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[[File:Brain human normal inferior view with labels en.svg|thumb|right|400px|Ventral brain showing labelled cranial nerves, WikiCommons]]

[[File:Brain human normal inferior view with labels en.svg|thumb|right|400px|Ventral brain showing labelled cranial nerves, WikiCommons]]

==Introduction==

==Introduction==

Cranial nerves are those nerves which arise from the brain and [[Hindbrain - Anatomy & Physiology|brain stem]] rather than the spinal cord. Nerves arising from the spinal cord are the [[PNS Structure - Anatomy & Physiology|peripheral nerves]]. There are 12 pairs of cranial nerves and these pairs of nerves passage through [[Skull and Facial Muscles - Anatomy & Physiology|foramina in the skull]], either individually or in groups. Cranial nerves are traditionally referred to by Roman numerals and these numerals begin cranially and run caudally.

Cranial nerves are those nerves which arise from the brain and [[Hindbrain - Anatomy & Physiology|brain stem]] rather than the spinal cord. Nerves arising from the spinal cord are the [[PNS Structure - Anatomy & Physiology|spinal nerves]]. There are 12 pairs of cranial nerves and these pairs of nerves passage through [[Skull and Facial Muscles - Anatomy & Physiology|foramina in the skull]], either individually or in groups. Cranial nerves are traditionally referred to by Roman numerals and these numerals begin cranially and run caudally.

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:'''Olfaction Example'''

:'''Olfaction Example'''

:''Priform cortex —→ Olfactory tubercle —→ Olfactory Bulb —→ [[Nose - Anatomy & Physiology|Smell]]''

:''Piriform cortex —→ Olfactory tubercle —→ Olfactory Bulb —→ [[Nose - Anatomy & Physiology|Smell]]''

:'''Taste Example'''

:'''Taste Example'''

===Olfactory Nerve (I)===

===Olfactory Nerve (I)===

Olfaction is part of the special senses cranial nerve group and represents the chemical senses of olfaction (smell) and gustation (taste). When chemical substances interact with our bodies they stimulate special sensory cells which in turn generate an action potential. The resultant impulse is sent to the brain via sensory afferent fibres and it is these fibres that represent the olfactory cranial nerve. Note: an action potential is only generated where a special sensory cell for that particular chemical substance exists. If no sensory cell exists, that chemical substance will go undetected. The special sensory cells are found within the olfactory mucous membrane in the nasal fundus and the olfactory neurosensory cells are found within the olfactory epithelium. The olfactory epithelium contains cilia on the surface of the cells to increase the surface area for chemical interactions.

Olfaction is part of the special senses cranial nerve group and represents the chemical senses of olfaction (smell) and gustation (taste). When chemical substances interact with our bodies they stimulate special sensory cells which in turn generate an action potential. The resultant impulse is sent to the brain via sensory afferent fibres and it is these fibres that represent the olfactory cranial nerve. Note: an action potential is only generated where a special sensory cell for that particular chemical substance exists. If no sensory cell exists, that chemical substance will go undetected. The olfactory neurosensory cells are found within the olfactory epithelium. The olfactory epithelium contains cilia on the surface of the cells to increase the surface area for chemical interactions.

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===Optic Nerve (II)===

===Optic Nerve (II)===

The optic nerve is part of the special senses cranial nerves and represents the connection between the receptor cells of the [[Eye - Anatomy & Physiology#The Wall (retina, uvea and sclera)|retina]] and the [[Forebrain - Anatomy & Physiology|diencephalon]]. The optic nerve is a sensory nerve and is composed of '''Special Somatic Afferent fibres'''. The optic nerve passes through the [[Skull and Facial Muscles - Anatomy & Physiology#Sphenoid Bone (os_sphenoidale)|'''optic chiasm''']] which is an area of the ventral brain where both optic nerves run in a medial direction and eventually decussate. The optic nerve runs through the [[Skull and Facial Muscles - Anatomy & Physiology#Sphenoid Bone (os_sphenoidale)|'''optic canal''']].

