mandibular nerve (V3): Afferent/sensory (GSA & SVE)
Abducens nerve (CN VI):
Efferent/motor (GSE)
Facial nerve (CN VII): 
Mixed (GSA, SVA, SVE, GVE)
Vestibulocochlear nerve (CN VIII): 
Afferent/sensory (SSA)
Glossopharyngeal nerve (CN IX): 
Mixed (GSA, GVA, SVA, SVE, GVE)
Vagus nerve (CN X): 
Mixed (GSA, GVA, SVA, SVE, GVE)
Accessory nerve (CN XI):
Efferent/Motor (GSE & SVE)
Hypoglossal nerve (CN XII):
Efferent/Motor (GSE)

Well done!

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