Cranial nerves
Encyclopedia
Cranial nerves are nerve
s that emerge directly from the brain
, in contrast to spinal nerve
s, which emerge from segments of the spinal cord
. In humans, there are traditionally twelve pairs of cranial nerves. Only the first and the second pair emerge from the cerebrum; the remaining ten pairs emerge from the brainstem.
s. Cranial nerves XI and XII evolved in other species to amniote
s (non-amphibian tetrapods), thus totaling twelve pairs. In some primitive cartilaginous fishes, such as the spiny dogfish
or mud shark (Squalus acanthias), there is a terminal nerve numbered zero, since it exits the brain before the traditionally designated first cranial nerve. Because they exit from the brainstem as opposed to the spinal column, these are part of the central nervous system.
devices in circulation to help remember the names and order of the cranial nerves. Because the mind recalls rhymes well, the best mnemonics often use rhyming schemes.
Six of the best known examples are:
"Oh Once One Takes The Anatomy Final, Very Good Vacations Are Had",
"On Old Olympus's Towering Tops, A Fine-Vested German Viewed Some Hops"
"Oh, Oh, Oh To Take A Family Vacation! Go Vegas After Hours!",
"Oh, Oh, Oh, To Touch And Feel Very Good Velvet, Ahh, Heaven"
"Oh, Oh, Oh, To Touch And Feel Veins Going Vertically And Horizontally".
A useful mnemonic for remembering which nerves are motor (M), sensory (S), or both (B) is, "Some Say Money Matters But My Brother Says Big Brains Matter Most". There are many more mnemonics from many sources, for example OLd OPie OCcasionally TRies TRIGonometry And Feels VEry GLOomy, VAGUe, And HYPOactive.
Nerve
A peripheral nerve, or simply nerve, is an enclosed, cable-like bundle of peripheral axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons. Nerves are found only in the peripheral nervous system...
s that emerge directly from the brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
, in contrast to spinal nerve
Spinal nerve
The term spinal nerve generally refers to a mixed spinal nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body...
s, which emerge from segments of the spinal cord
Spinal cord
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...
. In humans, there are traditionally twelve pairs of cranial nerves. Only the first and the second pair emerge from the cerebrum; the remaining ten pairs emerge from the brainstem.
Cranial nerves in non-human vertebrates
Human cranial nerves are nerves similar to those found in many other vertebrateVertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...
s. Cranial nerves XI and XII evolved in other species to amniote
Amniote
The amniotes are a group of tetrapods that have a terrestrially adapted egg. They include synapsids and sauropsids , as well as their fossil ancestors. Amniote embryos, whether laid as eggs or carried by the female, are protected and aided by several extensive membranes...
s (non-amphibian tetrapods), thus totaling twelve pairs. In some primitive cartilaginous fishes, such as the spiny dogfish
Spiny dogfish
The spiny dogfish, spurdog, mud shark, or piked dogfish, Squalus acanthias, is one of the best known of the dogfish which are members of the family Squalidae in the order Squaliformes. While these common names may apply to several species, Squalus acanthias is distinguished by having two spines ...
or mud shark (Squalus acanthias), there is a terminal nerve numbered zero, since it exits the brain before the traditionally designated first cranial nerve. Because they exit from the brainstem as opposed to the spinal column, these are part of the central nervous system.
