Cranial Nerves of face, mastication, and movements of the eye Flashcards
Where do cranial nerves V (trigeminal) and VII (facial) arise from?
the pons
Does a sensory or motor root arise from the pons of the brainstem for Trigeminal nerve (V)?
both
Where are the sensory bodies of Cranical Nerve V (trigeminal) from the pons located?
the semilunar ganglia located in the cranial cavity (similar to dorsal root ganglion, containing cell bodies of general sensory axons)
What does the motor compartment of the trigeminal nerve innervate?
muscles of mastication
How many major branches arise from the trigeminal nerve after he sensory trigeminal fanglia? What are they called?
Three- 1) V1 or Opthalmic, 2) V2 or Maxillary, 3) V3 or Mandibular
Which branch of the trigeminal nerve is the only branch with a motor component?
mandibular or V3 (motor to the muscles of mastication).
Which is the main sensory nerve to the face that brings sensory information from the face to the brainstem?
Cr. V (trigeminal)
What are the three nerves that branch off of the opthalmic nerve (V1 of the trigeminal nerve)?
1) frontal– which branches into supratrochlear and supraorbital. Sensation from the skin above the eye and nose. 2) Lacrimal– general sensation to the lacrimal gland (also carries postganglionic parasympathetics from CN VII that synapsed in pterygopalatine gangla). 3)nasociliary nerve– sensation to ethmoid sinuses, upper nose. Long and short ciliary nerves are associated.
Describe the maxillary nerve (V2)
There are no branches of V2 to identify in lab except the maxillary nerve (V2), which ends on the face as infraorbital. Supplies general sensation to the skin below the eye– infraorbital nerve. Also supplies upper teeth, lower nasal septum, and lateral nose palate. Part of the meninges.
What are the two branches of V3, or the mandibular nerve branch of the trigeminal nerve.
1) inferior alveolar nerve– goes into the mandibular foramen. Sensation to the lower teeth and skin of the lower jaw, where it ends as the mental nerve. Nerve to the mylohyoid is a branch.
2) lingual nerve– general sensation to the anterior two thirds of the tongue– V3. But also carries taste fibers to the anterior two thirds from CN VII. Also preganglionic parasympathetic fibers from CN VII to the submandibular ganglia.
Where is the main component of the facial nerve (CN VII) derived from?
facial nucleus in brain stem, which contains somatic motor axons that innervate muscles of facial expression.
What does the facial nerve main component contain?
somatic motor axons that innervate muscles of facial expression.
What are the muscles that are innervated by the facial nerve?
Obicularis oculi, obicularis oris, buccinator, posterior belly of the digastric, stylohyoid, and the stapedius.
Which gland does the facial nerve pass through when it exits the skull?
the parotid gland
What causes Bell’s palsy?
lower motor neuron lesion of motor components of the facial nerve.
What is Bell’s palsy?
flaccid paralysis on one side of the face.
What are the two sources of the facial nerve (CN VII)
facial nucleus and nervous intermedius
*What is the significance of the nervous intermedius portion of the facial nerve?
1) taste from anterior two thirds of the tongue, 2) preganglionic parasympathetic fibers to lacrimal gland, mucuous glands of the nose, sublingual and submandibular gland (secretions), 3) general sensation to a small area of the skin near the ear.
Axons from the preganglionic parasympathetic neurons in the superior salivatory nucleus synapse in either the ____ or the ____
submandibular ganglion or the pterygopalatine ganglion. These ganglia contain cell bodies of postganglionic parasympathetic neurons.
*What glands do the postganglionic parasympathetic axons from the pterygopalatine ganglion stimulate?
lacrimal gland and mucous glands in the nose and palate
*what glands do the postganglionic parasympathetic axons from the submandibular ganglion stimulate to secrete?
submandibular and sublingual
What nerve is responsible for you sensing irritation to the eye? What is responsible for causing you to blink the eye in response?
Afferent – V1 of trigeminal, nasociliary nerves.
Efferent – facial nerve for orbicularis oculi muscle.
When one eye is irritated does just that eye blink?
No– both eyes blink. The irritated eye response is called a direct response, while the other eye blinking is a consensual response.
where in the brain stem are the axons that carry the motor information to the muscles of mastication?
masticatory nucleus
which branch of the trigeminal nerve is responsible to innervating the muscles of mastication
V3 or the mandibular branch
What is the TMJ?
temperomandibular joint– a modified hinge type of synovial joint between mandibular condyle and mandibular fossa of zygomatic process. An articular fibrocartilage disc separates the condyloid process from the mandibular fossa. There is an atricular tubercle just anterior to the fossa. The movements of the TMJ are rotational (depression and elevation) and translational (protrusion and retraction), and can move the jaw from side to side.
What are the ligaments of the TMJ?
