Cranial nerves Flashcards
1
Q
What is the CN I
A
olfactory
2
Q
what is the origin of the CN1
A
roof of nasal cavity
3
Q
what type of fibers does the CNI contain
A
special visceral afferent
4
Q
What type of information does the CN I carry?
A
sensory
5
Q
what is the function of CN1?
A
smell
6
Q
what is the cranial exit point of CN1?
A
olfactory foramina of the cribiform plate of ethmoid bone
7
Q
what is the name of the nucleus associated with the CN I ?
A
anterior olfactory nucleus, in the olfactory tract
8
Q
what is the brainstem attachment of the CN1?
A
the telecephalon
9
Q
what is the origin of CN II?
A
retina
10
Q
what are the structures supplied by CN II?
A
photoreceptors
11
Q
what type of fibers does the CNII contain?
A
special sensory afferent
12
Q
What is the function of CN II?
A
vision
13
Q
What type of nerve is CN II?
A
sensory
14
Q
What is the cranial point exit of the CNII?
A
optic canal
15
Q
What is the nucleus associated with the CN II?
A
lateral geniculate, in the thalamus
16
Q
What is the CN II?
A
optic nerve
17
Q
What is the cranial nerve III?
A
oculomotor
18
Q
what is the origin of the CNIII?
A
upper midbrain
19
Q
What are the structures innervated by the CN III?
A
superior middle inferior rectus
levator palpebrae superioris
inferior oblique (GSE)
pupil, ciliaris
20
Q
What types of fibers does the CN III contain?
A
general somatic efferent (from the oculomotor nucleus)
general visceral efferents (from the Edinger westphal nucleus)
21
Q
What is the function of the CN III?
A
eye movement + eye lid movement
22
Q
What type of nerve is the CN III?
A
motor
23
Q
What is the cranial point exit of the CN III?
A
superior orbital fissure
24
Q
What is the CN IV?
A
trochlear nerve
25
What is the origin of the CN IV?
midbrain
26
What are the nuclei of the CN III?
```
Edinger Westphal (visceral)
Oculomor (general somatic)
```
27
What is the nucleus name of the CN IV?
trochlear nucleus
28
What is the nucleus location of the CN IV?
inferior colliculus of midbrain
29
What type of nerve is the CN IV?
motor
30
What is the cranial point exit of the CN IV?
superior orbital fissure
31
What structures does the CN IV innervate ?
superior oblique
32
What type of fibers does the CN IV contain?
general somatic efferent
33
What is the function of the CN IV?
control eye movement
34
What is the course of the CN III?
emerges form brainstem, from oculomotor sulcus
passes between posterior and superior cerebral arteries
pierces dura matter to enter cavernous sinus just superior to trochlear nerve
enters orbit via superior orbital fissure
divides into superior and inferior branches
35
What is the course of the CN IV?
emerges from dorsal surface of midbrain
decussates with nerve of opposite side
continues into middle cranial fossa
passes at edge of tentorium cerebelli
enters into lateral wall of cavernous sinus below occulomotor nerve
enters orbital through superior orbital fissure
lies medial to frontal nerve
in orbit passes medially to origin of levator palpebrae superioris
enters orbital surface of superior oblique
only supplies superior oblique
36
What is the nucleus name of the CN V?
mesencephalic nucleus
motor nucleus
main sensory nucleus
spinal nucleus
37
What are the nucleus names of the CN V?
mesencephalic nucleus
motor nucleus
main sensory nucleus
spinal nucleus
38
What is the nucleus location of the CN V?
midbrain
lateral pons
pons
lower pons to spinal chord
39
What type of nerve is the CN V?
sensory + motor
40
What is the cranial point exit of the CN V?
V1 branch: superior orbital fissure
V2 branch: foramen rotundum
V3 branch: foramen ovale
41
What structures does the CN V innervate ?
```
skin of scalp, chin, jaw, ear, nose, oral cavity, face
muscles of mastication
tensor
eyelids
conjunctiva
```
42
What type of fibers does the CN V contain?
special visceral efferent fibers
| general somatic efferent fibers
43
What is the function of the CN V?
pick up sensation of touch pain temp. pressure, mastication muscles
44
What is the CN VI?
Abducens nerve
45
What is the origin of the abducens nerve CN VI?
pons
46
What are the structures supplied by the CN VI?
lateral rectus
47
What type of fibers does the CN VI contain?
General somatic efferents
48
What is the function of the CN VI?
eye movement
49
What type of nerve is the CN VI?
motor
50
What is the cranial exit point of the CN VI?
superior orbital fissure
51
What is the nucleus of the CN VI?
abducens
52
What is the location of the CN VI nucleus?
in floor of the 4th ventricle, near midline,
53
What is the course of the visceral component of the Oculomotor nerve?