List of cranial nerves
| Number | Name | Sensory,Motor, or Both | Origin | Nuclei | Function >- | 0 |
Cranial nerve zero Cranial nerve zero The terminal nerve, or cranial nerve zero, was discovered by German scientist Gustav Fritsch in 1878 in the brains of sharks. It was first found in humans in 1913, although its presence in humans remains controversial... (CN 0 is not traditionally recognized.) |
Sensory | olfactory trigone Olfactory trigone The olfactory trigone is a small triangular area in front of the anterior perforated substance.Its apex, directed forward, occupies the posterior part of the olfactory sulcus, and is brought into view by throwing back the olfactory tract.... , medial olfactory gyrus, and lamina terminalis Lamina terminalis The median portion of the wall of the fore-brain vesicle consists of a thin lamina, the lamina terminalis, which stretches from the interventricular foramen to the recess at the base of the optic stalk and contains the organum vasculosum of the lamina terminalis, which regulates the osmolarity of... |
Olfactory nerve Olfactory nerve The olfactory nerve, or cranial nerve I, is the first of twelve cranial nerves. It is instrumental in the sense of smell. Derived from the embryonic nasal placode, the olfactory nerve is capable of regeneration.-Anatomy:... |
Purely Sensory | Telencephalon | Anterior olfactory nucleus Anterior olfactory nucleus The anterior olfactory nucleus is a portion of the forebrain of vertebrates.It is involved in olfaction.-Location:... |
olfactory foramina Olfactory foramina The olfactory foramina are holes in the cribriform plate which transmit the olfactory nerves.-External links:* http://bio.winona.edu/dapkus/211/Handouts/foramina.htm... in the cribriform plate Cribriform plate The cribriform plate of the ethmoid bone is received into the ethmoidal notch of the frontal bone and roofs in the nasal cavities.... of ethmoid. >- | II |
Optic nerve Optic nerve The optic nerve, also called cranial nerve 2, transmits visual information from the retina to the brain. Derived from the embryonic retinal ganglion cell, a diverticulum located in the diencephalon, the optic nerve doesn't regenerate after transection.-Anatomy:The optic nerve is the second of... |
Purely Sensory | Diencephalon | Ganglion cells of retina | >- | Oculomotor nerve Oculomotor nerve The oculomotor nerve is the 3rd of 12 paired cranial nerves. It enters the orbit via the superior orbital fissure and controls most of the eye's movements, including constriction of the pupil and maintaining an open eyelid by innervating the Levator palpebrae superiors muscle. The optic nerve is... |
Mainly Motor | Anterior aspect of Midbrain | Oculomotor nucleus Oculomotor nucleus The fibers of the oculomotor nerve arise from a nucleus in the midbrain, which lies in the gray substance of the floor of the cerebral aqueduct and extends in front of the aqueduct for a short distance into the floor of the third ventricle... , Edinger-Westphal nucleus Edinger-Westphal nucleus The Edinger-Westphal nucleus is the accessory parasympathetic cranial nerve nucleus of the oculomotor nerve , supplying the constricting muscles of the iris... |
superior orbital fissure. >- | IV |
Trochlear nerve Trochlear nerve The trochlear nerve is a motor nerve that innervates a single muscle: the superior oblique muscle of the eye.... |
Mainly Motor | Dorsal aspect of Midbrain | Trochlear nucleus Trochlear nucleus The nucleus of the trochlear nerve is located in the midbrain, at the level of the inferior colliculus. It is a motor nucleus, so is located near the midline.... |
superior oblique muscle Superior oblique muscle For the abdominal muscle see: Abdominal external oblique muscleThe superior oblique muscle, or obliquus oculi superior, is a fusiform muscle originating in the upper, medial side of the orbit which abducts, depresses and internally rotates the eye... , which depresses, rotates laterally, and intorts the eyeball. Located in the superior orbital fissure. >- | V |
Trigeminal nerve Trigeminal nerve The trigeminal nerve contains both sensory and motor fibres. It is responsible for sensation in the face and certain motor functions such as biting, chewing, and swallowing. Sensory information from the face and body is processed by parallel pathways in the central nervous system... |
Both Sensory and Motor | Pons Pons The pons is a structure located on the brain stem, named after the Latin word for "bridge" or the 16th-century Italian anatomist and surgeon Costanzo Varolio . It is superior to the medulla oblongata, inferior to the midbrain, and ventral to the cerebellum. In humans and other bipeds this means it... |
