Cranial Nerves Flashcards
What are the 12 cranial nerves?
1 olfactory 2 optic 3 oculomotor 4 trochlear 5 trigeminal 6 abducens 7 facial 8 vestibulocochlear (auditory) 9 glossopharyngeal 10 vagus 11 (spinal) accessory 12 hypoglossal
Where does CN I synapse?
Olfactory bulb
Which special sensory nerve doesn’t enter the thalamus?
Olfactory - CN I
How many pairs of olfactory nerves are there?
15-20
What is the function of CN I?
Special sensory - smell.
Where does CN I originate from?
Cerebrum
Which canal does CN I exit from?
Cribiform plate.
What is the function of CN II?
Vision - special sensory.
Where do axons for nasal retina of CN II decussate?
Optic chiasma
Do axons for the temporal retina cross?
No, they stay ipsilateral (same side).
What results with damage to the optic nerve?
Complete blindness in one eye.
What results with damage to the optic tract?
Loss of half field vision in both eyes.
Where does CN II originate from?
Cerebrum
Which canal does CN II exit from?
Optic canal
Where does CN III emerge from?
Midbrain-pontine junction (midbrain/pons).
What is the motor function of CN III?
Eye movement.
Motor: innervates 4 extrinsic eye muscles.
What is the parasympathetic function of CN III?
Supplies pupillary sphincter and ciliary muscles of the eye (via ciliary ganglion).
Where does CN III exit from?
Superior orbital fissure.
Where does CN IV originate from?
Posterior (dorsal) side of midbrain.
Which nerve has the longest intracranial length?
CN IV
Which canal does CN IV exit from?
Superior orbital fissure.
What is does CN IV innervate?
Provides motor innervation to superior oblique muscle.
What is the function of CN IV?
Downward, lateral and internal eye rotational movements.
What are the 3 branches of CN V?
Ophthalmic (V1), maxillary (V2) and mandibular (V3)
Where does V1 of CNV exit from?
Superior orbital fissure
Where does V2 of CNV exit from?
Foramen rotundum
Where does V3 of CNV exit from?
Foramen ovale
Where does CNV arise from?
Pons
Describe the central connection of the CN V
- It originates from 3 sensory nuclei (mesencephalic, principal sensory and spinal nuclei) and 1 motor nucleus extending from the midbrain to the medulla oblongata.
- At the level of the pons, the sensory nuclei merge to form a sensory root whilst the motor nuclei form a motor root.
- In the middle cranial fossa, sensory root expands to form trigeminal ganglion.
What does signals does the Mesencephalic Nucleus receive?
(In midbrain).
Receives proprioceptive input (from jaw and teeth).
What does signals does the Principle Sensory Nucleus receive?
(In mid-pons).
Receives light touch sensation from all three branches.
What does signals does the Spinal Nucleus receive?
(Mid-pons to top of spinal cord).
Receives pain and temperature sensation of the face.
Where is the trigeminal ganglion located?
Trigeminal cave – this is a depression of the temporal bone.
What are the branches of the Ophthalmic nerve (CN V)?
- Frontal nerve
- Lacrimal nerve
- Nasociliary nerve
What does the Nasociliary nerve branch into?
- Anterior/posterior ethmoidal nerve.
- Long ciliary nerve.
- Infratrochlear nerve.
- Sensory root of ciliary ganglion.
What does the frontal nerve (CN V1) innervate?
Skin of forehead and scalp.
What does the lacrimal nerve (CN V1) innervate?
Lacrimal glands, conjunctiva of eyes, upper eyelids.
What does the nasociliary nerve (CN V1) innervate?
Nasal mucous membranes
What are the branches of the Maxillary nerve (CN V)?
In meninges:
- Middle meningeal nerve.
In pterygopalatine fossa:
- Nasopalatine nerve.
- Greater palatine nerve.
- Lesser palatine nerve.
- Posterior SAN.
In infraorbital canal:
- Middle SAN.
- Anterior SAN.
- Infraorbital nerve
What are the branches of the Mandibular nerve (CN V)?
Before division (from main trunk of nerve): - Meningeal branch (sensory).
From anterior division:
- Masseteric nerve (motor)
- Deep temporal nerves – anterior and posterior (motor).
