CRANIAL NERVES AND CRANIAL PARASYMPATHETIC GANGLIA
CRANIAL NERVES:
Fibres: May be motor (efferent), sensory (afferent) or mixed.
Nomenclature: Named cranial nerves exit the skull via foramina and are covered by cranial meninges.
Location of nuclei:
1. Brainstem N3 - 10.
2. Spinal component N 11 (Accessory).
Types of Nuclei and Fibres carried:
1. Motory (efferent N3, 4, 5, 6, 7, 9, 10, 11, 12).
2. Sensory (afferent N5, 7, 9, 10).
3. Parasympathetic N3, 7, 9, 10.
4. Special sensory N1, 2, 7, 8, 9, 10, tractus solitarius.
Subdivision of Nuclei:
1. Somatic motor (efferent).
2. Visceral motor (efferent).
3. Visceral sensory (afferent).
4. Somatic sensory (afferent).
Cranial Nerves:
1. Olfactory.
2. Optic.
3. Oculomotor.
4. Trochlear.
5. Trigeminal.
6. Abducent.
7. Facial.
8. Vestibulocochlear.
9. Glossopharyngeal.
10. Vagus.
11. Accessory.
12. Hypoglossal.
OLFACTORY NERVE:
Type: Special sensory function - smell (special visceral afferent).
Elements:
1. Olfactory neurosensory cells in nasal olfactory mucosa (superior nasal concha, upper septum, roof).
2. Olfactory nerve, bulb, cribriform plate, olfactory tracts.
3. Unmyelinated axons/nerve filaments.
4. Central tracts: An olfactory tract divides into lateral and medial olfactory striae. Lateral striae relays in the anterior temporal lobe piriform cortex, the latter made up of Amygdala, uncus and anterior end of the parahippocampal gyrus. Medial olfactory striae is associated to the septal area (adjacent to the septum pellucidum) by the diagonal band of Broza. Close links exist between the olfactory cortex and the hypothalamus, brainstem and limbic system.
OPTIC NERVE:
Type: Special sensory function - sight, light reflexes.
Elements:
Optic retinal neuroepithelium, optic nerves, myelinated fibres (projection of white matter of cerebrum - covered by dura, pia, arachnoid and in continuity with the cerebral subarachnoid cerebro-spinal fluid), optic chiasma, optic tracts. Fibres terminate in the lateral thalamic geniculate bodies and via the optic radiations in the primary visual cortex sited on the calcarine sulci (occipital lobes of brain) - Striate cortex (areas 18, 19). Apart from the fibres passing to the lateral geniculate bodies (thalamus) a second pathway is via the temporal lobe and retrolentiforme part of the capsula interne (Meyer’s Loop) and terminates in the calcarine sulcus. There is also relay in the superior colliculus (i.e. for body reflexes to light). The pretectal region receives fibres related to pupil constriction.
Important Components of the Visual Pathways:
1. Retina.
2. Optic nerves (damage causes monocular blindness).
3. Optic chiasm (pressure by a tumour cause bilateral temporal hemianopia).
4. Optic tracts.
5. Corpus quadrigemina (lat. geniculate body).
6. Superior colliculus.
7. Pretectal region.
8. Meyer’s Loop, capsula interne.
9. Optic radiations in occipital lobe.
10. Calcarine sulcus and primary visual cortex (area 17 and 18) in the occipital lobe (visual stria of Gennari or striate cortex).
OCULOMOTOR NERVE- LR6 (SO4)3
Type: Motory - striated and smooth muscle - eye movements.
Supplies:
1. All extra ocular eye muscles (somatic efferent) except sup. Oblique and lat. rectus. These are supplied by trochlear and abducent, respectively.
2. Levator palpebral superioris, (also supplied by sympathetic nerves).
3. Sphincter papillae and ciliary smooth muscles via ciliary (parasympathetic) ganglion (visceral efferent) and short ciliary nerves. Via Edinger-Wesphal nucleus (sited in midbrain).
Orbital branches:
Superior: Sup. Rectus, levator palpebral. Superioris.
Inferior: Med. and inf. rectus muscles, inf. oblique.
Nuclei:
1. Somatic motor (midbrain): Floor of aqueduct of midbrain.
2. Somatic visceral (Edinger Wesphal accessory nucleus): Cranial end of main nucleus.
TROCHLEAR NERVE - LR6 (SO4)3
Type: Motor nerve to superior oblique (general) somatic efferent.
