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Biomed > Cranial nerves > Flashcards

Cranial nerves Flashcards

1
Q

What are cranial nerves?

A

PNS components that connect directly to the brain instead of the spinal cord

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2
Q

What do the numbers of cranial nerves correspond to?

A

The level they emerge from the brain
1. low numbers = most anterior
2. high numbers = most posterior

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3
Q

What is the special sensory for the olfactory nerve?

A

Smell

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4
Q

What type of fibres are in the olfactory nerves?

A

sensory only

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5
Q

What is cranial nerve I

A

The olfactory nerves

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6
Q

What is the origin of the olfactory nerves?

A

Receptors of the olfactory epithelium

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7
Q

What do the olfactory nerves pass through?

A

Cribiform plate of the ethmoid bone

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8
Q

What is the destination of the olfactory nerves?

A

Olfactory bulbs

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9
Q

What is the pathway of the olfactory nerve?

A
  1. Axons from special sensory neurons collect to form around 20 bundles that penetrate the cribiform plate
  2. olfactory afferents synapse in the olfactory bulb
  3. axon of post-synaptic neurons proceed to cerebrum as olfactory tracts, running along the underside of the frontal lobe
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10
Q

What happens if the olfactory nerve is damaged?

A

Loss of sense of smell (anosmia)

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11
Q

Is olfactory innervation ipsilateral or contralateral?

A

ipsilateral - information is processed by the olfactory bulb on the same side as the nostril detecting the stimulus

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12
Q

What is the clinical test for the olfactory nerve (CNI)?

A

Hold a strong smelling substance under each nostril

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13
Q

What is cranial nerve II?

A

The optic nerves

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14
Q

What is the special sensory of the optic nerve?

A

vision

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15
Q

What are the nerve fibres in the optic nerve?

A

sensory

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16
Q

What is the origin of the optic nerve?

A

Retina of eye

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17
Q

What does the optic nerve pass through?

A

optic canals of sphenoid bone

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18
Q

What is the destination of the optic nerves?

A

Diencephalon via the optic chiasm

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19
Q

Which side of the visual field hit the nasal part of the retina?

A

The temporal visual field

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20
Q

Which side of the retina field do images from the nasal visual field hit?

A

The temporal part of the retina

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21
Q

Where do the optic nerves converge?

A

At the anterior margin of the diencephalon at the optic chiasma

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22
Q

Where do axons from the temporal visual field cross?

A

At the chiasma

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23
Q

Where do axons from the nasal visual fields cross?

A

They remain uncrossed

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24
Q

Which axons diverge from the optic tract and why?

A

The retinotectal axons go to the midbrain for reflex activity of the eye

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25
Q

Where do most optic nerve axons synapse?

A

In the lateral geniculate nuclei of the thalamus, where they continue as optic radiation to the visual cortex

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26
Q

What happens if there is damage to the optic nerve before it reaches the chiasma?

A

Blindness in the same eye

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27
Q

What happens if there is damage at the optic chiama?

A

Bitemporal hemianopia (loss of temporal fields)

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28
Q

What happens if there is damage to the optic tract/ radiation?

A

Complex visual losses

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29
Q

What are the clinical tests for visual loss?

A
  1. Snellen charts
  2. Test visual fields in 4 quadrants of each eye
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30
Q

What is cranial nerve III?

A

The occulomotor nerve

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31
Q

What is cranial nerve IV?

A

The trochlear nerve

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32
Q

What is cranial nerve VI?

A

The abducens nerve

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33
Q

What do CN III, IV and VI do?

A

Motor nerves to the extraoccular muscles of the eye

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34
Q

What does cranial nerve III also do?

A

carries parasympathetic axons supplying pupillary constrictor muscles and ciliary muscles involved in eye reflexes

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35
Q

What types of nerve fibres are carried by the occulomotor nerve?

A

motor, and autonomic motor

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36
Q

What is the action of the superior rectus?

A

To pull the eye up and towards the nose

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37
Q

What is the action of the medial rectus?

A

Pull the eye towards the nose

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38
Q

What is the action of the superior oblique?

A

pull the eye down and away from the nose and roll it slightly out

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39
Q

What is the action of the inferior rectus?

A

To pull the eye down and towards the nose

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40
Q

What is the action of the lateral rectus?

