Head and neck: Cranial nerves I Flashcards
which CN do not pass through brainstem?
CN I and II
which CN originated/ enter the brainstem?
CN III - XII
name CN I - XII
I olfactory II optic III occulomotor IV trochlear V trigeminal VI abducens VII facial VIII vestibulocochlear IX glossopharyngeal X vagus XI accessory XII hypoglossal
enter/ exit features: CN I
- olfactory n pass cribiform plate - form olfactory bulb
- pass as olfactory tract to limbic lobe
enter/ exit features: CN II
- optic n exits retina through optic canal
- nasal fibres cross optic chiasm and pass optic tract -> thalamus in brain
enter/ exit features: CN III - XII
- enter/ exit skull to/from brainstem through foramina
- enclosed in sheath from meninges inside and outside cranium (to extent)
CN III - XII: feature
- have brainstem nuclei
- contains and process different functions of cranial n
cranial nerves: define nucleus
collection of neuronal cell bodies within CNS
cranial nerves: define ganglion
cluster of neuronal cell bodies in PNS
cranial nerves: efferent fibre types- name
- outgoing ‘motor’
- GSE
- GVE
- SVE
cranial nerves: afferent fibre types- name
- coming in ‘sensory’
- GSA
- GVA
- SVA
- SSA
cranial nerves: efferent fibre types- GSE
general somatic efferent:
- inn general motor tissues (muscle)
cranial nerves: efferent fibre types- GVE
general visceral efferent:
- have parasympathetic function
- secretions of glands, dilate pupils etc.
cranial nerves: efferent fibre types- SVE
special visceral efferent:
- motor fibres inn special branchiomeric mm of head and neck: mm of mastication and facial expression
cranial nerves: afferent fibre types- GSA
general somatic afferent:
- sensory input from head and neck (minimal body)
- trigeminal nucleus major input
cranial nerves: afferent fibre types- GVA
general visceral afferent:
- sensory input + input from specialised sensory receptors
- barareceptors
- chemoreceptors
cranial nerves: afferent fibre types- SVA
special visceral afferent:
- sensory input for taste
cranial nerves: afferent fibre types- SSA
special somatic afferent:
- sensory input of info about hearing and equilibrium
distribution: general somatic efferent (GSE)
- skeletal mm of orbit, tongue, SCM, trapezius
distribution: special visceral efferent (SVE)
- mm of mastication
- skeletal mm of face, palate, larynx, pharynx
- mm from pharyngeal arches
distribution: general visceral efferent (GVE)
- parasym supply to smooth mm and glands of head, neck, trunk
distribution: general visceral afferent (GVA)
sensation from viscera- carotid body and sinus, pharynx, larynx, airways, lungs, heart, GIT
distribution: general somatic afferent (GSA)
- general sensation (touch, pressure, temp etc.) from skin and mucous membranes of head
distribution: special visceral afferent (SVA)
- taste
- smell
distribution: special somatic afferent (SSA)
- vision
- hearing
- balance
CN have motor or sensory: olfactory
CN I
- sensory
CN have motor or sensory: optic
CN II
- sensory
CN have motor or sensory: occulomotor
CN III
- motor
CN have motor or sensory: trochlear
CN IV
- motor
CN have motor or sensory: trigeminal (opthalmic, maxillary, mandibular)
CN V
- motor
- sensory
CN have motor or sensory: abducens
CN VI
- motor
CN have motor or sensory: facial
CN VII
- motor
- sensory
CN have motor or sensory: vestibulococchlear
CN VIII
- sensory
CN have motor or sensory: glossopharyngeal
CN IX
- motor
- sensory
CN have motor or sensory: vagus
CN X
- motor
- sensory
CN have motor or sensory: accessory
CN XI
- motor
CN have motor or sensory: glossopharyngeal
CN XII
- motor
CN: parasympathetics- features
- CN III, VII, IX, X
- pre/post ganglionic fibres
- pre: cell bodies in CNS
- post: cell bodies outside CNS, ganglia close to structures they’re inn
parasympathetic ganglia: for occulomotor
CN III
- ciliary
parasympathetic ganglia: for facial
CN V
- pterygopalatine ganglion
- submandibular ganglion
parasympathetic ganglia: glossopharyngeal
CN IX
- otic ganglion
parasympathetic ganglia: vagus
CN X
- many, close to the organ supplied by brainches
olfactory nerve: part of CNS n enters/ exits
- limbic lobe of brain
CN I olfactory nerve: part of skull n enters/ exits
- foramina in cribiform plate of ethmoid bone
CN I olfactory nerve: site of cell bodies
- olfactory epithelium
CN I olfactory nerve: function
- smell from roof of nasal cavity
- sup aspect of nasal septum and sup conchae
eg. anosmia:
loss of sense of smell
- old age
- head injuries w cribiform plate
- fractures
- meningeomas in ant cranial fossa
eg. olfactory hallucinations
- false perception of smell
- result of lesion in temporal lobe
CN II optic nerve: enters/ exit skull
- optic canal
CN II optic nerve: enters/ exit CNS
- occipital lobe -> primary visual cortex
CN II optic nerve: features
- optic n
- optic chiasm
- optic tracts
CN II optic nerve: site of cell bodies
- retinal ganglion
- support cell axons create optic n
CN II optic nerve: function
- vision
- perceives lights and colours -> intergrates them centrally to create vision
CN II optic nerve: briefly describe visual field (R and L)
- temporal (lateral) retina and nasal (medial) retina
- R visual field from L temporal and R nasal
- L visual field from L nasal and R temporal
CN II optic nerve: which optic nerves cross/ don’t
cross:
- L nasal
- R nasal
don’t:
- L temporal
- R temporal
eg. papillodema:
- indicator of increased brain pressure
- CSF buildup
- brain tumour etc.