Supplies:
1. Sup. oblique only.
Nucleus: Floor of aqueduct of midbrain. Caudal to nucleus of N3 at the level of the inferior colliculus.
TRIGEMINAL NERVE:
Type: Mixed-general sensory and motory (branchial motor component as the special visceral efferent fibres supply muscles originating from the first branchial arch). Sensory to face/head and supplies muscles of mastication.
Three Sensory Divisions:
1. Ophthalmic (VI).
2. Maxillary (V2).
3. Mandibular (V3).
Nuclei:
1. Motory nucleus - pons, floor of the 4th ventricle.
2. Pontine trigeminal nucleus (chief sensory nucleus): floor of the 4th ventricle.
3. Mesencephalic nucleus (lateral to cerebral midbrain aqueduct).
4. Spinal nucleus (inferior pons and medulla).
Autonomic Ganglia of the Head and Neck:
Are related to and receive input from the trigeminal nerve and are thus briefly discussed here. There are four pairs of autonomic ganglia - ciliary, pterygopalatine, otic and submandibular - sited in the head. Each ganglion receives 3 roots:
a. Sympathetic root - pass through ganglia.
b. Parasympathetic root (N3, 7, 9, 10) - relay in the ganglia.
c. Sensory root (from trigeminal nerve) - pass through ganglia.
The end organ innervation is as follows:
a. Ciliary ganglion: Pupil sphincter, ciliary muscle (accommodation reflex).
b. Pterygopalatine ganglion: Lacrimal and nasal glands.
c. Submandibular ganglion: Submandibular and sublingual glands.
d. Otic ganglion: Parotid gland.
Elements: Trigeminal (semilunar) ganglion lodged in the trigeminal cave (depression near the apex of the petrous part of the temporal bone - i.e. dural recess of the middle cranial fossa).
Ophthalmic Nerve or Division (VI): Sensory.
Areas Supplied: Scalp, forehead, superior portion of face (eye, lacrimal gland, conjunctiva, nasal cavity, upper eyelid, and nose).
Branches:
1. Lacrimal (to lacrimal gland and conjunctiva).
2. Frontal (br. supratrochlear, supraorbital).
3. Nasociliary (br. Long ciliary, ganglionic to the ciliary ganglion, anterior and posterior ethmoidal and the infratrochlear nerve). Divides into medial and lateral terminal branches that supply the septal mucous membrane, lateral wall of nose, ala and tip of nose (external nasal nerve). Communicates with facial nerve.
Ciliary Ganglion:
Site: Posterior orbit, between optic nerve and the lateral rectus muscle.
Roots:
1. Long (sensory) root from naso-ciliary nerve - eyeball supplied.
2. Short (parasympathetic) motor root - from oculomotor nerve (Edinger - Wesphal nucleus) - relay in ganglion and supply pupillary and ciliary muscle.
3. Sympathetic - cavernous plexus from the sup. Cervical ganglion.
Distribution: Via short ciliary nerves (inf. and sup.) to ciliary muscle, iris and cornea (i.e. globe of eye).
Maxillary Nerve or Division (V2): Sensory
Areas Supplied: Dura, maxillary sinus mucosa, roots of the premolar and maxillary molar teeth, nasal septum, roots of the maxillary central, lateral and canine teeth, lower eyelid, nose and upper lip.
Course of Nerve: From the trigeminal ganglion passes through the foramen rotundum, pterygopalatine fossa, pterygomaxillary fissure, infratemporal fissure and exits the infraorbital canal and foramen as the infraorbital nerve.
Branches:
1. In Skull: Meningeal (recurrent).
2. In Pterygo-palatine fossa:
a. Zygomatic (br. Zygomatic - temporal and zygomatic - facial).
b. Ganglionic (to spheno-palatine ganglion).
c. Posterior superior alveolar (dental) (br. lat. and med. branch, the latter supplies the molar teeth).
3. In the infra-orbital canal:
a. Middle and anterior superior alveolar (dental) (br. middle - supplies biscuspid teeth if present and anterior - supplies incisor and canine teeth and anterior part of inferior concha.
4. In the Face:
a. Inferior palpebral (lower eye lid).
b. External nasal (side of nose).
c. Superior labial (upper lip, vestibule, gum).
Pterygo-palatine (Spheno-palatine) ganglion
Site: Pterygo-palatine fossa near spheno-palatine foramen.
