cranial nerves 1

the cranial nerves exit through

central nervous system via foramina or fissures

cranial nerve classifications

primarily sensory

primarily motor

mixed sensory and motor

rule of 4

4 CN above pons

4 CN in pons

4 CN in medulla

olfactory nerve

CN I

Olfactory nerve (CN I)

sensory nerve

smell

process of smelling t

process of smelling something

Olfactory sensory receptors stimulated → AP initiated →

olfactory bulb → olfactory tract → cortical olfactory are

olfactory bulb

turns action potential into electric signals

damage to CN I

anosmia

decrease sense of smell

CN II

optic nerve

CN II : Optic nerve

sensory nerve

carries sensory message from the retina to the cortical area in occipital lobe ( visual cortex)

optic nerve pathway

After optic chiasm, fibers

(optic tract) reach the occipital

lobe via the thalamus

lights and colors —> electrical signal action potential

Damage to CN II (optic nerve)

visual field loss

only see part of the screen/ pictures

not same as wearing glasses

Oculomotor Nerve

CN III

CN III : oculomotor nerve

pupil reflex

Motor nerve; originate from the midbrain

Motor: eyeball movement; controls eyelid, open and close eyes

Parasympathetic: pupil constrictor (reflex)

damage to CN III oculomotor

ptosis : loss of pupillary light reflex

drouping eye lids

CN IV

trochlear nerve

CN IV Trochlear Nerve

Motor nerve; originate from the midbrain

Carries motor fibers for eyeball movement

CN IV Trochlear damage

dipolopia when looking down

double vision - seeing 2 images of same picture

What cranial nerves control the eyes

2,3,4,6

CN V

Trigenminal Nerve

CN V : Trigeminal Nerve

Mixed nerve

originates from the pons

composed of 3 divisions of fibers from the pons

3 divisions of the the CN V (trigeminal Nerve)

Ophthalmic- sensory

Maxillary- sensory

Mandibular- sensory and motor

Ophthalmic fiber

CN V

sensory

sensation: pain, temp on face and mouth

Maxillary fiber

CN V

sensory

sensation: pain, temp on face and mouth

Mandibular fiber

CN V

sensory and motor

innovates muscles for chewing food, open and close mandible

Damage to CN V (trigeminal)

difficulty chewing( motor)

loss of sensation around the face (sensory)

CN VI

Abducens Nerve

CN VI - Abducens Nerve

motor nerve- originates from the pos

motor fibers control eye movements

CN VII

facial nerve

CN VII : facial nerve

mixed nerve (sensory and motor) exits from the pons

sensory: sensations near the ears, taste in the anterior 2/3 of the tongue

Parasympathetic : salivary glads - taste

motor: muscles of the face

CN VII Facial nerve lesions

upper- bilateral innovations (both sides)

lower- innovated by controlatwral ( one side)

CN VII Facial nerve damage

Bells palsy - Facial nerve dysfunction

ONLY LMN

LMN syndrome: sudden onset of paralysis of ipsilateral upper and lower facial muscles

can usually recover with time

UMN lesion- wouldn’t go away (stroke)

CN VIII

Vestibulocochlear nerve

CN VIII: Vesttibulocochear Nerve

Exit from pons/ medulla

Sensory only : sense of hearing and balance from the inner ear

has two divisions

• cochlear branch

• vestibular branch

CN VIII: Vesttibulocochear Nerve damage

hearing loss and balance problems

CN IX

glossopharyngeal nerve

CN IX- Glossopharyngeal nerve

mixed nerve

exits from the pons/ medulla junction

Sensory: pharynx, middle ear, posterior 1/3 of tongue (taste), gag reflex

motor: innervates pharyngeal muscles, swallowing and phonations

pharyngeal Muscles ( CN IX)

Pharyngeal Constrictor Muscles (PCM)

• superior, middle and inferior

Reduce pharyngeal space

swallowing

CN X

Vagus Nerve

What type of nerve is the vagus nerve (CN X), and where does it exit?

• Mixed nerve (sensory + motor)

• Exits from the medulla

• It is the largest and longest cranial nerve

• Has a large nerve distribution through the body

What are the 3 main branches of the vagus nerve (CN X)?

• Pharyngeal branch → innervates part of the pharynx

• Superior laryngeal nerve (SLN) → contributes to laryngeal function

• Recurrent laryngeal nerve (RLN) → controls intrinsic laryngeal muscles (abductors/adductors, vocal fold vibration)

What happens with a vagus nerve (CN X) lesion(damage)?

• Weak vocal fold vibration

• Impaired speech

• Swallowing difficulties

• Affects muscles of the velum, pharynx, and larynx

• May also cause symptoms in chest and abdominal organs because CN X has sensory supply there

CN X : Vagus nerve Motor and sensory functions

sensory: pharynx, larynx, chest, and abdominal organs

Motor: innervate muscles of velum, pharynx, larynx, speech muscles

CN XI

Accessory Nerve

CN XI- Accessory Nerve

Motor Nerve from medulla - exit from medulla

Motor : neck muscles (e.g. sternocleidomastoid & trapezius muscles) stablize head and turn head

CN XI - Accessory nerve damage

reduced neck movements and less muscle movements

CN XII

Hypoglossal nerve

CN XII - hypoglossal nerve

motor neuron exit from medulla

motor fibers to tongue muscles

• intrinsic and extrinsic muscles of the tongue

CN XII hypoglossal nerve damage

paralysis of tounge

change in tongue movements

chewing moments

CN XII hypoglossal intrinsic and extrinsic muscles

intrinsic tongue muscles- smaller precise fine articulatory movements

extrinsic tongue muscles- moves the tongue as a unit and set posture for articulation ( large movements)