Cranial Nerves Flashcards

1
Q

What are cranial nerves prone to? and what do the symptoms relate to?

A

compression due to inflammation, tumours and fractures

symptoms relate to the function of the nerves

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2
Q

What may cranial nerves contain?

A

Somatic motor fibres - supply striated muscle

Autonomic motor fibres - cranial division of the parasympathetic supply innervates smooth muscle & glands

Visceral sensory - afferent inputs from pharynx, larynx, heart, lung, gut etc - not normally conscious

General sensory - afferent inputs (eg touch, temperature, pain) from skin & mucous membranes

Special sensory – taste, smell, vision, hearing & balance

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3
Q

Why do cranial nerves not carry sympethetic fibres?

A

As sympathetic fibres arise form the thoraco-lumbar region

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4
Q

Name fibre type A?

A

sensory (afferent) fibres

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5
Q

Name fibre type B?

A

somatic motor (efferent) fibres

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6
Q

Name fibre type C?

A

autonomic motor (efferent) fibres

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7
Q

Do nerves carry sensory or motor fibres or both?

A

Some are purely sensory, some purely motor but lots of them are mixed and have both sensory and motor fibres in them

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8
Q

What fibres does the Olfactory (CNI) carry?

A

sensory (smell)

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9
Q

What fibres does the Optic (CNII) carry?

A

sensory (vision)

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10
Q

What fibres does the Oculomotor (CNIII) carry?

A

motor (eye movement)

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11
Q

What fibres does the Trochlear (CNIV) carry?

A

motor (eye movement)

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12
Q

What fibres does the Trigeminal (CNV) carry?

A

mixed (sensation from face & mouth, muscles of mastication)

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13
Q

What fibres does the Abducent (CNVI) carry?

A

motor (eye movement)

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14
Q

What fibres does the Facial (CNVII) carry?

A

mixed (muscles of facial expression, parasymp, taste)

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15
Q

What fibres does the Vestibulocochlear (CNVIII) carry?

A

sensory (hearing & balance)

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16
Q

What fibres does the Glossopharyngeal (CNIX) carry?

A

mixed (swallowing, sensation from tongue, parasymp)

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17
Q

What fibres does the Vagus (CNX) carry?

A

mixed (muscles of throat, parasymp, visceral sensory)

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18
Q

What fibres does the Accessory (CNXI) carry?

A

motor (soft palate, throat & neck)

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19
Q

What fibres does the Hypoglossal (CNXII) carry?

A

motor (tongue)

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20
Q

What is CNI?

A

olfactory nerve

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21
Q

What is the pathway of the olfactory nerve?

A

receptors in olfactory epithelium of nasal cavity, olfactory nerve fibres pass through foraminifera in cribriform plate of ethmoid bone and enter olfactory bulb in the anterior cranial fossa

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22
Q

What is the clinical application of the olfactory nerve?

A

fractured cribriform plate may tear olfactory nerve fibres causing anosmia (loss of sense of smell)

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23
Q

Whatis CN II?

A

optic nerve

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24
Q

What is the pathway of the optic nerve?

A

enters via optic canal, nerves join to form optic chiasm, fibres from medial (nasal) half of each retina cross to form optic tract

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25
Q

What is the clinical application of the optic nerve?

A

increase in CSF pressure can cause papilloedema (optic disc swelling that is caused by increased intracranial pressure due to any cause)

section of right optic nerve causes blindness through right eye

section of optic chiasm causes loss of peripheral vision (bitemporal hemianopsia)

section of right optic tract causes blindness in left temporal and right nasal fields (left homonymous hemianopsia)

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26
Q

What is CN III?

A

oculomotor nerve

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27
Q

What is the pathway of the oculomotor nerve?

A

emerges from midbrain and exits via superior orbital fissure

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28
Q

What are the components of the oculomotor nerve?

A

somatic motor - extraocular muscles (superior, medial & inferior rectus and inferior oblique) and eyelid (levator palpebrae superioris)

autonomic motor - parasympathetic to pupil causing constriction and to ciliary muscle causing accommodation of the lens

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29
Q

What is the clinical application of the oculomotor nerve?

A

drooping of upper eyelid (ptosis)

eyeball abducted and pointing down

no pupillary reflex

no accommodation of the lens - wont be able to focus on things close up

30
Q

What is cranial nerve IV?

A

trochlear nerve

31
Q

What is the pathway of the trochlear nerve?

A

emerges from dorsal surface of the mid brain and exits via the superior orbital fissure

32
Q

What are the components of the trochlear nerve?

A

somatic motor - extraocular muscle (superior oblique turns eye downwards)

33
Q

What is the clinical application of the trochlear nerve?

A

diplopia when looking down

34
Q

What is diplopia?

A

double vision

35
Q

What is CN VI?

A

abducent nerve

36
Q

What is the pathway of the abducent nerve?

A

emerges between pons and medulla and exits via the superior orbital fissure

37
Q

What are the components of the abducent nerve?

A

somatic motor - extraocular muscle (lateral rectus abducts the eye)

38
Q

What is the clinical application of the abducent nerve?

A

medial deviation of the affected eye causing diplopia

39
Q

What is cranial nerve V?

A

trigeminal nerve

40
Q

What is the pathway of Trigeminal (ophthalmic) CNV1?

A

emerges from the pons, travels through the trigeminal ganglion and exits via the superior orbital fissure

41
Q

What are the components of the Trigeminal (ophthalmic) CNV1?

A

General sensory - from cornea, forehead, scalp, eyelids, nose and mucosa of nasal cavity and sinuses

42
Q

What is the pathway of the Trigeminal (maxillary) CNV2?