The optic nerve is part of the special senses cranial nerves and represents the connection between the receptor cells of the [[Eye - Anatomy & Physiology#The Wall (retina, uvea and sclera)|retina]] and the [[Forebrain - Anatomy & Physiology|diencephalon]]. The optic nerve is a sensory nerve and is composed of '''Special Somatic Afferent fibres'''. Optic nerve axons  pass from the optic disc of the retina to the brain, entering the skull via the [[Skull and Facial Muscles - Anatomy & Physiology#Sphenoid Bone (os_sphenoidale)|'''optic canal''']]. The majority of axons decussate at the [[Skull and Facial Muscles - Anatomy & Physiology#Sphenoid Bone (os_sphenoidale)|'''optic chiasm''']] before continuing as the optic tracts.  

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===Oculomotor nerve (III)===

===Oculomotor nerve (III)===

The oculomotor nerve is part of the group of cranial nerves responsible for innervating the [[Skull and Facial Muscles - Anatomy & Physiology#Facial_Muscles|muscles of the head]]. The nerves originate from the ventral [[Midbrain - Anatomy & Physiology|midbrain]] and is a motor nerve. It is composed of '''general somatic efferent fibres''' and '''general visceral efferent fibres'''. The general somatic efferent fibres of the oculomotor nerve are responsible for the motor function of four of the six [[Eye - Anatomy & Physiology#Around_the_Eye|external muscles of the eyeball]]; the 'dorsal rectus', 'medial rectus', 'ventral rectus', 'ventral oblique' and 'levator of the upper eyelid'. The general visceral efferent fibres of the oculomotor nerve are responsible for the control of pupil diameter and therefore control the 'spincter pupillae' muscle and the 'ciliaris' muscle.

The oculomotor nerve is part of the group of cranial nerves responsible for innervating the [[Skull and Facial Muscles - Anatomy & Physiology#Facial_Muscles|muscles of the head]]. The nerves originate from the ventral [[Midbrain - Anatomy & Physiology|midbrain]] and is a motor nerve. It is composed of '''general somatic efferent fibres''' and '''general visceral efferent fibres'''. The general somatic efferent fibres of the oculomotor nerve are responsible for the motor function of four of the six [[Eye - Anatomy & Physiology#Around_the_Eye|external muscles of the eyeball]]; the 'dorsal rectus', 'medial rectus', 'ventral rectus', 'ventral oblique' and 'levator of the upper eyelid'. The general visceral efferent fibres of the oculomotor nerve control the 'sphincter pupillae' muscle (alters pupillary diameter) and the 'ciliaris' muscle (alters curvature of the lens).

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===Trigeminal nerve (V)===

===Trigeminal nerve (V)===

The trigeminal nerve is part of the cranial nerve group responsible for innervation of structures originating from branchial arches. The trigeminal nerve nuclei is in the area of the pons and medulla oblongata and is the nerve of the 1st branchial arch. In general terms the trigeminal represents the sensory nerve of the head but also provides motor fibres to structures also associated with the 1st branchial arch. There are three primary branches of the trigeminal nerve; the '''Opthalmic nerve (V1)''', the ''' Maxillary nerve (V2)''' and the '''Mandibular nerve (V3)'''.

The trigeminal nerve is part of the cranial nerve group responsible for innervation of structures originating from branchial arches. The trigeminal nerve nuclei are in the area of the pons and medulla oblongata and it is the nerve of the 1st branchial arch. In general terms the trigeminal represents the sensory nerve of the head but also provides motor fibres to structures also associated with the 1st branchial arch. There are three primary branches of the trigeminal nerve; the '''Opthalmic nerve (V1)''', the ''' Maxillary nerve (V2)''' and the '''Mandibular nerve (V3)'''.

