Cranial nerves

cranial nervecranialCNcerebral nervecranial nerve injuries cranial nervesCN1CN7cranial motor nervescranial nerve neoplasms
Cranial nerves are the nerves that emerge directly from the brain (including the brainstem), in contrast to spinal nerves (which emerge from segments of the spinal cord).wikipedia
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Central nervous system

CNScentralcentral nervous system (CNS)
The cranial nerves, however, emerge from the central nervous system above this level.
Many consider the retina and the optic nerve (cranial nerve II), as well as the olfactory nerves (cranial nerve I) and olfactory epithelium as parts of the CNS, synapsing directly on brain tissue without intermediate ganglia.

Brainstem

brain stembrain-stemback of the skull
Cranial nerves are the nerves that emerge directly from the brain (including the brainstem), in contrast to spinal nerves (which emerge from segments of the spinal cord).
The brainstem provides the main motor and sensory nerve supply to the face and neck via the cranial nerves.

Olfactory nerve

olfactory nervesOlfactoryOlfactory (I)
The terminal nerves (0), olfactory nerves (I) and optic nerves (II) emerge from the cerebrum or forebrain, and the remaining ten pairs arise from the brainstem, which is the lower part of the brain. Most typically, humans are considered to have twelve pairs of cranial nerves (I–XII), with the terminal nerve (0) more recently canonized . They are: the olfactory nerve (I), the optic nerve (II), oculomotor nerve (III), trochlear nerve (IV), trigeminal nerve (V), abducens nerve (VI), facial nerve (VII), vestibulocochlear nerve (VIII), glossopharyngeal nerve (IX), vagus nerve (X), accessory nerve (XI), and hypoglossal nerve (XII).
The olfactory nerve is typically considered the first cranial nerve, or simply CN I, that contains sensory nerve fibers relating to smell.

Oculomotor nerve

oculomotorIIIcranial nerve III
Most typically, humans are considered to have twelve pairs of cranial nerves (I–XII), with the terminal nerve (0) more recently canonized . They are: the olfactory nerve (I), the optic nerve (II), oculomotor nerve (III), trochlear nerve (IV), trigeminal nerve (V), abducens nerve (VI), facial nerve (VII), vestibulocochlear nerve (VIII), glossopharyngeal nerve (IX), vagus nerve (X), accessory nerve (XI), and hypoglossal nerve (XII).
The oculomotor nerve is the third cranial nerve (CN III).

Trigeminal nerve

trigeminalVfifth cranial nerve
Most typically, humans are considered to have twelve pairs of cranial nerves (I–XII), with the terminal nerve (0) more recently canonized . They are: the olfactory nerve (I), the optic nerve (II), oculomotor nerve (III), trochlear nerve (IV), trigeminal nerve (V), abducens nerve (VI), facial nerve (VII), vestibulocochlear nerve (VIII), glossopharyngeal nerve (IX), vagus nerve (X), accessory nerve (XI), and hypoglossal nerve (XII).
The trigeminal nerve (the fifth cranial nerve, or simply CN V) is a nerve responsible for sensation in the face and motor functions such as biting and chewing; it is the largest of the cranial nerves.

Facial nerve

facialcranial nerve VIIVII
Most typically, humans are considered to have twelve pairs of cranial nerves (I–XII), with the terminal nerve (0) more recently canonized . They are: the olfactory nerve (I), the optic nerve (II), oculomotor nerve (III), trochlear nerve (IV), trigeminal nerve (V), abducens nerve (VI), facial nerve (VII), vestibulocochlear nerve (VIII), glossopharyngeal nerve (IX), vagus nerve (X), accessory nerve (XI), and hypoglossal nerve (XII).
The facial nerve is the seventh cranial nerve, or simply CN VII. It emerges from the pons of the brainstem, controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue.

Abducens nerve

abducensabducent nerveVI
Most typically, humans are considered to have twelve pairs of cranial nerves (I–XII), with the terminal nerve (0) more recently canonized . They are: the olfactory nerve (I), the optic nerve (II), oculomotor nerve (III), trochlear nerve (IV), trigeminal nerve (V), abducens nerve (VI), facial nerve (VII), vestibulocochlear nerve (VIII), glossopharyngeal nerve (IX), vagus nerve (X), accessory nerve (XI), and hypoglossal nerve (XII).
It is also known as the abducent nerve, the sixth cranial nerve, sixth nerve, or simply CNVI. It is a somatic efferent nerve.

Glossopharyngeal nerve

glossopharyngealIXcranial nerve IX
Most typically, humans are considered to have twelve pairs of cranial nerves (I–XII), with the terminal nerve (0) more recently canonized . They are: the olfactory nerve (I), the optic nerve (II), oculomotor nerve (III), trochlear nerve (IV), trigeminal nerve (V), abducens nerve (VI), facial nerve (VII), vestibulocochlear nerve (VIII), glossopharyngeal nerve (IX), vagus nerve (X), accessory nerve (XI), and hypoglossal nerve (XII).
The glossopharyngeal nerve, known as the ninth cranial nerve (CN IX), is a mixed nerve that carries afferent sensory and efferent motor information.

