Cranial Nerves Flashcards
CN I
- Name, number, function, sensory/motor/mixed, central connection(s)
Olfactory Sensory Olfaction Information collected in olfactory epithelium Fibers of olfactory neurons Central connection: olfactory bulb
CN II
optic
*Sensory
*Transmits information from retina
*Central connection: lateral geniculate nucleus, pretectal nucleus
Vision, pupillary light reflex
The other cranial nerve that does not join up with the brainstem
CN of diencephalon
**Extracranial vs intracranial
Compression to the optic chiasm particularly affects the fibers that are crossing over from the nasal half of each retina.
This produces visual defect affecting the peripheral vision in both eyes, known as abitemporal hemianopia
III
Name, number, function, sensory/motor/mixed, central connection(s)
Oculomotor
*MOTOR
*through innervation to different areas, plays a role in- raises/depresses/adducts the eyeball, elevates, abducts and laterally rotates the eyeball, raise upper eyelid
- Central connection: oculomotor nucleus
- Movement of eyeball, elevation of upper lid
(parasympathetic role- the central connection is the Edinger-Westphal nucleus (accessory oculomotor nucleus))
The _____ nerve leaves the cranial cavity via the superior orbital fissure.
divisions
III: Oculomotor
-Divides intoSUPERIORandINFERIOR BRANCHES.
Once within the orbital cavity, both branches innervate accessory structures of the eye:
Superior branch Motor innervation to the superior rectus and levator palpabrae superioris.
Inferior branch Motor innervation to the inferior rectus, medial rectus and inferior oblique.
Parasympathetic fibers to the ciliary ganglion, which ultimately innervates the sphincter pupillae and ciliary muscles.
*Parasympathetic
Your sad pupils make my Edinger-Westphal nucleus make my pupils look sad, too.
Parasympathetic & Oculomotor
Innervates sphincter pupillae and ciliary muscle of the eyeball via ciliary ganglion
*Central connection: Edinger-Westphal nucleus (accessory oculomotor nucleus)
Pupillary constriction and accommodation
The anatomical organization of the general somatic efferent (GSE) cell columns of the oculomotor nerve (CN III) complex
The Edinger-Westphal nucleus, whose axons (general visceral efferent) serve as preganglionic parasympathetic neurons, innervate the ciliary ganglia. The postganglionic parasympathetic neurons from the ciliary ganglia (not shown in figure) innervate the constrictor muscles of the pupil and the ciliary muscle.
IV
- Trochlear
- Motor
*Central connection: trochlear nucleus
Movement of eyeball
Fewest axons, but longest intracranial axon path
Only CN to cross the midline
Arises from thetrochlear nucleusof the brain, emerging from the posterior aspect of the midbrain
Only cranial nerve to exit from the posterior midbrain
It runs anteriorly and inferiorly within thesubarachnoidspacebefore piercing the dura mater adjacent to theposterior clinoid processof the sphenoid bone.
The nerve then moves along the lateral wall of thecavernous sinus(along with the oculomotor nerve, the abducens nerve, the ophthalmic and maxillary branches of the trigeminal nerve and the internal carotid artery) before entering the orbit of the eye viathesuperior orbital fissure.
Origin and distribution of the trochlear nerve (cranial nerve IV) to the superior oblique muscle.
As indicated in the cross section of the brainstem, note that this nerve exits the brain from the dorsal aspect, and it is the only nerve that is crossed.
Arrow indicates direction of movement of the bulb downward and inward.
Only CN to emerge from dorsal aspect of midbrain/brainstem
IV: Trochlear
Only CN to cross the midline
Examination of the Trochlear Nerve
Examination of the Trochlear Nerve
Examined in conjunction with the oculomotor and abducens nerves by testing the movements of the eye.
Patient is asked to follow a point with their eyes without moving their head.
The target is moved in an ‘H-shape’ and the patient is asked to report any blurring of vision ordiplopia(double vision).
Damage to the Trochlear Nerve
The most common cause iscongenital fourth nerve palsy, a condition of abnormal development. This may be curable with surgery.