====Opthalmic nerve (V1)====

====Ophthalmic nerve (V1)====

The opthalmic nerve is a sensory nerve composed of '''general somatic afferent fibres''' and passes through the [[Skull and Facial Muscles - Anatomy & Physiology#Major Foramen and Canals|'''orbital fissue''']]. As it enters the orbit of the eye it splits further into the '''lacrimal nerve''', the '''frontal nerve''', the '''nasociliary nerve''' and the '''infratrochlear nerve'''. Therefore the nerve supplies sensory fibres to many aspects of the eye orbit.

The ophthalmic nerve is a sensory nerve composed of '''general somatic afferent fibres''' and passes through the [[Skull and Facial Muscles - Anatomy & Physiology#Major Foramen and Canals|'''orbital fissure''']]. As it enters the orbit of the eye it splits further into the '''lacrimal nerve''', the '''frontal nerve''', the '''nasociliary nerve''' and the '''infratrochlear nerve'''. Therefore the nerve supplies sensory fibres to many components of the orbit.

====Maxillary nerve (V2)====

====Maxillary nerve (V2)====

====Mandibular nerve (V3)====

====Mandibular nerve (V3)====

The mandibular nerve is a mixed sensory '''general somatic afferent fibres''' and motor '''general somatic efferent''' nerves. The mandibular nerve passes through the [[Skull_and_Facial_Muscles_-_Anatomy_%26_Physiology#Major_Foramen_and_Canals|'''oval foramen''']]. It provides motor branches to the [[Mastication|masticatory muscles]], the [[Larynx - Anatomy & Physiology#Intrinsic Musculature|ventral throat]] and [[Tongue - Anatomy & Physiology#Muscles|muscles of the palate]]. The mandibular nerve further branches into the '''masticatory nerve''', the '''masseteric nerve''' and the '''temporal nerve'''. The mandibular nerve provides sensory branches called the '''buccal nerve''', the '''auriculotemporal nerve''', and then itself divides into two smaller branches; the '''lingual nerve''' and the '''inferior alveolar nerve'''. The '''lingual nerve''' receives sensory taste fibres and also connects some sensory taste fibres to parasympathetic salivary glands via the [[Tongue - Anatomy & Physiology#Innervation|'''chorda tympani''']]. Via the chorda tympani branch, the mandibular branch supplies sensory fibres related to taste to the rostral 2/3 of the tongue. The lingual branch of the glossopharyngeal nerve supplies sensory fibres to the caudal 1/3 of the tongue.

The mandibular nerve is a mixed sensory '''general somatic afferent fibres''' and motor '''general somatic efferent''' nerves. The mandibular nerve passes through the [[Skull_and_Facial_Muscles_-_Anatomy_%26_Physiology#Major_Foramen_and_Canals|'''oval foramen''']]. It provides motor branches to the [[Mastication|masticatory muscles]], the [[Larynx - Anatomy & Physiology#Intrinsic Musculature|ventral throat]] and [[Tongue - Anatomy & Physiology#Muscles|muscles of the palate]]. The mandibular nerve further branches into the '''masticatory nerve''', the '''masseteric nerve''' and the '''temporal nerve'''. The mandibular nerve provides sensory branches called the '''buccal nerve''', the '''auriculotemporal nerve''', and then itself divides into two smaller branches; the '''lingual nerve''' and the '''inferior alveolar nerve'''. The '''lingual nerve''' receives sensory fibres to the rostral 2/3 of the tongue and also connects some sensory taste fibres to parasympathetic salivary glands via the [[Tongue - Anatomy & Physiology#Innervation|'''chorda tympani''']]. The lingual branch of the glossopharyngeal nerve supplies sensory taste fibres to the caudal 1/3 of the tongue, while the facial nerve supplies sensory taste fibres to the rostral 2/3 of the tongue.

===Abducent nerve (VI)===

===Abducent nerve (VI)===

The abducent nerve is part of the cranial nerve group responsible for innervation of the muscles of the head. The abducent nerve originates from the medulla oblongata and is a motor nerve. It is composed of '''general somatic efferent fibres''' which are responsible for controlling the 'lateral rectus' muscle and the 'restractor bulbi' muscle of the eye. The nerve passes through the '''orbital fissure''' and can be found within the same layer of the meninges as the opthalmic branch (V1) of the trigeminal nerve (V).

