Cranial Nerves Flashcards
All cranial nerves except CN XI originate where?
within the cranial cavity
CN I, II, III, and IV are called?
I-Olfactory Nerve
II- Optic Nerve
III-Oculomotor Nerve
IV-Trochlear Nerve
CN V is called what? What are the three divisions?
Trigeminal Nerve
V1=Ophthalmic division
V2=Maxillary division
V3=Mandibular division
CN VI, VII, VIII, and IX are called?
VI- Abducent Nerve
VII- Facial Nerve
VIII-Vestibulocochlear Nerve
IX- Glossopharyngeal Nerve
CN X, XI, and XII are called?
X- Vagus Nerve
XI- Accessory Nerve
XII- Hypoglossal Nerve
Which cranial nerves are sensory only?
I, II, and VIII
What cranial nerves are motor only?
III, IV, VI, XI, and XII
Which cranial nerves are mixed?
V, VII, IX, and X
Do any cranial nerves participate in plexus formation?
No, none
Notes on cranial nerves
Cranial nerves derive from the brain or brainstem and are typically NOT formed by the fusion of dorsal and ventral roots. Instead, motor and sensory fibers of the cranial nerves are combined and attached at approximately the same point on the brain, although a few cranial nerves do attach to the brain stem by multiple roots. Also note that cranial nerves do NOT divide into dorsal/ventral primary rami.
What is a sensory ganglia?
Sensory ganglia, (analogous to dorsal root ganglia of the spinal nerves), exist only for those cranial nerves that conduct sensory fibers (CN V, VII, VIII, IX and X).
The large trigeminal ganglion associated with CN V is an example of this type of sensory ganglia.
Only those cranial nerves with a sensory function are associated with a sensory ganglia. Sensory ganglia of cranial nerves are often further removed from the origin of the nerve from the central nervous system than are the sensory ganglia (dorsal root ganglia) of the spinal nerves.
CN I and II also transmit sensory fibers. Do the have associated sensory ganglia?
No, CN I and II are purely sensory in function, however, they are not associated with organized sensory ganglia.
The geniculate sensory ganglia is associated with which CN?
CN VII
The vestibular sensory ganglia is associated with which CN?
CN VIII
The spiral sensory ganglia is associated with which CN?
CN VIII
The trigeminal sensory ganglia is associated with which CN?
CN V
The superior and inferior sensory ganglia are associated with which CN?
CN IX and X
The GSA functional component of cranial nerves transmits sensory info from where?
sensation from somatic structures (skin, skeletal muscle, fascia, joint capsules, ligaments, tendons, aponeuroses, and periosteum),
sensation from the mucosal lining of the oral cavity, nasal cavity, nasal sinuses, and
sensation from the mucosal lining of the pharynx, esophagus larynx, trachea, and middle ear
The GVA functional component of cranial nerves transmits sensory info from where?
sensation from visceral structures of the head (carotid body and carotid sinus) and thoracic and abdominal viscera
The SA functional component of cranial nerves transmits sensory info from where?
sensation from specialized receptors in the head which are related to our special senses (vision, hearing, equilibrium, taste, and smell)
SA fibers are only present in which CNs?
I, II, VII, VIII, IX, and X
The GSE functional component of cranial nerves does what?
motor innervation to skeletal muscle in the head derived from somite mesoderm
The GVE functional component of cranial nerves does what?
parasympathetic motor innervation to smooth muscle and glands of the head.
GVE fibers in the head are found in which CNs?
III, VII, IX, and X
The BE functional component in the head does what?
motor to skeletal muscle in the head derived from brachia (pharyngeal arch) mesoderm
Muscular structures arise from the mesoderm of which pharyngeal arches?
1st, 2nd, 3rd, 4th and 6th pharyngeal arches. The 5th pharnygeal arch is rudimentary.
What skeletal muscles of the head are innervated by GSE?
1) Skeletal muscles of the tongue (XII) except the palatoglossus,
2) skeletal muscles of the orbit (eye) (III, IV & VI)
3) the sternocleidomastoid and trapezius muscles (XI)
These develop from somite mesoderm and these are not branchiomeric muscles.
What head muscles are derived from the first pharyngeal arch and what is their innervation?
MAST-MATT
muscles of mastication- medial and lateral pterygoid, temporalis, and masseter
Mylohyoid muscle
anterior belly of digastric muscle
tensor veli palatini muscle
tensor tympani muscle
innervated by CN V(3); mandibular
What head muscles are derived from the second pharyngeal arch and what is their innervation?
muscles of facial expression
posterior belly of digastric muscle
stylohyoid muscle
stapedius muscle
innervated by CN VII- facial
What head muscles are derived from the third pharyngeal arch and what is their innervation?
stylopharyngeus muscle
innervated by CN IX- glossopharyngeal
What head muscles are derived from the fourth and sixth pharyngeal arch and what is their innervation?
all muscles of larynx
all muscles of palate, except tensor veli palatine (V3)
all muscles of pharynx, except stylopharyngeus (CN IX)
innervated by CN X; vagus
Where are GSA spinal nerve cell bodies found?
dorsal root ganglia of T1-L2 (GVA cell bodies for spinal nerves are also found here)
Where are GSE spinal nerve cell bodies found?
ventral root (gray matter)
CN I and CN II have sensory function but are not associated with organized sensory ganglia (unlike CN V, VII, VIII, IX, and X). So where are their cell bodies?
