Ch. 14: Cranial Nerves Flashcards
cranial nerves involved in speaking
V, VII, X, XII
- X (larynx, soft palate)
- VII (lips)
- V (Jaw)
- XII (tongue)
Stages of Swallowing
- Oral (V, VII, XII)
- Laryngeal/Pharyngeal (IX, X)
- Esophageal (X)
CN X dysfunction
- hard to speak
- hoarse voice
- asymmetric elevation of soft palate
- loss efferent gag
- loss efferent swallow
- poor digestion
CN I Function
- Olfactory
- Sensory=smell
(olfactory nerves and olfactory tract)
CN II Function
- Optic
- Sensory=vision
conscious vision/reflex (orient head–sup colliculi)
3 Functions of CN
- motor innervation
- somatosensory and special sensory innervation
- parasympathetic innervation
CN I Dysfunction
- unable to smell
- linked with parkinson’s and alzheimers (neurodegeneration)
CN II Dysfunction
- blindness
- loss of visual field
-Disrupted pupillary light reflex
CN IV function
- Trochlear
- (midbrain)
- move eye medially and down toward tip of nose
Medial Longitudinal Fissure
- interconnects CN III, IV, VI, vestiular nuclei and CN XI in brainstem
- wiring bundle connect eye CN to each side to allow conjugate eye movement
3 Eye Reflexes
- Pupillary Light Reflex
- Consensual Light Reflex
- Accommodation Reflex
CN VI Function
- Abducens
- (border of pons/medulla)
- move eye toward ipsilateral ear
Parasympathetic Innervation to pupil and lens
- CN III
- innervates pupillary sphincter and ciliary Mm
- constricts pupil for (near vision)
- increases curvature of lens (for near vision)
Pupillary Light Reflex
- unconscious
- Stimulus: light in one eye (CN II)
- Response: constrict pupil (CN III)
Consensual Light Reflex
- reflex only
- Stimulus: light in one eye (CN II)
- Response: constriction of both pupils (CN III)
CN III Function
- occulomotor
- (Midbrain)
- sup rectus, med rectus, inf rectus, inf oblique
-move eye up, down and adduction
Ptosis
- eyelid droops
- (sign of Horner’s Syndrome)
- CN III dysfunction
Accommodation Reflex
- Consciously driven by visual cortex
- Input: object close to face
- Response: pupils constrict, eyes converge, lens more convex
(opposite with object far from face)
CN III dysfunction
- Ptosis
- affected eye looks down and out
- diplopia
- can’t move eye med, up or down
- dilation of pupil
- decreased pupillary light reflex
- decreased consensual light reflex
- decreased constriction of pupil for near objects
CN IV Dysfunction
- can’t look down and inward
- Extorsion due to unopposed action of inf oblique
- (can result in tilted head to compensate for rotated eye)
CN VI Dysfunction
- can’t abd eye
- resting position of eye drifts medially
Efferent CN V
- Mm of mastication
- muscles that move jaw
Medial Longitudinal Fasciculus Dysfunction
- no conjugate eye movement
- CN still work but signal from one side doesn’t reach other
Jaw Jerk Reflex
Stim: quick stretch to mastication Mm
Response: jaw Mm try to close mouth
Trigeminal Neuralgia
- trigeminal nerve pain
- allodynia/hyperalgesia
Afferent CN V
- light touch, conscious proprioception, fast/slow pain
- all enter brainstem and cross midline then go to contralat parietal lobe
CN V blink reflex
Stim: touch eye (CN V)
Response: blink/close eye (CN VII)
CN V Dysfunction
- decreased touch, pain, temp of face
- decreased blink and jaw jerk reflex
- trigeminal neuralgia
- decreased chewing/talking
CN VIII Dysfunction
- dizziness/disequilibrium
- hearing loss (conductive, sensorineural)
- decreased location of sounds
Sensorineural Hearing Loss
- damage to receptor cells/cochlear nerve
- Peripheral N (VIII): acoustic neroma, tinnitus, hearing loss (LMN)
- Cochlear Nuclei/central pathway: damage to brainstem/brain (UMN)
CN VII Dysfunction
- paralysis/paresis of facial expression Mm on ipsilateral face
- bell’s palsy: LMN damage to CN VII
- can’t produce tears
Conductive hearing Loss
- impairment of converting air waves to water waves
- extensive wax/otitis media (inflamed middle ear)
CN IV Dysfunction
- decreased afferent gag reflex
- decreased afferent swallow reflex
- decreased salivation
CN IX Function
- Glossopharyngeal N
- (sensory, motor, autonomic)
- Sensory: back of tongue, soft palate, pharynx, taste (bitter)
- sensory part of gag reflex
- Autonomic: salivary
CN XI Dysfunction
- LMN: “flaccid” paralysis of ipsilateral upper trap and SCM
- UMN: “spastic” paresis of contralaterals upper trap and SCM
CN XI Function
- spinal accessory nerve
- (Motor)
- Trap/SCM Mm
CN XII Function
- hypoglossal
- (motor)
- intrinsic and extrinsic tongue Mm
CN XII Dysfunction
- atrophy ipsilateral tongue
- tongue drift to side of lesion
- difficult to speak/swallow
CN VII Function
- Motor: facial expression muscles
- Parasymp: salivary, nasal and lacrimal glands
- Sensory: taste, ant 2/3 tongue
CN VIII Function
- Vestibulocochlear N
- (sensory)
- frequency coding
- different air cell area for each frequency
- Sound goes to 3 places (inf colliculus, reticular fomation, auditory cortex)
3 Places Sound Signals Go
- Inf Colliculus: localize sound
- Reticular formation: increase arousal in CNS
- Auditory cortex: conscious recognition of sound
3 Input Sources to CN LMN
- Corticobulbar tract (LMN)
- Descending Limbic Path (autonomic–>excitability)
- Sensory Input (reflexes)
CN V Function
- Trigeminal N
- (motor/sensory)
- Sensory: opthalmic, maxillary, mandibular
- Afferent: sensation face
- Efferent: mastication Mm
- 2 reflexes (jaw jerk, blink)
CN X Function
- Vagus
- (sens, motor, autonom)
- Sensory: larynx, pharynx, viscera
- Motor: larynx, pharynx, vocal cords
- Autonomic: larynx, pharynx, trachea, lungs, heart, upper GI, pancreas, gall bladder