The abducent nerve is part of the cranial nerve group responsible for innervation of the muscles of the head. The abducent nerve originates from the medulla oblongata and is a motor nerve. It is composed of '''general somatic efferent fibres''' which are responsible for controlling the 'lateral rectus' muscle and the 'retractor bulbi' muscle of the eye. The nerve passes through the '''orbital fissure''' and can be found within the same layer of the meninges as the opthalmic branch (V1) of the trigeminal nerve (V).

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During a clinical examination, medial deviation stribismus may indicate a problem with this nerve.

During a clinical examination, medial deviation strabismus may indicate a problem with this nerve.

===Facial nerve (VII)===

===Facial nerve (VII)===

===Hypoglossal nerve (XII)===

===Hypoglossal nerve (XII)===

The hypoglossal nerve is part of the group of cranial nerves responsible for the control of muscles of the head. It is in part a cervical nerve due to its caudal position on the [[Hindbrain_-_Anatomy_%26_Physiology|brain stem]]. The nerve is composed of '''general somatic efferent fibres''' which control the intrisic and exterinsic muscles of the tongue (together with other nerves including the lingual nerve, facial nerve, lingual branch of the glossopharyngeal nerve and the vagus nerve). The nuclei of the nerve is located within the medulla oblongata of the brain stem and it passes through the '''hypoglossal canal'''.  

The hypoglossal nerve is part of the group of cranial nerves responsible for the control of muscles of the head. It is in part a cervical nerve due to its caudal position on the [[Hindbrain - Anatomy & Physiology|brain stem]]. The nerve is composed of '''general somatic efferent fibres''' which control the intrinsic and extrinsic muscles of the tongue (together with other nerves including the lingual nerve, facial nerve, lingual branch of the glossopharyngeal nerve and the vagus nerve). The nucleus of the nerve is located within the medulla oblongata of the brain stem and it passes through the '''hypoglossal canal'''.  

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| '''II - Optic'''

| '''II - Optic'''

| Optic chiasma

| Diencephalon (via optic chiasm)

| Optic canal

| Optic canal

| SSA

| SSA

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| '''III - Occulomotor'''

| '''III - Oculomotor'''

| Midbrain

| Midbrain

| Orbital fissure and Round Foramen

| Orbital fissure

| GSE + GVE

| GSE + GVE

| Nuculi III

| Oculomotor motor nucleus

| Extraoccular mm.

| Extraoccular mm.

Constrictor pupulli

Constrictor pupilli

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| '''IV - Trochlear'''

| '''IV - Trochlear'''

| Midbrain (dorsal)

| Midbrain (dorsal)

| Round Foramen

| Orbital fissure

| GSE

| GSE

| Nuc IV

| Trochlear nucleus

| Dorsal oblique mm.

| Dorsal oblique mm.

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| Pons

| Pons

| V1 - Orbital fissure  

| V1 - Orbital fissure  

V2 - Round Foramen and Orbital Fissure

V2 - Round Foramen/Rostral alar foramen

V3 - Oval Foramen

V3 - Oval Foramen

V3 - GSA & GSE

V3 - GSA & GSE

| V1 - Trigeminal gangion

| V1 - Trigeminal gangion (GSA)

V2 - Trigeminal ganglion

V2 - Trigeminal ganglion (GSA)

V3 - Nuculi V

V3 - Trigeminal ganglion (GSA), Geniculate ganglion (SVA), Trigeminal motor nucleus (motor)

| V1 - Eye region

| V1 - Eye region

V2 - Upper jaw inc. teeth

V2 - Upper jaw inc. teeth

V3 - mm. of arch 1

V3 - mm. of arch 1, lower jaw, rostral 2/3 tongue

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| Orbital fissure

| Orbital fissure

| GSE

| GSE

| Nuc IV

| Abducent nucleus

| Lateral rectus and retractor bulbi mm.

| Lateral rectus and retractor bulbi mm.