Roots:
1. Nervus intermedius (parasympathetic - secret motor) via greater (superficial) petrosal nerve. Postganglionic fibres pass to the lacrimal gland and no other glands of the nasal cavity, palate and Paranasal sinuses (Hay fever ganglion i.e. “allergen stimulus” results in “tears and a running nose”).
2. Deep petrosal nerve (via nerve of the pterygoid canal) - carry sympathetic fibres that do not relay but result in vasoconstriction of the nose, palate and Paranasal sinuses).
3. Sensory: From the maxillary branch (trigeminal ganglion).
Distribution:
1. Ascending: to orbital periosteum.
2. Descending:
a. Greater palatine nerve (gums and hard palate mucous and membrane): (br. inferior nasal branches to the mucous membranes of the middle and inferior nasal concha).
b. Lesser palatine nerve: mucous and membrane of the soft palate, uvula and tonsil/soft palate.
3. Medial:
a. Short spheno-palatine - posterior and upper part of the lateral nasal wall.
b. Long spheno-palatine - septum, gums of incisor teeth.
4. Posterior: Pharyngeal to upper naso-pharynx and sphenoidal sinus ostium.
Summary: Mucous membrane of the nasal cavity, naso-pharynx, Paranasal sinuses and palate. Vasoconstrictor sympathetic fibres to the nose, naso-pharynx, Paranasal sinuses and palate.
Mandibular Nerve or Division (V3)
Type: Mixed sensory and motory.
Course of Nerve: Exits skull via the foramen ovale and divides into an anterior and posterior division after the motory and sensory roots have united. It is a major nerve of the infratemporal fossa.
Areas Supplied: Temporal skin, side of face, anterior position of auricle, mandibular and Submental skin, lower lip, teeth, gingiva, muscles of mastication, mucous membrane of part of the tongue and floor of the mouth.
Branches:
1. Meningeal (recurrent: nervus spinosus) - dura.
2. Medial pterygoid (also to lateral pterygoid muscle).
3. Masseteric (motor).
4. Temporal (motor) - temporal muscle.
5. Buccal (sensory) - mucous membrane and skin of cheek.
6. Auriculo - temporal nerve:
Branches:
a. External auditory meatus.
b. Tympanic membrane.
c. Temporal - skin of temple.
d. Parotid (with fibres from N9 via the otic ganglion).
e. Mandibular (to TM joint) - sensory.
7. Inferior alveolar (dental) nerve (molar and bicuspid teeth). Passes through the mental foramen as the mental nerve (supplies skin of chin, mucous membrane and skin of lower lip and labial mandibular gingivae.
Branches:
a. Mylo-hyoid muscle, anterior belly of digastric.
b. Dental (molars and bicuspids).
c. Incisor (canine and incisors).
d. Mental.
8. Lingual nerve (joined by Chordae tympani).
Branches: Communicating with inferior alveolar nerve.
Supplies: Sides and of tip of tongue, lingual gums, sublingual and submandibular gland, anterior two-thirds of mucous membrane of dorsum of tongue.
Submandibular Ganglion:
Site: Sited between the hypoglossus muscle and the deep portion of the submandibular gland.
Roots:
1. Sensory: Lingual nerve (trigeminal ganglion).
2. Parasympathetic: N. intermedius and chorda tympani.
3. Sympathetic: Plexus around facial artery (superior cervical ganglion).
Distribution:
1. Submandibular gland and sublingual glands (sympathetic branches).
2. Mucous membrane.
Otic Ganglion:
Site: Medial surface of the mandibular nerve adjacent to the foramen ovale.
Roots:
1. Sensory: from mandibular - auriculo temporal nerve (trigeminal ganglion).
2. Sympathetic: Plexus around middle meningeal artery (superior cervical ganglion).
3. Motor: From mandibular nerve - Nerve to medial pterygoid.
4. Parasympathetic: Lesser petrosal nerve and glossopharyngeal nerve.
Distribution:
1. Communicating to auriculo - temporal and to Chordae tympani.
2. Muscular: tensor tympani and tensor veli palatini
3. Parotid gland via auriculo - temporal.
Summary of Cranial Autonomic Ganglia:
Number: 4 Ganglia.
Names:
1. Ciliary ganglion.
2. Pterygo-palatine (spheno-palatine) ganglion.
3. Submandibular ganglion.
4. Otic ganglion.
Plan of Ganglia: Afferent branches (3): Motor, sensory, sympathetic.
