export_cranial nerves Flashcards
What are the six different modalities fibers may carry in cranial nerves
- General somatic efferent - GSE
- General visceral efferent - GVE
- Special visceral efferent - SVE
- General somatic afferent - GSA
- General visceral afferent - GVA
- Sensory afferent - SA
Which cranial nerves carry GSE fibers
Cranial nerves 3, 4, 6, and 12.
Eyes and tongue
Which cranial nerves carry GVE fibers
Cranial nerves 3, 7, 9, and 10
Which cranial nerves carry SVE fibers
Provide motor innervation to the muscles derived from the branchial arches.
5, 7, 9, 10, and 11
Which cranial nerves carry general somatic afferent fibers
Cranial nerves 5, 7, 9, and 10. They transmit visceral information but not pain.
Which cranial nerves carry general visceral afferent fibers
Cranial nerves 9 and 10.
Which cranial nerves carry sensory afferent fibers
Cranial nerves 1, 2, 7, 8, and 9
The occulomotor nerve is associated with what ganglion
The ciliary ganglion (AUTONOMIC)
The trigeminal nerve is associated with what ganglion
The trigeminal ganglion (SENSORY)
The facial nerve is associated with what ganglion
- Geniculate ganglion (SENSORY)
- Pterygopalatine (AUTONOMIC)
- Submandibular (AUTONOMIC)
The vestibulocochlear nerve is associated with what ganglion
The spiral and vestibular ganglion (both SENSORY)
The glossopharyngeal nerve is associated with what ganglion
The superior and inferior/petrosal ganglion (SENSORY)
The otic ganglion (AUTONOMIC)
The vagus nerve is associated with what ganglion
The superior/jugular ganglion (SENSORY)
The inferior/nodose ganglion (SENSORY)
The prevertebral and intramural ganglia (AUTONOMIC)
Features of the olfactory nerve
Sensory afferent nerve. Its primary neurons lie in the olfactory epithelium and function simultaneously as neurosecretory cells and sensory receptors. The primary neurons send bundles of axons across the cribiform plate to synapse with the secondary neurons - mitral and tufted cells - within the olfactory bulbs.
Mitral cells project to the….
Lateral olfactory area
Tufted cells project to the
Anterior olfactory nucleus (primarily)
Also the lateral, intermediate and medial olfactory areas.
The primary/lateral olfactory area is composed of:
- Uncus
- Entorrhinal area - anterior portion of the hippocampal gyrus
- Limen insula
- Part of the amygdala
What is the pyriform cortex
Three of the regions/areas which make up the primary/lateral olfactory area comprise the pyriform cortex:
- Uncus
- Entorrhinal area - anterior portion of the hippocampus
- Limen insula - insular and frontal lobe junction
The olfactory tract carries the axons of secondary olfactory neurons (mitral and tufted cells) to these three olfactory areas:
- Primary/lateral olfactory area via the lateral olfactory stria
- Anterior perforated substance/intermediate olfactory area via intermediate olfactory stria
- Medial olfactory area/septal area via medial olfactory stria. This area mediates emotional response to odors.
What connects the three olfactory areas
The diagonal band of Broca.
Efferent fiber output from the olfactory area travels in the following bundles/tracts:
- The medial forebrain bundle from all three olfactory areas to the hypothalamus
- Stria medullaris thalami from all three olfactory areas to the habenular nucleus
- Stria terminalis from the amygdala to the anterior hypothalamus and pre-optic area.
The hypothalamus sends olfactory information to which three areas
- Reticular formation
- Salvitory nuclei
- Dorsal motor nucleus of X - responsible for nausea, accelerated peristalsis and enhanced gastric secretions.
Where is the anterior olfactory nucleus located, where does it receive its input and where does it project to?
- Located between the olfactory bulb and tract
- Receives input from the tufted cells
- Projects to the contralateral olfactory bulb via the anterior commissure. It also projects to the ipsilateral olfactory areas.
What are the primary and secondary neurons of the second cranial nerve
Cranial nerve II/optic - carries sensory afferent fibers.
Primary sensory neurons are bipolar cells of the retina and they synapse with the retinal ganglion cells (secondary neurons)
What are the three types of retinal ganglion cells?
