cranial nerves 2 Flashcards
Nerve: I (CN, Type, Location of nuclei, foramen)
CN: Olfactory
Type: Special
Location of nuclei:
Foramen: Cribriform plate (olfactory foramina)
Nerve: II (CN, Type, Location of nuclei, foramen)
CN: Optic
Type: S
Location of nuclei:
Foramen: Optic Canal
Nerve: III (CN, Type, Location of nuclei, foramen)
CN: Oculomotor
Type: M*
Location of nuclei: midbrain
Foramen: superior orbital fissure
Nerve: IV (CN, Type, Location of nuclei, foramen)
CN: Trochlear
Type: M
Location of nuclei: midbrain
Foramen: superior orbital fissure
Nerve: V (CN, Type, Location of nuclei, foramen)
CN: Trigeminal
Type: B
Location of nuclei: pons
Foramen:
1. ophthalmic - superior orbital fissure
2. maxillary - foramen rotundum
3. mandibular - foramen ovale
Nerve: VIII (CN, Type, Location of nuclei, foramen)
CN: Vestibulocochlear
Type: S
Location of nuclei: pons/medulla
Foramen: auditory canal
Nerve: VII (CN, Type, Location of nuclei, foramen)
CN: Facial
Type: B*
Location of nuclei: pons
Foramen: stylomastoid foramen
Nerve: VI (CN, Type, Location of nuclei, foramen)
CN: Abducens
Type: M
Location of nuclei: Pons
Foramen: superior orbital fissure
Nerve: IX (CN, Type, Location of nuclei, foramen)
CN: Glossopharyngeal
Type: B*
Location of nuclei: medulla
Foramen: jugular foramen
Nerve: XII (CN, Type, Location of nuclei, foramen)
CN: Hypoglossal
Type: M
Location of nuclei: Medulla
Foramen: Hypoglossal foramen
Nerve: X (CN, Type, Location of nuclei, foramen)
CN: Vagus
Type: B*
Location of nuclei: Medulla
Foramen: Jugular foramen
Nerve: XI (CN, Type, Location of nuclei, foramen)
CN: Accessory nerve
Type: M
Location of nuclei: medulla
Foramen: Jugular foramen (first enters skull through foramen magnum)
How many pairs of cranial nerves?
- 12
Cranial nerves part of CNS or PNS?
- PNS
What do cranial nerve numbers indicate?
The order (rostral to caudal) that nerves arise from brain
Location of cell bodies for
1. Sensory nerves
2. Motor nerves
- Outside the brain
- Within the brain
Olfactory Nerve
- Shortest cranial nerve
Olfactory Epithelium location
- Superior nasal cavity
- Inferior surface of cribiform plate
- Along superior nasal concha
Olfactory epithelium 3 cell types
- Olfactory receptors
- Supporting cells
- Basal cells
Olfactory pathway
- Axons of olfactory receptors form the olfactory nerve
- Axons go through the olfactory foramina in cribriform plate
- Olfactory bulbs
- Olfactory tracts
- Primary olfactory area + limbic system + hypothalamus
- Frontal lobe
Olfactory sensations are the only sensations to do what?
- Reach the cerebral cortex without first synapsing in the thalamus
Hyperosmia
- Increased sense of smell
Anosmia
- Loss of sense of smell
- From infections of nasal mucosa, head injuries, lesions along olfactory pathway, meningitis, smoking, cocaine use
Sense of smell information
women, smoking, age
- women have keener sense of small than men, esp. during ovulation
- Smoking impairs smell in short term, may cause long term damage to olfactory receptors
- Sense of smell deteriorates with age
Hyposmia
- Reduced ability to smell
- Affects half people over 65 and 75% of people over 80
- Can be due to neurological changes
3 layers of retinal neurons in the optic nerve
- Photoreceptors
- Bipolar cell layer
- Ganglion cell layer
2 main parts of photoreceptors
Cones and rods
What photoreceptors do?
Start the process of converting light to nerve impulses
Cones
- stimulated in bright light
- colour vision
- high acuity
- concentrated in the center of retina
Rods
- allow us to see in dim light
- no colour (black/white/grey)
- low acuity
- concentrated in the periphery
Bipolar cell layer
- Also has horizontal + amacrine cells
(they form lateral connections,
involved in modifying signals)
Ganglion cell layer
their axons extend posteriorly to optic disc and exit the eye as the optic n
Optic nerve is made up of
ganglion cells bunched together
Optic Nerve pathway
- rods + cones (then to bipolar cells – then to ganglion cells)
- Optic nerve
- Through the optic foramen/canal
- Optic chiasm
- Optic tract
- Lateral geniculate nucleus
7.Superior colliculi
OR
7.Primary visual area
Anopia
- blindness due to a defect or loss of 1 or 2 eyes
- from fractures in orbit, brain lesions, damage along the pathway, disease of the nervous system, pituitary gland tumours, cerebral aneurysm
Extrinsic eye muscles extend from where?