```
edinger westphal
with main nerve to orbit
leave branch to inferior oblique
synapse in ciliary ganglion
postganglionic fibers emerge from ganglion in short ciliary nerve
pierce lamina cribosa of sclera
supply ciliaris + pupillae muscles
```
54
What does damage to the oculomotor nerve lead to?
| due to superficial position of nerve
```
lateral strabism
due to pressure on nerve
dilated pupil unresponsive to light
sign of growing masses on CN III
outflow to edinger westphal nucleus impaired
```
55
What is the pretectum?
poorly defined region located near the posterior diencephalon quadrigeminal plate of midbrain,
controls pupillary reflexes
56
What are the 2 main important reflexes carried out by the oculomotor nerve ?
pupillary reflexes and accomodation
57
What is the course of the abducens nerve?
originates at abducens nucleus located in caudal pons at level of facial colliculus
loop around abducens nucelus
give rise to bulge in floor of 4th ventricle
facial colliculus
travel ventrally to leave the abducens nucleus
exit brainstame at border of pons and medulla via Dorello's canal
bends sharply across upper border of petrous part of temporal bone
enter cavernous sinus
lies lateral to internal carotid artery
58
What does a lesion in the abducens nerve lead to ?
paralysis or weekness of ipsilateral rectus muscle
| therefor medial strabismus + diplopia
59
What is the specificity of the oculomotor nucleus?
4 paired subnuclei
| complex of paired + midline motor cells
60
What is the vagus nerve?
a branchiomeric nerve
61
What is the vagus nerve asssociated with?
• associated with the derivatives of the fourth and sixth pharyngeal arches.
62
What is the origin of the word vagus?
• vagus latin for “wandering”fibers of vagus nerve wander throughout thoracic + abdominal cavities
63
The vagus nerve contains 5 types of fibers, what are their names?
* somatic sensory fibers
* visceral sensory fibers
* special sense fibres
* branchial motor fibers
* visceral motor
64
What is the trajectory of the somatic sensory fibers of the vagus nerve?
from dura mater, outer ear to SPINAL NUCLEUS OF TRIGEMINAL NERVE via SUPERIOR JUGULAR GANGLION
65
What is the trajectory of the visceral sensory fibers of the vagus nerve?
Laryngopharynx –Superior aspect of larynx (above vocal folds) – Heart – Gastro intestinal tract (up to splenic flexure) --> CAUDAL PART OF SOLITARY NUCLEUS
66
What is the trajectory of the special sense fibers of the vagus nerve?
taste sensation to epiglottis + root of the tongue --> ROSTRAL PART OF THE SOLITARY NUCLEUS
67
What is the trajectory of the branchial motor fibers of the vagus nerve?
majority of muscles associated with pharynx + larynx --> responsible for initiation of swallowing + phonation -->NUCLEUS AMBIGUUS
68
What is the trajectory of the visceral motor fibers of the vagus nerve?
In thorax + abdomen, vagus nerve is main parasympathetic outflow to heart + gastro-intestinal organs --> DORSAL VAGAL NUCLEUS
69
What are the relations of the vagus nerve with the rhomboid fossa?
- motor nucleus in floor of fourth ventricle, just lateral to hypoglossal nucleus and underlying elevation in floor of the fourth ventricle called the vagal trigone.
70
What are the 4 nuceli of the vagus nerve?
spinal trigeminal nucleus
nucelus ambiguus
solitary nucleus
dorsal vagal nucleus
71
Which types of fibers are involved with the spinal trigeminal nucleus and what are their trajectory?
VISCERAL SENSORY FIBERS:
From Laryngopharynx –Superior aspect of larynx (above vocal folds) – the internal surfaces of the laryngopharynx and larynx - Heart – Gastro-intestinal tract (up to the splenic flexure) –to caudal part of the solitary nucleus via GANGLIUM NODOSUM (inferior ganglion).
72
Which types of fibers are involved with the solitary nucleus and what are their trajectory?
CAUDAL PART OF SOLITARY NUCLEUS
• SPECIAL SENSE FIBRES : taste sensation to the epiglottis and root of the tongue: NUCLEUS: rostral part of the solitary nucleus //GANGLION: inferior ganglion (ganglium nodosum)
(VISCERAL SPECIAL SENSORY NUCLEUS: ROSTRAL PART OF SOLITARY NUCLEUS)
73
Which types of fibers are involved with the nucleus ambiguus and what are their trajectory?