- X cells
- Y cells
- W cells
What are the features of the X-cells
Largest cell bodies of the three types of retinal ganglion cells.
They provide a tonic response to the pretectum and lateral geniculate body.
Their transmission rate is very slow.
What are the features of the Y cells
They provide a phasic response to the lateral geniculate body and the superior colliculus.
Their transmission rate is rapid.
What are the features of the W-cells
The smallest cell bodies of the retinal ganglion cells.
They provide tonic and phasic response to the superior colliculus and pretectum.
They have a very slow transmission rate.
What is the general pathway of information carried via cranial nerve 2.
Bipolar retinal cells synpase with the retinal ganglion cells. The latter then send axons to the optic nerve –> optic canal –> optic chiasm –> optic tract –> projections.
The optic tract projects information to the following areas:
- Thalamic lateral geniculate body
- which then sends tertiary neurons (optic radiations) to the primary visual cortex around the calcarine fissure. - Pretectal area - light reflex
- Superior colliculus - eye movement reflexes
- Suprachiasmatic nuclei - neuroendocrine/day night stuff
General features of Meyer’s loop
Courses anteriorly toward the temporal pole before turning posteriorly.
Carries fibers/information which represents the contralateral superior visual quadrant.
What is von Willebrand’s knee?
Contains fibers from the contralateral optic nerve which course into the other optic nerve before continuing down the optic tract.
What fiber modalities are found in cranial nerve III/occulomotor
General somatic efferent and general visceral efferent.
GSE and GVE.
Where is the occulomotor nuclear complex located and what are its three subnuclei
Occulomotor nuclear complex is found at the level of superior colliculus.
It has three subnuclei which supply individual muscles of the ocular region
- Lateral - ipsilateral inferior rectus, inferior oblique, and medial rectus.
- Medial - contralateral superior rectus
- Central - bilateral levator palpebrae superioris
What is the course of the GSE fibers in the third cranial nerve
Lower motor nerve axons travel through the tegmentum -> red nucleus -> medial aspect of the cerebral peduncles -> interpeduncular cistern.
From there they pass between the PCA and SCA -> oculomotor trigone in the posterior roof of the cavernous sinus -> superior orbital fissure -> anulus of Zinn -> orbit
Describe the anatomy of the third cranial nerve as it enters the orbit.
The third cranial nerve divides into the superior and inferior divisions once it enters the orbit.
Features of the superior division of the third cranial nerve
Ascends lateral to the optic nerve and supplies the superior rectus and levator palpebrae superioris
Features of the inferior division of the third cranial nerve.
Supplies the inferior rectus, inferior oblique, and medial rectus muscles.
Parasympathetic fibers (GVEs) branch off of the inferior division of CN3 or off of the nerves which supply the inferior oblique and then enter the ciliary ganglion.
Course of the general visceral efferent fibers within the third cranial nerve.
Originate from the Edinger-Westphal nucleus in the midbrain. They course in the dorsal and superficial aspect of the third nerve until they branch from the nerves that supply the inferior oblique and terminate in the ciliary ganglion.
Postganglionic fibers form the short ciliary nerves which travel with V1 anteriorly between the choroid and sclera to terminate in the ciliary body and iris
What is the role of the GVE fibers of the third nerve
They innervate the pupillary constrictor muscles –> constriction
They innervate the ciliary muscles in order to faciliate lens bending for accommodation.
What fiber modalities course through the 4th cranial nerve.
General somatic efferent (GSE)
Course of the fibers which lie within the 4th cranial nerve.
Originate at the trochlear nucleus at the level of the inferior colliculus. Then crosses in the superior medullary velum of the midbrain, it then exits the contralateral side just below the inferior colliculus and courses around the peduncles emerging between the PCA and SCA with the 3rd cranial nerve. After this it travels within the lateral wall of the cavernous sinus through the superior orbital fissure and into the orbit ABOVE the annulus of Zinn.
What does the fourth cranial nerve do
Innervates the superior oblique muscle.
Special/unique features of the 4th cranial nerve
- Only nerve to exit from the dorsum of the brainstem
- Smallest cranial nerve
- Longest intracranial course
- The only cranial nerve in which all the LMN axons decussate
- The only nerve to decussate outside the CNS.
What fiber modalities run through the 5th cranial nerve?
