BIO 004 · Human Anatomy
The Cranial Nerves
Block 5 · Module 5: The Peripheral Nervous System, the Cranial Nerves
A reference for the cranial nerve video and lab. This page covers the twelve pairs of cranial nerves: the number and name of each, its classification as sensory, motor, or mixed, its function, the skull foramen it passes through, and its nuclei. The focus is on the structures and the job each one does.
How to use this sheet Toggle the toolbar above. Notes prints the full reference for review. Study prints as a fill-in-the-blank worksheet. Print it, then write each definition while you watch the video or read your book. Quiz me is on-screen typing practice: type the term, click Reveal to check yourself. The comparison grids respond to Study and Quiz too, with a Reveal button on each row.
The Foundations video gives you a complete foundational understanding of this topic, enough on its own for a foundational course. Learn it first, then move on to the Deep dive, which adds the majors-level depth for this course.
- Name the twelve cranial nerves in order and give the number of each.
- Classify each cranial nerve as sensory, motor, or mixed.
- Identify the function, skull foramen, and nuclei of each cranial nerve.
Your pre-work
Work through these the evening before class. None of it is turned in. It is how you learn the material and build your spaced recall.
This is more than a checklist. Ticking these boxes is the start, not the finish. Committing this material to memory and being able to apply it takes considerable time and repeated effort. You are not done when the boxes are checked. Put in the real hours, and keep coming back for frequent recall and review until the material is genuinely yours.
The cranial nerves from below
Add a labeled inferior view of the brain showing where each cranial nerve attaches.
The skull foramina
Add a labeled view of the skull base showing the openings the cranial nerves pass through.
Sensory, motor, and mixed
Add a diagram sorting the twelve nerves by classification.
The Cranial Nerves, an Overview
Twelve pairs of cranial nerves arise from the brain. They are numbered I to XII from front to back by where they attach. The first two attach to the cerebrum and diencephalon; the rest attach to the brainstem.
- Cranial nervestwelve pairs of nerves that arise from the brain and brainstem, part of the peripheral nervous system
- Numberingthe nerves are numbered with Roman numerals I to XII, from anterior to posterior
- Olfactory (I) and optic (II)the only cranial nerves that attach above the brainstem, to the cerebrum and the diencephalon
- Brainstem nervescranial nerves III through XII all attach to the brainstem, where their nuclei sit
- Nucleusthe cluster of cell bodies in the brain that a cranial nerve arises from or projects to
- Foramenthe opening in the skull that a cranial nerve passes through to reach its target
Classifying the Cranial Nerves
Every cranial nerve is classed by the kind of signal it carries: sensory only, motor only, or both. A nerve carrying both is called mixed.
- Sensory nervescarry only sensory signals into the brain; CN I, CN II, and CN VIII
- Motor nervescarry mainly motor signals out to muscles; CN III, CN IV, CN VI, CN XI, and CN XII
- Mixed nervescarry both sensory and motor signals; CN V, CN VII, CN IX, and CN X
- Special sensorythe senses of smell, vision, taste, hearing, and balance
- Somatic motorvoluntary control of skeletal muscle
- Visceral motorparasympathetic control of smooth muscle and glands; carried by CN III, VII, IX, and X
A memory aid for the order of the names is the sentence "On Old Olympus' Towering Tops A Finn And German Viewed Some Hops." For the sensory, motor, or both pattern, "Some Say Marry Money But My Brother Says Big Brains Matter Most."
The Twelve Cranial Nerves
The twelve nerves in order, with the classification, the main function, and the skull foramen each one passes through. Compare them.
| Cranial nerve | Class | Primary function | Skull foramen |
|---|---|---|---|
| CN I · Olfactory | Sensory | smell | cribriform plate of the ethmoid |
| CN II · Optic | Sensory | vision | optic canal of the sphenoid |
| CN III · Oculomotor | Motor | most eye movements, raising the eyelid, and constricting the pupil | superior orbital fissure |
| CN IV · Trochlear | Motor | eye movement by the superior oblique muscle; the smallest cranial nerve | superior orbital fissure |
| CN V · Trigeminal | Mixed | sensation from the face and the muscles of chewing; the largest cranial nerve, with three branches | superior orbital fissure (V1), foramen rotundum (V2), and foramen ovale (V3) |
| CN VI · Abducens | Motor | eye movement by the lateral rectus muscle | superior orbital fissure |
| CN VII · Facial | Mixed | facial expression, taste from the front of the tongue, and tear and saliva production | internal acoustic meatus, then the stylomastoid foramen |
| CN VIII · Vestibulocochlear | Sensory | hearing and balance | internal acoustic meatus |
| CN IX · Glossopharyngeal | Mixed | taste from the back of the tongue, swallowing, and saliva from the parotid gland | jugular foramen |
| CN X · Vagus | Mixed | autonomic control of the thoracic and abdominal organs, plus voice and swallowing | jugular foramen |
| CN XI · Accessory | Motor | movement of the sternocleidomastoid and trapezius muscles | jugular foramen |
| CN XII · Hypoglossal | Motor | movement of the tongue | hypoglossal canal |
Cranial Nerve Nuclei
Each cranial nerve connects to one or more nuclei, the clusters of cell bodies in the brain that the nerve arises from or carries signals to. Most sit in the brainstem.
| Cranial nerve | Nuclei or origin |
|---|---|
| CN I · Olfactory | the olfactory epithelium projects to the olfactory bulb, then along the olfactory tract to the cortex |
| CN II · Optic | the retina projects through the optic nerve and the optic chiasm to the lateral geniculate nucleus |
| CN III · Oculomotor | the oculomotor nucleus and the Edinger-Westphal nucleus of the midbrain |
| CN IV · Trochlear | the trochlear nucleus of the midbrain |
| CN V · Trigeminal | the trigeminal ganglion and the trigeminal nuclei of the pons |
| CN VI · Abducens | the abducens nucleus of the pons |
| CN VII · Facial | the facial motor nucleus and the solitary nucleus of the pons |
| CN VIII · Vestibulocochlear | the cochlear and vestibular nuclei at the pons and medulla |
| CN IX · Glossopharyngeal | the solitary nucleus, the nucleus ambiguus, and the inferior salivatory nucleus of the medulla |
| CN X · Vagus | the dorsal motor nucleus, the nucleus ambiguus, and the solitary nucleus of the medulla |
| CN XI · Accessory | the spinal accessory nucleus of the medulla and the upper spinal cord, C1 to C5 |
| CN XII · Hypoglossal | the hypoglossal nucleus of the medulla |
See also: The Brainstem for the nuclei these nerves connect to, and The Peripheral Nervous System for the spinal nerves.
Study questions
Work on answering these in writing, in your own words. They are the questions to bring to class, and good practice for the reasoning the exams ask for.
- Classify the twelve cranial nerves as sensory, motor, or mixed.
- For three cranial nerves, name the foramen each one passes through.
- Describe how you would test one cranial nerve, and what a failure of that test would tell you.
- Compare the cranial nerves that move the eye and what each one contributes.
Step 2 . Retrieval check
Now explain it back, in your own words.
In 60 words or more, pull together what the video just taught you. Include the key concepts. This is the point where the learning actually sticks. After you submit, your spaced-recall cards for this topic unlock.