BRACHIAL MOTOR FIBERS:
the majority of the muscles associated with pharynx and larynx: responsible for initiation of swallowing + phonation.
o Muscles of the Pharynx: innervated by pharyngeal branches of vagus nerve: Superior, middle, inferior pharyngeal constrictor muscles. Palatopharyngeus. Salpingopharyngeus.
o Muscles of the Larynx. Innervation to intrinsic muscles of larynx achieved via recurrent laryngeal nerve + external branch of superior laryngeal nerve.
74
Which types of fibers are involved with the dorsal vagal nucleus and what are their trajectory?
VISCERAL MOTOR FIBERS:
In the thorax and abdomen, the vagus nerve is the main parasympathetic outflow to the heart and gastro-intestinal organs:
Parasympathetic Functions: In thorax + abdomen, vagus nerve main parasympathetic outflow to heart + gastro-intestinal organs.
The Heart: Cardiac branches arise in thorax, conveying parasympathetic innervation to sino-atrial and atrio-ventricular nodes of heart branches stimulate reduction in resting heart rate. They are constantly active, producing rhythm of 60 – 80 beats per minute. If vagus nerve was lesioned, resting heart rate would be around 100 beats per minute.
Gastro-Intestinal System: vagus nerve provides parasympathetic innervation to majority of abdominal organs: sends branches to esophagus, stomach, most of intestinal tract – up to splenic flexure of large colon. function of vagus nerve: to stimulate smooth muscle contraction + glandular secretions in these organs. Eg. stomach, vagus nerve increases rate of gastric emptying + stimulates acid production.
75
What is the first part of the trajectory of the vagus nerve?
emerges from brainstem from posterior olivary sulcus, together with CN IX
exits cranium via JUGULAR FORAMEN, with glossopharyngeal + accessory nerves (CN IX and XI respectively)
descends in neck within carotid sheath (posterior part) in angle between internal jugular + common carotid artery
76
In the neck, the vagus nerve splits into 5 cervical branches to 5 different locations, describe.
- Auricular nerve
- Meningeal nerve
- Pharyngeal branches
- Superior laryngeal nerve
- Branches to the carotid body
77
What is the trajectory of the auricular nerve of the vagus nerve?
leaves main trunk of vagus nerve running backward + upward outer ear.
78
What is the trajectory of the meningeal nerve of the vagus nerve?
enters cranial cavity through jugular foramen to innervate dura mater in posterior cranial fossa.
79
What is the trajectory of the pharygeal branches of the vagus nerve?
run downward, toward anterior surface of pharynx forming plexus (EFFERENT VISCERAL FIBERS – BRANCHIAL MOTOR FIBERS) for all pharyngeal muscles with the exception of stylopharigeus.
There are also VISCERAL SENSORY FIBERS from pharynx + soft palatus, although main component provided by IX CN.
80
What is the number of the vagus nerve?
X
81
What is the trajectory of the superior laryngeal nerve of the vagus nerve?
branch of vagus nerve from high in neck: divides into internal branch (provides sensory innervation to supraglottic area of larynx + base of the tongue (some VISCERAL SENSORY FIBERS)) + external branch (VISCERAL MOTOR FIBERS)(provides motor innervation to cricothyroid muscle (which tenses the vocal cords) + some branches to inferior pharyngeal constrictor muscle)
82
What is the trajectory of the branches to the carotid body of the vagus nerve?
variable in number, may arise from inferior ganglion or travel in pharyngeal branch, and sometimes insuperior laryngeal nerve. Form a plexus with glossopharyngeal rami and branches of cervical sympathetic trunk
83
What is the CN XII?
hypoglossal nerve
84
What is the specificity of the hypoglossal nerve?
- only a somatic motor (general somatic efferent) component
85
What kind of movement does the hypoglossal nerve control?
- controls all tongue movements.
86
What are the 2 pathologies associated with the hypoglossal nerve?
- Nuclear or infranuclear lesions produce paralysis, atrophy, fasciculations of tongue on involved side.
- Supranuclear lesions produce mild to moderate contralateral weakness that may be transient.
87
What is the trajectory of the hypoglossal nerve?
- hypoglossal nerve arises from hypoglossal nucleus in medulla oblongata (located along midline + forms hypoglossal triangle in floor of IV ventricle)
emerges from medulla laterally, between pyramid + olive as a number of rootlets
exits cranium via hypoglossal canal
passes laterally across posterior cranial fossa in subarachnoid space
emerges from canal in plane medial to internal jugular vein, internal carotid artery, ninth, tenth and eleventh cranial nerves
passes interval between artery and internal jugular vein
runs forwards with external carotid artery and uppermost loop of lingual artery located medial to it.
