Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

Cranial nerves










Cranial nerves (CN) are sensory or motor nerves innervating muscles/glands,
carry impulses from sensory receptors; can be combination of sensory/motor
12 CN nerves I-XII – olfactory, optic, oculomotor, trochlear, trigeminal,
abducent, facial, vestibulocochlear, glossopharyngeal, vagus, accessory,
hypoglossal
Anatomy Zone mnemonic for names of CN:
Oh, Oh, Oh, To Touch And Feel Very Good Velvet, Ah Heaven
Five main functional components of the cranial nerves
o Motor (efferent) fibres
 Motor fibres to voluntary (striated) muscle
 Somatic motor
 Motor fibres to involuntary (smooth) muscle or glands
 Visceral motor
o Sensory (afferent) fibres
 General sensation fibres from skin and mucous membranes
 Sensation from the viscera
 Unique sensations e
...
taste, smell, balance, vision, hearing
Some cranial nerves are purely sensory, others are motor, others are both
o CN I, II, and VIII – sensory
o CN III, IV, VI, XI, XII – motor
o CN V, VII, IX, X – both
Anatomy Zone mnemonic for nerve type (s – sensory, m – motor, b – both):
Some Say Marry Money But My Brother Says Big Boobs Matter More
Cranial nerve fibres connect centrally to cranial nerve nuclei (neurons where
sensory/afferent fibres terminate and motor/efferent fibres originate)
CN I and II are extensions of forebrain; nuclei of CN III-XII originate in brainstem

Taken from Wilson-Pauwels et al, Cranial Nerves: Function and Dysfunction, Third edition
...
com, cea1
...
pinterest
...


Olfactory nerve (CN I)








Function: special sensory – smell (olfaction)
Cell bodies of olfactory receptor neurons located in the olfactory organ
(olfactory part of nasal mucosa)
Olfactory receptor neurons are receptors and conductors
o Apical surfaces have olfactory cilia, covered in mucus (secreted by
olfactory glands)
o Basal surfaces give rise to sensory processes that collect into
~20 olfactory nerves per side (right and left olfactory nerves, CN I)
Olfactory nerves pass through tiny foramina in the cribiform plate of the
ethmoid bone to enter the olfactory bulb in the anterior cranial fossa
o Olfactory nerves synapse with mitral cells in the olfactory bulb; the
axons of these secondary neurons form the olfactory tract
o Olfactory bulb lies in contact with inferior surface of frontal lobe
ONLY CRANIAL NERVE TO ENTER THE CEREBRUM DIRECTLY

Taken from Wordpress
...
wordpress
...
com, Visual pathway, available at
http://www
...
com/medical-atlas
...


Trigeminal nerve (CN V)











Function: somatic sensory and somatic motor to derivatives of the first
pharyngeal arch
Nuclei: four of them; one motor (motor nucleus of trigeminal nerve) and three
sensory (mesencephalic, principal sensory, spinal nuclei of trigeminal nerve)
Largest of the cranial nerves (excluding the atypical optic nerves)
Emerges from pons (large sensory and small motor root)
Large sensory root forms the trigeminal ganglion
Three divisions of CN V – ophthalmic (V1), maxillary (V2), mandibular (V3)
Zones of innervation form dermatomes, with no overlap between
dermatomes
Fibres of the motor root pass inferior to the sensory ganglion and run with the
mandibular nerve (V3) via the foramen ovale
o Branches pass to muscles of mastication, mylohyoid, anterior belly of
digastric, tensor veli palatini, tensor tympani
Four parasympathetic ganglia are associated with divisions of CN V, and they
run with the sensory and motor fibres

Ophthalmic nerve (CN V1)




Unlike V2 and V3, V1 is a brachial nerve (doesn’t supply pharyngeal arch
derivatives)
Passes via superior orbital fissure into orbit
Somatic sensory to skin, mucous membranes and conjunctiva of the front of
the head and the nose
o Cornea, superior conjunctiva, anterosuperior nasal cavity, sinuses
(frontal, ethmoidal, sphenoid), parts of dura mater, skin dorsum of
external nose, superior eyelid, forehead, anterior scalp



Test integrity of the V1 division by checking corneal reflex

Maxillary nerve (CN V2)






Sensory innervation of derivatives of the maxillary prominence of the first
pharyngeal arch
Exits cranium via foramen rotundum to enter pterygopalatine fossa
Somatic sensory to skin and mucous membranes of the upper jaw
o Some dura mater, inferior conjunctiva, posteroinferior nasal cavity,
maxillary sinus, palate and anterior part of superior oral vestibule,
maxillary teeth, and skin (lateral external nose, inferior eyelid, anterior
cheek, upper lip)
Pterygopalatine parasympathetic ganglion associated with CN V2; innervates
lacrimal gland and glands of the nose and palate

Mandibular nerve (CN V3)






Sensory innervation to derivatives of the mandibular prominence of the first
pharyngeal arch
o Anterior 2/3 of the tongue, floor of mouth, anterior inferior oral
vestibule, mandibular teeth, skin of facial regions (lower lip, buccal,
parotid, temporal) and external ear (auricle, upper external acoustic
meatus), tympanic membrane)
Motor innervation to the muscles of mastication
o Mylohyoid, anterior digastric, tensor veli palatini, tensor tympani
Two parasympathetic ganglia associated (otic and submandibular), which
innervate the salivary glands
Passes via foramen ovale into infratemporal fossa

Taken from Moore et al, Clinically Oriented Anatomy, Seventh Edition
...