Other causes of trochlear nerve damage includediabetic neuropathy,thrombophlebitis of the cavernous sinusandraised intracranial pressure
V
Trigeminal
- Sensory and Motor
- General sensation and Opening and closing mouth (chew), tension on tympanic membrane
-plays a role in corneal reflex
Central connection (for the sensory portion) of the Trigeminal CN:
trigeminal sensory nuclei
Three sensory nuclei(mesencephalic, principal sensory, spinal nuclei of trigeminal nerve)
At the level of thepons, the sensory nuclei merge to form a sensory root
Take up more CNS real estate than any other cranial nerve cell group
(V2)
Maxillary Nerve (V2) (of CN 5)
- Maxillary nerve gives rise to 14 terminal branches, which innervate the skin, mucous membranes and sinuses of derivatives of theMAXILLARY PROMINENCE of the 1st pharyngeal arch:
- Lower eyelid and its conjunctiva
- Cheeks and maxillary sinus
- Nasal cavity and lateral nose
- Upper lip
- Upper molar, incisor and canine teeth and the associated gingiva
- Superior palate
Abduction def
“Abductionis movement away from the mid-line of the body. … abductor - amuscle that can act to cause anabductionmovement at a joint is called an abductor. For example, the abductor pollicis longusmuscle. toabduct(verb) - e.g. “heabducted his right arm up to shoulder height”.
VI
Abducens
Motor
Innervates lateral rectus muscle
*Central connection: abducens nucleus in the pons
Movement of eyeball
Sensory Portion of the VII
(: Facial)
Innervates anterior 2/3 of tongue
Central connection: nucleus solitarius (solitary nucleus)
Taste
Motor Portion of the VII: Facial
Motor Portion
Innervates muscles of facial expression, stapedius muscle
Central connection: facial nucleus
Facial movement, tension on bones of middle ear
Parasympathetic Portion of the VII: Facial
Parasympathetic Portion
Technically falls under motor
Innervates salivary and lacrimal glands via submandibular and pterygopalatine ganglia
Central connection: superior salivatory nucleus
Salivation and lacrimation
Helps with this as a parasympathetic resposne
Production of tears and saliva
Intracranial of the Facial
Intracranial
The nerve arises in thePONS
It begins as two roots; a largemotor root, and a smallsensory root.
The two roots travel through the internal acoustic meatus, a 1cm long opening in the petrous part of thetemporal bone. Here, they are in very close proximity to the inner ear.
Still within the temporal bone, the roots leave the internal acoustic meatus, and enter into theFACIAL CANAL
Within the facial canal, three important events occur:
Firstly the two rootsfuseto form the facial nerve.
Next, the nerve forms thegeniculate ganglion, L-shaped collection of fibers and sensory neurons of the facial nerve.
Lastly, the nerve gives rise to thegreater petrosal nerve(parasympathetic fibers to glands), the nerve tostapedius(motor fibers to stapedius muscle), and thechorda tympani(special sensory fibers to the anterior 2/3 tongue).
The facial nerve then exits the facial canal (and the cranium) via thestylomastoid foramen.This is an exit located just posterior to the styloid process of the temporal bone.
Facial: Intracranial Damage/Lesions
Intracranial Damage/Lesions
The muscles of facial expression will be paralysed or severely weakened.The other symptoms produced depend on the location of the lesion, and the branches that are affected:
Chorda tympani– reduced salivation and loss of taste on the ipsilateral 2/3 of the tongue.
Nerve to stapedius– ipsilateral hyperacusis (hypersensitive to sound).
Greater petrosal nerve– ipsilateral reduced lacrimal fluid production.
The most common cause of an intracranial lesion of the facial nerve is middle ear pathology – such as a tumor or infection.
If no definitive cause can be found, the disease is termed Bell’s palsy.
Nerve to stapedius damage
VII: Facial
Nerve to stapedius– ipsilateral hyperacusis (hypersensitive to sound).
VIII:
Vestibulocochlear
Sensory
Innervates vestibular apparatus, cochlea
Central connection: vestibular nuclei, cochlear nuclei
Vestibular sensation (position and movement of head), hearing
VIII: Vestibulocochlear damage
Vestibular neuritis: inflammation of thevestibular branchof the vestibulocochlear nerve.
Some cases are thought to be due to reactivation of the herpes simplex virus.
It presents with symptoms of vestibular nerve damage:
Vertigo– a false sensation thatoneself or the surroundings are spinning or moving.
Nystagmus– a repetitive, involuntary to-and-fro oscillation of the eyes.
Loss of equilibrium(especially in low light).
Nauseaandvomiting.