88
Where is the hypoglossal nucleus located?
in the medulla
89
What is the cranial exit point of the hypoglossal nerve?
hypoglossal canal
90
What is the CN XI?
Accessory nerve
91
What is the accessory nerve?
• motor nerve with cranial and spinal portions.
92
What is the trajectory of the spinal portion of the CN XI?
• spinal portion: from lower motor neurons in lateral part of upper four/five segments of cervical spinal cord.
o from the ventral horn cells of spinal cord segments C1 -C5
emerge laterally between anterior and posterior spinal nerve roots
form single trunk
ascends into skull through foramen magnum
exits skull through jugular foramen in same sheath of dura mater as vagus (separated from it by fold of arachnoid)
In jugular foramen: receives one/two filaments from cranial part of nerve or joins it for short distance and separates from it again
As it exits from jugular foramen
runs backwards then descends obliquely behind digastric and stylohyoid muscles to upper part of sternocleidomastoid
pierces muscle
gives several filaments to muscle and joins with branches from 2nd cervical nerve
courses obliquely across posterior triangle of the neck
unites with C2 and C3 there
end in deep surface of trapezius muscle
(beneath the trapezius
forms plexus with C3 and C4
fibers are distributed to muscle.
93
What is the trajectory of the cranial portion of the CN XI?
cranial part of the XI CN can be seen as functionally part of vagus nerve.
cranial portion (accessory portion): smaller
fibers arise from cells of nucleus ambiguus
four/five delicate rootlets from side of the medulla oblongata, below roots of vagus nerve
runs laterally to jugular foramen
interchanges fibers with spinal portion or becomes united to it for short distance
here also connected by one/two filaments with jugular ganglion of the vagus
then passes through jugular foramen
separates from spinal portion and continued over surface of ganglion nodosum of the vagus (adherent to surface)
distributed principally to pharyngeal and superior laryngeal branches of vagus
through pharyngeal branch: supplies musculus uvulae and levator veli palatini. Few filaments continued into trunk of vagus below ganglion
distributed with recurrent nerve and cardiac nerves
94
Which muscles does the CN XI innervate?
trapezius + sternocleidomastoid
95
What is the cranial exit point of the CN XI?
jugular foramen
96
Describe and explain the jugular foramen.
o Anterolateral to Hypoglossal canal, at level of the styloid process
o for Glossopharyngeal nerve, internal jugular vein, vagus nerve, emissary veins and the spinal accessory nerve
o three compartments: anterior, middle, posterior
97
what kind of fibers does the CN XI posses?
motor
98
What is CN VII?
Facial nerve
99
What does the CN VII supply?
supplies muscles of second embryological branchial arch (include superficial muscles of face (auricular muscles, orbicularis oculi, buccinator, nasolabialis muscle group), two strap muscles connected to hyoid bone (stylohyoid + posterior belly of digastric), stapedius muscle of middle ear.
100
Which 4 types of fibers does the CN VII possess?
* Special (visceral) sensory fibers: taste from anterior 2/3 of the tongue (solitary nucleus)
* Somatic sensory fibres: spinal nucleus of the V CN
* Branchiomeric motors fibers (from motor nucleus) supplies muscles of second pharyngeal arch.
* Visceral motor fibers (general visceral efferents): preganglionic autonomic axons (lacrimalgland + submandibular + sublingual glands: salivatory nucleus).
101
What are the names of the 4 nuclei of the facial nerve?
* Visceral sensory nucleus (taste)
* Somatic sensory nucleus
* Visceral motor nucleus of the VII CN
* FACIAL MOTOR NUCLEUS (branchial nucleus)
102
Describe the Visceral sensory nucleus of the CN VII
o Rostral end of solitary nucleus
o Solitary nucleus formed by column of neurons in lateral tegmentum of pons + medulladivided into 2 funcionally different sections: a rostral portion (special sense (taste)) + caudal portion (somatosensory innervation of viscera (e.g. pain))
o Special sense root of nerve has unipolar cell bodies in geniculate ganglion of facial nerve --> supplies taste buds in palate via greater petrosal nerve + taste buds in anterior 2/3 of tongue via chorda tympani.
103
Describe the Somatic sensory nucleus of the CN VII
o Spinal nucleus of trigeminal nerve.
o Receives fibres from external auditory meatus + small region on posterior aspect of the auricle.
o First order neurons located in geniculate ganglion.
o 2 sensory nuclei (second order neurons) related to unipolar cell bodies (first order neurons) in geniculate ganglion of facial nerve.
