Cranial Nerves Flashcards
Olfactory Bulb
Location:
• Lies on cribriform plate of ethmoid bone in anterior cranial fossa
• Ventral aspect of frontal lobe of brain
Description:
• Expanded anterior end of olfactory tract
• Site of synapse for olfactory neurons (CN I) after their axons pass through cribriform plate
Optic nerve (CN II)
Location:
• Orbit
• Middle cranial fossa
Special sensation:
• Vision
CNS connection:
• Lateral geniculate nucleus of thalamus
Cranial foramina:
• Optic canal
Comment:
• Optic nerve formed by axons of retinal ganglion cells
• Retinal ganglion cell axon pathway: optic nerve > optic chiasm > optic tract > brainstem nuclei (including lateral geniculate nucleus of thalamus)
Oculomotor nerve (CN III)
Location:
• Middle cranial fossa
• Orbit
Composition:
• Motor
• Parasympathetic
Motor: • Medial rectus muscle • Superior rectus muscle • Inferior rectus muscle • Inferior oblique muscle • Levator palpebrae superioris muscle
Parasympathetic:
• Pupillary sphincter muscle (constriction of pupil)
• Ciliary muscle (permits lens to thicken for accommodation)
CNS connection:
• Midbrain (oculomotor and accessory oculomotor nuclei)
Cranial foramina:
• Superior orbital fissure
Comment:
• Rectus and oblique muscles are extrinsic eye (extra-ocular) muscles
• Postganglionic parasympathetic cell bodies located in ciliary ganglion in the orbit
Trochlear nerve (CN IV)
Location:
• Middle cranial fossa
• Orbit
Motor:
• Superior oblique
CNS connection:
• Midbrain (nucleus of trochlear nerve)
Cranial foramina:
• Superior orbital fissure
Comment:
• Oculomotor nerve (CN III) and abducens nerve (CN VI) innervate remaining five extrinsic (extra-ocular) eye muscles
Trigeminal n. (CN V)
Composition:
• Ophthalmic nerve: general sensation
• Maxillary nerve: general sensation
• Mandibular nerve: motor and general sensation
Motor:
• Muscles of mastication (mandibular nerve)
• Mylohyoid (mandibular nerve)
• Anterior belly of digastric (mandibular nerve)
• Tensor tympani (mandibular nerve)
• Tensor veli palatini (mandibular nerve)
General sensation:
• Ophthalmic nerve: skin of superior face (forehead, scalp, and upper eyelid), eye, mucosa of anterior nasal cavity, and paranasal sinuses (frontal, ethmoidal, and sphenoidal)
• Maxillary nerve: skin of middle face (cheek, upper lip, and lower eyelid), maxillary teeth and gingiva (gums), mucosa of palate, posterior nasal cavity, and maxillary sinus
• Mandibular nerve: skin of inferior face (mandible, cheek, and lower lip), temple, mucosa lining cheek, mandibular teeth and gingiva (gums), and anterior 2/3 of tongue
Sensory ganglion:
• Trigeminal
CNS connection:
• Pons (principal sensory and motor nuclei of trigeminal nerve)
• Medulla oblongata (spinal nucleus of trigeminal nerve)
Cranial foramina:
• Ophthalmic nerve: superior orbital fissure
• Maxillary nerve: foramen rotundum
• Mandibular nerve: foramen ovale
Abducens nerve (CN VI)
Location:
• Middle cranial fossa
• Orbit
Motor:
• Lateral rectus muscle
CNS connection:
• Pons (abducens nucleus)
Cranial foramina:
• Superior orbital fissure
Vestibulocochlear n (CN VIII)
Location:
• Posterior cranial fossa
• Petrous portion of temporal bone
Special sensation:
• Hearing (cochlea)
• Balance (semicircular canals and vestibule)
Sensory ganglion:
• Cochlear (spiral) ganglion (cochlear part of CN VIII)
• Vestibular ganglion (vestibular part of CN VIII)
CNS connection:
• Pons (vestibular nuclei)
• Medulla oblongata (cochlear and vestibular nuclei)
Cranial foramina:
• Internal acoustic meatus
Facial nerve (CN VII)
Location:
• Posterior cranial fossa, Facial canal, Middle ear, Face, Infratemporal fossa, Oral cavity
Motor: • Muscles of facial expression • Posterior belly of digastric muscle • Stylohyoid muscle • Stapedius muscle
General sensation:
• Small area of skin of auricle of ear
Special sensation:
• Taste from anterior 2/3 of tongue
• Taste from palate
Parasympathetic:
• Lacrimal gland
• Submandibular and sublingual salivary glands
• Mucous glands of nasal cavity, paranasal sinuses, and palate
CNS connection:
• Motor: pons (motor nucleus of facial nerve)
• General sensation: medulla oblongata (spinal trigeminal nucleus)
• Special sensation: medulla oblongata (nucleus of solitary tract)
• Parasympathetic: medulla oblongata (superior salivatory nucleus
Sensory ganglion:
• Geniculate
Cranial foramina:
• Internal acoustic meatus
• Pterygomaxillary fissure
• Stylomastoid foramen
