Study Guide Cranial Nerves Half Midterm #2 Flashcards
Control of the autonomic nervous system is from the ____
Hypothalamus as well as certain brainstem nuclei.
Efferent preganglionic axons are always myelinated and enter the PNS via the ____ root of the spinal nerve
Anterior/ventral
Ventral root carries motor/efferent somatic and autonomic information
Efferent/motor Arising from the neuron cell body is the post-ganglionic axon, which is always ____
Un-myelinated. This axon now travels to the effector.
All preganglionic sympathetic nerve fibers leave the spinal cord ___ from __ to __.
Anteriorly/ventrally from T1 to L2 (thoracolumbar). This means sympathetic nerves found anywhere in the body emerge from spinal nerves in this region.
Sympathetic nerve fibers destined from the head exit from T1.
Upon sympathetic nerve fibers entering the sympathetic chain, there are 3 possible destinations for the axon.
- Synapse with post ganglionic neuron immediately. The postganglionic axon then exits via the grey ramus to the spinal nerve, then to its destination.
- Ascend or descend in the sympathetic chain and synapse with a post ganglionic axon then exit via the grey ramus to the spinal nerve, then its destination.
- Pass through the sympathetic chain without synapsing, exiting via the splanchnic nerves. These preganglionic axons synapse within the prevertebral sympathetic ganglia of the abdomen (celiac, renal, superior and inferior mesenteric ganglia)
These divisions from the splanchnic nerves receive sympathetics from which divisions of the spinal cord?
- Greater
- Lesser
- Least
- Lumbar
- T5-T9
- T10 and T11
- T12
- L1 and L2
The parasympathetic cranial nerve nuclei are (4):
- Edinger-Westphal of the midbrain supplies the oculomotor nerve, CN III.
- Superior salvitory of the pons supply the facial nerve, CN VII.
- The Inferior salvitory of the medulla supplies the glossopharyngeal nerve, CN IX.
- The dorsal nucleus of vagus of the medulla supplies the vagus nerve, CN X
Parasympathetic ganglia associated with the head and neck
- Edinger Westphal - CN III - Ciliary ganglion
2, 3. Superior salvitory - CN VII- pterygopalatine and submandibular ganglion
- Inferior salvitory- CN IX - otic ganglion
Parasympathetic. Edinger-Westphal nuclei pathway
Edinger-Westphal
CN III
Goes to ciliary ganglion, which is behind globe
Innervates spinster and ciliary muscles of globe
Parasympathetic. Superior salvitory nuclei pathway
Superior Salvitory nuclei pathway.
CN VII
- Goes to pterygopalatine ganglion, which is inferior and posterior to orbit.
Innervates lacrimal and nasal glands. - Goes to submandibular, which is near the salivary gland.
Parasympathetic. Inferior salvitory nuclei pathway
Inferior salvitory
CN IX, glossopharyngeal
Goes to Otic ganglion, which is inferior to foramen vale
Innervates the parotid salivary gland
2 Plexi of the enteric nervous system
- Inner sub mucous plexus (Meissner’s) controls glandular secretions
- Outer myenteric plexus (Auerbach’s) controls smooth muscles of the digestive tract will
Parastalsis depends upon these plexuses, but can occur even in the absence of innervation from the CNS. The system controls itself, but the autonomic input helps modulate activity.
The somatic nervous system has one peripheral synapse at the neuromuscular junction. The axon is a ____
Nicotinic cholinergic axon (ACH)
Receptor for NE/Epi
Receptor for ACH
Adrenergic
Cholinergic- nicotinic or muscarinic
ALL preganglionic autonomic axons are ___
Nicotinic cholinergic axons
Parasympathetic pre and post ganglionic axon synapses
Pre: Nicotinic cholinergic (ACH)
Post: Muscarinic cholinergic (ACH)
-Ending on smooth muscle, cardiac muscle, or glandular tissue.