104
Describe the visceral somatic nucleus of the CN VII
o Superior salivatory nucleus: located in dorso-lateral tegmentum of pons:
Parasympathetic preganglionic fibres run within intermedius nerve + at level of external genu of vii cn divide into two components:
• 1st group passes in pterygopalatine ganglion through greater petrosal nerve
• 2nd group run to submandibular ganglion through chorda tympani
Preganglionic fibres run within intermedius nerve
105
Describe the facial motor nucleus of the CN VII
o In middle of hindbrain at level of LATERAL TEGMENTUM IN CAUDAL PONS.
o Before exiting pons: loops, as internal genu, around abducens nucleus facial colliculus in floor of IV ventricle.
o receives bilateral projections from motor cortex.
106
What is the Nervus intermedius (nerve of Wrisberg)?
part of the CN VII
107
What types of fibers does the Nervus intermedius (nerve of Wrisberg) contin, and what does it innervate?
contains general somatic afferent, special visceral afferent, general visceral efferent fibers convey sensation from posterior region of external auditory canal + concha; taste from anterior two‐thirds of the tongue; secretomotor function for lacrimal glands, submandibular + sublingual glands, minor salivary glands in nasal cavity, paranasal sinuses, palate.
108
Where does the Nervus intermedius (nerve of Wrisberg) travel?
• In cerebellopontine angle, nervus intermedius travels from pons to internal auditory meatus between motor root of VII + CN VIII.
109
What is the name of the ganglion associated with the Nervus intermedius (nerve of Wrisberg)?
• Geniculate ganglion (in temporal bone along course of facial nerve): contains primary cell bodies of special visceral afferent taste fibers + general somatic afferent sensory fibers.
Preganglionic general visceral efferent fibers + special visceral efferent fibers pass through geniculate ganglion without synapsing.
110
Where does the Nervus intermedius (nerve of Wrisberg) subdivide?
• Chorda tympani + greater superficial petrosal nerve: subdivisions of this nerve.
111
What is the trajectory of the facial nerve?
Together with intermedius nerve : emerges from brainstem at pontomedullary junction at level of cerebello-pontine angle
travels in the subarachnoid space
leaves skull via internal acoustic meatus (very close to VIII CN vestibulocochlear nerve)
enters internal acoustic meatus
reaching medial wall of middle ear
bends sharply backwards above promontory forming its genu where geniculate ganglion found (facial canal in the temporal bone
different components of VII nerve begin to diverge
branches released)
arches downwards in medial wall of middle ear
reaches stylomastoid foramen
supplies the stapedius muscle
escapes canal at the stylomastoid foramen
main trunk emerges from stylomastoid foramen to form terminal branches
exits cranial cavity through stylopharingeal foramen
divides within substance of parotid gland into superior (temporofacial) + inferior (cervicofacial) trunks
collectively give off 5 main peripheral branches that radiate out across face (temporal, zygomatic, buccal, mandibular, cervical branches)
112
What are the pathologies associated with the CN VII?
Peripheral facial nerve palsy (smoothing out of forehead, eyebroy drop, dropping of corner of mouth)
113
Where are the nuclei of the CN VII located?
pons
114
What is the cranial entry point of the CN VII?
internal accoustic meatus
115
What is the cranial exit point of the CN VII?
stylomastoid foramen
116
What is the Middle ear: (tympanic cavity)?
o bony conduction of sounds via transference of sound waves in air collected by auricle to fluid of inner ear.
o In middle ear: petrous portion of temporal bone, filled with air, secondary to communication with nasopharynx via auditory (eustachian) tube.
117
What are the names and the important associations of the walls of the tympanic cavity complex?
lateral wall largely formed by tympanic membrane
posterior wall contains mastoid antrum + communicates with mastoid air cells
medial wall contains oval window; posterior to + separated by the promontory (basal turn of the coclhea) round window: also called the labyrinthine wall
anterior wall (carotid wall: because thin plate of bone separates carotid canal + tympanic cavity) perforated by tympanic branch of internal carotid artery + deep petrosal nerve (connects sympathetic plexus of carotid to tympanic plexus in tympanic cavity)+ houses auditory tube
roof of the tympanic cavity: tegmental wallseparates epitympanic recess (contains malleus + incus) from middle cranial fossa
floor of middle ear: jugular wallseparates tympanic cavity from internal jugular vein
118
What is the greater petrosal nerve of the CN VII and its trajectory?
```
(carries visceral motor fibres)
passes through greater petrosal foramen
leaves cranium through foramen lacerum
runs close to lesser petrosal nerve (related to the CN IX)
together form vidian nerve
```
119
Where does the greater petrosal nerve of the Facial nerve synapse?