A

To pull the eye away from the nose

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41
Q

What is the action of the inferior oblique?

A

Pulls the eye up and away from the nose and roll it slightly out

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42
Q

What muscles do the oculomotor nerve supply?

A

Superior, medial, and inferior rectus, inferior oblique, constrictor and ciliary muscles

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43
Q

What muscles does the trochlear nerve supply?

A

The superior oblique

44
Q

What muscles does the abducens supply?

A

The lateral rectus

45
Q

What occurs when there is damage to the occulomotor nerve?

A
  1. diplopia
  2. lateral strabismus (squint)
  3. dilated pupil in affected eye
46
Q

What happens if there is damage to the abducens nerve?

A
  1. diplopia
  2. medial strabismus
    These can be early signs of raised intracranial pressure, because they have the longest contact with the bone, so may become compressed
47
Q

What happens if there is damage to the trochlear nerve?

A
  1. vertical diplopia
  2. torsional diplopia
  3. patient often tilts head to other side to fuse the different images
48
Q

What is the clinical test for cranial nerves III,IV, and VI?

A

Ask a patient to follow the end of a pen or pen torch as you move it across the different visual fields

49
Q

Where does the occulomotor nerve arise?

A

midbrain

50
Q

Where does CN IV arise?

A

in the midbrain

51
Q

Where does CN VI emerge?

A

junction between pons and medulla

52
Q

What is the additional test for the occulomotor nerve?

A

Shine torch into eye to check for pupillary reflex. Pupil in affected eye won’t respond.

53
Q

What type of nerve fibres does CN IV use?

A

motor

54
Q

What type of nerve fibres does CN VI use?

A

motor

55
Q

How can the abducens nerve become damaged?

A

has longest contact with bone, so can become compressed if ICP increases

56
Q

What is cranial nerve V?

A

The trigeminal nerve

57
Q

Where does the trigeminal nerve arise?

A

In the pons

58
Q

What are the main functions of the trigeminal nerve?

A

sensory to face, scalp, and deep structures of the face, and motor to the muscles of mastication

59
Q

What are the branches of the trigeminal nerve?

A
  1. ophthalamic - sensory
  2. maxillary - sensory
  3. mandibular - sensory and motor to muscles of mastication
60
Q

Where are the cell bodies of the sensory neurons of the trigeminal branches found?

A

In the trigeminal ganglion

61
Q

What does the ophthalamic branch supply?

A

Sensory innervation to the eye and upper parts of the nasal cavity

62
Q

What are the major branches of the ophthalamic branch?

A
  1. frontal - skin of forehead
  2. lacrimal - lateral skin of eyelid and conjunctiva (blinking)
  3. nasociliary - medial upper eyelid, conjunctiva, globe, and upper part of nasal cavity
63
Q

What does the maxillary branch (V2) of the trigeminal nerve supply?

A

Sensory innervation to the skin from lower eyes to upper lip, maxillary teeth, palate, most of nasal cavity

64
Q

What does the mandibular branch (V3) of the trigeminal nerve supply?

A
  1. Sensory innervation to skin of lower lip and chin, lower teeth, anterior 2/3 tongue, floor of mouth
  2. motor to muscles of mastication
65
Q

What are the clinical function tests for the trigeminal nerve?

A
  1. Sharp-blunt test over all divisions
  2. Clench teeth and feel muscles
  3. Protrude jaw - will deviate to injured side
66
Q

Which nerve in cranial nerve VII?

A

The facial nerve

67
Q

Where does the facial nerve emerge?

A

between the pons and medulla

68
Q

What types of nerve fibres does the facial nerve use?

A

motor, sensory, autonomic

69
Q

What is the autonomic innervation of the facial nerve to?

A

salivary, lacrimal, and nasal glands

70
Q

What does the facial nerve supply?

A
  1. motor innervation to all muscles of facial expression
  2. taste to anterior of tongue (chorda tympani)
  3. parasympathetic secretomotor nerves to lacrimal glands
  4. submandibular and sublingual salivary glands
71
Q

What are the muscles of facial expression?

A
  1. frontalis
  2. orbicularis oculi
  3. lip elevator
  4. zygomaticus
  5. orbicularis oris
  6. buccinator
  7. lip depressors
72
Q

What are the branches of the facial nerve?

