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Nervous > Cranial nerves > Flashcards

Cranial nerves Flashcards

1
Q

What are the 12 cranial nerves?

A
  • CN I (the olfactory nerve)
  • CN II (the optic nerve)
  • CN III (the oculomotor nerve)
  • CN IV (the trochlear nerve)
  • CN V (the trigeminal nerve)
    - CN V1 (the ophthalmic nerve)
    - CN V2 (the maxillary nerve)
    - CN V3 (the mandibular nerve)
  • CN VI (the abducent nerve)
  • CN VII (the facial nerve)
  • CN VIII (the vestibulocochlear nerve)
  • CN IX (the glossopharyngeal nerve)
  • CN X (the vagus nerve)
  • CN XI (the accessory nerve)
  • CN XII (the hypoglossal nerve)
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2
Q

Describe the anatomy and function of CN I (the olfactory nerve)

A

• Pathway
- Receptors in the olfactory epithelium in the nasal cavity
- The olfactory nerve fibres pass through the foraminifera in the cribriform plate of the ethmoid bone
- They then enter the olfactory bulb in the anterior cranial fossa
• Components
- Special sensory: smell

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3
Q

Describe the anatomy and function of CN II (the optic nerve)

A 
• Pathway
	- Enters via the optic canal
	- Nerves join to form a chiasm
	- Fibres from nasal part of each retina cross to form optic tract
	• Components
	- Special sensory: vision
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4
Q

Describe the anatomy and function of CN III (the oculomotor nerve)

A

• Pathway
- Emerges from the midbrain
- Exits via the superior orbital fissure
• Components
- The inferior orbital
- The superior, inferior and medial rectus
- The levator palpebrae superioris (eyelid)
- Parasympathetic to constrictor pupilae and dilator pupilae causing constriction of ciliary muscles causing accommodation of the lens

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5
Q

Describe the anatomy and function of CN IV (the trochlear nerve)

A

• Pathway
- Emerges from the dorsal surface of the midbrain
- Exits via the superior orbital fissure
• Components
- The superior orbital muscle (turns eye downwards)

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6
Q

Describe the anatomy and function of CN V1 (the ophthalmic nerve)

A

• Pathway
- Emerges from the pons
- Travels through the trigeminal ganglion
- Exits via the superior orbital fissure
• Components
- General; sensory: from cornea, forehead, scalp, eyelids, nose and mucosa of nasal cavity

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7
Q

Describe the anatomy and function of CN V2 (the maxillary nerve)

A

• Pathway
- Emerges from the pons
- Travels through the trigeminal ganglion
- Exits through the foramen rotundum
• Components
- General sensory: from face over maxilla, maxillary teeth, temporomandibular joint, mucosa of nose, maxillary sinuses and palette

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8
Q

Describe the anatomy and function of CN V3 (the mandibular nerve)

A

• Pathway
- Emerges from pons
- Travels through the trigeminal ganglion
- Exits via the foramen ovale
• Components
- General sensory: face from over mandible, mandibular teeth, temporomandibular joint, mucosa of mouth and anterior 2/3 of the tongue
Somatic motor: muscles of mastication, part of the digastric, tensor veli palatini and tensor tympani

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9
Q

Describe the anatomy and function of CN VI (the abducent nerve)

A

• Pathway
- Emerges between the pons and medulla
- Exits via the superior orbital fissure
• Components
- Lateral rectus muscle (abducts the eye)

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10
Q

Describe the anatomy and function of CN VII (the facial nerve)

A

• Pathway
- Emerges between the pons and the medulla
- Exits via the internal acoustic meatus, facial canal and stylomastoid foramen
• Components
- Somatic motor: Muscles of facial expression and scalp, stapedius of middle ear, part of the digastric muscle
- Visceral motor: Parasympathetic innervation of submandibular and sublingual salivary glands, lacrimal glands, glands of the nose and pallet
- Special sensory: Taste from anterior 2/3 of the tongue and soft pallet
- General sensory: From acoustic meatus