Vestibulocochlear nerve (CN VIII)








Function: special sensory – hearing, equilibrium, and motion
(acceleration/deceleration)
Nuclei: vestibular nuclei located at pons-medulla junction; cochlear nuclei
are in the medulla
Emerges from pons-medulla junction and enters internal acoustic meatus,
where it separates into the vestibular and cochlear nerves
Within the internal acoustic meatus, the nerve is accompanied by facial
nerve (CN VII) and labyrinthine artery
Vestibular nerves go via vestibular ganglion to innervate
o Maculae of utricle and saccule (sensitive to acceleration and pull of
gravity relative to position of the head)
o Cristae of ampullae of semicircular ducts (sensitive to rotational
acceleration)
Cochlear nerve goes via spinal ganglions, extending to spiral organ for sense
of hearing

Taken from mskanatomy
...
co
...
blogspot
...
uk/2014/12/cranial-nerves-anatomy
...
blogspot
...
blogspot
...
uk/2014/12/cranial-nerves-anatomy
...


Spinal accessory nerve (CN XI)






Function: somatic motor to sternocleidomastoid and trapezius muscles
Nuclei: nucleus of the spinal accessory nerve
Emerges from same cranial root as CN X, origin as a series of rootlets from fist
5-6 cervical segments of the spinal cord
Passes via jugular foramen
Branches of cervical plexus sensory fibres from spinal nerves C2-C4 join CN XI
in posterior cervical region; provide pain and proprioception fibres to muscles

Taken from Moore et al, Clinically Oriented Anatomy, Seventh Edition
...

Oesophagus, stomach, intestine
to left colic flexure
Taste from epiglottis and palate
Auricle, external acoustic
meatus, dura mater
Sternocleidomastoid and
trapezius
Intrinsic and extrinsic muscles of
tongue (except palatoglossus)

Visceral motor
Visceral sensory

Vagus (CN X)

Special sensory
Somatic sensory
Somatic motor

Medulla

Visceral motor
Visceral sensory

Special sensory
Somatic sensory
Spinal accessory (CN XI)

Somatic motor

Hypoglossal (CN XII)

Somatic motor

Superior spinal
cord
Medulla

Hypoglossal
canal

Summary of cranial nerve lesions
Nerve
Olfactory (CN I)

Lesion
Cribiform plate fracture

Optic (CN II)

Trauma to orbit or eyeball,
fracture involving optic canal
Pressure on optic pathway,
laceration or intracerebral clot in
temporal, parietal or occipital
lobes
Pressure from herniating uncus
on the nerve; fracture involving
cavernous sinus; aneurysms
Stretching of nerve during its
course around the brainstem,
fracture of orbit
Injury to terminal branches (esp
...
g
...
thefreedictionary
...
g
...
g
...
g
...

Vertigo is sensation of spinning, swaying back and forth or falling



Usually due to vestibular nerve lesion; often accompanied by nausea and
vomiting

Glossopharyngeal nerve
Lesions of the glossopharyngeal nerve





Isolated lesions are uncommon and often not associated with perceptible
disability
Taste is absent on posterior 1/3 of the tongue, gag reflex absent on the side of
the lesion
Ipsilateral weakness may produce noticeable change in swallowing
Injuries affecting CN IX from infection or tumour usually also affect adjacent
nerves
o Tumours in the region of the jugular foramen will affect CN IX, X and XI;
causes multiple cranial nerve palsies – jugular foramen syndrome

Glossopharyngeal neuralgia



Uncommon and cause is unknown
Intensified pain initiated by swallowing, protruding the tongue, talking or
touching the palatine tonsil

Vagus nerve











Isolated lesions are uncommon
Injury to pharyngeal branches will result in dysphagia (difficulty swallowing)
Lesions of superior pharyngeal nerve
o Anaesthesia of the superior part of the larynx and paralysis of
cricothyroid muscle
o Voice is weak and tires easily
Injury of a recurrent laryngeal nerve
o May be caused by aneurysms of the arch of the aorta or during neck
operations
o Causes hoarseness and dysphonia due to difficulty in speaking due to
paralysis of vocal folds
Paralysis of both recurrent pharyngeal nerves
o Aphonia and inspiratory stridor
Paralysis of recurrent laryngeal nerves usually occurs due to tumours of the
larynx and thyroid gland or for injury/surgery
Due to its longer course, lesions of the left recurrent laryngeal are more
common than the right
Proximal lesions of CN X also affect the pharyngeal and superior laryngeal
nerves leading to difficulty in swallowing and speaking

Spinal accessory nerve


Because of its nearly subcutaneous passage through the posterior cervical
region, physician caused injury of CN XI may occur during surgery e
...
lymph
node biopsy, cannulation of internal jugular vein, etc
...
Moore et al
...

2

---