1. Motor (parasympathetic) root: Via oculomotor nerve (III) - Edinger Wesphal nucleus, nervus intermedius (VII) (superior salivary nucleus) and glossopharyngeal nerve (IX) (inferior salivary nucleus).
2. Sensory root - all from trigeminal ganglion.
3. Sympathetic root - all from superior cervical ganglion on the internal and external carotid arteries.
Distribution of Cranial Autonomic Ganglia:
1. Ciliary ganglion: supplies eyeball.
2. Pterygo-palatine ganglion: palate, nose, naso-pharynx, paranasal sinus, lacrimal gland and labial glands of the upper lip.
3. Submandibular ganglion: Glands of the floor of the mouth (sublingual and submandibular salivary glands).
4. Otic ganglion: Glands that open into the mouth i.e. parotid, buccal, molar and labial glands of the lower lip.
ABDUCENT NERVE - LR6 (SO4)3
Type: Motor (general somatic efferent).
Supplies: Lateral rectus muscle of the eye. Results in abduction of the eye.
Nucleus: Pons near median plane deep to facial colliculus in the 4th ventricle.
FACIAL NERVE
Type: Mixed motory and sensory (N. intermedius) (general visceral efferent, general somatic afferent, special visceral afferent and efferent).
Roots:
1. Motor component.
2. Sensory component (N. intermedius).
Course of Nerve: Internal acoustic meatus, petrous part of temporal bone, facial canal (geniculate ganglion) and exits the skull via the stylomastoid foramen. Within the parotid gland splits into two main divisions:
a. Temporo-facial division.
b. Cervico-facial division.
Terminates in 5 peripheral branches (temporal, zygomatic, buccal, mandibular, and cervical.
Supplies: Muscles of facial expression, scalp and auricle muscles, buccinator, platysma, stapedius, stylohyoid muscle and posterior digastric belly. Special sensory supply anterior two-thirds of tongue (taste fibres via chorda tympani nerve), soft palate taste fibres (via palatine and greater petrosal nerves and secretomotor parasympathetic fibres to the submandibular, sublingual, and lacrimal glands and glands of the nasal and palatine mucosa.
Nuclei:
1. Facial motor nucleus (PONS).
2. Nucleus solitarius (medulla - sensory taste fibres).
3. Geniculate ganglion (sensory).
Branches:
Within Facial Canal:
1. Greater (superficial) petrosal nerve - contains N. intermedius fibres - taste fibres.
2. Communicating (with lesser superficial petrosal nerve) and deep petrosal nerve (sympathetic fibres around the internal carotid artery) to form the nerve of the pterygoid canal that enters the pterygopalatine ganglion.
3. External petrosal.
4. Nerve to stapedius (dampens auditory signal).
5. Chorda tympani (passes in inner ear between handle of malleus and long process of the incus. Supplies anterior two-thirds of the tongue with taste fibres and secreto-motor fibres (via the submandibular ganglion) to the submandibular, sublingual and buccal glands (parasympathetic). Taste fibres are carried by the lingual nerve to the tongue.
At Exit from Stylo-mastoid foramen:
1. Posterior auricular (supplies auricularis posterior and posterior belly of occipito-frontalis).
2. Stylo-hyoid.
3. Digastric (posterior belly).
On Face via Parotid Plexus:
1. Temporal.
2. Zygomatic.
3. Buccal.
4. Mandibular.
5. Cervical.
Nervus Intermedius: Often termed sensory root of the facial nerve.
Origin: Secretomotor and sensory.
1. Secretomotor (para-sympathetic): floor of mouth, lacrimal gland, palate, nasal cavity, nasopharynx and paranasal sinuses.
2. Sensory (taste): cell bodies in the facial geniculate ganglion; nucleus tractus solitarius.
Branches:
1. Greater (superficial) petrosal nerve (secreto-motor to palate and taste fibres on the oral surface of the palate). Joined by deep petrosal nerve to form the nerve of the pterygoid canal which enters the pterygo-palatine ganglion.
2. Tympanic branches.
3. Chorda tympani (secreto-motor for the glands in the floor of the mouth and taste anterior two-thirds of tongue.
VESTIBULOCOCHLEAR NERVE
Function: Special somatic afferent (special sensory).