extend from the bony orbit
to the sclera`
Superior rectus
Elevates, adducts, and
medially rotates
eyeball
“upwards movements”
Inferior rectus
Depresses, adducts,
and laterally
rotates eyeball
“downward movement”
Lateral rectus
Abducts eyeball
“outward movement”
Medial rectus
Adducts eyeball
“Inward movement”
Superior oblique
- Abducts, depresses, and medially rotates eyeball
- “Downward and outward movement”
Inferior oblique
- Abducts, elevates, and laterally rotates eyeball
- “Upward and outward movement”
CNIII Motor nerve branches
Superior branch:
1. Superior Rectus
2. Levator palpebrae superioris
Inferior branch:
1. medial rectus
2. inferior rectus
3. inferior oblique
CNIII Autonomic Motor branch
Inferior branch:
- Cicilary ganglion
- Cicilary mm
- Circular mm of iris
Accomodation
When the eye is focusing on a close object, the lens becomes more spherical, causing greater refraction of light rays.
Cicillary mm
Adjusts the lens for near vision “accomodation”
Contraction of what causes constriction of pupil?
Contraction of what causes dilation of pupil?
Constriction: Circular mm
Dilation: Radial mm
Circular mm
Pupil constriction
Trochlear nerve
- Thinnest cranial nerve
- Only one arising from posterior brainstem
Trochlear nerve motor
Superior oblique mm
Abducens motor
Lateral rectus mm
Strabismus
a condition in which both eyes do not fix on the same object, since one or both eyes may turn inward or outward
ptosis
drooping of upper eyelid
Damage to oculomotor nerve causes
- Strabismus
- ptosis
- Dilation of pupil
- Movement of eyeball downward/outward
- Loss of accomodation for near vision
- Diploplia
Damage to trochlear nerve
- strabismus
- diplopia
Damage to abducens nerve
- Affected eye can’t move laterally beyond midpoint and eyeball is usually directed medially
- This leads to strabismus and diplopia
Trigeminal nerve
- Largest diameter cranial nerve
Trigeminal Nerve Ophthalmic branch
Foramen
Sensory from skin over upper lid, cornea, lacrimal glands, upper nasal cavity, side of nose, forehead, anterior half of scalp
Superior Orbital Fissure
Trigeminal Nerve
Maxillary Branch
foramen
- Sensory from mucosa of nose, palate, part of pharynx, upper teeth, upper lip, lower eyelid
- Foramen Rotundem
Trigeminal Nerve
Mandibular Branch
Foramen
- Sensory from anterior 2/3
of tongue (not taste), cheek + its mucosa, lower teeth, skin over mandible + side of head ant to ear,
mucosa of floor of mouth - Foramen Ovale
Trigeminal Nerve Motor function
- in mandibular branch
- supply muscles of mastication
- these motor neurons mainly control chewing
Trigeminal Neuralgia
- -what do we know about neuralgias?
- -sharp cutting, intense pain that lasts for a few seconds to a minute
- -pain is within the nerve’s distribution
Trigeminal Neuralgia causes
- local compression
- idiopathic, herpes zoster, vascular lesions, tumours, demyelinating conditions with subsequent scarring (MS)
Trigeminal Neuralgia
symptoms
- -sudden painful attacks
- -pain often occurs in clusters
-unilateral - -along one or more distributions of the nerve
- -any mechanical stimulation, chewing, smiling, a breeze felt on the cheek can trigger an attack
- -patients avoid stimulating the trigger zone
- -trigger zone may be lips, face, tongue (touch, temp, facial mvt)
Facial Nerve Sensory
- taste buds of anterior 2/3 of tongue
- stylomastoid foramen
- geniculate ganglion
- pons
- thalamus
- gustatory area of cerebral cortex
-also sensory axons from skin in ear canal (touch, pain, temp)
Facial Nerve Motor
- nucleus in pons
- stylomastoid foramen
- facial expression muscles, stylohyoid mm, posterior digastric mm, stapedius mm
Facial nerve autonomic (2 ganglions)
- pterygopalatine ganglion
- submandibular ganglion
pterygopalatine ganglion
lacrimal glands - Tears
nasal gland - Mucus
palatine gland - Saliva
submandibular ganglion
submandibular glands
sublingual glands
Bell’s palsy
-is a condition involving the facial nerve
-results in paralysis of the muscles of facial expression on the same side as the lesion
-is one of the most common neurological conditions
-it affects at least 25 people out of 100,000 each year
Bell’s Palsy Symptoms
-unilateral weakness followed by flaccid paralysis of muscles of facial expression
-onset of symptoms from weakness to flaccid paralysis is quite rapid
-if sensory + autonomic affected can’t control lacrimation, usually decrease in salivation, can’t taste on anterior 2/3 of tongue, heightened sensitivity of hearing symptoms
-sagging of face and eyelid with possible pulling toward
unaffected side
Bell’s palsy
cause
-nerve damage from:
- -viral infection (shingles)
- -bacterial infection (lyme’s dx)
-compression from edema with:
- pregnancy
- -middle ear infection
- -diabetes
- -hypertension
- -hypothyroidism
- -leprosy
-conditions involving the parotid gland
- -trauma
- -exposure to chill or draft
Bell’s Palsy Prognosis
-if only segmental demyelination (as with compression), recovery is usually in 2-8 weeks
-if Wallerian degeneration = poorer prognosis
Bell’s Palsy Treatment
- treat the cause, if known
- often no treatment because there is spontaneous recovery in 70% of cases
- protect the eye with eye patch and antibiotic drops
Bell’s palsy
stroke?