Vestibulocochlear nerve

cranial nerve VIIIvestibulocochleareighth cranial nerve
Most typically, humans are considered to have twelve pairs of cranial nerves (I–XII), with the terminal nerve (0) more recently canonized . They are: the olfactory nerve (I), the optic nerve (II), oculomotor nerve (III), trochlear nerve (IV), trigeminal nerve (V), abducens nerve (VI), facial nerve (VII), vestibulocochlear nerve (VIII), glossopharyngeal nerve (IX), vagus nerve (X), accessory nerve (XI), and hypoglossal nerve (XII).
The vestibulocochlear nerve (auditory vestibular nerve), known as the eighth cranial nerve, transmits sound and equilibrium (balance) information from the inner ear to the brain.

Vagus nerve

vagusvagalX
Most typically, humans are considered to have twelve pairs of cranial nerves (I–XII), with the terminal nerve (0) more recently canonized . They are: the olfactory nerve (I), the optic nerve (II), oculomotor nerve (III), trochlear nerve (IV), trigeminal nerve (V), abducens nerve (VI), facial nerve (VII), vestibulocochlear nerve (VIII), glossopharyngeal nerve (IX), vagus nerve (X), accessory nerve (XI), and hypoglossal nerve (XII).
The vagus nerve, historically cited as the pneumogastric nerve, is the tenth cranial nerve or CN X, and interfaces with parasympathetic control of the heart, lungs, and digestive tract.

Hypoglossal nerve

hypoglossalcranial nerve XIIXII
Most typically, humans are considered to have twelve pairs of cranial nerves (I–XII), with the terminal nerve (0) more recently canonized . They are: the olfactory nerve (I), the optic nerve (II), oculomotor nerve (III), trochlear nerve (IV), trigeminal nerve (V), abducens nerve (VI), facial nerve (VII), vestibulocochlear nerve (VIII), glossopharyngeal nerve (IX), vagus nerve (X), accessory nerve (XI), and hypoglossal nerve (XII).
The hypoglossal nerve is the twelfth cranial nerve, and innervates all the extrinsic and intrinsic muscles of the tongue, except for the palatoglossus which is innervated by the vagus nerve.

Accessory nerve

spinal accessory nerveaccessoryspinal accessory
Most typically, humans are considered to have twelve pairs of cranial nerves (I–XII), with the terminal nerve (0) more recently canonized . They are: the olfactory nerve (I), the optic nerve (II), oculomotor nerve (III), trochlear nerve (IV), trigeminal nerve (V), abducens nerve (VI), facial nerve (VII), vestibulocochlear nerve (VIII), glossopharyngeal nerve (IX), vagus nerve (X), accessory nerve (XI), and hypoglossal nerve (XII).
The accessory nerve is a cranial nerve that supplies the sternocleidomastoid and trapezius muscles.

Terminal nerve

cranial nerve zeroTerminalTerminal (0)
The terminal nerves (0), olfactory nerves (I) and optic nerves (II) emerge from the cerebrum or forebrain, and the remaining ten pairs arise from the brainstem, which is the lower part of the brain. Most typically, humans are considered to have twelve pairs of cranial nerves (I–XII), with the terminal nerve (0) more recently canonized . They are: the olfactory nerve (I), the optic nerve (II), oculomotor nerve (III), trochlear nerve (IV), trigeminal nerve (V), abducens nerve (VI), facial nerve (VII), vestibulocochlear nerve (VIII), glossopharyngeal nerve (IX), vagus nerve (X), accessory nerve (XI), and hypoglossal nerve (XII). Depending on definition in humans there are twelve or thirteen cranial nerves pairs, which are assigned Roman numerals I–XII, sometimes also including cranial nerve zero.
The terminal nerve appears just anterior of the other cranial nerves bilaterally as a microscopic plexus of unmyelinated peripheral nerve fascicles in the subarachnoid space covering the gyrus rectus.

Peripheral nervous system

peripheralperipheral nervesPNS
The cranial nerves are considered components of the peripheral nervous system (PNS), although on a structural level the olfactory (I), optic (II), and trigeminal (V) nerves are more accurately considered part of the central nervous system (CNS).
In the somatic nervous system, the cranial nerves are part of the PNS with the exception of the optic nerve (cranial nerve II), along with the retina.

Optic nerve

optic nervesoptical nerveoptic
The terminal nerves (0), olfactory nerves (I) and optic nerves (II) emerge from the cerebrum or forebrain, and the remaining ten pairs arise from the brainstem, which is the lower part of the brain. Most typically, humans are considered to have twelve pairs of cranial nerves (I–XII), with the terminal nerve (0) more recently canonized . They are: the olfactory nerve (I), the optic nerve (II), oculomotor nerve (III), trochlear nerve (IV), trigeminal nerve (V), abducens nerve (VI), facial nerve (VII), vestibulocochlear nerve (VIII), glossopharyngeal nerve (IX), vagus nerve (X), accessory nerve (XI), and hypoglossal nerve (XII).
The optic nerve is the second of twelve paired cranial nerves and is technically part of the central nervous system, rather than the peripheral nervous system because it is derived from an out-pouching of the diencephalon (optic stalks) during embryonic development.