Sympathetic pre and post ganglionic axon synapses
Pre: Nicotinic cholinergic (ACH)
Post: For the most part, adrenergic (NE)
Brachial/pharyngeal arches (look at SVE fibers)
Arch 1- V3 Arch 2- VII Arch 3- IX Arch 4- X Arch 6- X, and XI(s)
Cranial nerve origins within the brain
Proencephalon
- Telencephalon (CN I)
- Diencephalon (CN 2)
Mesencephalon (CN 3, 4)
Telencephalon
- Mesencephalon (CN 5, 6, 7,
- Myelencephalon (CN 8-12)
Sensory nerves typically exit the brainstem __
Motor nerves typically exit the brainstem___
Laterally
Medially
CN I enters the anterior cranial fossa via the
Olfactory foramina found in the cribriform plate of the ethmoid.
CN II exits the orbit via the ___ into the ____ above the __
Exits via the optic canal into the middle cranial fossa above the cavernous sinus
CN III palsy looks like
Down and out. Since the only two muscles that CN III doesn’t innervate are the LR (out) and SO (down).
Pupil may be blown, mydriasis.
Aneurysms of the internal carotid artery in cavernous sinus associated. Epsilateral.
CN IV is the only cranial nerve that
- Exits the CNS dorsally and travels a long course.
2. Innervates a contralateral structure. EX right CN IV palsy affects the left superior oblique.
Sensory innervated areas from V1 (ophthalmic division of CN V)
Eye and orbit, facial skin above orbits, midline region of nose to tip.
What is Hutchinson’s sign and why would a patient presenting with this sign possibly have an ocular involvement?
Hutchinson’s sign is the idea that 3/4 people who have herpes zoster (Shingles, reactivated chicken pox) present at the tip of their nose, also have the infection in their eye.
The tip of the nose and the eye are linked through the nasociliary nerve from CN V1. Nasociliary nerve innervates the cornea and the tip of the nose.
Eye is affected in 50% of cases of facial zoster infections.
3/4 have ocular involvement when the tip of the nose is involved (Hutchinson’s sign).
V2 (maxillary division of CN V) enters the middle cranial fossa from the ___
Pterygopalatine fossa via foramen rotunda then passes through cavernous sinus
Main branches of the maxillary division of CN V
Zygomatic nerve and infraorbital nerve.
The maxillary nerve begins at the pterygopalatine fossa, travels through the foramen rotundum to the middle cranial fossa and cavernous sinus. Then travels through the inferior orbital fissure. Splits: zygomatic nerve goes to the lateral wall and infraorbital nerve travels through infraorbital canal on maxilla to reach the cheek surface.
Sensory innervation from the maxillary division of CN V
Facial skin below orbits, above mouth, and lateral to orbit and maxillary sinus.
Mandibular branch of CN V motor innervation
Muscles of mastication- masseter, temporals, medial and lateral pterygoid. All elevate mandible except the lateral pterygoid depresses it.
Mandibular branch of CN V sensory innervation
Area below mouth arcing lateral and upward to just anterior to the external ear. Contains the nasal cavity and 2/3 of the tongue through the lingual nerve.
Lingual nerve- runs with Chordae tympani from CN VII
Mental nerve- Brach of inferior alveolar nerve. Evaluated for CN V3 facial testing of chin.
GSA innervated
Autonomic fibers from the chorda tympani (branch of CN VII) runs alongside the ___ nerve to the submandibular ganglion
Lingual nerve. From CN V3
Where does V3 enter/exit the middle cranial fossa
Enters through the foramen oval, but does not pass through the cavernous sinus because oval is in the floor below the cavernous sinus.
Gives off motor and sensory branches
Motor and sensory branches of V3
Motor- Mesenteric, temporalis, medial pterygoid and lateral pterygoid (depresses mandible, all others elevate)
Sensory- Lingual and mental (branch from the inferior alveolar nerve)
Why is the abducens nerve, CN VI, more susceptible to injury?
Runs over the ridge of petrous bone, so it is more susceptible to injury/damage
Where does CN VII enter/exit
Enters the posterior cranial fossa via the internal acoustic meatus and eventually exits the skull at the stylomastoid foramen (between the styloid and mastoid process of the temporal bone).