• synapses in pterygopalatine ganglion (whose postganglionic fibers run in nasopalatine + greater palatine nerves (V2)
in zygomatic nerve (V2)
zygomatico-temporal branch (V2)
lacrimal branch (V1))
stimulate nasal, palatal, nasopharyngeal glands + provides autonomic innervation to lacrimal gland.
120
What is the strapedius nerve of the Facial nerve?
innervates stapedius muscle, in facial canal: nerve releases chorda tympany--> joins lingual nerve (branch of V3) --> choarda tympani – visceral motor fibers: involved in conveying visceral motor fibres + special sense fibers. Sensory component of chorda tympani carries special sense (taste from anterior 2/3 of the tongue) + related to the solitary nucleus
121
What are the facial nerve branches?
o Within facial canal: Nerve to the Stapedius muscle; Chorda tympani; Greater petrosal nerve
o As it exits stylomastoid foramen (Extracranial): Posterior auricular; Digastric nerve; Stylohyoid nerve
122
What is the CN VIII?
Vestibulotrochlear nerve
123
What are the 2 nuclei of the vestibulotrochlear nerve?
Abducens (posterior surface of pons)
Cochlear (dorsal and ventral)
(pontomedullary junction)
124
What is the cranial exit point of the CN VIII?
internal accoustic meatus
125
What types of fibers does the CN VIII possess?
sensory
126
What does the vestibulotrochlear nerve innervate?
inner ear labyrinth structures
127
What is the CN IX?
Glossopharyngeal nerve
128
What are the main 4 types of fibers the CN IX contains and what are their courses?
o Somatic sensory fibers: from outer ear (superior ganglion of the ix cn) to spinal nucleus of trigeminal nerve
o Visceral sensory fibers: carotid body + sinus, pharyngeal mucosa, posterior tongue, middle ear (inferior ganglion of the ix cn) to nucleus of tractus solitarius (solitary nucleus) caudal portion.
o Special sense fibers taste buds on posterior 3rd of tongue (inferior ganglion of the ix cn) to nucleus of tractus solitarius (solitary nucleus) (rostral portion).
o Branchial motor fibers: to stylopharyngeus from nucleus ambiguus
o Visceral motor: to parotid gland (via otic ganglion) from nucleus salivatorius inferior (inferior salivatory nucleus)
129
What are the main nuclei of the glossopharyngeal nerve?
Somatic sensory nucleus: from outer ear. The nucleus is the spinal nucleus of the v .
Somatic sensory ganglion: the sensory ganglion cells lie in superior ganglion of ix cn. They convey somatic information to spinal tract of trigeminal nerve. In its short (~15 mm) subarachnoid course, it traverses cerebellomedullary cistern.
Superior ganglion (jugular ganglion): situated in upper part of groove in which nerve lodged during passage through jugular foramen; very small,usually regarded as detached portion of petrous ganglion.
Inferior ganglion (petrous ganglion): larger than superior, located in depression at lower border of petrous portion of temporal boneo
special sense ganglion: inferior ganglion of ix cn (petrous ganglion)
130
What is the trajectory of the glossopharyngeal nerve?
emerges from medulla oblongata in groove between inferior olive and inferior cerebellar peduncle
exits medulla oblongata from postolivary sulcus
passes laterally across flocculus
leaves skull through pars nervosa of jugular foramen (grooves lower border of petrous part of temporal bone) in separate sheath of dura mater
passes between internal jugular vein + internal carotid artery
descends in front of the IC. + beneath styloid process + muscles connected with it
131
What are the names of the 5 branches of the CN IX?
```
Jacobson nerve ( and its lesser petrosal nerve branch)
stylopharingeus branch
pharyngeal branches
tonsillar branches
lingual branches
```
132
What is the jacobson nerve of the glossopharyngeal nerve?
o tympanic branch of glossopharyngeal nerve (CN IX)
o arises from inferior ganglion.
o carries preganglionic parasympathetic fibres from inferior salivary nucleus --> eventually enter otic ganglion.
o Enters middle ear cavity via inferior tympanic canaliculus --> contributes to tympanic plexus (on cochlear promontory)
o parasympathetic fibres leave plexus as lesser petrosal nerve.
133
What is the lesser petrosal nerve?
part of the jacobson nerve of the glossopharyngeal nerve
o branch of the tympanic nerve
o exits cranium via foramen ovalesynapses in otic ganglion (located in infratemporal fossa, below foramen ovale, close to madibular branch of trigeminal nerve)
o Post-ganglionic fibres from otic ganglion (derived from glossopharyngeal nerve CN IX and located just below foramen ovale), travel with auriculotemporal branch of V3 --> innervate parotid gland.