The sensory neurons of CN I (SA) are diffusely dispersed in the olfactory epithelium.
The sensory neurons of CN II (SA) are diffusely dispersed in the retina.
remember that the GSA neuron bodies are found in the associated peripheral sensory ganglia for the other CNs with sensory ability (CN V, VII, VIII, IX, and X)
What is the morphology of SA and GSA cranial fibers?
pseudounipolar
GSE/BE Motor neurons are multipolar. Where are there cell bodies?
Their cell bodies are located in brain motor nuclei of those cranial nerves with motor function. These brainstem motor nuclei are analogous to the gray matter of the ventral horn of the spinal cord
GVA sensory cell bodies in spinal nerves are located where?
dorsal root ganglia (along with GSA for spinal nerves)
Review on GVE organization for spinal nerves
GVE function is divided among the sympathetic and parasympathetic systems. Remember that these are two neuron systems with pre‐ and post‐ganglionic neurons.
For the sympathetic system, the preganglionic fibers arise from spinal cord segments T1‐L2. The pre‐ ganglionic cell bodies are located in the spinal cord gray matter (lateral horn) of those segments. The post‐ganglionic cell bodies are found in either chain or collateral motor ganglia. Targets include visceral structures of the body wall (sweat glands, blood vessels, arrector pili smooth muscle), and viscera of the head, thorax and abdomen/pelvis.
For the parasympathetic system (sacral portion), the pre‐ganglionic fibers arise from spinal cord segments S2‐S4. The pre‐ganglionic cell bodies are located in the spinal cord gray matter of those segments. The post‐ganglionic cell bodies are found in terminal motor ganglia near their targets. These targets include hindgut and pelvic viscera.
GVE for the head can also be divided into sympathetic and parasympathetic divisions. How is the sympathetic GVE to the head organized?
Preganglionic sympathetic fibers destined for the head arise from spinal cord segments T1‐T2. Pre‐ ganglionic cell bodies are located in the spinal cord gray matter (lateral horn) of these segments. The preganglionic axons exit the spinal cord via the T1 & T2 spinal nerves to reach the sympathetic trunk. These fibers then ascend in the sympathetic trunk to reach the superior cervical chain ganglia where they synapse with the postganglionic neurons. Postganglionic fibers exit the sympathetic chain and form the carotid peri‐arterial plexus which surrounds the internal and external carotid arteries and their branches to reach their targets in the head.
Note that most (>95%) of these fibers do not travel with cranial nerves.
What are the targets of GVE sympathetic fibers in the head?
Sympathetic targets in the head and neck include sweat glands, dilator pupillae muscle, vascular smooth muscle and the superior tarsal muscle.
Which CNs have parasympathetic GVE components to the head?
Four cranial nerves (III, VII, IX and X)
Pre‐ganglionic cell bodies for parasympathetic GVE in the head are located where?
in the brainstem motor nuclei associated with those CNs. The preganglionic sympathetic fibers synapse with the post‐ganglionic neurons in terminal motor ganglia of the head (ciliary, otic, submandibular & pterygopalatine)
What are the terminal ganglia of CN III, VII, IX, and X?
CN III - Ciliary Ganglion
CN VII - Submandibular Ganglion and Pterygopalatine Ganglion
CN IX - Otic Ganglion
CN X - Intrinsic Ganglia of the Viscera of the Thorax, Foregut and Midgut
How do postganglionic parasympathetic GVE fibers reach their targets in the head?
they “hitchhike” primarily on named branches of the three divisions of the trigeminal nerve (CN V)
What are the GVE parasympathetic targets in the head and neck?
constrictor pupillae and ciliary smooth muscles, submandibular, parotid and sublingual salivary glands, mucous glands of the nasal cavity and hard palate, the lacrimal glands & the thoracic, foregut and midgut viscera.
What functional components does CN I (olfactory) have?
SA only- olfaction (smell)
one of three that are sensory only (CN II and VIII)
What functional components does CN II (optic) have?
SA only- vision
one of three that are sensory only (CN I and VIII)
What functional components does CN VIII (vestibulocochlear) have?
SA only- audition (hearing) and equilibrium
one of three that are sensory only (CN I and II)
What functional components does CN III (occulomotor) have?