- people often fear paralysis of one side of face is from stroke (UMN) but stroke generally affects the lower
muscles of face (not frontalis or muscles around eye) - so during a stroke, patient can close eye and wrinkle forehead but can’t smile
Vestibulocochlear Nerve
(type, function, branches)
Type: sensory
Function: hearing and equilibrium
2 branches
1. Vestibular
2. Cochlear
Vestibular branch
carries impulses for equilibrium
- Semicircular canals, the saccule + utricle of inner ear
- Vestibular ganglion
- Vestibular nuclei in pons + medulla
Cochlear branch
- carries impulses for hearing
PATHWAY:
- Spiral organ (organ of Corti) in cochlea of internal ear
- Spiral ganglion
- Internal acoustic meatus
- Cochlear nuclei in medulla
- Thalamus
- Primary Auditory Area
Injury to vestibular branch
- Vertigo
- Ataxia
- Nystagmus
- Tinnitus
- Deafness
- trauma, lesions,
middle ear infections
Vertigo
a subjective feeling that one’s own body or the environment is rotating
Ataxia
muscular incoordination
Nystagmus
involuntary rapid movement of the eyeball
Glossopharyngeal Nerve sensory functions
- Taste buds on posterior 1/3 of tongue
- Proprioceptors from some swallowing muscles
- Baroreceptors in carotid sinus that monitor BP
- Chemoreceptors in carotid sinus
- External ear to convey touch, pain, heat and cold
Glossopharyngeal nerve motor functions
stylopharyngeus muscle
Glossopharyngeal nerve autonomic functions
inferior salivary nucleus in medulla
parotid gland - Saliva production
Glossopharyngeal Nerve injuries
- Dysphagia
- Aptyalia - Reduced saliva creation
- Loss of sensation in throat
- Ageusia - Loss of taste
Glossopharyngeal Neuralgia
-recurrent attacks of severe pain in the CN IX nerve distribution
(posterior pharynx, tonsils, back of tongue, middle ear)
-from nerve compression
-rare, more common in men, usually after 40
-(like in trigeminal neuralgia) get paroxysmal attacks of unilateral brief, excruciating pain
-occurs spontaneously or are precipitated by certain movements (eg, chewing, swallowing, talking, sneezing)
-pain lasts seconds to a few minutes, usually begins in tonsil area or at base of tongue and may radiate to ipsilateral ear
-is distinguished from trigeminal neuralgia by location of pain
-also, in glossopharyngeal neuralgia, swallowing or touching the tonsils with an applicator triggers pain
Vagus Nerve Sensory functions
- Skin of external ear for touch, pain, heat and cold
- Taste buds in epiglottis and pharynx
- Proprioceptors in mm of neck and throat
- Baroreceptors & chemoreceptors in carotid sinus & aortic bodies
- Most sensory axons come from visceral sensory receptors in most organs of thoracic & abdominal cavities that convey sensations (ie hunger, fullness, discomfort)
Vagus nerve motor functions
Muscles of the pharynx, larynx & soft palate (swallowing, vocalization, coughing)
Vagus nerve autonomic functions
- smooth muscle of lungs
- cardiac muscle
- glands of GI tract
- smooth mm of respiratory passageways
- esophagus
- stomach
- gallbladder
- small intestine
- most of large intestine
Injury to Vagus nerve
- Vagal paralysis – interruptions of sensations from many organs in thoracic and abdominal cavities
- Dysphagia - difficult swallowing
- Tachycardia - increased heart rate
Accessory Nerve Pathway
- Motor axons from anterior grey horn c1-c5
- Ascend through foramen magnum
- Exit through jugular foramen
- SCM and trapezius
Accessory Nerve motor functions
SCM & trapezius
Hypoglossal nerve motor functions
muscles of tongue
Hypoglossal Nerve injury
- difficulty chewing
- dysarthria - difficult speaking
- dysphagia - difficult swallowing
*
Development of the nervous system
-begins in 3rd week of gestation
-starts with a thickening of the ectoderm called the neural plate
-neural plate folds inward and forms a longitudinal groove, called the neural groove
-raised edges of the neural plate are called the neural folds
-as the whole thing grows and forms a tube, now called the neural tube
Layers of cells from walls
- outer/marginal layer cells = white matter of nervous system
- middle/mantle layer cells = gray matter
- inner/ependymal layer cells = lining of central canal (spinal cord) and ventricles of brain
Neural crest
- mass of tissue between the neural tube + skin ectoderm
becomes:
- posterior (dorsal) root ganglia of spinal nerves
- spinal nerves
- ganglia of cranial nerves
- cranial nerves
- ganglia of autonomic nervous system
- adrenal medulla
- meninges