1. Hearing.
2. Balance (equilibrium).
Components:
1. Vestibular nerve (control of balance).
2. Cochlear nerve (control of hearing).
Point of Origin: Groove between pons and medulla of the brainstem.
Relevant Nuclei:
1. Vestibular nuclei (4): floor of the 4th ventricle.
2. Cochlear nuclei (2): dorsal and ventral. Sited in the medulla.
GLOSSOPHARYNGEAL NERVE
Function: Mixed motor and sensory.
1. General visceral efferent (parasympathetic): Parotid gland secretion (secretomotor fibres).
2. General visceral afferent: Tongue (posterior third) and pharynx sensation (sensory fibres).
3. Special visceral efferent: Innervation of stylopharyngeus muscle.
4. Special visceral afferent: Taste function.
Nuclei: (Shares 4 nuclei with the vagus and accessory nerve - two motory and two sensory).
1. Nucleus ambiguous (parasympathetic to heart, branchial muscles i.e. stylopharyngeus, constrictors, intrinsic muscles of the larynx, levator vela palatini).
2. Inferior salivary nucleus.
3. Nucleus of the tractus solitarius (taste, respiratory, baroreceptors, etc).
4. Sensory nucleus of the trigeminal nerve.
Course: Exits from the brain via 3 or 4 rootlets sited at the lateral aspect of the lateral portion of the medulla between the olive and inferior cerebellar peduncle; passes through the jugular foramen of the skull. Enters pharynx by passing down between the superior and middle pharyngeal constrictor.
Glossopharyngeal Ganglia: Sited in the nerve as it passes through the foramen.
Branches:
1. Communicating from inferior ganglion to superior cervical ganglion of the sympathetic chain, auricular of vagus, and superior ganglion of the vagus.
2. Meningeal.
3. Tympanic (from inferior ganglion) (Jacobson): communicates with the facial nerve and continues as the lesser (superficial) petrosal nerve. Ends in otic ganglion to relay in the parotid gland.
4. Pharyngeal: supplies mucous membrane of the oro-pharynx. Together with filaments of the vagus and laryngopharyngeal branches of the sympathetic they form the pharyngeal plexus.
5. Sino-carotid (carotid sinus) - pressor receptors and carotid body - chemoreceptors).
6. Motory: Stylo-pharyngeus.
7. Tonsillar: tonsil, oro-pharyngeal isthmus and soft palate.
8. Lingual: posterior third of tongue, vallate papillae.
Summary of Innervation:
1. Sensory (sensation) pharyngeal, oropharyngeal, isthmus and tonsil mucous membranes.
2. Motory: stylopharyngeus.
3. Taste: posterior third of tongue.
4. Secretomotor: parotid gland, mucous glands of pharynx.
VAGUS NERVE
Function: Mixed - motor and sensory.
1. General visceral efferent (parasympathetic): Heart, smooth muscle of lungs, GUT.
2. Special visceral efferent: Control of pharyngeal muscle movement.
3. General visceral afferent: Sensation from heart, lungs and GUT. Aortic arch baroreceptors and aortic body chemoreceptors.
4. Special visceral afferent: Taste function (epiglottis, pharynx).
5. General somatic afferent: Visceral reflexes (pain sensation from ear, pharynx and larynx.)
Nuclei: (4, two motory - two sensory) - thus shared with glossopharyngeal and accessory nerves.
1. Nucleus ambiguous.
2. Nuclei of the tractus solitarius.
3. Sensory nucleus of the trigeminal.
4. Dorsal nucleus of vagus.
Origin:
1. Sulcus between the inferior cerebellar peduncle and olive.
2. Vagal triangle - floor of the 4th ventricle and nucleus ambiguous of the medulla.
Course: Passes through the jugular foramen with the accessory nerve and forms the superior ganglion. On exiting the foramen it forms the inferior ganglion. The cranial root of the accessory nerve joins the inferior vagal ganglion. Passes down the neck on both sides in the carotid sheath. In the chest the right nerve forms the right posterior pulmonary plexus. Together with the opposite nerve it forms the esophageal plexus. Passes through the esophageal orifice in the diaphragm to enter the abdomen as the anterior aspect of the stomach and ends in the Coeliac ganglion.
Branches: Come of at the level of the head, neck, thorax and abdomen.
1. Meningeal (dura of posterior cranial fossa).
2. Auricular (Arnold): Supplies (sensory) adjacent skin of the external auditory meatus and auricle and part of the tympanic membrane.