Principal sensory trigeminal nucleus, Spinal trigeminal nucleus Spinal trigeminal nucleus The spinal trigeminal nucleus is a nucleus in the medulla that receives information about deep/crude touch, pain, and temperature from the ipsilateral face. The facial, glossopharyngeal, and vagus nerves also convey pain information from their areas to the spinal trigeminal nucleus.This nucleus... , Mesencephalic trigeminal nucleus, Trigeminal motor nucleus Trigeminal motor nucleus The trigeminal motor nucleus contains motor neurons that innervate muscles of the first branchial arch, namely the muscles of mastication, the tensor tympani, tensor veli palatini, mylohyoid, and anterior belly of the digastric.-External links:*... |
muscles of mastication Muscles of mastication During mastication, four muscles of mastication are responsible for adduction and lateral motion of the jaw. Other muscles, usually associated with the hyoid such as the sternohyomastoid, are responsible for opening the jaw.-Muscles:*The masseter... . Located in the superior orbital fissure (ophthalmic nerve Ophthalmic nerve The ophthalmic nerve is one of the three branches of the trigeminal nerve, the fifth cranial nerve. The ophthalmic nerve carries only sensory fibers.-Branches:*Nasociliary nerve**sensory root of ciliary ganglion**posterior ethmoidal nerve... - V1), foramen rotundum Foramen rotundum The foramen rotundum is a circular hole in the sphenoid bone that connects the middle cranial fossa and the pterygopalatine fossa.-Structure:... (maxillary nerve - V2), and foramen ovale Foramen ovale There are multiple structures in the human body with the name foramen ovale :* In the fetal heart, the foramen ovale is a shunt from the right atrium to left atrium.... (mandibular nerve Mandibular nerve The mandibular nerve is the largest of the three branches of the trigeminal nerve.-Roots:It is made up of two roots:* a large sensory root proceeding from the inferior angle of the trigeminal ganglion.... - V3). >- | VI |
Abducens nerve | Mainly Motor | Posterior margin of Pons Pons The pons is a structure located on the brain stem, named after the Latin word for "bridge" or the 16th-century Italian anatomist and surgeon Costanzo Varolio . It is superior to the medulla oblongata, inferior to the midbrain, and ventral to the cerebellum. In humans and other bipeds this means it... |
Abducens nucleus Abducens nucleus The abducens nucleus is the originating nucleus from which the abducens nerve emerges - a cranial nerve nucleus. This nucleus is located beneath the fourth ventricle in the caudal portion of the pons, medial to the sulcus limitans.... |
superior orbital fissure. >- | VII |
Facial nerve Facial nerve The facial nerve is the seventh of twelve paired cranial nerves. It emerges from the brainstem between the pons and the medulla, and controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue and oral cavity... |
Both Sensory and Motor | Pons Pons The pons is a structure located on the brain stem, named after the Latin word for "bridge" or the 16th-century Italian anatomist and surgeon Costanzo Varolio . It is superior to the medulla oblongata, inferior to the midbrain, and ventral to the cerebellum. In humans and other bipeds this means it... (cerebellopontine angle) above olive |
Facial nucleus, Solitary nucleus Solitary nucleus The solitary tract and nucleus are structures in the brainstem that carry and receive visceral sensation and taste from the facial , glossopharyngeal and vagus cranial nerves.-Anatomy:... , Superior salivary nucleus Superior salivary nucleus The Superior salivary nucleus of the facial nerve is a visceromotor cranial nerve nucleus located in the pontine tegmentum.... |
digastric muscle Digastric muscle The digastric muscle is a small muscle located under the jaw. so digastric muscles are muscle fibers in ligament of treitz ,omohyoid , occipitofrontalis.... , and stapedius Stapedius The stapedius is the smallest skeletal muscle in the human body. At just over one millimeter in length, its purpose is to stabilize the smallest bone in the body, the stapes.... muscle. Also receives the special sense of taste from the anterior 2/3 of the tongue and provides secretomotor Secretomotor Secretomotor refers to the capacity of a structure to induce a gland to secrete a substance .Secretomotor nerve endings are frequently contrasted with sensory neuron endings and motor nerve endings. An example of secretomotor activity can be seen with the lacrimal gland, which secretes the aqueous... innervation to the salivary gland Salivary gland The salivary glands in mammals are exocrine glands, glands with ducts, that produce saliva. They also secrete amylase, an enzyme that breaks down starch into maltose... s (except parotid) and the lacrimal gland Lacrimal gland The lacrimal glands are paired almond-shaped glands, one for each eye, that secrete the aqueous layer of the tear film. They are situated in the upper, outer portion of each orbit, in the lacrimal fossa of the orbit formed by the frontal bone. Inflammation of the lacrimal glands is called... . Located in and runs through the internal acoustic canal to the facial canal Facial canal The facial canal is a Z-shaped canal running through the temporal bone from the internal acoustic meatus to the stylomastoid foramen. In humans it is approximately 3 centimeters long, which makes it the longest human osseous canal of a nerve... and exits at the stylomastoid foramen Stylomastoid foramen Between the styloid and mastoid processes of the temporal bone is the stylomastoid foramenIt is the termination of the facial canal, and transmits the facial nerve and stylomastoid artery.- Clinical Relevance :... . >- | VIII |