A
  1. temporal
  2. zygomatic
  3. buccal
  4. mandibular
  5. cervical
73
Q

What are the clinical tests of function for the facial nerve?

A
  1. ask patient to make exaggerated facial expressions
  2. facial droop
  3. wrinkle forehead
  4. puff out cheeks
  5. stimulate taste on anterior 2/3 tongue
74
Q

What happens if there is damage to cranial nerve VII between brainstem and middle ear?

A

All branches and function are lost

75
Q

What happens if there is damage to the facial nerve after the middle ear?

A

taste and lacrimation intact, but facial expression is lost on that side

76
Q

What happens if there is damage to the facial nerve on the face?

A

Individual muscle groups are lost depending on the branches damaged

77
Q

What is cranial nerve VIII?

A

The vestibulocochlear nerve

78
Q

What part of the brainstem does the vestibulocochlear nerve arise from?

A

the medulla and the pons

79
Q

What types of nerve fibres are carried by the vestibulocochlear nerve

A

sensory only

80
Q

What is the special sensory of the vestibulocochlear nerve?

A

hearing and balance

81
Q

What is conductive hearing loss caused by?

A

blockage of or damage to the outer or middle ear

82
Q

What is sensorineural hearing loss caused by?

A

damage to cochlear or vestibulocochlear nerve

83
Q

What are the clinical tests for function for the vestibulocochlear nerve?

A
  1. strike high frequency tuning fork and hold 2cm from patient’s ear
  2. if cannot hear, place it on mastoid process - sensorineural if not
84
Q

What is cranial nerve IX?

A

the glossopharyngeal nerve

85
Q

What part of the brain does the glossopharyngeal nerve arise from?

A

medulla

86
Q

What types of nerve fibres does the glossopharyngeal nerve use?

A

motor, sensory, and autonomic

87
Q

What does the glossopharyngeal nerve innervate?

A
  1. sensory to mucosa of pharynx, posterior 1/3 tongue
  2. visceral sensation from carotid sinuses and bodies
  3. parasympathetic secretomotor to parotid salivary glands
  4. motor to stylopharyngeus muscle
88
Q

What happens if there is damage to glosspharyngeal nerve?

A

Swallowing and gag reflexes are damaged

89
Q

What is the clinical test for the glossopharyngeal nerve?

A

touch the pharyngeal wall to test gag reflex

90
Q

What is cranial nerve X?

A

The vagus nerve

91
Q

What part of the brain does the vagus nerve emerge from?

A

medulla

92
Q

What autonomic innervation does the vagus nerve supply?

A

afferent to aortic arch, efferent to thorax and abdomen

93
Q

What does the vagus nerve do?

A
  1. motor to muscles of pharynx, larynx, and soft palate
  2. sensory to mucosa of larynx
  3. parasympathetic to viscera of thorax and abdomen
94
Q

What can occur if there is damage to the vagus nerve?

A

dysarthria, dysphagia, dysphonia

95
Q

What are the clinical tests for function for the vagus nerve?

A
  1. ask patient to say ahhhh - soft palate should raise symmetrically
  2. ask patient to cough
96
Q

What is cranial nerve XI?

A

The accessory nerves

97
Q

What is unusual about the accessory nerves?

A

arises from C1-4 of the spinal cord

98
Q

What does the accessory nerve supply?

A

Motor to sternocleidomastoid and trapezius muscles

99
Q

What types of fibres are the accessory nerve?

A

motor only

100
Q

What is the clinical test for the accessory nerves?

A

Ask a patient to shrug or turn their head against resistance

101
Q

What are the effects of damage to the accessory nerve?

A
  1. weakness or paralysis
  2. head and neck movement issues
  3. shoulder girdle dysfunction
  4. shoulder droop
  5. muscle atrophy
102
Q

What is cranial nerve XII?

A

hypoglossal nerve

103
Q

Where does the hypoglossal nerve emerge?

A

medulla

104
Q

What does the hypoglossal nerve supply?

A

motor to muscles of tongue, voluntary over tongue movements

105
Q

What nerve fibres does the hypoglossal nerve use?

A

motor

106
Q

What is the clinical test for the hypoglossal nerve?

A

Ask patient to protrude tongue, will deviate to injured side

Biomed (29 decks)

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