GSE and GVE
one of five that are motor only
What does the GSE component of CN III do?
motor to 5 extraocular muscles- levator palpebrae superioris, superior rectus, inferior rectus, medial rectus, and inferior oblique
What does the GVE component of CN III do?
parasympathetic motor innervation to sphincter pupillae and ciliary muscles (smooth muscles of the eyeball.)
What functional components does CN IV (trochlear) have? What does that/those component do?
just GSE- responsible for motor to 1 extraocular muscle (superior oblique)
What functional components does CN VI (abducent) have? What does that/those component do?
just GSE- motor to 1 extraocular muscle (lacteral rectus)
What functional components does CN XI (accesory) have? What does that/those component do?
just GSE- motor to trapezius and sternocleidmastoid muscles
What functional components does CN XII (hypoglossal) have? What does that/those component do?
just GSE- motor to 3 intrinsic muscles of the tongue (hyoglossus, genioglossus, styloglossus) and all intrinsic muscles of the tongue
What functional components does CN V (trigeminal) have? What does that/those component do?
GSA and BE
What does the GSA component of CN V do?
sensory from skin of face and scalp, conjunctive, globe, orbit, meninges, teeth, gums, external ear, nasal cavity, oral cavity and anterior 2/3 of tongue, soft palate, and nasopharynx
What does the BE component of CN V do?
branchiomeric motor innervation to the muscles of the 1st pharyngeal arch (V3 only)
one of four CNs with both motor and sensory ability (also CN VII, IX, and X)
What functional components does CN VII (facial) have? What does that/those component do?
GSA, SA, BE, and GVE
What does the GSA component of CN VII do?
sensory from external ear
What does the SA component of CN VII do?
taste from the anterior 2/3 of the tongue and soft palate
What does the BE component of CN VII do?
branchiomeric motor innervation to the muscles of the 2nd pharyngeal arch
What does the GVE component of CN VII do?
parasympathetic motor innervation to lacrimal, submandibular, and sublingual glands, mucous glands of the membranes of the oral cavity, nasal cavity, and soft palate
What functional components does CN IX (glossopharyngeal) have? What does that/those component do?
GSA, GVA, SA, BE, and GVE
What does the GSA component of CN IX do?
sensory from external ear, mucous membrane of tympanic cavity and tympanic membrane, auditory tube, posterior 1/3 of tongue, oropharynx, and poster aspect of nasopharynx
What does the GVA component of CN IX do?
sensory from carotid sinus and body
What does the SA component of CN IX do?
taste from posterior 1/3 of tongue
What does the BE component of CN IX do?
branchiomeric motor innervation to the muscles of the 3rd arch
What does the GVE component of CN IX do?
parasympathetic innervation to the parotid gland
What functional components does CN X (vagus) have? What does that/those component do?
GSA, GVA, SA, BE, and GVE
What does the GSA component of CN IX do?
sensory from the external ear, lower 1/3 of the pharyngeal mucosa and esophagus, laryngeal mucosa, and the root of the tongue
What does the GVA component of CN IX do?
sensory from the carotid body and baroreceptors and viscera of the throat, foregut, and midgut
What does the SA component of CN IX do?
taste from the base of the tongue and epiglottis (root of the tongue)
What does the BE component of CN IX do?
branchiomeric motor innervation to the muscles of the 4th and 6th arches
What does the GVE component of CN IX do?
parasympathetic innervation to viscera, smooth muscle and glands in the trachea, esophagus and thoracic and abdominal viscera (foregut and midgut)
What functional components do CN XI and XII have?
GSE only
The vagus nerve exits the cranial cavity via what?
the jugular foramen
What are the main branches of the vagus nerve (CN X)?
1) auricular nerve
2) meningeal nerve
3) sinus nerve
4) pharyngeal branch
5) internal branch of superior laryngeal nerve
6) external branch of superior laryngeal nerve
7) recurent (inferior) laryngeal nerve
8) cardiac branches
APE-SCRIM
What does the auricular nerve carry?
GSA to external ear
What does the meningeal nerve carry?
GSA to the dura in the posterior cranial fossa
What does the sinus nerve carry?
GVA to carotid body
What does the pharyngeal branch carry?
BE to palatoglossus, all muscles of the pharynx (except stylopharyngess) and all muscles of the soft palate 9except tensor veil palatini)
What does the internal branch of superior laryngeal nerve carry?
GSA to mucosal lining of the laryngopharynx down to the vocal folds, GVE (parasympathetic) to glands of the pharynx, GSA to root of tongue and epiglottis, SA (taste) to root of tongue and epiglottis
What does the external branch of superior laryngeal carry?
BE to cricothyroid muscle
What does the sinus nerve carry?
BE to all other muscle of the vocal folds (except cricothyroid) and GSA to mucosal lining of the larynx below the vocal folds
What do the cardiac branches of the vagus nerve carry?
GVE (parasympathetic) to the heart
