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cranial nerves > fibres and innervation > Flashcards

fibres and innervation Flashcards

1
Q

what type of fibres does CN I carry and what does it innervate

A

special sensory - smell

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2
Q

what type of fibres does CN II carry and what does it innervate

A

special sensory - vision

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3
Q

what type of fibres does CN III carry and what does it innervate

A

motor fibres - to extraocular muscles except superior oblique and lateral rectus

parasympathetic fibres - to ciliary muscle and pupillae constrictor

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4
Q

what type of fibres does CN IV carry and what does it innervate

A

motor fibres - to superior oblique muscle of eye

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5
Q

what type of fibres does CN V1 carry and what does it innervate

A

general sensory - to upper third of face (forehead, cornea, nose)

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6
Q

what type of fibres does CN V2 carry and what does it innervate

A

general sensory - to middle third of face (maxilla, upper lip, palate)

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7
Q

what type of fibres does CN V3 carry and what does it innervate

A

general sensory - to lower third of face (mandible, lower lip, anterior 2/3 of tongue)

motor:
- muscles of mastication
- mylohyoid
- anterior belly of diagastric (both inferior alveolar branch)
- tensor veli palatini (soft palate)
- tensor tympani (middle ear)

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8
Q

what are the muscles of mastication

A

massester, temporalis, medial pterygoid, lateral pterygoid

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9
Q

what type of fibres does CN VI carry and what does it innervate

A

motor fibres - lateral rectus muscle of eye

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10
Q

what type of fibres does CN VII carry and what does it innervate

A

motor fibres:

  • muscles of facial expression
  • posterior belly of digastric muscle
  • stylohyoid muscle
  • stapedius muscle (stapes bone in ear)

special sensory - taste to anterior 2/3 of tongue (chorda tympani)

general sensory - skin of external acoustic meatus (ear)

parasympathetic fibres - innervates all glands in head and neck except parotid (greater petrosal nerve innervates lacrimal and mucosal glands, chorda tympani innervates submandibular and sublingual glands)

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11
Q

what are the muscles of facial expression

A
  • orbicularis oculi (around eyes)
  • nasal muscles
  • orbicularis oris (around mouth)
  • buccinator (helps puff cheeks out)
  • occipitofrontalis
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12
Q

describe the course of the facial nerve

A
  • enters internal acoustic meatus with CN VIII
  • exits IAM and enters facial canal
  • forms geniculate ganglia in facial canal
  • gives off greater petrosal nerve (parasymp), chorda tympani (taste), and nerve to stapedius
  • exits skull via stylomastoid foramen
  • gives off posterior auricular nerve (general sensory to ear), digastric and stylohyoid nerves
  • passes through parotid gland
  • gives off 5 branches to muscles of facial expression:
    - temporal
    - zygomatic
    - buccal
    - mandibular
    - cervical
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13
Q

describe the course of the mandibular division of the trigeminal nerve

A
  • gives off 4 branches in the infra-temporal fossa:
  • buccal nerve
  • auriculotemporal nerve
  • lingual nerve
  • inferior alveolar nerve (passes through mandibular foramen to innervate the lower teeth)
  • superior alveolar nerve is branch of V2
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14
Q

what type of fibres does CN VIII carry and what does it innervate

A

special sensory - balance

special sensory - hearing

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15
Q

what type of fibres does CN IX carry and what does it innervate

A

special sensory - posterior 1/3 of tongue

parasympathetic - parotid gland

motor - stylopharyngeus muscle (pharynx)

general sensory - oropharynx, carotid body and sinus, posterior 1/3 of tongue, middle ear, eustachian tube

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16
Q

what are the carotid body and sinus?

A

both found at the bifurcation of the CCA

carotid body:

  • chemoreceptor
  • measures O2, CO2 and pH in the blood
  • important modulator of cardiorespiratory function

carotid sinus:

  • baroreceptor
  • measures blood pressure in the CCA
17
Q

what type of fibres does CN X carry and what does it innervate

A

parasympathetic - smooth muscle of trachea, bronchi, GI tract, cardiac muscle

special sensory - taste to epiglottis and base of tongue/palate

general sensory - skin of external acoustic meatus, laryngopharynx, larynx. visceral sensation to heart and abdominal organs

motor fibres:

  • muscles of soft palate (except tensor veli palatini)
  • muscles of pharynx (except stylopharyngeus)
  • muscles of larynx (recurrent layrngeal nerve supplies all but cricothyroid muscle - innervated by superior laryngeal nerve) - both are branches of CN X
18
Q

what are branches of the vagus nerve

A
  • left recurrent laryngeal nerve (loops under aortic arch)
  • right recurrent laryngeal nerve (loops under right subclavian artery)
  • superior laryngeal nerve
  • pharyngeal branches
  • cardiac branches
  • abdominal branches
19
Q

what does the superior laryngeal nerve supply

A

cricothyroid muscle

the only intrinsic laryngeal muscle not innervated by the left recurrent laryngeal nerve

20
Q

what type of fibres does CN XI carry and what does it innervate

what triangle of the neck is this nerve found in?

A

motor - to trapezius and sternocleidomastoid muscles

posterior triangle

21
Q

what type of fibres does CN XII carry and what does it innervate

where on the skull base is the CN XII canal found?

A

motor - intrinsic and extrinsic muscles of the tongue

posterior cranial fossa, on the rim of the foramen magnum

22
Q

what cranial nerves travel through the cavernous sinus?

what other important structure passes through this sinus?

A
  • oculomotor nerve
  • trochlear nerve
  • ophthalmic and maxillary divisions of trigeminal nerves (V1 & V2)
  • abducens nerve
  • internal carotid artery
  • (this sinus is important clinically as it is a site of thrombosis and spread of infection)
23
Q

why does stroke spare the forehead?

A

each side of the upper part of the face is innervated by both hemispheres. (dual innervation)

fibres going from one hemisphere to the upper face either decussate to go the contralateral side or don’t decussate to go to ipsilateral side of upper face.

so lesion in one hemisphere due to stroke spares contralateral forehead because it is also innervated by the other hemisphere

fibres going to each side of middle and lower face come from one hemisphere only (all decussate)

24
Q

why does bell’s palsy affect a whole unilateral side of the face?

A

it is a lower motor neuron disease so it simply affects all the motor neurons going to the face from the right or left facial nerve (CN VII) - is not concerned with the origin of the fibres

25
Q

what innervates the geniohyoid and thyrohyoid

A

C1 nerve fibres travelling in hypoglossal nerve

26
Q

what innervates the sternohyoid, sternothyroid and omohyoid (infrahyoid muscles)

A

ansa cervicalis (C1-3) of cervical plexus

27
Q

what innervates the digastric anterior belly, and mylohyoid (suprahyoid)

A

CN V3

28
Q

what innervates digastric posterior belly and stylohyoid (suprahyoid)

A

CN VII

29
Q

what innervates soft palate muscles

A

CN X - except tensor veli palatini

30
Q

what innervates tensor veli palatini and tensor tympani

A

CN V3

cranial nerves (2 decks)

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