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| '''VII - Facial'''

| '''VII - Facial'''

| Medulla oblongata

| Medulla oblongata

| Stylomastoid foramen

| Internal acoustic meatus/facial canal/stylomastoid foramen

| SVA + GVE + GSE

| SVA + GVE + GSE + GSA

| Nuc III

| Facial motor nucleus

(Taste - gleniailate ganglion)

Geniculate ganglion

| mm. of arch 2

| mm. of arch 2

Submaxillary and sublingual glands

Submaxillary and sublingual glands

Rostral 2/3 taste

Rostral 2/3 tongue

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| '''VIII - Vestibulocochlear'''

| '''VIII - Vestibulocochlear'''

| Medulla oblongata

| Medulla oblongata

| Inner accoustic meatus

| Internal acoustic meatus

| SSA

| SSA

| Vestibular ganglion  

| Vestibular ganglion, spiral ganglion  

| Maculae and cristae

| Maculae and cristae

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| '''IX - Glossopharyngeal'''

| '''IX - Glossopharyngeal'''

| Medulla oblongata

| Medulla oblongata

| Jugular foramen

| Jugular foramen/tympanooccipital fissure

| GSE GVA GVE GSA SVA

| GSE GVA GVE GSA SVA

| Ganglia IX - SVM

| Glossopharyngeal ganglion

Nuculi ambiguous - mm. arch 3  

Glossopharyngeal parasympathetic nucleus, nucleus ambiguus - mm. arch 3  

| Carotid gland

| Carotid gland

Caudal 1/3 taste

Caudal 1/3 tongue

mm. of arch 3

mm. of arch 3

| '''X - Vagus'''

| '''X - Vagus'''

| Medulla oblongata

| Medulla oblongata

| Jugular foramen

| Jugular foramen/tympanooccipital fissure

| GSE GVA GVE SVA GSA

| GSE GVA GVE SVA GSA

| Ganglion X - (amongst others)

| Vagal ganglion - (amongst others)

| Thoracic and abdominal organs

| Thoracic and abdominal organs

mm. of arches 4-6

mm. of arches 4-6

| '''XI - Accessory'''

| '''XI - Accessory'''

| Medulla oblongata

| Medulla oblongata

| Jugular foramen

| Jugular foramen/tympanooccipital fissure

| GSE

| GSE

| Cervical spinal cord

| Nucleus ambiguus, accessory motor nucleus (cervical spinal cord)

| Trapezius m. etc

| Trapezius m. etc

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| Hypoglossal canal

| Hypoglossal canal

| GSE

| GSE

| Medulla nuculi XII

| Hypoglossal nucleus

| Tongue mm.

| Tongue mm.

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| Provides motor innervation to the intrinsic muscles of the tongue and other glossal muscles

| Provides motor innervation to the intrinsic muscles of the tongue and other glossal muscles

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==Learning Mnemonic==

==Learning Mnemonic==

There are various ways to memorise the cranial nerves including both the names of the actual nerves themselves and also their functions/type of nerve fibre. Here are some examples for the nerve names and also some for the type of nerve.

There are various ways to memorise the cranial nerves including both the names of the actual nerves themselves and also their functions/type of nerve fibre. Here are some examples for the nerve names and also some for the type of nerve.

* '''S'''eems (''S''pinal/Accessory XI)

* '''S'''eems (''S''pinal/Accessory XI)

* '''H'''eavenly (''H''ypoglossal XII)

* '''H'''eavenly (''H''ypoglossal XII)

===Nerve Type Mnemonics===

===Nerve Type Mnemonics===

For the mnemonic below ''S = sensory'', ''M = motor'' and ''B = both'' (sensory and motor).

For the mnemonic below ''S = sensory'', ''M = motor'' and ''B = both'' (sensory and motor).

* '''M'''oney

* '''M'''oney

[[Category:Nervous System - Anatomy & Physiology]]

[[Category:Nervous System - Anatomy & Physiology]]

[[Category:To Do - Review]]

[[Category:A&P Done]]