BIO 201: cranial nerve study guide

bell's palsy: causes

-degeneration of the 7th CN: the facial nerve -(mostly) occurs due to herpesvirus that causes cold sores

trigeminal neuralgia: who is susceptible?

-affects more women than men -people above age 50

trigeminal neuralgia: description

*aka tic douloureux -a syndrome characterized by recurring episodes of intense stabbing pain on one side of the face -compared to the feeling of an electrical shock with painless intervals between

bell's palsy: description

-degenerative disorder characterized by paralysis/weakness of facial muscles on 1 side results in: -interference with speech -prevention of eye closure -inhibitation of tear secretion (causes dry-eye) -distortion of facial features: sagging of mouth or eyelid - sometimes partial loss of the sense of taste

trigeminal neuralgia: treatment

-medication -vascular surgery: relieves pressure on nerve -gamma knife radiosurgery: uses targeted gamma rays to injure nerve to stimulate a healing process

bell's palsy: unique feature

-this disorder may appear abruptly (sometimes overnight) & often disappears spontaneously within 3-5 weeks

which 2 cranial nerves are an exception to the ipsilateral traits seen in most cranial nerves? why?

1. optic nerve (II) why?: half of the fibers decussate to opposite side of brain 2. trochlear nerve (IV) why?: all efferent fibers lead to a muscle of the contralateral eye

2 cranial nerve disorders:

1. trigeminal neuralgia 2. bell's palsy

which cranial nerves are classified as sensory nerves?

2 of them: olfactory (I), & optic (II)

which cranial nerves are classified as motor nerves?

5 of them: oculomotor (III), trochlear (IV), abducens (VI), accessory (XI), & hypoglossal (XII)

which cranial nerves are classified as mixed nerves?

5 of them: trigeminal (V), facial (VII), vestibulocochlear (VIII), glossopharyngeal (IX), & vagus (X)

more specifically, sensory fibers of cranial nerves begin in ___________ located mainly in the ___________ & _______ & lead mainly to the ____________.

receptors, head & neck, brainstem

CN XII: hypoglossal nerve

number: twelve composition: motor function: tongue movements for speech, food manipulation, & swallowing damaged: impaired tongue movements for speech & swallowing

CN II: optic nerve

number: two composition: sensory function: vision damaged: partial or complete blindness

cranial nerves: definition

any of 12 pairs of nerves connected to the base of the brain & passing through foramina of cranium

where do cranial nerves primarily arise from? where do they exit & lead to?

arise from: the base of the brain exit: through cranium's foramina lead to: muscles & sense organs located mainly in head & neck

trigeminal neuralgia: causes & triggers

causes: -usually caused by a nearby blood vessel putting pressure on the 5th CN: the trigeminal nerve -sometimes caused by a tumor putting pressure on nerve as well triggers: -triggered by touch: brushing teeth, drinking, shaving, washing face, etc... -pain lasts for around a couple seconds - a minute or 2; may happen up to 100x per day

how do lesions of the brainstem contrast to lesions of the motor & somatosensory cortex of the cerebrum?

deficit is on same side of body as lesion, rather than contralateral.

a lesion in one side of the brainstem causes a sensory or motor deficit _________________________.

ipsilaterally

more specifically, motor fibers of cranial nerves begin in ___________ of the _____________ & lead to ____________ & ____________.

nuclei of the brainstem, glands & muscles

CN VIII: vestibulocochlear nerve

number: eight composition: sensory function: hearing & balance damaged: deafness & impaired balance

CN XI: accessory nerve

number: eleven composition: motor function: swallowing + head, neck, & shoulder movements damaged: impaired movement of head, neck, & shoulders

CN V: trigeminal nerve

number: five composition: 3 divisions: 1. ophthalmic division (sensory) 2. maxillary division (sensory) 3. mandibular division (mixed) function: x2 sensory-> allows for facial sensation x1 motor-> allows for chewing damaged: loss of facial sensation & impaired chewing

CN IV: trochlear nerve

number: four composition: motor function: eye movement: directing gaze slightly down & rotating top of eye towards nose (by superior oblique muscle) damaged: weakened ability to look downward, double vision

CN IX: glossopharyngeal nerve

number: nine composition: mixed function: sensory-> taste, touch, pressure, pain & temperature on posterior 1/3rd of tongue motor-> salivation, swallowing, & gagging damaged: loss of taste, impaired swallowing

CN I: olfactory nerve

number: one composition: sensory function: smell damaged: impaired smell or anosmia: loss of smell

CN VII: facial nerve

number: seven composition: mixed function: sensory-> taste on anterior 2/3rds of tongue motor-> various facial/neck muscles & glands damaged: inability to control facial muscles (facial sag/lack of muscle tone), impaired/distorted sense of taste

CN VI: abducens nerve

number: six composition: motor function: lateral movement/gaze of eye (nerve controls lateral rectus muscle) damaged: inability to turn eye laterally

CN X: vagus nerve

number: ten composition: mixed function: sensory-> taste, hunger, & fullness motor-> swallowing, speech, & regulation of heart & GI tract damaged: impaired swallowing, GI motility, hoarse/weak voice, & inability to cough forcibly *fatal if both vagus nerves are damaged

CN III: oculomotor nerve

number: three composition: motor function: eye movement: gazing up, down & medially, opening of eyelid (nerve controls levator palpebrae superioris muscle), focusing & pupil constriction/diameter damaged: drooping eyelid, dilated/ unequal R & L pupils, inability to move eye in some directions