Cranial Nerves Flashcards
Most of the cell bodies of sensory nerves are found:
In ganglia outside brain
Cell bodies of motor nerves are found;
In nuclei in brain
Why do motor nerves contain some sensory neurons?
Receive signals from muscle spindles
Cranial Nerve I
Olfactory Neve
Only CN that doesn’t synapse in thalamus (synapses at olfactory bulb).
Foramina: olfactory foramina in cribiform plate of ethmoid.
Route of Olfactory nerve
olfactory epithelium
Olfactory nerve
Olfactory foramina
Olfactory bulbs
Olfactory tracts
Primary olfactory area (28), limbic system, hypothalamus
Common integrative (5,7,39,40) and orbitofrontal (2) areas
Anosmia
Loss of sense of smell
Hyposmia
Reduced sense of smell
Hyperosmia
Increased sense of smell
CN II
Optic Nerve
Foramen: optic foramen (sphenoid)
Route of optic nerve
Retina (rods & cones, bipolar nerves, ganglion cells)
Optic nerves
Optic foramen
Optic chiasm
Optic tract
Lateral geniculate nucleus, superior colliculi
Primary visual area (17)
Three layers of retinal neurons.
- Photoreceptors (convert light to nerve impulses)
- Bipolar cells
- Ganglion cells (axons become optic nerve)
Cones
Photoceptors
Stimulated in bright light
Colour, visual acuity
Concentrated in centre if retina
Rods
Allows us to see in dim light
No colour, low acuity
Concentrated in periphery.
Lateral geniculate nucleus
In thalamus
Relays visual impulse from retina to cerebral cortex.
Superior colliculi
In tectum of midbrain
Reflex centre responding to visual stimuli.
Anopia
Blindness due to deficit in or loss of one or both
Orbital fracture, pituitary tumour, aneurysm etc.
Medial rectus
Moves eye towards nose Occulomotor nerve (III)
Lateral rectus
Moves eye away from nose
Abducens nerve (VI)
Superior rectus
Moves eye up
Occulomotor (III)
Inferior rectus
Moves eye down
Occulomotor (III)
Superior oblique
Looks down and out (inferior and lateral)
Trochlear (IV)
Inferior oblique
Looks up and away
Occulomotor (III)
Cranial Nerve III
Occulomotor
Motor AND autonomic
Foramen: superior orbital fissure
Superior branch of occulomotor nerve (III)
Motor Nucleus in midbrain
Superior orbital fissure
Superior rectus (looks up) + levator palpebrae superioris (lifts eyelid)
Inferior branch of occulomotor nerve (III)
Motor Nucleus of midbrain
Superior orbital fissure
Medial rectus (looks to nose) + inferior rectus (looks down) + inferior oblique (looks up and away)
Autonomic branch of occulomotor (III)
Motor nucleus in midbrain Superior orbital fissure Inferior branch Ciliary ganglion Ciliary and circular muscles of the iris
Parasympathetic
Adjusts lens for near vision (accommodation) or to constrict (not dialate) in response to light.
Numbers of cranial nerves indicate;
Order (anterior to posterior) that nerves arise from the brain.
Accommodation
Changing shape of lens to focus on nearby (
Cranial Nerve IV
Trochlear nerve
Smallest cranial nerve
Only cranial nerve that arises from posterior aspect of brain stem.