A

emerges from the pons, travels through the trigeminal ganglion and exits via the foramen rotundum

43
Q

What are the components of the Trigeminal (maxillary) CNV2?

A

General sensory - from face over maxilla, maxillary teeth, temperomandibular joint, mucosa of nose, maxillary sinuses and palate

44
Q

What is the pathway of the Trigeminal (mandibular) CNV3?

A

emerges from the pons, travels through the trigeminal ganglion and exits via the foramen ovale

45
Q

What are the components of the Trigeminal (mandibular) CNV3?

A

General sensory - from face over mandible, mandibular teeth, temperomandibular joint, mucosa of mouth & anterior 2/3rds of tongue

Somatic motor - muscles of mastication, part of digastric, tensor veli palatini & tensor tympani

46
Q

What is the clinical application of the trigeminal nerve?

A

paralysis of muscles of mastication

loss of corneal or sneezing reflex

loss of sensation in the face

trigeminal neuralgia

47
Q

What is CN VII?

A

facial nerve

48
Q

What is the pathway of the facial nerve?

A

emerges between pons and medulla and exits via internal acoustic meatus, facial canal and stylomastoid foramen

49
Q

What are the components of the facial nerve?

A

somatic motor - muscles of facial expression & scalp, stapedius of middle ear, part of digastric muscle

autonomic motor - parasympathetic innervation of submandibular & sublingual salivary glands, lacrimal glands, glands of nose & palate

special sensory - taste from anterior 2/3rd of tongue & soft palate

general sensory - from external acoustic meatus

50
Q

What is the clinical application of the facial nerve?

A

most frequently injured - due to long pathway through bone

Bell’s palsy - cannot frown, close eyelid, or bare teeth

51
Q

What is CN VIII?

A

Vestibulocochlear

52
Q

What is the pathway of the vestibulocochlear nevre?

A

emerges from between pons and medulla and exits via internal acoustic meatus, dividing into vestibular & cochlear nerves

53
Q

What are the components of the vestibulocochlear nevre?

A

special sensory :

vestibular sensation from semicircular ducts, utricle, saccule gives sense of position & movement

hearing from spiral organ - organ of corti

54
Q

What is the clinical application of the vestibulocochlear nerve?

A

tinnitus (ringing in the ears)

deafness (conductive vs sensorineural)

vertigo (loss of balance)

nystagmus (involuntary rapid eye movements)

55
Q

WHat is CN IX?

A

glossopharyngeal nerve

56
Q

What is the pathway of the glossopharyngeal nerve?

A

emerges form the medulla and exits via the jugular foramen

57
Q

What are the components of the glossopharyngeal nerve?

A

special sensory - taste from posterior 3rd of tongue

general sensory - cutaneous sensations from middle ear and posterior oral cavity

visceral sensory - sensation from carotid body & carotid sinus

autonomic motor - parasympathetic innervation of parotid gland

somatic motor - to stylopharyngeus, helps with swallowing

58
Q

What is the clinical application of the glossopharyngeal nerve?

A

loss of gag reflex and taste from back of tongue

associated with injuries to CNs X and XI - jugular foramen syndrome

59
Q

What is CN X?

A

vagus nerve

60
Q

What is the pathway of the vagus nerve?

A

emerges from medulla and exits via jugular foramen, then everywhere!

61
Q

What are the components of the vagus nerve?

A

special sensory - taste from epiglottis and palate

general sensory - sensation from auricle, external acoustic meatus

visceral sensory - from pharnyx, larynx, trachea, bronchi, heart, oesophagus, stomach, intestine

autonomic motor - parasympathetic innervation of muscle in bronchi, gut, heart

somatic motor - to pharynx, larynx, palate & oesophagus

62
Q

What is the clinical application of the vagus nerve?

A

damage to pharyngeal branches cause difficulty in swallowing

damage to laryngeal branches causes difficulty in speaking

63
Q

What is CN XI?

A

accessory nerve

64
Q

What is the pathway of the accessory nerve?

A

small cranial (medulla) and large spinal roots exit via jugular foramen

65
Q

What are the components of the accessory nerve?

A

somatic motor - striated muscle of soft palate, pharynx & larynx, and to sternocleidomastoid & trapezius

66
Q

What is the clinical application of the accessory nerve?

A

weakness in turning head and shrugging shoulder

67
Q

What is CN XII?

A

hypoglossal nerve

68
Q

What is the pathway of the hypoglossal nerve?

A

emerges form medulla and exists through hypoglossal canal

69
Q

What are the components of the hypoglossal nerve?

A

somatic motor - to muscles of tongue

70
Q

What is the clinical application of the hypoglossal nerve?

A

vulnerable to damage during tonsillectomy

causes paralysis & atrophy of ipsilateral half of tongue. Tip deviates towards affected side

71
Q

Study this list

A
  • Smell - Olfactory
  • Sight - Optic
  • Taste - Facial, Glossopharyngeal & Vagus
  • Hearing & Balance - Vestibulocochlear
  • Movement of the eyes - Oculomotor, Trochlear & Abducent
  • Accomodation of the eye – Oculomotor
  • Constriction of the pupil - Oculomotor
  • Movement of muscles in the face - Facial
  • Sensation from the face - Trigeminal
  • Chewing - Trigeminal (mandibular)
  • Swallowing - Glossopharyngeal & Accessory
  • Movement of the tongue - Hypoglossal
  • Movement of the vocal cords – Vagus
  • Movement of the neck - Accessory