exam 4 anatomy- cranial nerves

cranial nerves

Attach to the brain and pass through specific foramina (holes) of the skull

numbered I-XII

SENSORY:afferent signals

MOTOR: efferent signals

CN X (vagus N) is the only cranial nerve that extends to the abdomen

most are in head or neck

oh oh oh they traveled and found volemort guarding very ancient horcruxes

CN I- olfactory nerves

sensory function: smell

origin: olfactory receptor cells located in the olfactory epithelium of the nasal cavity

peripheral→ to the brain centrally

pathway: passes through cribriform foramina of the ethmoid bone

olfactory sensory neuron (nasal cavity) → cribriform foramin → olfactory nerve→ olfactory cortex (frontal/temporal lobes)

CN II- optic nerve

sensory function: vision

origin: retina- neural tissue inside the eye

peripherally→ centrally sensory

pathway: passes through the superior orbital fissure

synapses in the thalamus before terminating in the primary visual cortex

retina→ optic nerves→ optic canal→ thalamus→ primary visual cortex (occipital lobe)

CN III- oculomotor nerves

motor function: eye movement

Superior rectus: elevates eye

medial rectus: adducts eye

inferior rectus: depresses eye (eye looks down)

inferior oblique: elevates and abducts eye

visceral motor function: constricts pupil

ciliary muscle: controls shape of lens

central=motor

pathway: oculomotor nuclei in midbrain→ passes through superior orbital fissure

primary motor cortex→ midbrain→superior orbital fissure→ extrinsic eye muscles→ ciliary body→ pupillary constriction muscle

CN IV- trochlear nerves

motor function: euperior oblique muscle: depression and abduction of the eye

pathway: trochlear nuclei in pons→ passes laterally around midbrain to enter orbit through superior orbital fissure

Primary motor cortex→ midbrain→ superior orbital fissure→ superior l=oblique muscle

CN V- trigeminal nerves

both sensory and motor functions

Opthalmic division V1 → superior orbital fissure

maxillary division V2→ foramen rotundum

mandibular division V3 → foramen ovale→ mandibular forament

all divisions pass through the trigeminal ganglion

CN V1- ophthalmic division

sensory function: conjunctiva of eye, skin of forehead, nose, and eyelids

pathway: superior orbital fissure

Sensory stimulus→ superior orbital fissure→ trigeminal ganglion→ thalamus→ post central gyrus

CN V2: maxillary division

sensory function:

• nasopharynx

• hard and soft palate

• upper teeth

• maxillary sinuses

pathway: foramen rotundum

sensory stimulus→ foramen rotundum→ trigeminal ganglion→ thalamus→ post central gyrus

CN V3: mandibular division

motor and sensory function:

• motor: muscles of mastication

• sensory: cheeks, tongue (taste), lips, gums, upper and lower teeth

• parasympathetic innervation of salivary glands

Pathway: foramen ovale

CN VI- abducens nerves

motor function: lateral rectus muscle: abduction of the eye

pathway: abducens nuclei in the pons→ superior orbital fissure

primary mortor cortex→ pons→ superior orbital fissure

CN VII- facial nerves

sensory function: taste buds on anterior 2/3 of tongue

motor function: five branches innervate muscles of facial expression

sensory and motor pathways pass through the internal acoustic meatus

pathway: internal acoustic meatus

top to bottom of face

• frontal

• temporal

• buccal

• marginal mandibular

• cervical

primary motor→ the pons→ internal acoustic meatus→ geniculate ganglion→ muscles of facial expression

CN VIII- vestibulocochlear nerves

sensory function

• vestibular branch: equilibrium

• cochlear branch: hearing

Origin

• vestibular branch: semicircular canals and vestibule

• cochlear branch: cochlea

pathway: internal acoustic meatus

Sensory stimulus→ vestibular/cochlear nerves→ internal acoustic meatus→ thalamus→ primary auditory cortex

CN IX- glossopharyngeal nerves

sensory function

• taste buds on posterior 1/3 of tongue

• pharyngeal mucosa

• chemoreceptors in carotid body

• baroreceptors of carotid body

motor function

• elevates pharynx during swallowing

• parotid salivary gland

pathway: jugular foramen

Sensory stimulus→jugular foreman→ thalamus→ post central gyrus

CN X- vagus nerves

sensory functions:

• thoracic and abdominal viscera

motor functions:

• skeletal muscles of the pharynx and larynx

parasympathetic innervation to

• heart

• lungs

• abdominal viscera

pathway: jugular foramen

sensory stimulus→ jugular foremen→ thalamus→ post central gyrus

CN XI- accessory nerves

motor function: trapezius and sternocleidomastoid

formed from spinal (ventral) rootlets of C1-C5

• do not arise from the brain stem

pathway:

• enters into skull through foramen magnum

• exits skull through jugular foramen

primary mortor cortex→ ventral spinal nerves C1-C5→ foramen magnum→ jugular foramen→ trapezius and sternocleidomastoid

CN XIII- hypoglossal nerves

motor function: intrinsic and extrinsic tongue muscles

• feeding, swallowing, and speech

origin: medulla oblongata

pathway: hypoglossal canal

primary motor cortex→ medulla oblongata→ hypoglossal canal→ intrinsic and extrinsic tongue muscles→ eating, swallowing and speech