Cranial Nerves, General Sensation

1. Cranial Nerves,General Sensation

2. Cranial Nerves • Nerves that arise from the CNS • part of the PNS • can contain • sensory • somatic motor • parasympathetic motor

3. I - Olfactory • I Olfactory • pure sensory to the nose for smell • Damage: no sense of smell (anosmia) • Test: have someone smell something

4. II - Optic • II Optic • pure sensory to retina for conducting vision • damage: loss of vision (peripheral or central), abnormal fundoscopic exam • test: check vision • eye chart • peripheral vision • fundoscopic exam

5. III - Occulomotor • III Occulomotor • motor to most of the eye muscles (except for movements controlled by CN IV and VI) • parasympathetic to iris (constriction) and lens • damage: loss of symmetric motor movement (double vision), ptosis, dilated pupil • test: check pupils for equal size and shape, pupillary reflex, eye movement

6. III - Occulomotor Normal eye is the patient’s left eye

7. IV - Trochlear • IV Trochlear • motor to superior oblique muscle • damage: outward rotation of affected eye, vertical diploplia • test: check eye movments

8. V - Trigeminal • V Trigeminal • sensory to face (including eye) • muscles of mastication (mandibular branch) • damage: loss of jaw strength, loss of facial sensation, loss of corneal reflex, trigeminal neuralgia • test: check jaw strength, test facial sensation, corneal reflex

9. V - Trigeminal • V Trigeminal • three branches • ophthalmic • maxillary • mandibular

10. VI - Abducens • VI Abducens • motor to lateral rectus • damage: at rest affected eye deviates medially, when attempt to abduct eye moves only to midline • test: inability to abduct eye

11. VI - Abducens

12. VII - Facial • VII Facial • motor to muscles of facial expression • parasympathetic efferent to lacrimal and salivary glands • sensory: taste to anterior 2/3 of tongue • damage: weakness of facial muscles, loss of taste, dry eye or excessive tearing • test: facial muscle strength, stimulate tearing, taste

13. VII - Facial

14. VII - Facial • Branches of Facial Nerve • Temporal • Zygomatic • Buccal • Mandibular • Cervical

15. VIII - Vestibulocochlear • VIII Vestibulocochlear • sensory for hearing and balance • damage: vertigo, deafness • test: hearing test, Romberg

16. IX - Glossopharyngeal • IX Glossopharyngeal • motor to muscles of pharynx • sensory to pharynx and taste to posterior 1/3 of tongue • parasympathetic efferent to salivary glands • damage: loss of gag reflex, difficulty swallowing, loss of taste to post 1/3 of tongue • test: gag reflex, swallowing tests, palate and uvula elevate when says AHHH, taste on post tongue

17. X - Vagus • X Vagus • motor to muscles of pharynx and larynx • sensory to pharynx and larynx • parasympathetic efferent to heart and abdominal viscera • damage: loss of gag reflex, difficulty swallowing, hoarse voice • test: gag reflex, swallowing tests

18. XI - Spinal Accessory • XI Spinal Accessory • motor to SCM and trapezius • damage: manifests mostly in weakness in shoulder and scapula: winging, uneven shoulder • test: shoulder shrug strength, head turn strength

19. XII - Hypoglossal • XII Hypoglossal • motor to tongue • damage: tongue weakness on side of injury • test: stick out tongue, deviates to side of the injury

20. Sensation • Sensation is generally divided into two parts • general sensation • pain, touch, pressure, etc • sensory receptors usually simple • special sensation • smell, taste, hearing, balance, vision • highly modified sensory receptors

21. Sensation • You can also classify based on where the monitoring takes place • Exteroceptors: hot/cold,vision, hearing, equilibrium • react to stimuli in the external environment • usually aware of stimulus • Interoreceptors: chemoreceptors, visceral stretch receptors • responds to stimuli arising from within the body • usually not aware of stimulus

22. Sensation • Types of sensory modalities • Nociceptors: pain receptors • Thermoreceptors: temperature receptors • free nerve endings • Chemoreceptors: detects chemicals • taste, smell, blood osmolarity • Mechanoreceptors: mechanically gated channels that open when force is applied • proprioceptors, baroreceptors, tactile receptors • (see next slides)

23. Mechanoreceptors • 3 types of mechanoreceptors: • Tactile Receptors: touch, pressure, vibration • free nerve endings, hair root plexus, Merkel’s disks, Meissner’s (tactile) corpuscle, Pacinian (lamellated) corpuscle • Baroreceptors: pressure receptors • detect pressure changes in blood vessels, digestive tract and urinary tract. • Proprioceptors: detects positions of joints and muscles • Pacinian and Ruffini corpuscles play a role in this

24. Mechanoreceptors • Pacinian Corpusle • dermal/hypodermal border • deep pressure • vibration detection • rapidly adapting

25. Mechanoreceptors • Meissner’s Corpusle • in dermal papillae • light touch • rapidly adapting

26. General Sensation • Punctate Distrubution • The sensitivity to different sensory modalities varies by location • back has fewer touch receptors than the hands • sensory receptors are grouped where they are needed most • touch receptors are concentrated in areas like the hands • two point discrimination • used to test how sensitive an area of skin is

27. Referred Pain • Visceral pain that is felt just deep to the skin overlying the stimulated organ or in a surface area far from the organ. • Skin area & organ are served by the same segment of the spinal cord. • Heart attack is felt in skin along left arm since both are supplied by spinal cord segment T1-T5

28. Referred Pain