Download cranial nerves - The Silver Sword

CRANIAL NERVES
OUTLINE
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Cranial nerve nuclei locations
Cranial nerves I-XII
– Origin and Location
– Course
– General arrangement
– Function
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Nerves that are formed from nuclei in the brain
12 Cranial nerves
CN I and II are components from the forebrain
CN III-XII are from the brainstem
CN –Sensory, motor, mixed
Overview
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CN I, II, and VIII are devoted to special sensory input.
CN III, IV, and VI control eye movements and pupillary constriction.
CN XI and XII are pure motor (XI: sternocleidomastoid and trapezius; XII:
muscles of tongue).
CN V, VII, IX, and X are mixed.
CN III, VII, IX, and X carry parasympathetic fibers
Functional components
• Somatic efferent
• Brachial efferent
• Visceral efferent
• Visceral afferent
• Somatic afferent
• Special sensory
OPTIC NERVE
• Formation of image on retina
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Retina encodes information and project it to the brain via the optic nerve
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Optic nerve undergoes semi decussation in optic chiasm and project to
the lateral geniculate body
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Thalamocortical neurons project image to the primary visual cortex
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Visual pathway is a typical sensory pathway in the sense that:
– It consists of 3 neurons
– 1st order-bipolar cells of the retina synapse with ganglion cells
– 2nd order- optic nerve, optic chiasm and optic tract
– 3rd order- from the lateral geniculate bodies (thalamus) to the
visual cortex
OCLOMOTOR NERVE
• Emerges from the midbrain
• Nerve runs anteriorly from midbrain.
• Enters orbit through superior orbital fissure (SOF)
• Contains somatic efferent & visceral efferent fibers.
Nuclei & distribution
• Somatic efferent- oculomotor nucleus-extraocular muscles & levator
palpebrae superioris
• Visceral efferent: Edinger-Westphal nucleus; ciliary ganglion- pupillary
sphincter & ciliary muscle
TROCHLEAR NERVE
• Emerges from posterior aspect of brainstem near midline, courses
anteriorly around cerebral peduncle, enters orbit through SOF
• Only cranial nerve which all fibers cross to opposite side
• Only nerve that emerges from the dorsal side of brainstem
Nucleus & distribution
• Located in midbrain.
• Supply superior oblique m.
TRIGEMINAL NERVE
• Motor and sensory roots
• Has three branches that supplies different areas of the face:
– Opthalmic
• Mainly sensory but also gives secrotomotor
– Maxillary
• Sensory
– Mandibular
• Sensory and motor
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Largest division V3
Sensory and motor
Exits the cranium via foramen ovale
Three sensory branches
– Supply the area of skin around the embryonic mandibular
prominence
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– Auricotemporal (secretomotor to parotid gland), buccal, mental
Motor fibres to muscles of mastication, anterior belly of digastric, tensor
veli pallatini, tensor tympani and mylohyoid
ABDUCENT
• Contains only somatic efferent fibers
• Follows long extradural path before entering SOF
• Lies at the pontomedullary junction
Nucleus & distribution
• Located in pons
• Supply lateral rectus
Facial
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Motor and sensory/parasympathetic root
Exits cranial cavity via internal acoustic meatus
Emerges in cerebellopontine angle between pons & olive.
Passes through internal acoustic meatus into petrous part of temporal
bone, where it divides into its branches
Visceral efferent fibres pass through the styloidmastoid foramen----parotid
plexus
Parasympatheic, visceral efferent & visceral afferent fibres pass through
the petrotympanic fissure to base of skull
While still in petrous bone, facial nerve gives off greater petrosal, stapedial
& chorda tympani
Nuclei, ganglia & distribution
• Special visceral efferent: efferent from facial nucleus supply following
muscles
-facial expression
-stylohyoid
-posterior belly of diagastric
-Stapedius
• Visceral efferent (parasympathetic): PS preganglionic fibers arising from
superior salivatory nucleus synapse with neurons in pterygopalatine
ganglion or submandibular ganglion to innervate: lacrimal, submandibular
& sublingual glands
• Chorda tympani branch special sensory for taste to anterior 2/3rds
• Of tongue (nucleus of solitary tract)
REVIEW TABLE 8:1 FROM ONLINE TEXT
CN VIII-XII will be done in class.