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Cranial Nerves: Sensory, Motor & Mixed Fibers
Cranial Nerves: Sensory, Motor & Mixed Fibers
Includes labeled diagrams, downloadable notes, anatomy quizzes, and interactive learning tools
The nerves attached to the brain are called cranial nerves. They are mainly responsible for the sensory and motor functions of the head and neck. One exception is a nerve that also connects to organs in the thoracic and abdominal cavities as part of the parasympathetic nervous system.
There are twelve cranial nerves in total. They are numbered from I to XII using Roman numerals. These nerves can be sensory, motor, or a combination of both.
Sensory fibers come from sensory ganglia outside the skull and enter the brain, where they connect to nuclei. Motor fibers begin in the brain stem and connect to muscles in the head and neck.
Cranial nerves are divided into three groups based on their function:
three of them are purely sensory
five are purely motor
four are mixed nerves that carry both sensory and motor fibers.
Sensory nerves carry information into the brain. Motor nerves send commands from the brain to muscles. Mixed nerves do both.
Each cranial nerve has a specific role. The olfactory nerve (I) is responsible for the sense of smell. The optic nerve (II) is responsible for vision.
The oculomotor nerve (III) controls most eye movements. It also lifts the upper eyelid and causes the pupil to constrict.
The trochlear nerve (IV) and the abducens nerve (VI) also control eye movements, but each acts on different eye muscles. The trigeminal nerve (V) provides sensation to the face and controls the muscles used for chewing.
The facial nerve (VII) controls facial expressions. It also plays a role in taste and helps produce saliva. The vestibulocochlear nerve (VIII) is responsible for hearing and balance. The glossopharyngeal nerve (IX) controls muscles in the throat and contributes to taste and saliva production.
The vagus nerve (X) helps regulate organs in the thoracic and upper abdominal cavities and plays a role in maintaining internal balance. The spinal accessory nerve (XI) controls muscles of the neck. The hypoglossal nerve (XII) controls muscles of the tongue and lower throat.
Need a recap? Take a look at the cranial nerves anatomy notes here.
Need a recap? Take a look at the cranial nerves anatomy notes here.
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References
References
Gray, H. (1918). Anatomy of the human body (W. H. Lewis, Ed.; 20th ed.). Lea & Febiger.
J. Gordon Betts, Kelly A. Young, James A. Wise, Eddie Johnson, Brandon Poe, Dean H. Kruse, Oksana Korol, Jody E. Johnson, Mark Womble, Peter DeSaix. (2013, April 25). Anatomy and Physiology. OpenStax. https://openstax.org/books/anatomy-and-physiology-2e/pages/13-4-the-peripheral-nervous-system.
Based on OpenStax, Anatomy and Physiology (2013), licensed under CC BY 4.0.
Access for free at https://openstax.org/books/anatomy-and-physiology/pages/1-introduction.
Content paraphrased; adaptations were made.
Image Credis
Image Credis
Images used in this guide and games are by Dr. Johannes Sobotta. They are in the public domain; modifications have been made to the originals.
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