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11
Q

Describe the anatomy and function of CN VIII (the vestibulocochlear nerve)

A

• Pathway
- Emerges between the pons and medulla
- Exits through the internal acoustic meatus
- Divides into vestibular and cochlear nerves
• Components
- Special sensory: Vestibular sensation from semi-circular ducts, utricle, saccule gives sense of position and movement
- Hearing from cochlea

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12
Q

Describe the anatomy and function of CN IX (the glossopharyngeal nerve)

A

• Pathway
- Emerges from the medulla
- Exits via the jugular foramen
• Components
- Special sensory: taste from posterior 1/3 of the tongue
- General sensory: Cutaneious sensation from the middle ear and posterior oral cavity
- Visceral sensory: Sensation from the carotid body and carotid sinus
- Visceral motor: Parasympathetic innervation of the parotid gland
- Somatic motor: The stylopharyngeus, helps with swallowing

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13
Q

Describe the anatomy and function of CN X (the vagus nerve)

A

• Pathway
- Emerges from the medulla
- Exits via the jugular foramen
- Then goes everywhere
• Components
- Special sensory: taste from epiglottis and pallet
- General sensory: sensation from auricle, external acoustic meatus
- Visceral sensory: from pharynx, larynx, trachea, bronchi, heart, oesophagus, stomach and intestine
- Visceral motor: Parasympathetic innervation of muscle in the bronchi, gut and heart
- Somatic motor: To pharynx , larynx, pallet and oesophagus

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14
Q

Describe the anatomy and function of CN XI (the accessory nerve)

A 
• Pathway
	- Emerges from the medulla
	- Exits via the jugular foramen
	• Components
	- Somatic motor: Striated muscle of the soft pallet, pharynx and larynx and to sternomastoid and trapezius
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15
Q

Describe the anatomy and function of CN XII (the hypoglossal nerve)

A 
• Pathway
	- Emerges from the medulla
	- Exits via the hypoglossal canal 
	• Components
	- Somatic motor: Muscles of the tongue
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16
Q

What happens if CN I is damaged?

A
  • Fractured cribriform plate may tear the olfactory nerve fibres causing anosmia
17
Q

What happens if CN II is damaged?

A
  • Increase in CSF pressure can cause palpilloedema
    • Section of the 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 hemianopia)
18
Q

What happens if CN III is damaged?

A
  • Drooping of upper eyelid (ptosis)
    • Eyeball abducted and pointing down
    • No pupillary reflex
    • No accommodation of the lens
19
Q

What happens if CN IV is damaged?

A

Diplopia when looking down

20
Q

What happens if CN V is damaged?

A
  • Paralysis of muscles of mastication
    • Loss of corneal sneezing reflex
    • Loss of sensation to the face
    • Trigeminal neuralgia
21
Q

What happens if CN VI is damaged?

A

Medial deviation of the affected eye causing diplopia

22
Q

What happens if CN VII is damaged

A
  • Most frequently injured due to long pathway through bone

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

23
Q

What happens if CN VIII is damaged

A
  • Tinnitus (ringing in the ears)
    • Deafness (conductive vs sensorineural)
    • Vertigo (loss of balance)
    • Nystagmus (involuntary rapid eye movements)
24
Q

What happens if CN IX is damaged

A
  • Loss of gag reflex and taste from back of tongue

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

25
Q

What happens if CN X is damaged?

A
  • Damage to pharyngeal branches cause difficulty swallowing

- Damage to laryngeal branches cause difficulty speaking

26
Q

What happens if CN XI is damaged?

A

Weakness in turning head and shrugging shoulders

27
Q

What happens if CN XII is damaged?

A
  • Vulnerable to damage during tonsillectomy

- Causes paralysis and atrophy of ipsilateral half of tongue (tip deviates towards the affected side)

Nervous (21 decks)

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