The condition is usually self-resolving. Treatment is symptomatic, usually in the form of anti-emetics or vestibular suppressants
inflammation of the_____ of the vestibulocochlear nerve leads to Vestibular neuritis:
vestibular branch
Tinnitus
The perception of chronic tinnitus has also been associated with hyperactivity in the central auditory system, especially in the auditory cortex.
In such cases, the tinnitus is thought to be triggered by damage to the cochlea (the peripheral hearing structure) or the vestibulocochlear nerve.
IX: Glossopharyngeal
One of the smallest cranial nerves
Has many functional components:
Taste
Sensation from 1/3 of tongue
Sensation from pharyngeal wall
Sensation from carotid sinus (baroceptors/blood pressure)
Sensation from external ear
Branchiomotor innervation of the stylopharyngeus muscle (swallowing)
Parasympathetic innervation to parotid gland (major salivary gland)
Functional parts of the IX: Glossopharyngeal
Functional parts
SVA (special visceral afferent)- taste
Inferior glossopharyngeal ganglion (or solitary nucleus)
GVA (general visceral afferent)- sensation from posterior tongue, pharyngeal wall, carotid sinus
Inferior glossopharyngeal ganglion
GSA (general somatic afferent)- sensation from external ear
Superior glossopharyngeal ganglion
*SVE (special visceral efferent)- branchiomotor to stylopharyngeus muscle
-Nucleus ambiguus
GVE (general visceral efferent)- parasympathetic to parotid (salivary gland)
Inferior salivatory nucleus
IX: Glossopharyngeal very important to help with
swallowing
IX: Glossopharyngeal
Supplies sensory innervation to the oropharynx, and thus carries the AFFERENTinformation for the gag reflex.
When a foreign object touches the back of the mouth, this stimulates CNIX, beginning the reflex.
The efferent nerve in this process is thevagus nerve.
An absent gag reflex signifies damage to the glossopharyngeal nerve.
X: Vagus
Large nerve
Largest !!! Cranial nerve
Has the most extensive distribution in the body of all cranial nerves
Innervates all the way down into the abdomen
Also has 5 functional components like the glossopharyngeal nerve (SVA, GVA, GSA, SVE, GVE)
2 rootlets that originate from the brain and join together
X: Vagus (In the Head)
In the Head
Originates from the medulla of the brainstem.
Exits the cranium via thejugular foramen,with the glossopharyngeal and accessory nerves (CN IX and XI respectively).
Within the cranium, theauricular brancharises.
Thissupplies sensation to the posterior part of the external auditory and canal external ear.
X: Vagus = In the Neck
In the Neck
Passes into the carotid sheath, travelling inferiorly with the internal jugular vein and common carotid artery.
At the base of the neck, the right and left nerves have differing pathways:
Theright vagus nervepasses anterior to the subclavian artery and posterior to the sternoclavicular joint, entering the thorax.
Theleft vagus nervepasses inferiorly between the left common carotid and left subclavian arteries, posterior to the sternoclavicular joint, entering the thorax.
X: Vagus - Several branches arise in the neck:
Several branches arise in the neck:
Pharyngeal branches– Provides motor innervation to the majority of the muscles of the pharynx and soft palate.
Superior laryngeal nerve– Splits into internal and external branches. The external laryngeal nerve innervates the cricothyroid muscle of the larynx. The internal laryngeal provides sensory innervation to the laryngopharynx and superior part of the larynx.
Recurrent laryngeal nerve(right side only) – Hooks underneath the right subclavian artery, then ascends towards to the larynx. It innervates the majority of the intrinsic muscles of the larynx.
X: Vagus - In the Thorax
In the Thorax
The right vagus nerve forms the posterior vagal trunk, the left forms theanterior vagal trunk.
Branches from the vagal trunks contribute to the formation of the oesophageal plexus, which innervates the smooth muscle of the oesophagus.
Two other branches arise in the thorax:
Left recurrent laryngeal nerve– hooks under the arch of the aorta, ascending to innervate the majority of the intrinsic muscles of the larynx.
Cardiac branches– these innervate regulate heart rate and provide visceral sensation to the organ.
This leads to ? Referred pain ?
The vagal trunks enter the abdomen via the oesophageal hiatus, (opening in the diaphragm)
X: Vagus -In the Abdomen
In the Abdomen
In the abdomen, the vagal trunks terminate by dividing into branches that supply the oesophagus, stomach and the small and large bowel (up to the splenic flexure).
