Lab Activity 19 & 20
Cranial Nerves
General Senses
Portland Community College
BI 232
2
Cranial Nerves
• Nerves that originate from the brain rather
than the spinal cord
• Part of the peripheral nervous syste...
3
CN I: Olfactory Nerve
• Function:
• Sensory for smell
• Test: Have patient
identify aromatic
substances like vanilla or
...
4
CN II: Optic Nerve
• Function:
• Sensory for vision
• Tests:
1. Eye chart
2. Check peripheral vision
3. Funduscopic exam
5
CN II: Optic Nerve
• Optic chiasm: Fibers
from the nasal half of
each retina cross over to
the opposite side of the
brai...
6
CN II: Optic Nerve Pathology
Papilledema. Note swelling of the
disc, hemorrhages, and exudates,
with preservation of the...
7
Cranial Nerves III, IV & VI
(Control Eye Movements)
8
CN III: Oculomotor nerve
• Function:
• Somatic Motor to extraocular
muscles (voluntarily move the eye)
• Parasympathetic...
9
CN III: Oculomotor Nerve Injury
• Symptoms of nerve damage:
• Double vision (diplopia): The affected eye
turns outward w...
10
Oculomotor Nerve Injury
Right Eye
Normal
side
Injured
side
11
Pupillary Reflex
Efferent Afferent
Consensual reflex: Both pupils should constrict at the same time
12
CN IV: Trochlear Nerve
• Function:
• Somatic motor to superior oblique muscle of the eye.
• Test: Check eye movements
•...
13
CN VI: Abducens Nerve
• Function:
• Somatic Motor to lateral rectus
muscle of the eye.
• Test: Check eye movements
• Sy...
14
CN V: Trigeminal Nerve
3 Branches
1. Ophthalmic
2. Maxillary
3. Mandibular
15
CN V: Trigeminal Nerve
• Function:
• Somatic Motor (mandibular branch) to
muscles of mastication (chewing)
• Sensory (a...
16
CN V: Trigeminal Nerve
Test: Have patient bite
down while you palpate
the masseter muscle
Test: Touch patient with an o...
17
CN V: Trigeminal Nerve
• Symptoms of nerve damage:
• Inability to firmly bite down (mandibular branch
only)
• Loss of s...
18
CN VII: Facial Nerve
5 Branches
1. Temporal
2. Zygomatic
3. Buccal
4. Mandibular
5. Cervical
• Function:
• Somatic Moto...
19
CN VII: Facial Nerve
20
CN VII: Facial Nerve Testing
• Tests:
1. Check taste on anterior 2/3 of
tongue by having patient taste
sugar, salt, sou...
21
CN VII: Facial Nerve
• Symptoms of nerve damage:
• Mild weakness to total paralysis of facial
muscles (may include twit...
22
CN VII: Facial Nerve Injury
(Bell’s Palsy)
Paralyzed facial muscles
Patients can still feel their face because sensory ...
23
CN VIII: Vestibulocochlear
• Function: Sensory
• Vestibular system for balance & equilibrium
• Cochlea for hearing
• Te...
24
CN VIII: Vestibulocochlear Tests
• Simple hearing test:
• Rub fingers together near the ear
and ask “right or left” If ...
25
CN VIII: Vestibulocochlear Tests
Romberg Test
• Have patient stand with arms at side
and feet together
• Have patient s...
26
CN IX: Glossopharyngeal
• Function:
• Somatic Motor to muscles of pharynx
• Parasympathetic (motor) to salivary glands
...
27
CN IX: Glossopharyngeal
• Tests:
• Gag reflex: Touch each side of the throat with
the tongue depressor
• Evaluate swall...
28
CN X: Vagus Nerve
• Function:
• Somatic Motor to
muscles of pharynx
and larynx
• Parasympathetic
(motor) fibers of
the ...
29
CN X: Vagus Nerve
• Test:
• Inspect palate
• Test gag reflex
• Symptoms of nerve damage:
• Loss of gag reflex
• Difficu...
30
CN XI: Accessory Nerve
• Function: Somatic Motor to sternocleidomastoid
and trapezius muscles
Originates in the medulla
31
CN XI: Accessory Nerve
• Test:
• Shrug shoulders against
resistance
• Turn head against
resistance.
32
CN XI: Accessory Nerve
• Symptoms of
nerve damage:
• Weakness
• Uneven
shoulders
• Winged
scapula
33
CN XII: Hypoglossal Nerve
• Function: Somatic Motor to tongue
Originates in the medulla
34
Hypoglossal Nerve Injury
• Test:
• Ask patient to stick out
tongue
• Symptoms of nerve
damage:
• When paralyzed, the to...
Lab Activity 20
General Senses
36
General Senses: Receptors
• Nociceptors: Pain receptors
• Thermoreceptors: Temperature receptors (free
nerve endings)
•...
