Cranial Nerves Flashcards
What are the cranial nerves?
- olfactory (smell)
- optic (vision)
- oculomotor (eye movement [most extraocular movements], elevation of upper eyelid, pupillary constriction)
- trochlear (eye movement [down and in])
- trigeminal (Motor: mm of mastication; Sensory: face, tongue [not taste])
- abducens (eye movement [lateral deviation])
- facial (sensory: taste [ant 2/3 tongue]; motor: facial mm)
- accoustic (balance/equilibrium: vestibular division; hearing: cochlear division)
- glossopharyngeal (motor: pharynx; sensory: pharynx and posterior tongue, including taste)
- vagus (motor: palate, pharynx and larynx; sensory: pharynx and larynx, PaNS)
- accessory (controls trapezius and SCM)
- hypoglossal (tongue)
Which cranial nerves originate in the brainstem?
CN 3-12
Cranial nerves are numbered according to what sequence?
order in which they leave the brain (from sup. to inf.)
The olfactory nerve is a collection of sensory nerve rootlets that pass through the many openings of the:
cribiform plate of the ethmoid
Hair cells in the nose have ___ on one side and an ___ on the other side in order to transduce chemical activity into APs.
cilia; axon
About how many olfactory receptors are in humans? In german sheppards?
40 million; 2 billion
People with no sense of smell have a disorder called:
anosmia
An olfactory hallucination is called:
phantosmia
A condition in which a smell that’s present in the environment is distorted:
parosmia
What’s the aka for the blind spot in the eye?
scotoma
The clinical term for near-sightedness.
myopia (means you can see better close up than far away
The clinical term for far-sightedness.
hyperopia (mean you can see better far away than close up)
Myopia and hyperopia are due to:
a misshapen cornea, the transparent part of the eye that covers the iris and pupil
With ___ a person has difficulty focusing on an object that is close up.
presbyopia
A ___ is a clouding of the lens most commonly due to aging.
cataract
The central portion of the retina is called the:
macula
___ is a term for a group of disorders that result in optic nerve damage, often associated with increased fluid intraocular pressure.
glaucoma
What does the oculomotor (CN 3) supply?
- most of the extrinsic muscles of the eye, except the lateral rectus and superior oblique
- also supplies levator palpebrae superioris which lifts the upper eyelid
- supplies the ciliary muscle which adjusts the lens of the eye
- also supplies the sphincter pupillae which constricts the pupil
What does the trochlear nerve (CN 4) do?
motor to the superior oblique muscle; turns eye downward
What does the abducens (CN VI) do?
motor to lateral rectus muscle; abducts eye
The largest and most complex of the cranial nerves, what does the trigeminal nerve (CN V) supply?
- supplies sensations to the face, mucous membranes and other structures of the head
- motor nerve for muscles of mastication and contains proprioceptive fibres
What are the divisions of the trigeminal nerve (CN V)?
- ophthalmic division (CN Vi)
- maxillary division (CN Vii)
- mandibular division (CN Viii)
What’s the sensory function of the trigeminal nerve (CN V)?
carry somatic sensory info (touch, pain, thermal) from the skin of the face, mucous membranes of the nasal and oral cavities including sinuses
What’s the motor function of CN Viii?
muscles of mastication
This condition, dealing with CN V, is considered to be one of the most painful afflictions known
trigeminal neuralgia
What does the facial nerve (CN VII) supply and detect?
- all muscles of facial expression including orbicularis oculi but NOT levator palpebrae superioris (that’s CN 3)
- CN 7 closes the eye, CN 3 opens the eye
- taste
- lacrimal glands
- sublingual and submandibular glands (salivvary glands)
- muscous glands of the nose
This form of flaccid paralysis or weakening develops suddenly. It’s associated with damage to CN 7 due to viral infections, trauma, pressure from a tumor. Can strike any age but disproportionately attacks pregnant women and people with diabetes. 85% of people start recovering in three week, even without treatment.
bell’s palsy
Flaccid paralysis is weakness or loss of muscle tone resulting from injury or disease of ___; spastic paralysis is cause by injury or disease affecting ___
PNS (LMNs); CNS (UMNs)
What are the akas for the vestibulocochlear nerve (CN 8)?
acoustic nerve, auditory nerve
What are the two separate components that travel together from the inner ear as CN 8?
- vestibular nerve carries impulses for equilibrium (balance)
- cochlear nerve carries impulses for hearing
Sound waves converge through the ___ (part of the ear that’s outside the head) and outer ear canal to strike the tympanic membrane
auricle (aka pinna)
The vibrations of the tympanic membrane are transmitted by way of 3 ___ to the ___
ossicles (malleus, incus, stapes); cochlea (“snail-like”)
The ___ contains hair cells whose mechanical distortions are transduced into APs
cochlea
What are the sensory functions of the vagus nerve (CN 10)?
viscera and glands of the neck (larynx, trachea, esophagus), thoracic viscera, abdominal viscera, proximal colon
What are the motor functions of the vagus nerve (CN 10)?
organs and glands of the neck, thorax and abdomen up to the proximal colon
what does the vagus nerve innervate?
- levator veli palantini (elevates the soft palate to help prevent food from entering the nasopharynx)
- pharyngeal constrictors
- muscles of the larynx (speech)
- regulate heart rate, gastrointestinal peristalsis and sweating
- afferent vagus nerve fibres innervating the pharynx are responsible for the gag reflex
- regulates the chemical levels in the digestive system so that the intestines can process food and keep track of what types of nutrients are being gained from the food that is taken in
Which nerves control eye movement?
- oculomotor (eye movement [most extraocular movements], elevation of upper eyelid, pupillary constriction)
- trochlear (eye movement [down and in])
- abducens (eye movement [lateral deviation])
Which nerves sense taste?
- CN VII facial
- sensory: taste (ant 2/3 tongue)
- motor: facial mm
- CN IX glossopharyngeal
- motor: pharynx
- sensory: pharynx and posterior tongue, including taste
What does the accessory nerve (CN 11) innervate?
motor to SCM and trapezius
Patients with ___ ___ present with the head twisted to the affected side and chin pointed toward the opposite shoulder.
acquired torticollies
What does the hypoglossal nerve (CN12) innervate?
- all intrinsic tongue mm
- most extrinsic tongue mm (ex genioglossus)
What’s the translation of malleus, incus and stapes?
hammer, anvil, stirrup
What are some things that can happen as a result of an underactive vagus nerve?
- can lead to gastroparesis, a frequent and severe complication of diabetes
- sufferers may experience:
- stomach pain
- nausea
- heartburn
- stomach spasms
- weight loss
- therapy can include vagus nerve stimulation via a device, similar to a pacemaker, attached to the nerve
What are some things that can happen as a result of an overactive vagus nerve?
- over activation of the vagus nerve during emotional stress is a parasympathetic overcompensation of a strong sympathetic nervous system response associated with stress, can cause:
- vasovagal syncope
- can also lead to temporary loss of bladder control under moments of extreme fear
- can cause vasovagal syncope (fainting) due to a sudden drop in cardiac output. triggers include:
- prolonged standing, especially when combined with warm temperatures, confined spaces, and/or crowding
- emotional situations especially those of sudden onset
- pain
- fasting
- fatigue/lack of sleep
- menstruation
- illness with fever
- standing quickly