Vestibulocochlear nerve Vestibulocochlear nerve The vestibulocochlear nerve is the eighth of twelve cranial nerves, and is responsible for transmitting sound and equilibrium information from the inner ear to the brain... (or auditory-vestibular nerve or statoacoustic nerve) |
Mostly sensory | Lateral to CN VII (cerebellopontine angle) | Vestibular nuclei Vestibular nuclei The vestibular nuclei are the cranial nuclei for the vestibular nerve.In Terminologia Anatomica they are grouped in both the pons and medulla.-Subnuclei:There are 4 subnuclei; they are situated at the floor of the fourth ventricle.... , Cochlear nuclei Cochlear nuclei The cochlear nuclei are two heterogeneous collections of neurons in the mammalian brainstem that receive input from the cochlear nerve, which carry sound information from the cochleae... |
>- | Glossopharyngeal nerve Glossopharyngeal nerve The glossopharyngeal nerve is the ninth of twelve pairs of cranial nerves . It exits the brainstem out from the sides of the upper medulla, just rostral to the vagus nerve... |
Both Sensory and Motor | Medulla Medulla oblongata The medulla oblongata is the lower half of the brainstem. In discussions of neurology and similar contexts where no ambiguity will result, it is often referred to as simply the medulla... |
Nucleus ambiguus Nucleus ambiguus The nucleus ambiguus is a region of histologically disparate cells located just dorsal to the inferior olivary nucleus in the lateral portion of the upper medulla... , Inferior salivary nucleus, Solitary nucleus Solitary nucleus The solitary tract and nucleus are structures in the brainstem that carry and receive visceral sensation and taste from the facial , glossopharyngeal and vagus cranial nerves.-Anatomy:... |
parotid gland Parotid gland The paired parotid glands are the largest of the salivary glands. They are each found wrapped around the mandibular ramus, and secrete saliva through Stensen's ducts into the oral cavity, to facilitate mastication and swallowing and to begin the digestion of starches.-Location:The parotid glands... , and provides motor innervation to the stylopharyngeus. Some sensation is also relayed to the brain from the palatine tonsils. Located in the jugular foramen Jugular foramen The jugular foramen is a large aperture in the base of the skull. It is located behind the carotid canal and is formed in front by the petrous portion of the temporal, and behind by the occipital; it is generally larger on the right than on the left side.... . >- | X |
Vagus nerve Vagus nerve The vagus nerve , also called pneumogastric nerve or cranial nerve X, is the tenth of twelve paired cranial nerves... |
Both Sensory and Motor | Posterolateral sulcus of Medulla Medulla oblongata The medulla oblongata is the lower half of the brainstem. In discussions of neurology and similar contexts where no ambiguity will result, it is often referred to as simply the medulla... |
Nucleus ambiguus Nucleus ambiguus The nucleus ambiguus is a region of histologically disparate cells located just dorsal to the inferior olivary nucleus in the lateral portion of the upper medulla... , Dorsal motor vagal nucleus, Solitary nucleus Solitary nucleus The solitary tract and nucleus are structures in the brainstem that carry and receive visceral sensation and taste from the facial , glossopharyngeal and vagus cranial nerves.-Anatomy:... |
splenic flexure Splenic flexure The splenic flexure is a sharp bend between the transverse and the descending colon in the left upper quadrant of humans. The left colic flexure is near the spleen, and hence called the splenic flexure. There are two colic flexures in the transverse colon — the other being the hepatic... . Receives the special sense of taste from the epiglottis. A major function: controls muscles for voice and resonance and the soft palate. Symptoms of damage: dysphagia Dysphagia Dysphagia is the medical term for the symptom of difficulty in swallowing. Although classified under "symptoms and signs" in ICD-10, the term is sometimes used as a condition in its own right. Sufferers are sometimes unaware of their dysphagia.... (swallowing problems), velopharyngeal insufficiency. Located in the jugular foramen Jugular foramen The jugular foramen is a large aperture in the base of the skull. It is located behind the carotid canal and is formed in front by the petrous portion of the temporal, and behind by the occipital; it is generally larger on the right than on the left side.... . >- | XI |