Timpanic nerve – lesser petrosal nerve –otic ganglion – auricolotemporal nerve (V3) – parotid gland
134
What is the stylopharyngeal branch of the glossopharyngeal nerve?
to lower border of stylopharyngeus --> then curves forward forming arch on side of neck --> lying on stylopharyngeus + middle pharyngeal constrictor muscle.
135
What is the pharyungeal branch of the glossopharyngeal nerve?
3/4 filaments which unite with pharyngeal branches of vagus + sympathetic nerves (opposite middle pharyngeal constrictor) --> form pharyngeal plexus
136
what is the tonsilar branch of the glossopharyngeal nerve?
supply palatine tonsil --> forms plexus from which filaments distributed to soft palate + fauces --> there: communicate with palatine nerves
137
What are the 2 inguinal branches of the glossopharyngeal nerve?
a. one supplies vallate papillae + mucous membrane covering base of tongue;
b. other supplies mucous membrane + follicular glands of posterior part of tongue + communicates with lingual nerve
138
What is the special sensory function of the glossopharyngeal nerve?
provides taste sensation to posterior 1/3 of the tongue, via lingual branch
139
What can a lesion of the glosspharyngeal nerve cause?
* loss of motor fibers to stylopharyngeus muscle;
* loss of taste on posterior one-third of tongue + vallate papillae;
* loss of parasympathetic supply to parotid via fibers to otic ganglion;
* loss of visceral afferents fibers to pharynx, carotid body + sinus, posterior one-third of tongue, tympanic cavity, mastoid antrum, air cells, auditory tube;
* loss of general sensory fibers to external ear.
* Loss of afferent limb of gag (pharyngeal) reflex.
* Pharyngitis can lead to glossopharyngeal neuralgia (sore throat + horrible ear pain without ear infection)
-->Testing gag reflex by lightly touching wall of pharynx
140
What is the main function of the vagus nerve?
main parasympathetic outflow to heart + gastro-intestinal organs.
141
What is th function of the CN X in the gastrointestinal organs?
vagus nerve provides parasympathetic innervation to majority of abdominal organs: sends branches to esophagus, stomach, most of intestinal tract – up to splenic flexure of large colon. function of vagus nerve: to stimulate smooth muscle contraction + glandular secretions in these organs. Eg. stomach, vagus nerve increases rate of gastric emptying + stimulates acid production.
142
What is the main function of the vagus nerve in the heart?
Cardiac branches arise in thorax, conveying parasympathetic innervation to sino-atrial and atrio-ventricular nodes of heart --> branches stimulate reduction in resting heart rate.
They are constantly active, producing rhythm of 60 – 80 beats per minute. If vagus nerve was lesioned, resting heart rate would be around 100 beats per minute.
143
In the thorax, the vagus nerve splits into a right side and a left side, describe the trajectory of the right vagus nerve.
On right side: nerve passes across subclavian artery between it + right innominate vein -->descends by side of trachea to back of root of lung --> spreads out in posterior pulmonary plexus
right vagus nerve passes anterior to subclavian artery + posterior to sternoclavicular joint -->entering thorax -->descends in thorax, first lying posterolateral to brachiocephalic artery, then lateral to trachea + medial to terminal part of azygos vein.
144
In the thorax, the vagus nerve splits into a right side and a left side, describe the trajectory of the left vagus nerve.
vagus enters thorax between left carotid + subclavian arteries, behind left innominate vein --> crosses left side of arch of aorta --> descends behind root of left lung, forming posterior pulmonary plexus --> from this runs along anterior surface of esophagus --> unites with nerve of right side in esophageal plexus --> continued to stomach
145
There are 5 branches that emerge from the vagus nerve in the thorax, the first one is called the recurrent laryngeal nerve, what is its trajectory?
Right recurrent laryngeal nerve:originates at root of neck --> loops posteriorly around subclavian artery --> ascends behind right lobe of thyroid --> enters larynx behind cricothyroid muscle and inferior cornu of thyroid cartilage --> innervates all intrinsic laryngeal muscles except cricothyroid.
Left recurrent laryngeal nerve comes from left vagus nerve --> loops posteriorly around arch of aorta --> ascends in tracheoesophageal groove posterior to left lobe of thyroid --> enters larynx + innervates muscles in similar fashion as right nerve.
146
What is the trajectory of the Cardiac branches (inferior cardiac nerve) of the vagus nerve?
(superior and inferior cardiac branches),regulate heart rate + provide visceral sensation to organ. Inferior cardiac branch or ramus cardiaci inferior:
On right side: arises from trunk of vagus as it lies beside trachea.
