Cranial nerve

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Cranial nerves with labels

A cranial nerve is any nerve which is attached directly to the brain or brainstem. This is different from spinal nerves which are attached to segments of the spinal cord.[1] Cranial nerves relay information more directly between the brain and body (mostly parts of the head and neck).[2]

Each cranial nerve exists as a pair and is present on both sides of the central nervous system. All cranial nerves appear above the first vertebra in the neck (cervical vertebra).[3]

In humans there are twelve cranial nerves pairs. They are numbered using Roman numerals I–XII[4] based on their order from the front of the brain to the back, where the brainstem is.[1]

Function[change | change source]

Cranial nerves provide motor and sensory stimulation mainly to places within the head and neck. This sensory stimulation includes sensations such as temperature, touch, taste, vision, smell, balance and hearing.[1][5]

Smell (I)[change | change source]

The olfactory nerve (CN I) transmits information about odors to the brain.

Vision (II)[change | change source]

The optic nerve (CN II) transmits visual information from the retina to the brain.[3][5]

Eye movement (III, IV, VI)[change | change source]

The oculomotor nerve (CN III) controls most of the muscles related to the movement of the eye, including the eyelids and control of the pupil. The trochlear nerve (CN IV) and abducens nerve (CN VI) are each responsible for their own single eye muscles.

Facial sensation, jaw movement (V)[change | change source]

The trigeminal nerve (CN V) is called "trigeminal" because it is made of 3 parts. Together, all these parts are responsible for sensation in the face and larger facial movements such as biting and chewing.

Facial expression (VII)[change | change source]

The facial nerve (CN VII) controls the muscles of facial expression, and helps carry taste sensations from the back of the tongue and mouth.

Hearing and balance (VIII)[change | change source]

The vestibulocochlear nerve (CN VIII) transmits sound and equilibrium (balance) information from the inner ear to the brain.

Oral sensation, taste, and salivation (IX)[change | change source]

The glossopharyngeal nerve (CN IX) is a mixed nerve that carries a wide range of sensory and motor information.

Control of heart and digestion (X)[change | change source]

The vagus nerve (CN X) allows for parasympathetic control of the heart and digestive tract. It is the longest nerve of the autonomic nervous system in the human body.[6]

Shoulder elevation and head-turning (XI)[change | change source]

The accessory nerve (CN XI) is a cranial nerve that controls the sternocleidomastoid and trapezius muscles.

Tongue movement (XII)[change | change source]

The hypoglossal nerve (CN XII) is involved in controlling tongue movements required for speech and swallowing.

Routes out of the brain[change | change source]

After leaving the brain, the cranial nerves travel inside the skull. Some must leave this bony compartment to reach their destinations. Often the nerves pass through holes in the skull, called foramina. Other nerves pass through bony canals, longer pathways enclosed by bone. These foramina and canals may have more than one cranial nerve, and may also contain blood vessels.[7]

References[change | change source]

  1. 1.0 1.1 1.2 Vilensky, Joel A.; Robertson, Wendy; Suarez-Quian, Carlos (2015). The clinical anatomy of the cranial nerves: the nerves of "on Olympus towering top". Ames, Iowa: Wiley-Blackwell. ISBN 978-1-118-49201-7. 
  2. Standring, Susan; Borley, Neil R. (2008). "Overview of cranial nerves and cranial nerve nuclei". Gray's anatomy: the anatomical basis of clinical practice (40th ed.). [Edinburgh]: Churchill Livingstone/Elsevier. ISBN 978-0-443-06684-9. 
  3. 3.0 3.1 Kandel, Eric R. (2013). Principles of neural science (5 ed.). Appleton and Lange: McGraw Hill. pp. 1019–1036. ISBN 978-0-07-139011-8. 
  4. Sometimes. depending on definition, they are listed as 13 nerves.
  5. 5.0 5.1 FitzGerald, M.J.T.; Gruener, Gregory; Mtui, Estomih (2012). Clinical neuroanatomy and neuroscience (6th ed.). [Edinburgh?]: Saunders/Elsevier. p. 198. ISBN 978-0-7020-3738-2. 
  6. Shubin, Neil (2009). Your Inner Fish: The amazing discovery of our 375-million-year-old ancestor. Penguin Books Limited. p. 201. ISBN 978-0-14-190863-2. 
  7. Richard L. Drake (Ph.D.); Wayne Vogl, Adam W. M. Mitchell, Henry Gray (2005). Gray's anatomy for students. Churchill Livingstone. p. 800. ISBN 978-0-8089-2306-0.