Accessory nerve Accessory nerve In anatomy, the accessory nerve is a nerve that controls specific muscles of the shoulder and neck. As part of it was formerly believed to originate in the brain, it is considered a cranial nerve... (or cranial accessory nerve or spinal accessory nerve) |
Mainly Motor | Cranial and Spinal Roots | Nucleus ambiguus Nucleus ambiguus The nucleus ambiguus is a region of histologically disparate cells located just dorsal to the inferior olivary nucleus in the lateral portion of the upper medulla... , Spinal accessory nucleus Spinal accessory nucleus The spinal accessory nucleus lies within the cervical spinal cord in the ventral horn. The nucleus ambiguus is classically said to provide the "cranial component" of the accessory nerve.... |
jugular foramen Jugular foramen The jugular foramen is a large aperture in the base of the skull. It is located behind the carotid canal and is formed in front by the petrous portion of the temporal, and behind by the occipital; it is generally larger on the right than on the left side.... . >- | XII |
Hypoglossal nerve Hypoglossal nerve The hypoglossal nerve is the twelfth cranial nerve , leading to the tongue. The nerve arises from the hypoglossal nucleus and emerges from the medulla oblongata in the preolivary sulcus separating the olive and the pyramid. It then passes through the hypoglossal canal... |
Mainly Motor | Medulla Medulla oblongata The medulla oblongata is the lower half of the brainstem. In discussions of neurology and similar contexts where no ambiguity will result, it is often referred to as simply the medulla... |
Hypoglossal nucleus Hypoglossal nucleus The hypoglossal nucleus is a cranial nerve nucleus, and it extends the length of the medulla, and being a motor nucleus, is close to the midline... |
Provides motor innervation to the muscles of the tongue (except for the palatoglossus Palatoglossus muscle The palatoglossus, glossopalatinus, or palatoglossal muscle is a small fleshy fasciculus, narrower in the middle than at either end, forming, with the mucous membrane covering its surface, the glossopalatine arch.... , which is innervated by the vagus nerve) and other glossal muscles. Important for swallowing (bolus formation) and speech articulation. Located in the hypoglossal canal Hypoglossal canal The hypoglossal canal is a bony canal in the occipital bone of the skull.-Anatomy:It transmits the hypoglossal nerve from its point of entry near the medulla oblongata to its exit from the base of the skull near the jugular foramen... . |
Mnemonic devices
As the list is important to keep in mind during the examination of the nervous system, there are many mnemonicMnemonic
A mnemonic , or mnemonic device, is any learning technique that aids memory. To improve long term memory, mnemonic systems are used to make memorization easier. Commonly encountered mnemonics are often verbal, such as a very short poem or a special word used to help a person remember something,...
devices in circulation to help remember the names and order of the cranial nerves. Because the mind recalls rhymes well, the best mnemonics often use rhyming schemes.
Six of the best known examples are:
"Oh Once One Takes The Anatomy Final, Very Good Vacations Are Had",
"On Old Olympus's Towering Tops, A Fine-Vested German Viewed Some Hops"
"Oh, Oh, Oh To Take A Family Vacation! Go Vegas After Hours!",
"Oh, Oh, Oh, To Touch And Feel Very Good Velvet, Ahh, Heaven"
"Oh, Oh, Oh, To Touch And Feel Veins Going Vertically And Horizontally".
A useful mnemonic for remembering which nerves are motor (M), sensory (S), or both (B) is, "Some Say Money Matters But My Brother Says Big Brains Matter Most". There are many more mnemonics from many sources, for example OLd OPie OCcasionally TRies TRIGonometry And Feels VEry GLOomy, VAGUe, And HYPOactive.
See also
- Cranial nerve nucleusCranial nerve nucleusA cranial nerve nucleus is a collection of neurons in the brain stem that is associated with one or more cranial nerves. Axons carrying information to and from the cranial nerves form a synapse first at these nuclei. Lesions occurring at these nuclei can lead to effects resembling those seen by...
- List of mnemonics for the cranial nerves
- Cranial nerve examinationCranial nerve examinationThe cranial nerve exam is part of the neurological examination. It is used to identify problems with the cranial nerves by physical examination.-Components:-See also:* Cranial nerves* Cranial nerve nucleus* List of mnemonics for the cranial nerves...