From Simple English Wikipedia, the free encyclopedia
Cranial nerves with labels
Acranial nerve is anynerve which is attached directly to thebrain orbrainstem. This is different fromspinal nerves which are attached to segments of thespinal cord.[1] Cranial nerves relay information more directly between the brain and body (mostly parts of the head and neck).[2]
In humans there are twelve cranial nerves pairs. They are numbered usingRoman numerals I–XII[4] based on their order from the front of the brain to the back, where thebrainstem is.[1]
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 andhearing.[1][5]
Theolfactory nerve (CN 1) sends information about smells from the nose up to the brain.[6] In the brain, this information is processed and becomesolfaction, or our sense of smell. The olfactory nerve is an is an afferent sensory nerve, meaning it takes in information from the outside world and sends it to thecentral nervous system.[7]
Head anatomy with olfactory nerve, including labels for the nasal cavity, olfactory nerves, cribiform plate, olfactory bulb, and olfactory tract
The olfactory nerve is the shortest cranial nerve.[6] It is one of two cranial nerves that does not connect to thebrain stem, the other being theoptic nerve (CN 2).[8]
The olfactory nerve is not just one nerve, but a group ofneurons working together to perform the same task.[9] The olfactory neurons start branched out in thenasal cavity. From here, they reach up through the roof of the nasal cavity and connect to theolfactory bulb.[6]
The olfactory nerve is unique because it is the only cranial nerve that canregenerate parts of itself if it is damaged.[10]
Smellmolecules calledaromatics come up the nose and into the nasal cavity. Here, they are detected by olfactory neurons. These neurons are branched out along the lining of the nasal cavity. Olfactory neurons take in the signal from the smell molecules and make electric signals calledaction potentials.[7] The action potentials move up the olfactory neurons through the roof of the nasal cavity, also known as the cribiform plate. After passing through the cribiform plate, the olfactory neurons send the action potentials to the olfactory bulb.[9] From here, signals are sent through the olfactory tract and out to different parts of the brain. For example, some signals are sent to thefrontal lobe, where smells are identified and labeled.[6]
Damage to this path can causeanosmia, or loss of the ability to smell.
Theoculomotor nerve (CN III) controls most of the muscles related to the movement of the eye, including the eyelids and control of the pupil. Thetrochlear nerve (CN IV) andabducens nerve (CN VI) are each responsible for their own single eye muscles.
Thetrigeminal 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.
After leaving the brain, the cranial nerves travel inside theskull. Some must leave this bony compartment to reach their destinations. Often the nerves pass through holes in the skull, calledforamina. 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.[12]
↑1.01.11.2Vilensky, 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.ISBN978-1-118-49201-7.
↑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.ISBN978-0-443-06684-9.
↑Vilensky, Joel; Robertson, Wendy; Suarez-Quian, Carlos (2015).The Clinical Anatomy of the Cranial Nerves: The Nerves of "On Old Olympus Towering Top". Ames, Iowa: Wiley-Blackwell.ISBN978-1118492017