Special visceral efferent and general somatic afferent.
SVE and GSA
Where is the nucleus of 5 located and what are its subcomponents?
Motor nucleus
Sensory nucleus: three subnuclei
- Mesencephalic nucleus
- Chief sensory nucleus
- Spinal nucleus
What is the role of the mesencephalic sensory nucleus of 5
Conveys proprioceptive information from the muscles of mastication.
What is the role of the chief sensory nucleus of cranial nerve 5
Conveys light touch from the face
What is the role of the spinal nucleus of 5
It conveys pain, temperature, and deep pressure information.
Where does the trigeminal nerve exit the brainstem
Exits the brainstem at the midlateral surface of the pons as a large sensory root (portio major) and a smaller motor root (portio minor)
Where is the sensory nucleus of 5 located and what are its nerve divisions
The sensory ganglion - aka the semilunar/gasserian/trigeminal ganglion lies in Meckel’s cave on the floor of the middle fossa.
V1, V2, and V3 which exit at the superior orbital fissure, foramen rotundum and the foramen ovale respectively. V1 fibers lie ventral and V3 fibers lie dorsal in the trigeminal nerve.
What are the sensory branches of V1
- Lacrimal
- Frontal
- Nasociliary w/ long and short ciliary nerves
- Meningeal - dura of the anterior and middle cranial fossa
What are the sensory branches of V2
- Zygomatic
- Infraorbital w/ superior alveolar nerves
- Pterygopalatine
- Meningeal - dura of the anterior and middle cranial fossa
What are the branches of V3
- Buccal
- Auriculotemporal
- Lingual
- Inferior alveolar
- Motor
- Meningeal - dura of the anterior and middle cranial fossa
Course of sympathetic fibers to the orbit.
The post-ganglionic fibers course along the ICA and then with the long and short ciliary nerves from V1 to the eye.
What do the special visceral efferent branches from the motor nucleus of 5 supply
- Muscles of mastication - Temporalis, masseter, medial and lateral pterygoids
- Mylohyoid
- Anterior belly of the digastric
- Tensor tympani
- Tensor veli palatini
The branches to the latter two pass through the otic ganglion without synapsing.
What is the course of the GSA fibers of cranial nerve 5.
Fibers from V1-V3 enter the semilunar ganglion -> spinal trigeminal tract -> spinal trigeminal nucleus -> trigeminothalamic tracts -> thalamic VPM
What sensory information courses in the ventral and dorsal trigeminothalamic tracts
Ventral trigeminothalamic tracts - pain, touch, and pressure - are crossed
Dorsal trigeminothalamic tracts - touch and pressure are uncrossed
What are the general features of the spinal trigeminal nucleus
The spinal trigeminal nucleus extends from the pons to C2.
Rostrally it merges with the primary sensory nucleus of 5 and dorsally it merges with the substantia gelatinosa at C2.
It receives input from the 7th, 9th and 10th cranial nerves.
What are the subcomponents of the spinal trigeminal nucleus
- Pars oralis:
- extends from the pons to the hypoglossal nucleus [nose and mouth] - Pars interpolaris: extends down to the obex [face]
- Pars caudalis: extends down to C2 [forehead, jaw and cheek]
What are the reflexes which involve the 5th cranial nerve
- Bilateral blinking - corneal from V1 -> CN7
- Elevation of the eyes (Bell’s phenomenon) - CN3
- Tearing - V1 -> superior salivatory nucleus
- Salivation - CN5 -> inferior salvitory nucleus
- Sneezing - CN5 -> nucleus ambiguous -> respiratory center of the reticular formation -> phrenic nerves-> intercostal nerves
- Vomiting CN 5-> X
- Jaw jerk -> mesencephalic nucleus -> LMN of temporalis and masseter muscles
What fiber modalities run in the 6th cranial nerves
General somatic efferent
What is the course of the 6th cranial nerve
Originate from the abducens nucleus just ventral to the fourth ventricle in the pontine tegmentum. Course ventrally and emerge from the pontomedullary junction just lateral to the pyramid. The nerve travels over the petrous apex and enters the cavernous sinus via Dorello’s canal and enters the orbit at the medial end of the superior orbital fissure and then goes through the anulus of Zinn to innervate the lateral rectus muscle.