- Lateral pterygoid nerve (motor).
- Medial pterygoid nerve (motor).
- Buccal nerve (sensory).
From posterior division
- Auriculotemporal nerve (sensory)
- Lingual nerve (sensory) –
- Inferior alveolar nerve (motor and sensory).
What are the route and branches of the inferior alveolar nerve?
- Traves behind lateral pterygoid muscle.
- Branches into mylohyoid nerve and enters mandibular foramen.
- In mandibular canal, sensory branches form into inferior dental plexus - gives small gingival/dental nerves to teeth.
- Exits anteriorly at mental foramen.
- Gives off mental nerve.
- Continues anteriorly as mandibular incisive nerve.
What does the mylohyoid nerve innervate?
(Motor/sensory) - mylohyoid muscle and anterior belly of digastric.
What does the mental nerve innervate?
Chin, lower lip, labial gingiva, mandibular anterior/premolar teeth.
What does the incisive nerve innervate?
Anterior teeth
Where does the auriculotemporal nerve exit from’?
Otic ganglion.
What does the auriculotemporal nerve supply?
Auricle and temporal region, TMJ, external acoustic meatus.
Parasympathetic root carries postganglionic fibres to parotid gland.
What does the lingual nerve supply?
Sensory fibres to anterior 2/3 of tongue and lingual mucosa.
Where does the middle meningeal nerve exit from and what does it accompany?
Foramen spinosum before V2 enters foramen rotundum.
Accompanies middle meningeal artery/vein as they enter cranium through foramen spinosum.
What does the middle meningeal nerve supply?
Dura mater.
Where does the nasopalatine nerve exit from?
Incisive foramen.
Where does the greater palatine nerve exit from?
Greater palatine foramen
Where does the lesser palatine nerve exit from?
Lesser palatine foramen
What does the nasopalatine nerve supply?
Palatal mucosa, gingiva and palatal alveolar bone.
What does the greater palatine nerve supply?
Hard palate mucosa, palatal alveolar bone and posterior gingiva (3-8).
What does the lesser palatine nerve supply?
Soft palate.
What does the posterior SAN supply?
Molars (except MB root of 6), maxillary sinus and buccal gingiva.
What does the middle SAN supply?
Premolars and MB root of 6.
What does the anterior SAN supply?
Anterior teeth
What does the infraorbital nerve supply?
Lower eyelid, upper lips and part of nasal vestibule.
Where does the infraorbital nerve exit from?
Infraorbital foramen of maxilla.
Which is the largest division of CN V?
V3 - mandibular
Where does CN VI exit from?
Superior orbital fissure
Where does CN VI arise from?
Pontine-medulla junction
What does CN VI innervate?
Lateral rectus - lateral movements of pupil of the eye.
Where does CN VII exit from?
Internal acoustic meatus.
Where does CN VII arise from?
Pontine-medulla junction (pons)
What is the central connections of CN VII?
- Motor and sensory roots travel through internal acoustic meatus and enters facial canal.
- 2 roots fuse to form the facial nerve.
- The nerve forms the geniculate ganglion.
- Exits skull at stylomastoid foramen
Where is the internal acoustic meatus located?
In petrous part of temporal bone
Where does CN VII leave the cranium?
Stylomastoid foramen
What are the intracranial branches of CN VII?
- Greater petrosal nerve
- Nerve to stapedius
- Chorda tympani nerve
What are the extracranial branches of CN VII?
- Posterior auricular nerve
- Facial branches: Temporal, Zygomatic, Buccal, Mandibular, Cervical
Where does the Greater petrosal nerve run through and where does it synapse?
Runs through Pterygoid canal.
Synapses at pterygopalatine ganglion.
What does the Greater petrosal nerve innervate?
Parasympathetic fibres to nasal glands, palatine glands, lacrimal gland and pharyngeal gland.
What does the nerve to stapedius innervate?
Motor innervation for stapedius muscle in middle ear.
What does the chorda tympani nerve supply?
Special sensory taste fibres to anterior 2/3 tongue.
Parasympathetic innervation to submandibular/sublingual glands.
What does the posterior auricular nerve innervate?
Supplies the movement of scalp muscles around the ear.
What other muscles does the facial nerve supply after leaving the stylomastoid foramen?