Glossopharyngeal nerve (CN IX)
Location:
• Posterior cranial fossa
• Neck
Motor:
• Stylopharyngeus muscle
General sensation:
• From middle ear, posterior 1/3 of tongue, and pharynx
Special sensation:
• Taste from posterior 1/3 of tongue
Sensory ganglion:
• Superior and inferior ganglia of glossopharyngeal nerve
Parasympathetic:
• Parotid gland
CNS connection:
• Motor: medulla oblongata (nucleus ambiguus)
• General sensation: medulla oblongata (spinal nucleus of trigeminal nerve)
• Special sensation: medulla oblongata (nucleus of solitary tract)
• Parasympathetic: medulla oblongata (inferior salivatory nucleus)
Cranial foramina:
• Jugular foramen
Comment:
• Has two sensory ganglia (superior and inferior) on nerve in jugular foramen
• Glossopharyngeal nerve also conducts visceral afferent (sensory) impulses from carotid sinus (monitors blood pressure) and carotid body (monitors blood oxygen and carbon dioxide)
• Postganglionic parasympathetic cell bodies located in otic ganglion in infratemporal fossa
Hypoglossal nerve (CN XII)
Location:
• Posterior cranial fossa
• Neck
• Oral cavity
Composition:
• Motor
Motor: • Genioglossus • Hyoglossus • Styloglossus • Intrinsic muscles of tongue
CNS connection:
• Medulla oblongata (nucleus of hypoglossal nerve)
Cranial foramina:
• Hypoglossal canal
Comment:
• Hypoglossal nerve innervates all tongue muscles except palatoglossus (vagus nerve)
• Intrinsic tongue muscles originate and insert within tongue
Vagus nerve (CN X)
Vagus n. (CN X)
Location:
• Posterior cranial fossa, Head, Neck, Thorax, Abdomen
Motor:
• Muscles of palate
• Muscles of pharynx
• Intrinsic muscles of larynx
General sensation:
• Thoracic and abdominal viscera
• Epiglottis and laryngopharynx
• External acoustic meatus
Special sensation:
• Taste from epiglottis and surrounding region
Parasympathetic:
• Mucous glands of respiratory and digestive systems in neck (pharynx and larynx), thorax, and abdomen
• Smooth muscle of respiratory and digestive systems in neck (pharynx and larynx), thorax, and abdomen
• Cardiac muscle
Cranial foramina:
• Jugular foramen
Comment:
• General sensation from thoracic and abdominal viscera only involves stretch (e.g., distention of stomach)
• General sensation from epiglottis and laryngopharynx includes pain, touch, and temperature
• Vagus nerve also innervates carotid and aortic bodies
• Parasympathetic impulses from CNS to effector organ involve two neurons in series (preganglionic and postganglionic)
• Only cranial nerve that extends beyond head and neck
Accessory nerve (CN XI)
Location:
• Vertebral canal (spinal root only), Posterior cranial fossa, Neck
Motor:
• Cranial part: joins vagus nerve (CN X) to distribute to muscles of palate (except tensor veli palatini), pharynx (except stylopharyngeus), and larynx (intrinsic muscles)
• Spinal part: trapezius and sternocleidomastoid
CNS connection:
• Cranial root: medulla oblongata (nucleus ambiguous)
• Spinal root: ventral horn of C1-4 spinal cord
Cranial foramina:
• Foramen magnum (spinal root only)
• Jugular foramen
Comment:
• Cranial and spinal roots unite in jugular foramen to form accessory nerve
• Cranial part of accessory nerve joins vagus nerve (CN X) and is distributed along its branches to muscles of palate, pharynx, and larynx
Olfactory tract
Location:
• Ventral aspect of frontal lobe
• Between olfactory bulb and medial aspect of temporal lobe
Description:
• Bundles of afferent and efferent axons
Ophthalmic n. (CN V1)
General sensation:
• Skin of superior face (forehead, scalp, and upper eyelid)
• Dorsum and tip (apex) of nose
• Eye
• Mucosa of anterior nasal cavity, and paranasal sinuses (frontal, ethmoidal, and sphenoidal)
Sensory ganglion:
• Trigeminal
Branches:
• Frontal
• Nasociliary
• Lacrimal
CNS connection:
• Pons (principal sensory nucleus of trigeminal nerve)
• Medulla oblongata (spinal nucleus of trigeminal nerve)
Maxillary Nerve
General sensation:
• Skin of middle face (cheek, upper lip, and lower eyelid), maxillary teeth and gingiva (gums)
• Lateral aspect of nose (including ala)
• Mucosa of palate, posterior nasal cavity, and maxillary sinus
Sensory ganglion:
• Trigeminal
Branches: • Palatine (greater and lesser) • Pharyngeal • Nasal (including nasopalatine) • Nasopalatine • Superior alveolar • Infra-orbital • Zygomatic
CNS connection:
• Pons (sensory nucleus of trigeminal nerve)
• Medulla oblongata (spinal nucleus of trigeminal nerve)