The abducens nucleus is associated with what gaze center
The horizontal gaze center.
Motor fibers to the ipsilateral rectus muscle
+
Interneurons to the medial longitudinal fasciculus -> contralateral medial rectus.
Where is the vertical gaze center located and how is it connected to the horizontal gaze center
It is located in the rostral interstitial nucleus of the medial longitudinal fasciculus.
The parapontine reticular formation connects the horizontal and vertical gaze centers.
Input to the 6th cranial nerve
- Medial vestibular nucleus
- Parapontine reticular formation - PPRF
- Reticular formation
- Nucleus prepositus
A lesion of the 6th cranial nerve causes:
Impaired ipsilateral lateral gaze
A lesion to the abducens nucleus causes:
Impaired ipsilateral gaze of both eyes.
What fiber modalities run in the 7th cranial nerve
SVE
GVE
GSA
SVA
Course of the special visceral efferent fibers of the 7th nerve from the nucleus to the brainsteam
Originate from the facial motor nucleus in the pontine tegmentum and sends axons dorsally which wrap around the nucleus of 6 forming the facial colliculus. It then travels ventrally to emerge from the pontomedullary junction between cranial nerves 6 and 8.
Course of the special visceral efferent fibers of the 7th nerve once its exits the brainstem at the pontomedullary junction.
Travels with CN8 through the internal acoustic meatus to the petrous temporal bone and travels in the facial canal between the cochlea and vestibular organs. N erve to the stapedius arises first above the stylomastoid foramen. The branchial branches then exit the facial canal at the stylomastoid foramen - where they innervate the stylohyoid, posterior belly of the digastric and occipitalis. The rest travel in the parotid innervate the muscles of facial expression, platysma and buccinator
The GVE, GSA and SVA fibers travel in what portion of the facial nerve
Nervus intermedius.
This portion of CN 7 exits the brainstem lateral to the major portion of CN 7, medial to CN 8.
The GVE fibers of the seventh cranial nerve originate from what nucleus
The superior salivatory nucleus.
What two branches of the facial nerve carry the GVE fibers
- Greater superficial petrosal nerve
2. Chorda tympani
Features and course of the greater superficial petrosal nerve.
The GSPN exits the petrous temporal bone via the greater petrosal foramen to the middle fossa and passes deep to the trigeminal ganglion and down the foramen lacerum to the pterygoid canal where it joins the deep petrosal nerve (ICA sympathetics) to form the nerve of the pterygoid canal –> pterygopalatine ganglion (suspended by V2) –> lacrimal gland.
Features and course of the chorda tympani
The chorda tympani exits the petrotympanic fissure to join the lingual branch of V3 under the foramen ovale. It then enters Submandibular nerve (suspended from the lingual nerve) and then goes on to innervate the sublingual gland.
Features of the GSA fibers of the 7th cranial nerve
Sensory receptors from the external auditory meatus and the back of the ear —> geniculate ganglion at the facial genu in the petrous bone –> spinal trigeminal tract
Features of the special visceral afferent/SVA fibers which course in the seventh cranial nerve
Sensory receptors from the anterior 2/3 of the tongue which then travel in the chorda tympani –> enter the geniculate ganglion and end in the rostral nucleus solitarius.
What are the branches of the 7th cranial nerve
- Greater superficial petrosal nerve
- Nerve to the stapedius
- Chorda tympani
- Motor branches -> temporal, zygomatic, buccal, mandibular, and cervical.
Upper motor neuron lesions to the seventh cranial nerve produce:
Contralateral lower face paresis
Emotional or mimetic innervation to the face can occur after a corticobulbar lesion
Lesions to the LMN of CN 7 produce:
Paresis to the ipsilateral lower face, decreased sensation and taste, impaired salivation and lacrimation and hyperacusis.
What fiber modalities run in the 8th cranial nerves
Special somatic afferent. SSA
What is the course of the SSA fibers in the 8th cranial nerve
Hearing is detected in the organ of Corti which sends fibers(1) -> spiral ganglion -> cochlear nerve -> cochlear nuclei sends axons (2) -> ventral/intermediate/dorsal striae -> lateral lemniscus -> inferior colliculus (3) -> medial geniculate body(4) -> temporal lobe Heschl’s convolutions(5) .