Superior oblique muscle of the eye (looks down and out)
Foramen: superior orbital fissure
Path of trochlear nerve
Trochlear nucleus in midbrain
Superior orbital fissure
Superior oblique muscle
Cranial Nerve VI
Abducens nerve
Lateral rectus muscle (abducts eye)
Foramen: superior orbital fissure
Route of abducens nerve
Abducens nucleus in pons
Superior orbital fissure
Lateral rectus muscle
Damage to occulomotor nerve
Strabismus (lazy eye) Ptosis (drooping eye) Dilation of pupil Down & out movement of eyeball Loss of accommodation Diplopia (double vision)
Damage to trochlear nerve
Strabismus (lazy eye)
Diplopia (double vision)
Damage to abducens
Affected eyeball can’t move laterally beyond midpoint (eyeball usually directed medially)
Strabismus (lazy eye)
Diploplia (double vision)
Circular muscle
Constricts pupil (doesn’t dilate)
PNS
Occulomotor (III)
Ciliary muscle
Accommodation of lens
PNS
Occulomotor (III)
CN V
Trigeminal nerve
Largest cranial nerve
Mixed
Three branches
- Opthamalmic nerve
- Maxillary nerve
- Mandibular nerve.
Opthalmic Nerve
Superior branch of trigeminal nerve (CN 5)
Sensory
Sensory nerves from around eye, nose
–> superior orbital fissure –> opthalmic nerve –> trigeminal ganglion –> pons nuclei
Maxillary nerve
Middle branch of Trigeminal Nerve (CN 5)
Sensory nerves from mucosa of nose, palate, part of pharynx, upper teeth, upper lip, lower eyelid
—> foramen rotundum –> maxillary nerve –> trigeminal ganglion –> pons nuclei
Mandibular nerve
Inferior branch of trigeminal nerve (CN 5)
Afferent and efferent
Sensory: anterior tongue (not taste), cheek, skin over mandible, side of head anterior to ear, mucosa of cheek and roof of mouth
–> foramen ovale –> mandibular nerve –> trigeminal ganglion –> pons nuclei
Motor:
From mandibular nerve to muscles of mastication, tensor veil palontini muscle and tensor tympani.
Trigeminal neuralgia
Sharp, cutting or tearing pain
Transient
Paralysis of muscles of mastication, reduced sensation in lower face.
Unilateral, along nerve distribution(s)
Caused: compression, herpes zoster, vascular lesions, low B12, MS …
May be triggered by manual stimulation
Theory: hyperexcitable demyelinated fibres
CN VII
Facial nerve
Motor, sensory and autonomic
Foramen: stylomastoid foramen (temporal bone)
Sensory pathway of Facial nerve
Taste buds on anterior 2/3 tongue, sensory receptors from skin in ear canal Stylomastoid foramen Geniculate ganglion Pons Thalamus Gustatory Area (43)
Geniculate ganglion
Cluster of sensory cell bodies of facial nerve
In temporal bone.
Motor pathway of facial nerve
Nucleus in pons
Stylomastoid foramen
Muscles of facial expression, scalp, middle ear, neck (stylohyoid, posterior digastric, stapedius)
Autonomic pathway of facial nerve
Superior salivatory nucleus (pontine tegmentum)
Geniculate ganglion
Pterygopalatine ganglion to lacrimal, nasal and palatine glands
OR
Submandibular ganglion to submandibular and sublingual glands
Bells Palsy
Paralysis of facial muscles due to lesion of facial nerve.
Idiopathic. Bacterial, viral infection; compression; parotid issues.
Same side as lesion
Unilateral weakness followed by flaccid paralysis of muscles of facial expression
Decreased salivation, uncontrolled lacrimation, can’t taste anterior 2/3 tongue, hypersensitive hearing
CN VIII
Vestibularcochlear.
Sensory
Nucleus in pons and medulla
Foramen: auditory meatus
2 branches:
- Vestibular
- Cochlear
Vestibular branch of vestibule cochlear nerve
(Balance, equilibrium)
Semicircular canals, saccule, utricle of inner ear
Vestibular ganglion
Vestibular nuclei
Cochlear branch of vestibulococclear nerve
(Hearing)
Spiral organ (organ or Corti)
Spiral ganglion
Medulla
Thalamus (medial geniculate)
Primary auditory area
Injuries to vestibular branch
Vertigo
Ataxia
Nystagmus
Injuries to cochlear branch
Tinnitus
Deafness
CN IX
Glossopharyngeal nerve
Sensory. Motor. Autonomic.