37
Classes of Mechanoreceptors
• Tactile receptors: sensations of touch, pressure
and vibration
• Free nerve endings
• Roo...
38
Pancinian Corpuscle
(aka: Lamellated Corpuscle)
• Lie deep in the dermis
• Respond only when deep pressure is first app...
39
Meissner’s Corpuscle
(aka: Tactile Corpuscle)
• Lie in the dermal papillae of the skin
• Respond to light touch
40
The End
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  1. 1. Lab Activity 19 & 20 Cranial Nerves General Senses Portland Community College BI 232
  2. 2. 2 Cranial Nerves • Nerves that originate from the brain rather than the spinal cord • Part of the peripheral nervous system (not the central nervous system) • May contain one or more of the following: • Sensory • Somatic Motor (voluntary movement) • Parasympathetic Motor (involuntary “rest and digest” part of the autonomic nervous system)
  3. 3. 3 CN I: Olfactory Nerve • Function: • Sensory for smell • Test: Have patient identify aromatic substances like vanilla or coffee (avoid irritating substances like smelling- salts, cloves, mint) • Symptoms of nerve damage: Anosmia: diminished or absent sense of smell
  4. 4. 4 CN II: Optic Nerve • Function: • Sensory for vision • Tests: 1. Eye chart 2. Check peripheral vision 3. Funduscopic exam
  5. 5. 5 CN II: Optic Nerve • Optic chiasm: Fibers from the nasal half of each retina cross over to the opposite side of the brain. • Symptoms of nerve damage: • Loss of vision (peripheral or central) • Abnormal funduscopic appearance
  6. 6. 6 CN II: Optic Nerve Pathology Papilledema. Note swelling of the disc, hemorrhages, and exudates, with preservation of the physiologic cup. Proliferative Diabetic Retinopathy. Note the multiple hemorrhages throughout the retina.
  7. 7. 7 Cranial Nerves III, IV & VI (Control Eye Movements)
  8. 8. 8 CN III: Oculomotor nerve • Function: • Somatic Motor to extraocular muscles (voluntarily move the eye) • Parasympathetic (motor) to iris and lens (pupillary constriction) • Tests: 1. Check pupils for size, shape and equality 2. Shine light in each eye and check for pupil constriction 3. Have patient follow an object in all directions to check for symmetric eye movements Originates in the midbrain
  9. 9. 9 CN III: Oculomotor Nerve Injury • Symptoms of nerve damage: • Double vision (diplopia): The affected eye turns outward when the unaffected eye looks straight ahead • The affected eye can move only to the middle when looking inward and cannot look upward and downward. • Ptosis: eyelid droop • Pupil may be dilated and sometimes fixed
  10. 10. 10 Oculomotor Nerve Injury Right Eye Normal side Injured side
  11. 11. 11 Pupillary Reflex Efferent Afferent Consensual reflex: Both pupils should constrict at the same time
  12. 12. 12 CN IV: Trochlear Nerve • Function: • Somatic motor to superior oblique muscle of the eye. • Test: Check eye movements • Symptoms of nerve damage: • Outward rotation of the affected eye • Vertical diplopia Injured sideNormal side Originates in the midbrain
  13. 13. 13 CN VI: Abducens Nerve • Function: • Somatic Motor to lateral rectus muscle of the eye. • Test: Check eye movements • Symptoms of nerve damage: • The affected eye will tend to be deviated inward because of the unopposed action of the medial rectus muscle. • Cannot move eyeball laterally beyond the midpoint Injured side Normal side Originates in the pons
  14. 14. 14 CN V: Trigeminal Nerve 3 Branches 1. Ophthalmic 2. Maxillary 3. Mandibular
  15. 15. 15 CN V: Trigeminal Nerve • Function: • Somatic Motor (mandibular branch) to muscles of mastication (chewing) • Sensory (all branches)to face and cornea. Originates in the pons
  16. 16. 16 CN V: Trigeminal Nerve Test: Have patient bite down while you palpate the masseter muscle Test: Touch patient with an open paperclip and ask “sharp or dull” Test: Touch cornea with a wisp of cotton. Patient should blink
  17. 17. 17 CN V: Trigeminal Nerve • Symptoms of nerve damage: • Inability to firmly bite down (mandibular branch only) • Loss of sensation (each branch can be affected independently) • Loss of corneal reflex (may indicate brain stem injury) • Trigeminal Neuralgia (Tic Douloureux): debilitating intermittent pain on one side of the face
  18. 18. 18 CN VII: Facial Nerve 5 Branches 1. Temporal 2. Zygomatic 3. Buccal 4. Mandibular 5. Cervical • Function: • Somatic Motor to muscles of facial expression • Parasympathetic (motor) to lacrimal and salivary glands • Sensory taste to anterior 2/3 tongue Originates in the pons
  19. 19. 19 CN VII: Facial Nerve