(Order neurons)
The cochlear nucleus has what type or organization
Tonotopic:
The ventral cochlear nucleus: low frequencies
The dorsal cochlear nucleus: high frequencies.
What are the acoustic reflexes which are involved in the suppression of auditory input.
Superior olivary complex to both motor CN 8 nuclei to the stapedius muscles. Decrease the amplitude of sound waves by decreasing the movement of ossicles.
Superior olivary complex to CN 5 nuclei -> tensor tympani muscles. Decrease the sensitivity of the tympanic membrane by pulling it taut.
What are the vestibular nuclei
- Lateral/Deiter’s nucleus
- Medial
- Superior
- Inferior
Features of the lateral vestibular/Dieter’s nucleus
Sends fibers/axons to the ipsilateral lateral vestibulospinal tract which go on to innervate the antigravity extensors.
Which vestibular nuclei have reciprocal connections with the cerebellum
The medial and inferior vestibular nuclei
Which vestibular nuclei give rise to the medial vestibulospinal tract
The medial, inferior and superior vestibular nuclei.
The medial vestibulospinal tract then descends bilaterally to the cervical segments of the spinal cord.
The descending medial longitudinal fasciculus continues as the…..
medial vestibulospinal tract which projects to the cervical LMN
The utricle sends fibers to the
Lateral vestibular nucleus via the superior vestibular ganglion
The saccule sends fibers to the
Inferior vestibular nucleus via the inferior vestibular ganglion.
The superior vestibular nucleus does what:
Coordinates head/eye movements
The medial vestibular nucleus does what:
Coordinates eye with head movements.
Lesions to the lateral lemniscus produce
Contralateral deafness
Lesions to the vestibular nuclei produce
Equilibrium, vertigo and nystagmus
Unilateral lesions to the MLF produce
Weakness of the ipsilateral lateral rectus, contralateral nystagmus, and normal convergence.
Bilateral lesions to the MLF produce
Internuclear opthalmoplegia - no eye adduction.
Pathway of the glossopharyngeal nerve
CN 9 leaves the medulla between the olive and the inferior cerebellar peduncle. It sends off a tympanic branch prior to exiting the skull via the jugular foramen anterior to CN 10 and 11 and then performates the dura and arachnoid to form the superior and inferior glossopharyngeal ganglia.
What fiber modalities run in the 9th cranial nerve.
- General somatic afferent
- General visceral afferent
- Special visceral afferent
- General visceral efferent
- Special visceral efferent.
CN 9 provides GSA sensation to:
- Back of the ear
- Inner surface of the tympanic membrane
- Posterior 1/3 of the tongue
- Upper pharynx-> superior ganglion->spinal trigeminal nucleus.
What is Hering’s nerve
Its a branch of the 9th CN from the carotid body and sinus.
Course/role of the GVA fibers of the 9th cranial nerves. (Carotid body/Sinus)
Fibers from the carotid body/sinus go to the inferior/petrosal ganglion and from there to the caudal nucleus solitarius and then the reticular formation hypothalamus.
Course/role of the SVA fibers of the 9th cranial nerves. (Taste)
Taste buds from the posterior 1/3 of the tongue, posterior pharynx and eustachian tube all go to the petrosal ganglion and then the rostral nucleus solitarius which ascend in the central tegmental tract and go to the contralateral thalamic VPM.
The efferent portion of the carotid sinus reflex is mediated by:
The 10th cranial nerve. CN 9 mediates the afferent portion.
Baroreceptors at the carotid bifurcation sense increases in blood pressure->CN9-> nucleus solitarius-> dorsal nucleus of 10-> decrease in blood pressure and heart rate.
Role of GVE fibers of the 9th cranial nerve
Parotid salivation is controlled by GVE fibers of CN9. Fibers from the inferior salivatory nucleus travel in CN9 via the tympanic/Jacobson’s nerve to the lesser petrosal nerve after which they synpase in the otic ganglion and travel with the auriculotemporal nerve (V3) to the parotid gland.
Role of the SVE fibers of CN9.
Innervation of the stylopharyngeus muscle and part of the superior pharyngeal constrictor. These fibers originate in the rostral nucleus ambiguous.
What are the consequences of a glossopharyngeal nerve injury.
Difficult to detect in isolation.
