The Cranial Nerves
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Transcript of The Cranial Nerves
The Cranial Nerves
Honors Anatomy & Physiologyfor copying
CRANIAL NERVES
• 12-pair• named “cranial” because each passes thru a
foramina of the cranium• part of PNS• each with roman numeral (order from anterior
posterior in which nerves arise from base of brain) & a name that indicates nerve distribution
CRANIAL NERVES
• classified as:1. sensory2. motor3. mixed (sensory & motor)
Cranial Nerve I: Olfactory
• olfact = to smell• sensory• olfactory epithelium on superior surface of
nasal cavity just inferior to cribiform plate of ethmoid bone
• olfactory receptors are bipolar neurons– each: single odor-sensitive dendrite– their unmyelinated axons join above plate form rt or lt
olfactory nerves
Course of Olfactory Nerve
• olfactory nerves end in pair of olfactory bulbs: masses of gray matter resting just above cribiform plate where they synapse with next neurons in olfactory pathway
Course of Olfactory Nerve
• axons of these neurons make up the olfactory tracts posteriorly to primary olfaction center in temporal lobe
Cranial Nerve II: Optic Nerve
• optic = eye• sensory• rods & cones in retina: receptors initiating visual
signals & relay them bipolar cells optic ganglion neurons their axons join forming optic nerves
• pass thru optic foramen optic chiasm: a cross-over of medial half of each eye to opposite side (lateral half does not cross
Optic Tracts
• from optic chiasm optic tracts– most axons thalamus synapse with neurons whose
axons primary visual area of occipital lobe– some axons synapse with motor neurons in midbrain
extrinsic eye muscles
Cranial Nerve III: Oculomotor
• oculo = eye• mixed, mainly motor• its motor nucleus in
ventral part of midbrain• 2 branches pass thru
superior orbital fissure
Superior Branch Inferior Branch• axons innervate:1. superior rectus2. levator palpebrae
superioris (upper eyelid)
• axons innervate:1. medial rectus2. inferior rectus3. inferior oblique
Oculomotor Nerve Extrinsic Muscles of Eye
Oculomotor Nerve
• inferior branch also:– parasympathetic innervation to intrisic muscle of eye
(smooth muscle)1. ciliary muscle: adjusts lens for near/far vision
2. circular muscle of iris: contracts/relaxes in response to amt of light (pupils constrict/dilate)
Oculomotor Nerve: Sensory
• proprioception: nonvisual perception of movements & positions of body
Cranial Nerve IV: Troclear Nerve
• trochle = pulley• mixed, mainly motor• smallest of the 12 cranial nerves• only 1 that arises from posterior of midbrain
Cranial Nerve IV: Troclear Nerve
• motor:• axons from nucleus in midbrain superior
orbital fissure• innervates superior oblique muscle
• sensory: proprioception in superior oblique
Trigeminal Nerve
• largest of 12 cranial nerves• mixed:– sensory: ganglion in temporal bone– motor: neurons in pons
Cranial Nerve V: Trigeminal Nerve
• tri: has 3 branches1. Ophthalmic: sensory only: upper eyelids, eyes,
lacrimal glands, upper nasal cavity, side of nose, forehead, anterior ½ of scalp
2. Maxillary: sensory only: mucosa of nose, palate, part of pharynx, upper teeth, upper lip, lower eyelids
3. Mandibular: sensory: anterior 2/3 of tongue (not taste), cheek, lower teeth
motor: muscles of mastication
Cranial Nerve VI: Abducens Nerve
• ab: away / ducens: to lead (nerve impulses causes abduction of eyeball)
• mixed mainly motor• nucleus in pons (motor): innervates lateral
rectus muscle• sensory: proprioception in lateral rectus
Cranial Nerve VII: Facial Nerve• mixed• sensory:
– taste buds anterior 2/3 of tongue, proprioceptors in face & scalp
• motor: – nucleus in pons– innervates muscles of facial expression + stylohyoid muscle &
posterior belly of digastric muscle
• parasympathetic: lacrimal glands, palatine glands, salivary glands: sublingual & sub-mandibular
Cranial Nerve VIII: Vestibulocochlear Nerve
• vestibule:small cavity; cochlear: snail-like• mixed, mainly sensory• 2 branches1. Vestibular:– equilibrium
2. Cochlear:– hearing– motor: hair cells of spiral organ
Cranial Nerve IX: Glossopharyngeal Nerve• glosso:tongue, pharyngeal: throat• Mixed• sensory: taste buds & somatic sensory receptors on
posterior 1/3 tongue, proprioceptors in swallowing muscles, baroreceptors (stretch) in carotid sinus, chemoreceptors in carotid bodies
• motor: from nuclei in medulla, exit thru jugular foramen, innervate stylopharyngeus muscle (elevates pharynx & larynx)
• parasympathetic: motor: stimulate parotid gland to secrete saliva
Cranial Nerve X: Vagus Nerve
• vagus: wanderer, vagrant• mixed• distributed from head abdomen
Vagus Nerve
• sensory:– skin of external ear– taste buds in epiglottis & pharynx– proprioceptors in muscles of neck & throat– baroreceptors in arch of aorta & chemoreceptors in aortic
bodies – visceral sensory receptors in most organs of thorax &
abdominal cavities
Vagus Nerve
• parasympathetic motor: – heart & lungs– glands in GI tract– smooth muscle of airways, esophagus, stomach, gall
bladder, small intestine, most of large intestine
Cranial Nerve XI: Accessory Nerve
• mixed• originates from both the brainstem & spinal
cord• cranial root:
– motor: from medulla thru jugular foramen– supplies voluntary muscles of pharynx, larynx, & soft palate
• spinal root:– mixed, mainly motor– motor:
Cranial Nerve XI: Accessory Nerve
• spinal root:– mixed, mainly motor– motor: neurons in anterior gray horn of C1 – C5 axons
come together fpramen magnum jugular foramen– innervates sternocleidomastoid & trapezius muscles– sensory: proprioceptors in muscles it supplies
Cranial Nerve XII: Hypoglossal
• hypo: below, glossal: tongue• mixed• sensory:proprioceptors in tongue muscles
medulla• motor: nucleus in medulla hypoglossal canal
muscles of the tongue (speech, swallowing)
Development of the Nervous System
• begins developing in 3rd wk from a thickening of ectoderm called the neural plate
Development of the Brain & Spinal Cord