1) capsule, 2) lateral temperomandibular ligament. It is part of the capsule and prevents excessive side to the side movements and depression
What is the stable position of the TMJ?
elevation
Which ligament of the TMJ prevents excessive side to side movements and depression?
lateral temperomandibular
Which ligament of the TMJ prevents excessive protrusion and depression?
stylomandibular
Which ligament of the TMJ prevents excessive depression?
sphenomandibular
What is the difference between an upper motor lesion and lower motor lesion with Bell’s Palsy?
Upper motor = opposite side of the damage. DOES NOT affect the forehead. The lesion comes from the pons. Lower motor lesion = affects same side of the nerve damage. The entire side of the face droops.
What carries information for taste or special sensation to the anterior two thirds of the tongue to the lingual nerve?
chorda tympani
If a bug flies in your eye what nerve carries pain or sensation fibers from the cornea of your eye?
V1 (nasociliary) of the trigeminal nerve.
What nerve causes the reflex of you blinking from the bug in your eye?
VII (facial) as reflex.
A patient’s face droops downward on the left side and she cannot wrinkle the left side of her forehead. A) What structure is affected that would result in these symptoms? B) is this an upper motor or lower motor type lesion?
A) the facial nerve– motor components, B) lower motor
Which two eye muscles are not innervated by the occulomotor nerve (CN III)?
superior oblique and lateral rectus
What would happen if there were complete damage to CN III?
1) loss of levator palpebrae, so there would be a droopy eyelid ipsilaterally, 2) only the superior oblique and lateral rectus are in-tact, so the eye would be stuck in the “down-and-out” position. 3) loss of sphincter pupillae (unopposed dilator pupillae innervated by sympathetics) results in dilated pupil and loss of pupillary light reflex in affected eye. 4) loss of ciliary muscle– no accommodation of lens
What is lateral strabismus?
when the eye is stuck in the down and out position (due to damage to CN III – oculomotor nerve). This results in double vision.
What happens if there is partial CN III damage due to compression of CN III against the petrous portion of the temporal bone by intracranial pressure caused by a hematoma?
parasympathetic fibers of CN III are damaged first (b/c they are more superficial). This results in dilated pupil (loss of pupillary light reflex and accomodation). Called internal opthalmoplegia. You could also have external opthalmoplegia, where somatic motor fibers of CN III are damaged by the parasympathetics are intact.
What is the acccommodation reflex?
CN II and CN III. Eye focuses on near object sensory signal sent down CN II to the brain and the message is interpreted and motor signal is sent down CN III to the ciliary muscle, which changes the shape of the lens to bring the eye into focus.
What is the pupillary light reflex?
CN II and CN III. When you shine a light near the eye a sensory signal is sent down CN II to the brain and the message is interpreted and a motor signal is sent down CN III by parasympathetic fibers via short ciliary nerve to the sphincter pupillae muscle, which constricts the pupil in response to the light.
What are the two accessory muscles of mastication?
mylohyoid and anterior digastric
What are the muscles of mastication?
lateral pterygoid, temporalis, medial pterygoid, masseter,
What innervates the mylohyoid and anterior digastric?
nerve to mylohyoid, motor branch of V3 (mandibular branch of trigeminal nerve)
What are the steps of mastication?
First step is to move the mandibular condyle forward onto the articular process of the temporal bone. The lateral pterygoid protracts the mandible. The condyle is depressed (rotation) and then protruded (translation). The second step is to open wider. The mylohyoid and anterior digastric can depress the mandible further. Step 3 is to return to a stable position. In this step the anterior temporalis, masseter, and medal pterygoid elevate the mandible. The posterior temporalis is the retractor. The jaw returns to the stable position in the mandibular fossa.
Which step of mastication is unstable? Why? What can result from this?
step 2. The jaw can be dislocated in front ofthe anterior tubercle. The ligaments can become stretched. This could lead to TMJ syndrome, which could be pain and clicking.
What is the difference between incisal chewing and side-to-side chewing?
incisal chewing is when the condyles rotate forward on both sides and depress the mandible symmetrically. To return the mandibular condyles rotate and the condyles are elevated. Side to side chewing is when one condyle is forward on an articular tubercle, while the other is not. This is assymetrical.
Which nerve exits through the stylomastoid foramen?
the motor portion of the facial nerve (VII)
Taste or special sensation of the tongue is innervated by?
CN VII (Facial)
Anterior two thirds of the tongue gets general sensation from?
V3 (Lingual) of CN V (Trigeminal)
Posterior one third of the tongue gets general sensation and taste from?
CN IX Glossopharyngeal
What provides motor innervation to the tongue?
hypoglossal nerve (CN XII). Hypoglossal nerve arises from the medulla. There are two hypoglossal nerves. When the tongue is stuck out, the genioglossus muscles on both sides pull the tongue forward.