  20. 20. 20 CN VII: Facial Nerve Testing • Tests: 1. Check taste on anterior 2/3 of tongue by having patient taste sugar, salt, sour and bitter 2. Check symmetry of facial muscles: • Close eyes, smile, whistle, puff out cheeks (make funny faces) 1. Check tearing with ammonia fumes
  21. 21. 21 CN VII: Facial Nerve • Symptoms of nerve damage: • Mild weakness to total paralysis of facial muscles (may include twitching), • Drooping eyelid • Drooping corner of the mouth • Drooling or dry mouth • Impairment of taste • Excessive tearing in the eye or dry eye
  22. 22. 22 CN VII: Facial Nerve Injury (Bell’s Palsy) Paralyzed facial muscles Patients can still feel their face because sensory is supplied by the trigeminal nerve Injured side Normal side
  23. 23. 23 CN VIII: Vestibulocochlear • Function: Sensory • Vestibular system for balance & equilibrium • Cochlea for hearing • Tests: • Auditory component of the nerve: • Hearing test • Vestibular control of balance and movement: • Romberg test (tests equilibrium) Originates in the medulla
  24. 24. 24 CN VIII: Vestibulocochlear Tests • Simple hearing test: • Rub fingers together near the ear and ask “right or left” If there is lateralization (hearing louder on one side) there is a problem • Other hearing tests: • Performed by an audiologist with special equipment to determine tones, frequencies and degree of hearing loss
  25. 25. 25 CN VIII: Vestibulocochlear Tests Romberg Test • Have patient stand with arms at side and feet together • Have patient stand with their eyes closed • Stand close to prevent falls • Normally, they should maintain position for 20 seconds with only minimal swaying • If they loose their balance, they have failed the equilibrium test.
  26. 26. 26 CN IX: Glossopharyngeal • Function: • Somatic Motor to muscles of pharynx • Parasympathetic (motor) to salivary glands • Sensory to pharynx and taste to posterior tongue
  27. 27. 27 CN IX: Glossopharyngeal • Tests: • Gag reflex: Touch each side of the throat with the tongue depressor • Evaluate swallowing movements • Say AHH, and watch the palate and uvula elevate. • Evaluate taste on posterior 1/3 of tongue • Symptoms of nerve damage: • Loss of gag reflex • Difficulty swallowing • Loss of taste Originates in the medulla
  28. 28. 28 CN X: Vagus Nerve • Function: • Somatic Motor to muscles of pharynx and larynx • Parasympathetic (motor) fibers of the heart and other viscera • Sensory to pharynx and larynx Originates in the medulla
  29. 29. 29 CN X: Vagus Nerve • Test: • Inspect palate • Test gag reflex • Symptoms of nerve damage: • Loss of gag reflex • Difficulty swallowing • Hoarse voice
  30. 30. 30 CN XI: Accessory Nerve • Function: Somatic Motor to sternocleidomastoid and trapezius muscles Originates in the medulla
  31. 31. 31 CN XI: Accessory Nerve • Test: • Shrug shoulders against resistance • Turn head against resistance.
  32. 32. 32 CN XI: Accessory Nerve • Symptoms of nerve damage: • Weakness • Uneven shoulders • Winged scapula
  33. 33. 33 CN XII: Hypoglossal Nerve • Function: Somatic Motor to tongue Originates in the medulla
  34. 34. 34 Hypoglossal Nerve Injury • Test: • Ask patient to stick out tongue • Symptoms of nerve damage: • When paralyzed, the tongue will point to the damaged side Normal side Injured side
  35. 35. Lab Activity 20 General Senses
  36. 36. 36 General Senses: Receptors • Nociceptors: Pain receptors • Thermoreceptors: Temperature receptors (free nerve endings) • Chemoreceptors: Detect small changes in the concentration of specific chemicals or compounds • Mechanoreceptors: Sensitive to stimuli that distort their cell membranes (contain mechanically gated ion channels) • Tactile receptors • Baroreceptors • Proprioceptors
  37. 37. 37 Classes of Mechanoreceptors • Tactile receptors: sensations of touch, pressure and vibration • Free nerve endings • Root hair plexus • Tactile discs (Merkel’s discs) • Tactile corpuscles (Meissner’s corpuscles) • Lamellated corpuscles (Pancinian corpuscles) • Baroreceptors: Detect pressure changes in the walls of blood vessels and portions of the digestive, reproductive and urinary tracts • Proprioceptors: Monitor the positions of joints and muscles.
  38. 38. 38 Pancinian Corpuscle (aka: Lamellated Corpuscle) • Lie deep in the dermis • Respond only when deep pressure is first applied • Monitor high frequency vibrations
  39. 39. 39 Meissner’s Corpuscle (aka: Tactile Corpuscle) • Lie in the dermal papillae of the skin • Respond to light touch
  40. 40. 40 The End

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