Jugular foramen
Sensory pathway of glossooharyngeal nerve
Taste buds on posterior 1/3 of tongue, proprioceptors from swallowing muscles, bar preceptors, chemoreceptors
Superior and inferior ganglia
Jugular foramen
Medulla
Motor pathway of glossooharyngeal nerve
Nuclei in medulla
Jugular foramen
Stylopharyngeal muscle (elevates pharynx and larynx, helps with swallowing)
Autonomic pathway of glossopharyngeal nerve
Inferior salivary nucleus in medulla
Otic ganglion
Parotid gland
Glossopharyngeal neuralgia
Similar to trigeminal neuralgia (post pharynx, tonsils, back of tongue, middle ear)
Pain along nerve path
More common in men
Spontaneous, or triggered by movement
Cranial nerve X
Vagus
Sensory motor autonomic
80-90% of PNS function
Sensory pathway of vagus nerve
Skin of external ear, taste buds in epiglottis and pharynx, proprioceptors in muscles of neck and throat, baroreceptors, chemoreceptors and
Mostly visceral sensory receptors
Superior and inferior ganglia
Jugular foramen
Medulla
Motor pathway of vagus nerve
Medulla
Jugular foramen
Pharynx, larynx, soft palate (swallowing, vocalization, coughing)
Autonomic pathway of vagus nerve
Medulla to:
Lungs Heart GI glands Smooth muscles of respiratory pathway Esophagus Stomach Gallbladder Small intestine.
Injury to vagus nerve
Vagal paralysis
Dysphagia
Tachycardia
CN XI
Accessory nerve
Motor
Anterior grey horn C1-5
Foramen magnum
Jugular foramen
SCM & Trapezius, pharynx and larynx
CN XII
Hypoglossal
Motor
Hypoglossal nucleus
Hypoglossal canal
Muscles of tongue
What cranial nerves are involved with taste?
Facial nerve (VII) anterior 2/3 tongue
Glossopharyngeal (IX) posterior 1/3 tongue
Vagus (X) tastebuds in epiglottis, pharynx
What cranial nerves are involved with salivation?
Facial (VII) submandibular, sublingual (superior salivatory nucleus)
Glossopharyngeal (IX) parotid gland (inferior salivatory nucleus)
What cranial nerves are involved with the mechanics of chewing/swallowing?
Hypoglossal (XII) tongue movement Vagus (X): Pharynx/Larynx/Soft palate Trigeminal (V): chewing Glossopharyngeal(IX): Lift pharynx/larynx Facial (VII): elevate hyoid
When does the nervous system develop
Around the 3rd week of gestation
Neural plate
In utero
Thickening of ectoderm.
Folds inward and becomes neural groove, flanked by neural folds
Groove deepens, folds meet, now a cylinder called the Neural Tube
Neural Crest
Mass of tissue between neural tube and skin ectoderm Differentiates and eventually forms: Posterior (dorsal) root ganglia of spinal nerves Spinal nerves Ganglia of cranial nerves Cranial nerves Ganglia of ANS Adrenal medulla Meninges.
Neural tube eventually forms
CNS
What happens to the wall that encloses the neural tube:
Marginal (outer) layer: white matter of nervous system
Mantle (middle) layer: grey matter of nervous system
Ependymal (inner) layer: lining of central canal and ventricles
What are the primary brain vesicles?
Prosencephalon
Mesencephalon
Rhomencephalon
Development of Prosencephalon
–> telencephalon –> cerebral cortex and lateral ventricles
–> diencephalon –> thalamus, hypothalamus, epithalamus, third ventricle
Development of Mesencephalon
–> midbrain and midbrain aquaduct
Development of Rhombencephalon
–> metencephalon –> pons, cerebellum, top 1/2 of fourth ventricle
–> myelencephalon –> medulla oblongata, bottom 1/2 of fourth ventricle
