Cranial Nerves - Anatomy & Physiology

From WikiVet English
Jump to navigation Jump to search



()Map NERVOUS AND SPECIAL SENSES (Map)



Introduction

The brainstem, cranial nerves and pyramids. © BioMed Archive.

Cranial nerves are those nerves which arise from the brain and brain stem rather than the spinal cord. Nerves arising from the spinal cord are the peripheral nerves. There are 12 cranial nerves, although the trigeminal nerve (V) has 3 branches. These are:

Opthalmic (V1)

Maxillary (V2)

Mandibular (V3)

Cranial Nerve Location and Routes

A summary of the cranial nerves is shown below:


Nerve Attatchment to brain Exit Foramen Fibre Type Location of cell bodies Distribution
I - Olfactory Olfactory bulb Cribriform plate SVS Olfactory epithelium Olfactory epithelium
II - Optic Optic chiasma Optic canal SSS Retina Retina
III - Occulomotor Midbrain Orbital fissure and Round Foramen GSM + GVM Nuculi III

parasympathetic nuculi III

Extraoccular mm.

Constrictor pupulli

IV - Trochlear Midbrain (dorsal) Round Foramen GSM Nuc IV Dorsal oblique mm.
V - Trigeminal Pons V1 - Orbital fissure

V2 - Round Foramen and Orbital Fissure

V3 - Oval Foramen

V1 - GSS

V2 - GSS

V3 - SVM

V1 - Trigeminal gangion

V2 - Trigeminal ganglion

V3 - Nuculi V

V1 - Eye region

V2 - Upper jaw inc. teeth

V3 - mm. of arch 1

VI - Abducens Medulla oblongata Orbital fissure GSM Nuc IV Lateral rectus and retractor bulbi mm.
VII - Facial Medulla oblongata Stylomastoid foramen SVM + GVM + SVS Nuc III

(Taste - gleniailate ganglion)

mm. of arch 2

Submaxillary and sublingual glands

Rostral 2/3 taste

VIII - Vestibulocochlear Medulla oblongata Inner accoustic meatus SSS Vestibular ganglion Maculae and cristae
IX - Glossopharyngeal Medulla oblongata Jugular foramen G/S V M/S Ganglia IX - SVM

Nuculi ambiguous - mm. arch 3

Carotid gland

Caudal 1/3 taste mm. of arch 3

Carotid body

X - Vagus Medulla oblongata Jugular foramen GVM + SUM + GVS + GSS Ganglion X - (amongst others) Thoracic and abdominal organs

mm. of arches 4-6 Pharynx and larynx External ear

XI - Accessory Medulla oblongata Jugular foramen GSM Cervical spinal cord Trapezius m. etc
XII - Hypoglossal Medulla oblongata Hypoglossal canal GSM Medulla nuculi XII Tongue mm.

Cranial Nerve Fibre Types

Cranial nerves are best explained by function:


  • General Somatic Motor (GSM)

Motor cortex —→ Motor nuculi —→ Muscle


  • General Visceral Motor (GVM)

Brainstem —→ Parasympathetic nuculi —→ Parasympathetic ganglion —→ Gland etc


  • "Branchial motor" - Special Visceral Motor (SVM)

Motor cortex —→ Motor nuculi —→ Muscle


  • General Somatic Sensory (GSS) and General Visceral Sensory (GVS)

Sensory cortex —→ Thalamus —→ Trigeminal nuculi —→ Trigeminal ganglion —→ Skin etc


Special sensory fibres (SSS + SVS):

Smell SVS

Priform cortex —→ Olfactory tubercle —→ Olfactory Bulb —→ SMELL


Vision SSS

Occipital cortex —→ Thalamus MGN —→ Rostral colliculus/Retinal ganglion cell —→ Bipolar cell —→ VISION


Hearing/Balance SSS

Temporal cortex —→ Thalamus MGN —→ Caudal colliculus and hindbrain —→ Spiral ganglion —→ HEARING


Taste SVS

Sensory cortex —→ Thalamus —→ Hindbrain (VII, IX, X) —→ Ganglion —→ TASTE

Cranial Nerves and their Functions

# Name Nuclei Function
I Olfactory nerve Anterior olfactory nucleus Transmits the sense of smell
II Optic nerve Lateral geniculate nucleus Transmits visual information to the brain
III Oculomotor nerve Oculomotor nucleus, Edinger-Westphal nucleus Innervates the dorsal rectus, medial rectus, ventral rectus, and ventral oblique, which collectively perform most eye movements
IV Trochlear nerve Trochlear nucleus Innervates the superior oblique muscle, which depresses, pulls laterally, and intorts the eyeball
V Trigeminal nerve Principal sensory trigeminal nucleus, Spinal trigeminal nucleus, Mesencephalic trigeminal nucleus, Trigeminal motor nucleus Receives sensation from the face and innervates the muscles of mastication
VI Abducens nerve Abducens nucleus Innervates the lateral rectus, which abducts the eye and the retractor bulbi which forces the third eyelid across the surface of the cornea as a protective mechanism.
VII Facial nerve Facial nucleus, Solitary nucleus, Superior salivary nucleus Provides motor innervation to the muscles of facial expression and stapedius, receives the special sense of taste from the anterior 2/3 of the tongue, and provides secretomotor innervation to the salivary glands (except parotid) and the lacrimal gland
VIII Vestibulocochlear nerve Vestibular nuclei, Cochlear nuclei Senses sound, rotation and gravity (essential for balance & movement)
IX Glossopharyngeal nerve Nucleus ambiguus, Inferior salivary nucleus, Solitary nucleus Receives taste from the posterior 1/3 of the tongue, provides secretomotor innervation to the parotid gland, and provides motor innervation to the stylopharyngeus
X Vagus nerve Nucleus ambiguus, Dorsal motor vagal nucleus, Solitary nucleus Supplies branchiomotor innervation to most laryngeal and pharyngeal muscles; provides parasympathetic fibers to nearly all thoracic and abdominal viscera down to the splenic flexure; and receives the special sense of taste from the epiglottis
XI Accessory nerve Nucleus ambiguus, Spinal accessory nucleus Controls muscles of the neck and overlaps with functions of the vagus
XII Hypoglossal nerve Hypoglossal nucleus Provides motor innervation to the intrinsic muscles of the tongue and other glossal muscles