- compresses central vein and suppresses venous return from retina
eg. visual fields: R monocular blindness
- cut at R optic nerves (before chiasm)
- no vision in R eye
- L eye unaffected
eg. visual fields: bitemporal hemianopsia
- lesion in optic chiasm: no crossing over
- nasal visual field inaffected in both eyes
- no temporal (peripheral vision)
eg. visual fields: L homonymous hemianopsia
- lesion in R optic tract
- no L temporal and no R nasal visual field
- L nasal and R temporal visual field unaffected
CN III occulomotor nerve: enters/ exits skull
- superior orbital fissure
CN III occulomotor nerve: enters/ exits CNS
- midbrain pierces dura
- enters and passes in lateral wall of cavernous sinus
CN III occulomotor nerve: site of cell bodies (fibre types)
- GSE: midbrain
- GVE: presynaptic (midbrain), postsynaptic (ciliary ganglion)
CN III occulomotor nerve: function (fibre types)
- GSE: supplies 4 extraocular mm (sup/ medial/ inf rectus, inf oblique) + levator palpebrae superioris
- GVE: sphincter pupillae, ciliary mm of eye
CN III occulomotor nerve- mm action: sup rectus
- elevation
- adduction
- medial rotation of eyeball
CN III occulomotor nerve- mm action: inf rectus
- depression
- adduction
- lateral rotation of eyeball
CN III occulomotor nerve- mm action: medial rectus
- adduction of eyeball
CN III occulomotor nerve- mm action: inf oblique
- moves eyeball up and out
CN III occulomotor nerve- mm action: constrictor pupillae
- constricts pupil
CN III occulomotor nerve- mm action: levator palpebrae superioris
- elevation of upper eyelid
CN III occulomotor nerve- mm action: ciliary mm
- contricts ciliary body
- relaxes tension on lens = allowing for accomodation
eg. light reflex: normal
- both pupils constrict
eg. light reflex: CN III lesion
- loss of consensual pupillary light reflex
- only 1 pupil constricted (shined on)
eg. light reflex: CN II lesion
- loss of direct pupillary light reflex
- not shined on pupil constricts
CN IV trochlear nerve: enters/ exits skull
- superior orbital fissure
CN IV trochlear nerve: enters/ exits CNS
- midbrain (only CN emerging dorsally from brainstem)
- pierces dura and passes in the lateral wall of cavernous sinus
CN IV trochlear nerve: site of cell bodies
- midbrain
CN IV trochlear nerve: function (fibre types)
- GSE: supplies sup oblique mm (eye ‘down and out’)
CN V trigeminal nerve: enters/ exits skull
- V1: sup orbital fissure
- V2: foramen rotundum
- V3: foramen ovale
CN V trigeminal nerve: enters/ exits CNS
- pons
CN V trigeminal nerve: site of cell bodies
- sensory fibres: trigeminal ganglion
- motor fibres: pons
CN V trigeminal nerve: divisions (V1 etc)
V1: opthalmic
V2: maxillary
V3: mandibular
CN V trigeminal nerve: function (V1)
opthalmic GSA sensory from:
- cornea
- skin of forehead
- scalp
- eyelids
- nose
- mucous membranes of nasal cavity
- paranasal sinuses
CN V trigeminal nerve: function (V2)
maxillary GSA sensory from:
skin over: maxilla
- upper lip
- upper row of teeth and gums
- mucous membranes of nose, maxillary sinuses, palate
CN V trigeminal nerve: function (V3)
mandibular GSA sensory from:
skin over:
- lower part of face
- jaw
- lower lip
- lower row of teeth and gums
- TMJ
- mucous membranes of mouth
- ant 2/3 of tongue
SVE motor to:
- mm of mastication, mylohyoid, ant belly digastric, tensor veli palatini, tensor tympani
CN V trigeminal nerve branches: ophthalmic
- tentorial
- lacrimal
- frontal (supraorbital, supratrochlear)
- nasociliary (short/ long ciliary, infratrochlear, ant/ post ethmoidal etc.)
CN V trigeminal nerve branches: maxillary
- orbital branches
- greater/ lesser palatine n
- nasal n
- pharyngeal n
- zygomatic
- ant/ post/ middle superior alveolar n
- infraorbital n
CN V trigeminal nerve branches: mandibular
- motor + sensory roots = meningeal branch, n to medial pterygoid
then divides into:
- ant trunk (buccal, masseteric, deep temporal, n to lateral pterygoid)
- post trunk (auriculotemporal, lingual, inf alveolar n)
CN VI abducens nerve: enters/ exits skull
- sup orbital fissure
CN VI abducens nerve: enters/ exits CNS
- btw pons and medulla, has longest course of CN
- also pierce dura and passes through cavernous sinus
CN VI abducens nerve: site of cell bodies
pons
CN VI abducens nerve: function (fibre types)
- GSE: supplies lateral rectus mm (abducts eye)
eg. abducens palsy
- contraction of lateral rectus mm
- doesn’t allow eye to turn outward