Nerve

nervesinnervationinnervated
Cranial nerves are the nerves that emerge directly from the brain (including the brainstem), in contrast to spinal nerves (which emerge from segments of the spinal cord).
Cranial nerves innervate parts of the head, and connect directly to the brain (especially to the brainstem). They are typically assigned Roman numerals from 1 to 12, although cranial nerve zero is sometimes included. In addition, cranial nerves have descriptive names.

Diplopia

double visionMonocular diplopiadouble-vision
For example an acoustic schwanoma may initially cause disturbance in hearing but with further growth of tumor it may involve other cranial nerves and the patient may present with pain resembling trigeminal neuralgia when the tumor involves trigeminal nerve or diplopia due to abducent nerve involvement similarly facial palsy with facial nerve compression.
Problems with EOMs may be due to mechanical problems, disorders of the neuromuscular junction, disorders of the cranial nerves (III, IV, and VI) that stimulate the muscles, and occasionally disorders involving the supranuclear oculomotor pathways or ingestion of toxins.

Parasympathetic nervous system

parasympatheticparasympathetic nerveparasympathetic nerves
Some of the cranial nerves have sensory or parasympathetic ganglia (collections of cell bodies) of neurons, which are located outside the brain (but can be inside or outside the skull).
Specific nerves include several cranial nerves, specifically the oculomotor nerve, facial nerve, glossopharyngeal nerve, and vagus nerve.

Trigeminal neuralgia

trifacial neuralgiatrigeminal
For example an acoustic schwanoma may initially cause disturbance in hearing but with further growth of tumor it may involve other cranial nerves and the patient may present with pain resembling trigeminal neuralgia when the tumor involves trigeminal nerve or diplopia due to abducent nerve involvement similarly facial palsy with facial nerve compression.
The trigeminal nerve is a paired cranial nerve that has three major branches: the ophthalmic nerve (V 1 ), the maxillary nerve (V 2 ), and the mandibular nerve (V 3 ).

Maxillary nerve

maxillarymaxillary divisionpalatine nerve
Trigeminal neuralgia occurs later in life, from middle age onwards, most often after age 60, and is a condition typically associated with very strong pain distributed over the area innervated by the maxillary or mandibular nerve divisions of the trigeminal nerve (V 2 and V 3 ).
The maxillary nerve (CN V 2 ) is one of the three branches or divisions of the trigeminal nerve, the fifth (V) cranial nerve.

Cranial nerve ganglia

cranial gangliacranial autonomic gangliacranial sensory ganglia
The sensory ganglia are directly correspondent to dorsal root ganglia of spinal nerves and are known as cranial sensory ganglia.
In neuroanatomy, the cranial nerve ganglia are either parasympathetic or sensory ganglia of the cranial nerves.

Orbit (anatomy)

orbitorbitseye socket
The oculomotor nerve (III), trochlear nerve (IV), abducens nerve (VI) and the ophthalmic branch of the trigeminal nerve (V1) travel through the cavernous sinus into the superior orbital fissure, passing out of the skull into the orbit. These nerves control the small muscles that move the eye and also provide sensory innervation to the eye and orbit.
In the adult human, the volume of the orbit is 30 ml, of which the eye occupies 6.5 ml. The orbital contents comprise the eye, the orbital and retrobulbar fascia, extraocular muscles, cranial nerves II, III, IV, V, and VI, blood vessels, fat, the lacrimal gland with its sac and nasolacrimal duct, the eyelids, medial and lateral palpebral ligaments, check ligaments, the suspensory ligament, septum, ciliary ganglion and short ciliary nerves.

Temporal bone

temporaltemporalstympanomastoid fissure
The facial nerve (VII) and vestibulocochlear nerve (VIII) both enter the internal auditory canal in the temporal bone. The facial nerve then reaches the side of the face by using the stylomastoid foramen, also in the temporal bone. Its fibers then spread out to reach and control all of the muscles of facial expression. The vestibulocochlear nerve reaches the organs that control balance and hearing in the temporal bone and therefore does not reach the external surface of the skull.
The lower seven cranial nerves and the major vessels to and from the brain traverse the temporal bone.

Midbrain

mesencephalonmid-brainmesencephalic
In terms of specific cranial nerve nuclei, the midbrain of the brainstem has the nuclei of the oculomotor nerve (III) and trochlear nerve (IV); the pons has the nuclei of the trigeminal nerve (V), abducens nerve (VI), facial nerve (VII) and vestibulocochlear nerve (VIII); and the medulla has the nuclei of the glossopharyngeal nerve (IX), vagus nerve (X), accessory nerve (XI) and hypoglossal nerve (XII).
The nuclei of two pairs of cranial nerves are similarly located at the ventral side of the periaqueductal grey – the pair of oculomotor nuclei (which control the eyelid, and most eye movements) is located at the level of the superior colliculus

Spinal nerve

spinal nervescervical nervessacral nerves
Cranial nerves are the nerves that emerge directly from the brain (including the brainstem), in contrast to spinal nerves (which emerge from segments of the spinal cord).
* Cranial nerves