Lab Activity 19

1
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 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
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
CN II Optic Nerve

• Function
• Sensory for vision
• Tests
• Eye chart
• Check peripheral vision
• 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
  brain.
• Symptoms of nerve damage
• Loss of vision (peripheral or central)
• Abnormal funduscopic appearance

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
Cranial Nerves III, IV VI(Control Eye
Movements)
8
CN III Oculomotor nerve
Originates in the midbrain

• Function
• Somatic Motor to extraocular muscles
  (voluntarily move the eye)
• Parasympathetic (motor) to iris and lens
  (pupillary constriction)
• Tests
• Check pupils for size, shape and equality
• Shine light in each eye and check for pupil
  constriction
• Have patient follow an object in all directions
  to check for symmetric eye movements

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
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
Originates in the midbrain

• 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 side
Normal side
13
CN VI Abducens Nerve
Originates in the pons

• 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

Normal side
Injured side
14
CN V Trigeminal Nerve

• 3 Branches
• Ophthalmic
• Maxillary
• Mandibular

15
CN V Trigeminal Nerve
Originates in the pons

• Function
• Somatic Motor (mandibular branch) to muscles of
  mastication (chewing)
• Sensory (all branches)to face and cornea.

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
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
CN VII Facial Nerve
Originates in the pons

• 5 Branches
• Temporal
• Zygomatic
• Buccal
• Mandibular
• Cervical
• Function
• Somatic Motor to muscles of facial expression
• Parasympathetic (motor) to lacrimal and salivary
  glands
• Sensory taste to anterior 2/3 tongue

19
CN VII Facial Nerve
20
CN VII Facial Nerve Testing

• Tests
• Check taste on anterior 2/3 of tongue by having
  patient taste sugar, salt, sour and bitter
• Check symmetry of facial muscles
• Close eyes, smile, whistle, puff out cheeks (make
  funny faces)
• Check tearing with ammonia fumes

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
CN VII Facial Nerve Injury (Bells Palsy)
Paralyzed facial muscles
Injured side
Normal side
Patients can still feel their face because
sensory is supplied by the trigeminal nerve
23
CN VIII Vestibulocochlear
Originates in the medulla

• 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)

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
CN VIII Vestibulocochlear TestsRomberg 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
CN IX Glossopharyngeal

• Function
• Somatic Motor to muscles of pharynx
• Parasympathetic (motor) to salivary glands
• Sensory to pharynx and taste to posterior tongue

27
CN IX Glossopharyngeal
Originates in the medulla

• 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

28
CN X Vagus Nerve
Originates in the medulla

• Function
• Somatic Motor to muscles of pharynxand larynx
• Parasympathetic (motor) fibers of the heart and
  other viscera
• Sensory to pharynx and larynx

29
CN X Vagus Nerve

• Test
• Inspect palate
• Test gag reflex
• Symptoms of nerve damage
• Loss of gag reflex
• Difficulty swallowing
• Hoarse voice

30
CN XI Accessory Nerve
Originates in the medulla

• Function Somatic Motor to sternocleidomastoid
  and trapezius muscles

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
Originates in the medulla

• Function Somatic Motor to tongue

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
Lab Activity 20

• General Senses

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
Classes of Mechanoreceptors

• Tactile receptors sensations of touch, pressure
  and vibration
• Free nerve endings
• Root hair plexus
• Tactile discs (Merkels discs)
• Tactile corpuscles (Meissners 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
Pancinian Corpuscle (aka Lamellated Corpuscle)

• Lie deep in the dermis
• Respond only when deep pressure is first applied
• Monitor high frequency vibrations

39
Meissners Corpuscle (aka Tactile Corpuscle)

• Lie in the dermal papillae of the skin
• Respond to light touch

40
The End
The End