SVE branches from CN VII
- Stapedial (controls amplitude of sound waves to inner ear)
- Posterior auricular (motor to occipital muscle)
- Two motor branches to the stylohyoid and posterior belly of digastric muscle (aids in swallowing)
- Five motor branches to the muscles of facial expression
- Temporal
- Zygomatic
- Buccal
- Mandibular
- Cervical
All of these are SVE
GVE branches from CN VII
- Greater petrosal: autonomic innervation to lacrimal gland and nasal gland
- Chorda tympani: Autonomic innervation to submandibular and sublingual glands via submandibular ganglion and alongside lingual nerve.
Which CN does sensory for taste from anterior 2/3rds of tongue.
Facial. Chroda tympani SVA innervation. Runs alongside lingual nerve.
SVA fibers from CN VII
Chroda Tympani for anterior 2/3 of tongue taste.
The geniculate ganglion
Sensory ganglion for CN VII. Parasympathetic fibers will NOT synapse there.
CN VIII enters posterior cranial fossa where and along with which other nerve?
At the internal acoustic meatus along with CN VII.
Where does the glossopharyngeal nerve enter/exit?
In the posterior cranial fossa via the jugular foramen.
How does CN IX innervate the tongue
Taste and touch for posterior 1/3 of tongue.
GSA for touch
SVA for taste (Similar to how CN VII is SVA for taste for anterior 2/3 of tongue)
Two divisions of CN VIII
Vestibular (balance) and cochlear (hearing) Two sensory ganglia, each associated with balance and hearing
Sensory innervation for CN IX
SVA
-Taste 1/3 posterior tongue
GSA
- Touch 1/3 posterior tongue
- Tympanic cavity
- Eustachian tube
- Oropharynx (back of oral cavity, mouth)
GVA
-Chemo and barn receptors in carotid
Motor innervation for CN IX
SVE
-Innervates muscles of the pharynx for swallowing
GVE
-Parotid gland via the otic ganglion from the inferior salivary
CN X enters where
Jugular foramen
Where does CN X run
Enters through the jugular foramen then runs inferiorly with the carotid sheath (between internal carotid and common carotid to supply neck, thorax, and abdomen).
Has the most extensive distribution of all CNs
Sensory innervation of CN X
GSA
- Ear
- Larynx
- Dura mater in posterior cranial fossa
SVA
-Taste from pharynx and epiglottis
GVA
-Aortic arch, esophagus, heart, lungs, abdomen
Motor innervation of CN X
SVE
-Skeletal muscles of pharynx/larynx and one tongue muscle palatoglossus
GVE
-Smooth muscle innervation of pharynx/larynx and adbomen
CN XI SVE possibly originates from
The sixth brachial arch for the cranial root
CN XI spinal root route
GSE
Enters cranium via foramen magnum into posterior cranial fossa. Then exits via jugular foramen along with the cranial root.
Innervates two superficial neck structures- sternocleidomastoid and trapezius.
Assessed by having pt shrug shoulders and/or having patient turn their head while evaluating resistance.
CN XI cranial root route
SVE
Possibly originates from the sixth brachial arch
Exits skull along with the spinal root via the jugular foramen and then travels with CN X. Innervates skeletal muscles of the larynx.
CN XII exits skull where
Exits in the posterior cranial fossa through the hypoglossal canal
Which tongue muscle does CN XII innervate
Genioglossus. Clinically assessed by asking patient to stick their tongue out.
Which two nerves join together, enter through the carotid canal with the internal carotid to form the vidian nerve?
What does the vidian nerve innervate?
Greater petrosal (preganglionic parasympathetic from CN VII) merges with the deep petrosal (postganglionic sympathetic) to enter the middle cranium via the carotid canal with the internal carotid. This forms the vidian.
The vidian innervates nasal glands and lacrimal glands. Direct route to lacrimal gland via nerve plexus. Does not take long route like previously thought.
Innervation of tonuge
Anterior 2/3-
Taste: CN VII by chordae tympani
General sensation: CN V3 by lingual from mandibular
Posterior 1/3
Taste and general sensation: CN IX