3. Pharyngeal: Motory to pharyngeal constrictors (striated) and soft palate muscles except palatoglossus and tensor veli palatini. The fibres are originally from the N. accessorius.
4. Superior laryngeal divides into:
a. External laryngeal nerve: supplies crico-thyroid and crico-pharyngeus and
b. Internal laryngeal nerve: to mucous membrane of the piriform fossa and larynx i.e. sensory to larynx superior to the vocal cords.
5. Recurrent laryngeal nerves (right and left). After hooking around the subclavian artery (right) and aortic arch (left) the nerves ascend in the groove between the trachea and esophagus to enter the larynx by passing under the inferior constrictor. Both sensory and motory function. Supplies all laryngeal intrinsic muscles (except crico-thyroid) and crico-pharyngeus. Sensory to larynx below the vocal cords.
6. Cervical and thoracic cardiac: carotid branches to the carotid sinus; cardiac plexus.
7. Bronchial: pulmonary plexus.
8. Esophageal.
9. Gastric (anterior and posterior).
ACCESSORY NERVE:
Function: Motory.
1. Special visceral efferent (cranial root): Control of soft palate, pharynx, larynx movement.
2. General somatic efferent (spinal root): Motory to sternomastoid, trapezius.
Origin: Two parts.
1. Cranial root (fibres given to and hitchhike with N. vagus). They supply the skeletal muscles of the pharynx and palate.
2. Spinal root (spinal accessory nerve).
Nuclei: Two motory.
1. Cranial root from the nucleus ambiguous.
2. Spinal root from the spinal nucleus (anterior horn cells in the superior 5 - 6 cervical segments of the spinal cord - C 6 to C 1). Filaments ascend through the foramen magnum. Joins the cranial nerve briefly and then exits via the jugular foramen.
Supply:
1. Cranial root (N. ambiguous): motory to skeletal muscles in the pharynx and larynx. Exits brain from the lateral aspect of the medulla as 4 or 5 rootlets. Unite with spinal root at the jugular foramen.
2. Spinal part: Sternomastoid and trapezius.
HYPOGLOSSAL NERVE:
Function: Motor.
1. General somatic efferent: Motory to intrinsic tongue muscles except palatoglossus. (This is supplied by the vagus).
Nucleus: Sited between dorsal nucleus of the vagus and median plane of the 4th ventricle - i.e. hypoglossal triangle in the floor of the 4th ventricle.
Exits: by two bundles from the groove between the olive and pyramid (10 - 15 rootlets), pass through the hypoglossal canal.
Branches:
1. Communicating from
a. Inferior ganglion of the vagus.
b. Superior cervical ganglion of the sympathetic.
c. From 1st and 2nd cervical nerves (loop).
2. Meningeal (C1 fibres) - diploë of the occipital bone, and posterior cranial fossa dura.
3. Thyro-hyoid and genio-hyoid: C1 hitch-hiking fibres.
4. Motory (muscular): Styloglossus, hyoglossus, genioglossus and intrinsic muscles of the tongue. Genio hyoid via C1.
5. Superior root (C1 fibres) of ansa cervicalis (descendens hypoglossi). Descending down over carotid sheath, forms the ansa cervicalis with a branch from C2 + 3 (inferior root of ansa or descending cervical nerve). From the loop the following muscular branches are given off to:
a. Sterno-hyoid.
b. Sterno-thyroid.
c. Omo-hyoid (both bellies).
Summary:
The loop or ansa cervicalis is formed by two contributing roots.
a. Superior root of ansa cervicalis (descendens hypoglossi): C1 fibres.
b. Inferior root of ansa cervicalis (descendens cervicalis): C2 + C3 fibres.
SUMMARY OF CRANIAL NERVE NUCLEI:
1. Olfactory nerve (CN 1): Special sensory: Olfactory areas of the brain.
2. Optic nerve (CN 2): Special sensory: visual cortex.
3. Oculomotor nerve (CN 3): Motor-striated and smooth muscle (eye movements).
a. Somatic motor nucleus (midbrain).
b. Somatic visceral nucleus (Edinger- Wesphal or accessory oculomotor nucleus).
4. Trochlear nerve (CN 4): Motor. Motor nucleus sited in the periaqueductal grey matter of the midbrain (level of inferior colliculus). Supplies sup. oblique muscle.