What happens if there is a lesion to the hypoglossal nerve on one side?
The tip of the tongue will deviate toward the side of the lesion. The genioglossus on the affected side is not working, so it can’t pull the tongue forward on that side. Fasciculations and atrophy of the tongue can occur on the side that is deinnervated.
How do you check the integrity of the hypoglossal nerve and the medulla?
stick the tongue out. If it deviates towards one side then there is a lesion on that side to the hypoglossal.
Which portion of the temporalis is a retractor of the mandible?
posterior
What is the innervation of the extraocular muscles of the eye?
LR6SO4AO3. Lateral rectus = CN VI, Superior oblique = CN IV, All others = CN III
Which nerve provides motor innervation to the levator palpebral, superior rectus, medial rectus, inferior oblique, and inferior rectus muscles?
occulomotor (CN III)
Which motornerves derive from the midbrain?
CN III and CN IV, oculomotor and trochlear.
What motor innervation does the trochlear nerve (CN IV) provide?
superior oblique
What motor nerve/s derive from the pons?
Abducens (CN VI)
What muscle does the abducens (CN VI) provide motor innervation for?
lateral rectus
What are the branches of Ci (Opthalmic) nerve?
1) Frontal– divides into supratrochlear and supraorbital. Lacrimal– to lacrimal gland. Nasociliary - to the nose, ethmoidal sinuses, and long ciliary branches to the cornea. Corneal reflex.
Which nerve innervates levator palpebrae?
CN III (superior division)
what would happen to the eye if there were a lesion to CN III?
drooping of eyelid
The Z axis of the eyeball has which types of movements?
adduction and abduction (lateral rectus = abduction; medial rectus = adduction)
The X axis of the eye has which types of movement?
elevation and depression. The superior rectus elecates and the inferior rectus depresses.
The Y axis has which types of movement?
extorsion and intorsion. oblique muscles.
What muscles would activate if I were to look to the right?
lateral rectus of right eye abducts while medial rectus of left eye adducts
what muscles would be activated if I were to look upward and out?
the inferior oblique is active on the outer eye (up and out). The superior rectus looks up and in for the opposite eye.
What muscles would be activated if I were to look downward and out?
The superior oblique would be the prime mover for the outer eye. The inferior rectus would look down and in for the other eye.
What muscles are activated to look straight up?
superior rectus and inferior oblique on both eyes
What muscles are activated if I were to look straight down?
superior oblique and inferior rectus for both eyes.
What is diplopia?
double vision. common symptom for eye muscle problems.
What is strabismus?
can be lateral or medial. The eye cannot move to the side of the lesion. It can be pulled in the opposite direction by the muscle that is not lesioned.
What is ptosis?
drooping of upper eyelid
What would cause loss of constriction or accomodation?
loss of parasympathetic fibers with the oculomotor nerve (III)
Lesion of what nerve would cause lateral strabismus?
oculomotor
Lesion of what nerve would cause double vision?
oculomotor (III), trochlear (IV), or abducens (VI)
What are the five branches of facial nerve that innervate muscles of facial expession?
Tell Ziggy Bob Marley Called: Temporal, Zygomatic, Buccal, Mandibular, Cervical
Loss of corda tympani results in?
loss of taste to anterior 2/3 of the tongue.
Which nerve is vulnerable to damage during neck surgeries?
Accessory XI
Summarize the cranial nerve related to the tongue
1) anterior two thirds of the tongue: general sensation is CN V V3 lingual branch, special sensation– taste is from CN VII chorda tympani branch.
2) posterior 1/3 of tongue. General sensation is the CN IX glossopharyngeal nerve. The special sensation is CN IX glossopharyngeal nerve.
The hypoglossal nerve (XII) arises from?
the medulla
What are the branches of the opthalmic nerve?
Frontal, lacrimal, and nasociliary
What does the opthalmic nerve (V1) do?
sensory to the orbit, frontal scalp, upper eyelids, cornea, and ethmoidal air sinuses.
Describe the corneal reflex?
Corneal reflex = VI brings sensory information from cornea to brain via long ciliary nerves. The facial nerve (VII) innervates the obicularis occuli, closing the eyelids, and the preganglionic parasympathetic axons oto the pterygopalatine ganglion that leads to tearing.
In strabismus is the eye pulls ipsilaterally or contralaterally with regards to the injured muscle?
eye is pulled in opposite direction of injured muscle (contralaterally)
If a patient has to tilt her head downward to use the unaffected side to see downward, what nerve is likely lesioned?
Trochlear nerve (CN IV) because the superior oblique is affected, leading to a weak downward gaze.
If the patient cannot move the affected eye outward, what nerve is likely lesioned and why?
CN VI (Abducens) because the lateral rectus is affected. This is medial strabismus– the eye stays fixed because of tension generated by the medial rectus.