On left side: originates from recurrent laryngeal nerve only. Branches end in deep part of cardiac plexus.
147
What is the trajectory of the Esophageal branches of the vagus nerve?
anterior + posterior branches --> form esophageal plexus. Posterior surface of pericardium supplied by filaments from this plexus.
148
What are the 2 last throacic branches of the vagus nerve'
- Anterior bronchial (anterior vagal trunk)
| - Posterior bronchial (posterior vagal trunk).
149
The vagal trunks enter abdomen via esophageal hiatus: opening in diaphragm, the vagus then splits into 3 abdominal branches, what are their names?
gastric branches
celiac branches
hepatic branches
150
What is the trajectory of the gastric branch of the vagus nerve?
(rami gastrici) supply stomach.
Right vagus forms posterior gastric plexus and left forms anterior gastric plexus. Branches lie on posteroinferior and anterosuperior surfaces, respectively.
151
What is the trajectory of the celiac branch of the vagus nerve?
(rami celiaci) derived mainly from right vagus nerve --> join celiac plexus + supply pancreas, spleen, kidneys, adrenals, intestine
152
What is the trajectory of the hepatic branch of the vagus nerve?
originate from left vagus --> join hepatic plexus and through it are distributed to liver
153
WHat are th 2 components of the oculomotor nerve?
o Somatic motor: Supplies inferior, medial, superior rectus muscles and to the inferior oblique muscle of the eye and the levator palpebrae superioris muscle of the upper eyelid.
o Visceral motor: Parasympathetic innervation of constrictor pupillae and ciliary muscles.
154
What are the subnuclei of the oculomotor nuclei?
o nucleus composed of complex of paired + midline motor cells.
o four paired subnuclei supplying innervation to inferior, medial, superior rectus muscles, inferior oblique muscle.
o single caudal, dorsal midline nucleus providing innervation to levator muscle.
o motor fibers to superior rectus decussate within 3rd nerve nucleus + join fascicle of contralateral oculomotor nerve.
155
Describe the Edinger Westphal nucleus
o for 2 juxtaposed + intermingled cell groups of midbrain that differ i connectivity + neurochemistry.
o part of oculomotor complex: source of parasympathetic preganglionic motoneuron input to the ciliary ganglion, through which it controls pupil constriction + lens accommodation.
o Composed of small, multipolar, preganglionic parasympathetic neurons,
o lies dorsal to main oculomotor nucleus.
o Its neurons give rise to axons that travel in oculomotor nerve + synapse with postganglionic neurones in ciliary ganglion.
o lies at level of superior colliculi
o Laterally: medial longitudinal fasciculus (MLF)
o Through tegmentum and Red nucleus and medial to Crus cerebri
156
How are pupillary relfexes achieved?
Light shining in one eye causes constriction of pupil in eye (direct response) + in other eye (consensual response).
set of fibers leave optic tract --> terminate in pretectal nuclei (rostral to superior colliculus on each side) --> cells in pretectal area project bilaterally to preganglionic parasympathetic neurons in Edinger-Westphal (or accessory oculomotor) nucleus (adjacent to neurons ofoculomotor (cranial nerve III) nucleus) --> contralateral nucleus reached though the POSTERIOR COMMISSURE --> Preganglionic neurons in Edinger-Westphal nucleus send axons out of brain stem in oculomotor nerve to innervate ciliary ganglion --> ganglion contains postganglionic neurons (short CILIARY NERVE) that innervate smooth muscle of pupillary sphincter that constricts pupil --> sympathetic pathway innervates pupillary radial iris muscles that dilate pupils.
157
What is accomodation and how does it occur?
o to observe object close up, ciliary muscle contracts reflexly and lens bulges passively .
o thicker lens has greater refractive power to bring close-up objects into focus on retina.
o ACCOMODATION REFLEX involves:
1. Converging of the 2 eyes, as a result of increased tone in medial rectus (VERGENCE)
2. contraction of sphicter pupilae to eliminate passage of light through thinner periferal portion of lens.
158
Describe the trochelar nucleus
o Nerve fibers leaving nucleus pass posteriorly to reach posterior surface of midbrain.
o nucleus receives corticonuclear fibers from both cerebral hemispheres.
o receives tectobulbar tract from superior colliculus (to connect trochlear nucleus with visual cortex)
o Receives fibers from medial longitudinal fasciculus by which it is connected to nuclei of 3rd (oculomotor), 6th (abducent) and 8th (vestibulocochlear) cranial nerves
159
Where is the trochlear nucleus?
Lies at level of the inferior colliculus of the midbrain, near the cerebral aqueduct.