5. Trigeminal nerve (CN 5): Mixed motory and general sensory. Mastication and sensation of the head.
Four Nuclei: One motor, three sensory.
a. Motor nucleus (pontine tegmentum) i.e. pons.
b. Pontine trigeminal nucleus (chief sensory nucleus) - pons.
c. Spinal tract nucleus (inferior pons and throughout medulla).
d. Mesencephalic nucleus (cerebral aqueduct).
6. Abducent nerve (CN 6): Motor to lateral rectus muscle. Abducts eye.
Nucleus: Motor - median plane of pons, deep to facial colliculus - floor of the 4th ventricle.
7. Facial nerve (CN 7): Mixed motory and sensory (N. intermedius). Facial expression and taste anterior two thirds of tongue.
Nuclei:
a. Facial motor nucleus - pons.
b. Nucleus solitarius - rostral end in medulla: special sensory root (taste).
c. Associations: geniculate ganglion, sensory nucleus of CN 5.
8. Vestibular nerve (CN 8): Equilibrium (vestibular) and hearing (cochlear).
Nuclei:
a. Vestibular nucleus (4): junction of pons and medulla, floor of the 4th ventricle.
b. Cochlear nucleus (2): dorsal and ventral. Rostral end of medulla, adjacent to base of the inferior cerebellar peduncle.
9. Glossopharyngeal nerve (CN 9): mixed motor and sensory: supplies posterior third tongue and pharynx.
Nuclei: Shares 4 nuclei with CN 10 and 11 (two motory, two sensory).
a. Nucleus ambiguous - medulla.
b. Inferior salivary nucleus - pons.
c. Nucleus of the tractus solitarius - medulla.
d. Sensory nucleus of the trigeminus - medulla.
10. Vagus nerve (CN 10): Motory and sensory: Wide distribution to head, neck, thorax and abdomen.
Nuclei: (4): two motory and two sensory.
a. Nucleus ambiguous.
b. Nucleus of tractus solitarius.
c. Dorsal nucleus of the vagus.
d. Sensory nucleus of the trigeminus (CN 5).
11. Accessory nerve (CN 11): Motor: Sternomastoid and trapezius muscle.
Nuclei: (2)
a. Nucleus ambiguous (medulla) - cranial root.
b. Spinal nucleus (spinal root) - C1 - C5 segments of the spinal cord.
12. Hypoglossal nerve (CN 12) Motor: Motor nerve of the tongue.
Nucleus: Dorsal part of the medulla, floor of the 4th ventricle.
Levels of Nuclei:
1. Midbrain: 3, 4, mesencephalic 5, sensory 5.
2. Pons: Motor 5, mesencephalic 5, sensory 5, 6, 7, N. intermedius.
3. Medulla: Spinal 5, 8, 9, 10, 11, 12.
4. Clustered around, pons-medulla interface and floor of the 4th ventricle: 6, 7, 8, spinal 5, nucleus ambiguous (9 + 10), 10, 11, 12, salivary nuclei (7 + 9).
SUMMARY OF CRANIAL NERVE FUNCTIONS
1. Olfactory: smell.
2. Optic: sight.
3. Oculomotor:
a. Eye movements.
b. Movement of pupil and ciliary muscle.
c. Extrinsic eye muscle proprioception.
d. Blood vessel control in orbit.
4. Trochlear: Eye movement (superior oblique muscle).
5. Trigeminus:
a. Sensation (mouth, face and scalp).
b. Proprioception function (chewing muscles, TM joints and teeth).
c. Chewing.
6. Abducent: Control of eye movements (lateral rectus muscle).
7. Facial:
a. Secretion (lacrimal gland and salivary glands).
b. Sensation (external auditory meatus and tympanic membrane).
c. Facial expression.
d. Taste (anterior two-thirds of tongue).
8. Vestibulocochlear: Control of hearing and balance.
9. Glossopharyngeal.
a. Secretion (parotid gland).
b. Sensation (tongue and pharynx).
c. Motory (stylopharyngeus).
d. Taste.
10. Vagus:
a. Autonomic control of heart, smooth muscle (gut and lungs).
b. Motory (pharyngeal muscle).
c. Sensory (heart, lungs, gut).
d. Taste.
e. Visceral reflexes (pain - ear, pharynx, larynx).
11. Accessory:
a. Motory (sternomastoid, trapezius).
12. Hypoglossal:
a. Motory (tongue, muscles).
Labels: Basic Science: Neuroanatomy