- Posterior belly of digastric muscle.
- Stylohyoid muscle.
- Muscles of facial expression.
Where are the 5 facial branches (CN VII) located? What do they supply?
Parotid gland.
Motor fibres of muscles of mastication.
What is an Upper Motor Neuron Lesion?
Upper Motor Neuron Lesion on one side.
- Upper region is normal but lower region will be defective.
What is a Lower Motor Neuron Lesion?
Causes the entire face on one side to be affected.
What is an example of an Upper Motor Neuron Lesion?
Central facial palsy or Corticobulbar palsy.
- Damage occurs prior to reaching brainstem.
Can be caused by lesions in:
- Face area of primary motor cortex.
- Descending Corticobulbar fibres.
What is an example of a Lower Motor Neuron Lesion?
Peripheral facial palsy or Bell’s palsy.
- Damage occurs after leaving brainstem, prior to reaching muscles.
Includes lesions in:
- Motor facial nucleus.
- Facial nerve in CNS or on its course of peripheral distribution.
What is an example of a Lower Motor Neuron Lesion?
Peripheral facial palsy or Bell’s palsy.
- Damage occurs after leaving brainstem, prior to reaching muscles.
Includes lesions in:
- Motor facial nucleus.
- Facial nerve in CNS or on its course of peripheral distribution.
Where does CN VIII arise from?
Pontine-medulla junction (pons).
Where does CN VIII exit from?
Internal acoustic meatus
What are the 2 branches of CN VIII?
- Vestibular nerve
- Cochlear nerve
What is the function of CN VIII?
- Vestibular nerve monitors balance, position and movement (vestibular system).
- Cochlear nerve monitors hearing (inner ear).
What type of neurons does CN VIII consist of?
Bipolar neurons
Where does CN IX arise from?
Medulla oblongata
Where does CN IX leave the cranium from?
Jugular foramen.
What are the functions of CN IX?
- Special sensory: - Taste posterior 1/3 tongue.
- General Sensory: - posterior 1/3 and oropharynx.
- Brachial Motor: - stylopharyngeus muscle.
- Visceral sensory: - monitors blood CO2 / Hydrogen ions via the carotid body (role in BP control).
- Parasympathetic (visceral motor): parotid gland via otic ganglion and to auriculotemporal nerve and CN V3.
Where does CN X arise from?
Medulla oblongata.
Where does CN X leave the cranium from?
Jugular foramen
What are the sensory functions of CN X?
- Somatosensory: - mucous membrane of laryngopharynx, larynx, upper trachea.
- Visceral sensory: - trachea, lungs, carotid sinus, abdominal veins, gut (to splenic flexure).
What are the motor functions of CN X?
- Somatic motor: - most muscles of pharynx and larynx, upper oesophagus (swallowing, vomiting), palatoglossus of the tongue.
- Parasympathetic: - cardiac muscle, GI tract, trachea/bronchi.
Where does CN XI arise from?
Medulla oblongata
Where does CN XI leave the cranium from?
Jugular foramen
Where do the roots of CN XI arise from?
Roots from cervical segments of spinal cord travel through foramen magnum and join cranial fibres to form accessory nerve.
What are the divisions of CN IX?
- Spinal division
- Cranial division
What are the functions of CN IX?
- Spinal division: - trapezius and SCM (head and shoulder movements).
- Cranial division: - muscles of voluntary swallowing (soft palate, pharynx).
Where does CN XII arise from?
Medulla oblongata.
Where does CN XII leave the cranium from?
Hypoglossal canal
What are the functions of CN XII?
Swallowing and speech
What does CN XII innervate?
Motor to intrinsic and extrinsic tongue muscles (except palatoglossus) and muscles surrounding hyoid bone.
What nerves are associated with Nucleus Ambiguus?
CN IX & CN X.
Efferent motor to muscles of larynx, pharynx, and upper oesophagus.
- Associated with speech (phonation), swallowing, vomiting.
What nerves are associated with Nucleus Tracts Solitarius (Solitary Nucleus)?
CN VII, CN IX & CN X.
Visceral sensory to tongue, carotid body, carotid sinus, GI tract, trachea/bronchi.
- Associated with chemoreception - taste, blood CO2/hydrogen ion monitoring, BP monitoring, gut distension.
