Cranial nerves Flashcards
motor nerves
their cell bodies are in nuclei within the brain
sensory nerves
most of their cell bodies are outside of the brain in ganglia
CN 1
Olfactory nerve, sensory (smell) Olfactory receptors (Superior part of nasal cavity, inferior surface of the cribriform plate along the superior nasal concha) ->olfactory epithelium -> olfactory nerve -> olfactory foramina in the cribriform plate -> olfactory bulbs -> olfactory tracts -> primary olfactory area 28 + limbic system + hypothalamus + habenular nuclei (Ephithalamus) emotional response to odors -> Frontal lobe #11
Loss of sense of smell from infections of nasal mucosa, head injuries, meningitis, smoking, cocaine use
Anosmia
Reduced ability to smell
hyposmia
increased sense of smell
hyperosmia (only sensation reach the cerebral cortex without first synapsing in the thalamus)
CN II
Optic Nerve (sensory nerve - optic) Rods and cones in retina (photoreceptor->Bipolar cell -> Ganglion) -> Optic nerves -> optic foramen (under pituitary gland) ->optic chiasm (medial half cross opposite site, lateral half does not cross) -> optic tract ->lateral geniculate nucleus in thalamus -> primary visual area #17 Occipital lobe (a few axons go to superior colliculi (tectum) in midbrain
cone
Stimulated in bright light, color vision, high acuity, concentrated in the center of retina
rod
allow us to see in dim light
no color
low acuity
concentrated in the periphery
Bipolar cells
lateral connections
Ganglion cell layer
their axons extend posteriorly to optic disc and exit the eye as the optic nerve
Optic disc
blind spot
blindness due to a defect or loss of 1 or 2 eyes
Anopia
from fractures in orbit, brain lesions, damage along the pathway disease of the nervous system, pituitary gland tumours, cerebral aneurysm
Make your eyes trick
CN III (Oculomotor), IV (Trochlear nerve), VI (Abducens nerve)
CN III
Oculomotor nerve (Motor, eye movement and upper eye lid)
Nucleus in midbrain -> superior orbital fissure -> superior branch ->superior rectus and levator palpebrae superioris
also
->inferior branch ->medial rectus, inferior rectus, inferior oblique mm
Autonomic (smooth muscle)
Motor nucleus in midbrain -> superior orbital fissure -> inferior branch -> ciliar ganglion -> ciliary muscle and circular muscle of iris
image formation
- reflection n bending of light by the lens and cornea
- Accommodation (the change in the shape of the lens) when the eye is focusing on a close object, the lens become more spherical causing greater reflection of light rays (less than 20 feet)
Ciliary muscle
controls the shape of lens
adjust the lens for near vision “accommodation’
CN IV
Trochlear nerve
Motor eye movement superior oblique (look down and out)
Smallest cranial nerve
only on the arises from the posterior brain stem
trochlear nucleus ->superior orbital fissure -> superior oblique mm of eye ball
CN VI
Abducens nerve (motor abducts the eye) in pons Abducens nucleus ->superior orbital fissure -> lateral rectus muscle
Superior oblique muscle
makes you look down and out
Inferior oblique muscle
make you look up and out
moves the eye towards the nose
Medial rectus
moves eye away from the nose
lateral rectus
moving eye up
superior rectus
moves eye down
Inferior rectus
makes you look down and out
Superior oblique rotates
makes you look up and out
Inferior oblique
CN III eye muscles
medial rectus
superior rectus
inferior rectus
inferior oblique
CN IV eye muscle
Superior oblique
CN VI eye muscle
lateral rectus
Damage to occulomotor
Strabismus : lazy eye, condition in which both eyes do not fix on the same object since one or both eyes may turn inword or outword
Ptosis
dilation of pupil
movement of eyeball downward and outward on damaged side
loss of accommodation for near vision
diplopia (double vision)
Damage to trochlear nerve
strabismus
diplopia
damage to abducens
affected eyeball can’t move laterally beyond midpoint and eyeball is usually directed medially
CN V 3 branches
Trigeminal nerve (both motor and sensory) Sensory 3 branches 1. Ophthalmic V1 2. Maxillary V2 3. Mandibular V3
Ophthalamic nerve covers
sensory from skin over upper lid, cornea lacrimal glands upper nasal cavity side of nose forehead anterior half of scalp
where does Ophthalmic pass to get trigeminal ganglion
superior orbital fissure
Maxillary covers
sensory from mucosa of nose palate part of pharynx upper teeth upper lip lower eyelid
where does maxillary pass through to join trigeminal ganglion
foramen rotundum
Mandibular nerve covers
sensory from anterior 2/3 of tongue (not taste), cheek and its mucosa, lower teeth skin over mandible side of head anterior to ear mucosa of floor of mouth
where does mandibular nerve pass to join trigeminal ganglion
foremen ovale
What is the uniqueness of CNV?
Largest cranial nerve has both motor and sensory
what does trigeminal motor nerve do? and where is it?
in mandibular branch
supply mm of mastication
these motor neurons mainly control chewing
What is main pathology of Trigeminal nerve?
Trigeminal neuralgia (tic douloureaux)
Sharp cutting intense pain that last for a few seconds to a minute
is caused by anything that presses on the trigeminal nerve on its branches (V2 or V2 and V3 - lip, face, tongue)
pain is within the nerve’s distribution
what are possible causes of trigeminal neuralgia
local compressions
herpes zoster, vascular lesions, tumours
demyelinating conditions with subsequent scarring (MS)
ideopathic
CN VII
facial nerve
sensory and motor and autonomic
CNVII sensory route
Taste buds of anterior 2/3 of tongue ->stylomastoid foremen (temporal bone) -> genuculate ganglion -> pons -> thalamus ->gustatory area of cerebral cortex #43
also sensory axons from skin in ear canal (relay touch, pain, heat and cold)
CN VII motor nerve route
nucleus in pons -> stylomastoid foremen -> fascial expression mm, stylohyoid mm, posterior digastric mm, stapedius mm
CNVII autonomic nerve route
Superior salivatory nucleus ->
1. pterygopalatine ganglion ->lacrimal gland (tears), nasal gland (snot), palatine gland
- Submandibular ganglion -> submandibular + sublingual glands
CNVII pathology
Bell’s palsy: paralysis of the muscles of facial expression on the same side as the lesion. unilateral weakness. onset can be rapid. If sensory and autonomic affected, the patient can’t control lacrimation, decrease in salivation, can not taste on anterior 2/3 of tongue, heightened sensitivity of hearing. Sagging of face and eyelid
how do you differentiate stroke and Bell’s palsy?
Stroke affect lower half of facial muscles. The patient can control eye brow or can close eyes. The patient with Bell’s palsy can not.
