cranial nerves Flashcards by juliana Bartoletti

CN Bundles of nerve fibers (mostly) arising on

Exit/enter

Bundles of nerve fibers (mostly) arising on the ventral brain and brainstem

¨Exit/enter cranial cavity via foramina

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¨Fibers are

Generally innervate

¨Fibers are sensory, motor or both

Generally innervate head and neck¨

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¨Three letter classification system for types of neurons making up cranial nerves
¨

anatomy and embrology

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¨General vs. Special

¤General = Found in cranial nerves and spinal nerves
¤Special = Cranial nerve specific

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¨Somatic vs. Visceral

¤Somatic-Innervate structures derived from somites (skeletal muscle, cartilage, tendons, dermis)

¤Visceral- Innervate gut/structures associated with gut and pharyngeal (branchial) arches
Vascular system, smooth muscle, cardiac muscle, and glands

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GSE

¨Somatic motor (GSE)
¤innervate striated muscles NOT derived from embryonic pharyngeal (branchial) arches
¤includes extraocular muscles of orbit and tongue muscles

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SVE

¨Branchial motor (SVE)
¤innervate striated muscles derived from pharyngeal (branchial) arches
¤includes muscles of mastication, facial expression, pharyngeal & laryngeal muscles

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GVE

¨Parasympathetic (visceral motor) (GVE)
¤parasympathetic fibers innervating smooth muscle and glands
¤e.g., pupillary sphincter and lacrimal gland

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SVA and GVA

¨Visceral sensory- special (SVA) & general (GVA)
¤Taste (smell)
¤convey sensory information from cardiac muscle, smooth muscle, muscle derived from branchial arches, glands

¤e.g., parotid gland, carotid body & sinus, middle ear, pharynx, larynx, thoracic viscera and abdominal viscera (GI tract)

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GSA

¨General somatic sensory (GSA)
¤general sensation from skin & mucous membranes which may or may not be experienced consciously
¤travel mainly via CN V (also CN VII, IX and X)

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SSA

¨Special somatic sensory (SSA)
¤Hearing, balance, vision, smell

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CN II

Function

CN II optic nerve

Vision

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CN II optic Nerve

entry and unique feature

¨Entry: Optic canal

Unique feature-Does not attach to brainstem

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CN V SVE

Muscle of Mastication, Mylohyoid, Anterior belly of digastric, Tensor Tympani

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CN V

GSA

Sensation for face, mouth, tongue, meninges

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CN V

entry

location

¨Exit/Entry
¤V1 (Ophthalmic): Superior orbital fissure
¤V2 (Maxillary): Foramen rotundum
¤V3 (Mandibular): Foramen ovale
¨Location: Ventrolateral brainstem in mid-pons area

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CN I

SVA

CN I Olfactory

¨SSA (SVA)- Olfaction (Smell)

¨Entry: Cribriform plate

Unique features-Does not attach to brainstem
¤Only sensory system not synapsing in thalamus before cerebral cortex

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CN III GVE

¤Pupillary constriction
Pupillary constrictor (iris sphincter) muscle
¤Visual accommodation
Ciliary body

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CN III

GSE

Eye movements (adduction, elevation, depression)
All extraocular muscles except superior oblique & lateral rectus
Eyelid elevation
nLevator palpebrae superioris

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CN III

Exit:

location:

¨Exit: Superior orbital fissure
¨Location: Interpeduncular fossa at midbrain/pons junction

CN VIII

all

CN VIII (vestibulocochlear Nerve)

¨SSA- Hearing (Cochlea), Equilibrium (Vestibular organs)¨

Entry: Internal auditory meatus
¨Location: Ventrolateral brainstem at pontomedullary junction (immediately lateral to CN VII)

CN VII

SVE

¤Motor to muscles of facial expression, scalp, stapedius, stylohyoid, digastric (posterior belly)

CN VII

SVA

Taste ( anterior 2/3 of tongue)

CN VII GSA

Sensation near External auditory meatus

CN VII GVE

parasympathetic innervation to salivary and lacrimal glands

CN IV All

CN IV Trochlear Nerve GSE- Eye movement (Intorsion), Superior oblique Exit: Superior orbital fissure ¨Location: Medial dorsal midbrain caudal to inferior colliculus Unique features ¤Exits brainstem on dorsal side ¤Decussates before innervation ¤Smallest CN

CN VII Location entry/exit

¨Location: Ventrolateral brainstem at pontomedually junction (inferior pontine sulcus) ¨Exit/Entry ¤Internal auditory meatus ¤Stylomastoid foramen Muscles of facial expression

Importance of stylomastoid foramen

CN VII SVE muslce of facial expression

CN IX SVE

¨SVE ¤Stylopharyngeus muscle (elevation of larynx & pharynx during swallowing)

CN IX SVA

¨SVA ¤Taste (posterior 1/3 of tongue)

CN IX GSA

¨GSA ¤Sensation (skin near EAM, pharynx, tongue)

CN VI All

¨GSE ¤Eye movement (Abduction), Lateral rectus muscle Exit: Superior orbital fissure ¨Location: Ventral brainstem near midline at pontomedullary junction (inferior pontine sulcus) ¨

CN IX exit/entry location

¨Exit/Entry: Jugular foramen ¨Location: Rostral medulla at postolivary sulcus

CN IX GVE

GVE ¤ Parotid gland (salivation)

CN IX GVA

GVA ¤ Sensation (Chemo/baroreceptors of carotid body, pharynx)

CN X SVE

SVE ¤ Motor to constrictor muscles of pharynx, intrinsic muscles or larynx, muscles of palate, upper esophagus (swallowing, speaking)

CN X SVA

SVA ¤ Taste (epiglottis, palate, pharynx)

CN X GSA

GSA ¤ Sensation (EAM, meninges)

CN X GVE

GVE ¤ Parasympathetics to cardiac muscle, smooth muscle of trachea, bronchi, digestive tract

CN X GVA

GVA ¤ Sensation (Chemo/Baroreceptors (aortic arch), pharynx, larynx, trachea, bronchi, heart, esophagus, stomach, intestines)

CN X Entry/exit/location

Exit/Entry: Jugular foramen Location: Medulla at postolivary sulcus, caudal to CN IX (made up of several rootlets)

CN XI SVE

GSE (SVE)\* ¤ Sternocleidomastoid and trapezius muscles (turning of head, elevation of scapula)

CN XI Entry/exit/location

Exit: Jugular foramen (enters via foramen magnum) Location: Lateral spinal cord between dorsal and ventral roots (rootlets form common trunk)\* Considered by some sources to be somatic, others consider it to be of branchial arch origin

CN XII GSE

GSE ¤ Intrinsic & extrinsic muscles of tongue (tongue movement)

CN XII Entry/exit/location

Exit: hypoglossal canal Location: Medulla at preolivary sulcus (rootlets form trunk)

Most cranial nerve fibers run ¤Exceptions: ¤In general lesion in right brainstem causes

Most cranial nerve fibers run ipsilateral Exceptions: optic nerve (half the fibers decussate); trochlear nerve (fibers innervate muscle of the contralateral eye) In general lesion in right brainstem causes sensory or motor deficit on right side

Motor fibers of cranial nerves come from Sensory fibers of cranial nerves begin in Some have special sensory organs as their

Motor fibers of cranial nerves come from brainstem nuclei to innervate glands and muscles¨ Sensory fibers of cranial nerves begin in receptors generally located in the head and neck and generally lead to the brainstem Some have special sensory organs as their sensory receptors