CN 9 injury leads to a decreased gag reflex, sinus reflex, and taste.
Glossopharyngeal neuralgia leads to pain behind the ear or in the mouth, and is often precipitated by swallowing and coughing.
General pathway of the vagus/CN10 nerve
The vagus nerve leaves the medulla between the olive and inferior cerebellar peduncle and exits via the jugular foramen.
What are the fiber modalities which run in the vagus nerve/CN 10.
GSA.
GVA.
SVA.
GVE.
SVA.
Role of the GSA fibers in the 10th cranial nerve.
- Sensation from the ear, external auditory meatus, and external surface of the tympanic membrane travel in the auricular branch/Arnold’s nerve.
- Sensation from the posterior fossa dura -> superior ganglion of CN10-> spinal trigeminal tract.
- Sensation from the larynx and pharynx -> inferior ganglion of 10 -> trigeminal spinal nucleus and tract.
What does the recurrent laryngeal supply
- Vocal cords
2. Subglottis
What does the inferior laryngeal supply
Larynx above the vocal folds.
It pierces the thyrohyoid membrane and unites with the external laryngeal nerve to form the superior laryngeal nerve.
Role of the GVA and SVA fibers of CN 10
Sensation of the pharynx, larynx, trachea, lungs, heart, esophagus, stomach, and thoracoabdominal viscera down to the splenic flexure. (GVA)
Aortic arch baroreceptors, aortic body chemoreceptors, and taste sensation in the epiglottis.
These fibers go to the inferior ganglion of 10 and then the tract solitarius.
What comprises the medullary respiratory center
- Nucleus ambiguous
- Nucleus solitarius
- Reticular formation
This area responds to vagal input and CO2 accumulation.
Role of GVE fibers in CN 10.
Dorsal motor nucleus of 10-> vagus-> thorax and abdomen where it branches into the right and left vagus nerves to innervate the abdominal viscera up to the splenic flexure.
The dorsal motor nucleus of 10 receives input from:
- Hypothalamus
- Olfactory system
- Reticular formation
- Solitary nucleus
Role of the SVE fibers in CN 10.
Innervate the pharyngeal constrictor muscles and the internal muscles of the larynx.
What are the three branches of the vagus nerve in the neck
- Pharyngeal branch
- Laryngeal nerve
- Cervical cardiac branches
Role of the pharyngeal branch of CN 10.
Innervates all muscles of the pharynx and soft palate except the stylopharyngeus and tensor veli palatini.
Role of the laryngeal branch of CN 10
Superior laryngeal nerve divides into the internal and external laryngeal nerves. The external branch supplies the inferior constrictor, cricothyroid, pharyngeal plexus and superior cardiac nerve.
Recurrent laryngeal nerve supplies the intrinsic laryngeal muscles except the cricothyroid.
Course of the cervical cardiac branches
- Right sided - travel behind the subclavian artery -> deep cardiac plexus.
- Left sided - travel with the trachea to the deep cardiac plexus. Also travels with the arch of the aorta and supplies the superficial cardiac plexus.
Features of unilateral CN 10 injury
- Hoarseness
- Dysphagia
- Dyspnea
- Uvular deviation to the normal side
- Ipsilateral decreased cough reflex
- Ipsilateral decreased carotid sinus reflex.
Features of bilateral CN 10 injury
- Asphyxia
- Dysphagia
- Dysarthria
- Paralysis of the esophagus and stomach with pain and emesis
- Tachycardia.
Cranial portion of CN 11.
Contains SVE fibers and arises from the nucleus ambiguous and joins with CN 10 and forms the recurrent laryngeal nerve.
Motor cortex fibers of CN 11.
Rootlets exit from between the ventral and dorsal roots of C1-C6 as rootlets and ascend posterior to the dentate ligament to enter the foramen magnum and join CN 10, following which it foes on the innervate the SCM and upper trap.
Pathway of CN 12.
Hypoglossal nucleus lies at the floor of the 4th ventricle beneath the hypoglossal trigone. The nerve exits the medulla between the inferior olive and the pyramid. It travels through the hypoglossal foramen and innervates intrinsic muscles of the tongue and all the extrinsic muscles of the tongue except the palatoglossus (CN X). Geniglossus, styloglossus and hypoglossus (CN XII)
