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Neurology Year 3 > Cranial nerves > Flashcards

Cranial nerves Flashcards

1
Q

How many cranial nerves is there?

A

12

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2
Q

What is the first cranial nerve?

A

Olfactory - special sensory nerves for the sense of smell.

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3
Q

What is the route of the olfactory nerve?

A

Originate in the receptors of the olfactory epithelium and pass through the cribriform plate of the ethmoid bone, ending at the olfactory bulbs.

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4
Q

What is the second cranial nerve?

A

Optic nerve - Special sensory information for vision

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5
Q

What is unique about the optic nerve?

A

Developed from the optic vesicle, an out pocketing of the forebrain. Therefore is considered part of the CNS, and examination of the nerve enables an assessment of intracranial health.

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6
Q

Describe the intracranial course of the optic nerve

A

Within the middle cranial fossa, the optic nerves from each eye unite to form the optic chiasm.

At the chiasm, fibres from the nasal (medial) half of each retina cross over to the contralateral optic tract, while fibres from the temporal (lateral) halves remain ipsilateral:

  • Left optic tract – contains fibres from the left temporal (lateral) retina, and the right nasal (medial) retina.
  • Right optic tract – contains fibres from the right temporal retina, and the left nasal retina.
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7
Q

The right and left optic tracts of the optic nerve travel to the lateral geniculate nucleus. Where is this?

A

The thalamus where the two optic tracts synapse.

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8
Q

The axons from the LGN (optic nerve) then carry visual information via a pathway known as the optic radiation. The pathway itself can be divided into two other RADIATIONS, what are they?

A

Upper optic radiation

Lower optic radiation

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9
Q

What is the third cranial nerve?

A

Oculomotor nerve - MOTOR

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10
Q

The oculomotor nerve has a motor and parasympathetic role, what is the motor role?

A

Innervates the majority of the extraocular muscles (levator palpebrae superioris, superior rectus, inferior rectus, medial rectus, and inferior oblique).

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11
Q

The oculomotor nerve has a motor and parasympathetic role, what is the parasympathetic role?

A

Supplies the sphincter pupillae (constrict the pupil in bright light) and the ciliary muscles of the eye (change shape for focusing)

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12
Q

What does the levator palpebrae superioris do

A

Raise the upper eyelid and to maintain the upper eyelid position

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13
Q

What does the superior rectus do?

A

Elevates the eyes upwards

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14
Q

What does the inferior rectus do?

A

Depresses the eyes downwards

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15
Q

What does the medial rectus do?

A

Adducts the eye medially (inwards)

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16
Q

What is the function of the inferior oblique?

A

Responsible for elevation, and abduction (upwards and out)

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17
Q

What is the function of the superior oblique?

A

Move the eye in the down-and-inwards direction

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18
Q

What is the fourth cranial nerve?

A

The trochlear nerve is the fourth paired cranial nerve.

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19
Q

What is the smallest cranial nerve but has the longest intracranial nerve?

A

The trochlear nerve

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20
Q

What kind of nerve is the trochlear nerve?

A

Somatic motor

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21
Q

What is the function of the trochlear nerve?

A

Innervates the superior oblique

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22
Q

What is the fifth cranial nerve?

A

The trigeminal nerve - motor and sensory

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23
Q

What is the largest cranial nerve?

A

The trigeminal nerve

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24
Q

What does the sensory portion of the trigeminal nerve do?

A

The three terminal branches of CN V innervate the skin, mucous membranes and sinuses of the face.

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25
Q

What is the motor function of the trigeminal nerve?

A

Only the mandibular branch of CN V has motor fibres.

It innervates the muscles of mastication: medial pterygoid, lateral pterygoid, masseter and temporalis. The mandibular nerve also supplies other 1st pharyngeal arch derivatives: anterior belly of digastric, mylohyoid, tensor veli palatini and tensor tympani.

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26
Q

What are the three divisions of the trigeminal nerve?

A

Ophthalmic (V1), maxillary (V2) and mandibular (V3)

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27
Q

What one of the three branches of the trigeminal nerve has motor functions?

A

Only the mandibular branch of CN V has motor fibres.

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28
Q

What is the 6th cranial nerve?

A

The abducens nerve

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29
Q

What is the role of the abducens nerve

A

It has a purely somatic motor function – providing innervation to the lateral rectus muscle. Abducts the eyeball

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30
Q

Where does the abducens nerve arise from?

A

The pons of the brainstem

It exits the brainstem at the junction of the pons and the medulla.

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31
Q

What is the name of the 7th cranial nerve?

A

The facial nerve

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32
Q

What kind of nerve is the facial nerve?

A

A combination of sensory, motor and parasympathetic fibres.

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33
Q

Where does the 7th cranial nerve arise?

A

The pons where two roots arise - a large motor root, and a small sensory root

34
Q

The motor and sensory roots of the facial nerve travel in close proximity to the temporal bone through the internal acoustic meatus; when they exit here, where do they enter?

A

The roots leave the internal acoustic meatus, and enter into the facial canal

35
Q

Once the two roots (motor and sensory that arise from the pons) of the facial nerve enter the facial canal, two important events occur, what are they?

A

Firstly the two roots fuse to form the facial nerve.

Next, the nerve forms the geniculate ganglion (a ganglion is a collection of nerve cell bodies).

36
Q

The facial nerve which arises from the fusion of two roots (motor and sensory) becomes three branches, what are they?

A

1) Greater petrosal nerve – parasympathetic fibres to mucous glands and lacrimal glands.
2) Nerve to stapedius – motor fibres to stapedius muscle of the middle ear.
3) Chorda tympani – special sensory fibres to the anterior 2/3 tongue and parasympathetic fibres to the submandibular and sublingual glands.

37
Q

What is the role of the 7th cranial nerve (facial)?

A

Controls facial movement and expression. The facial nerve also carries nerves that are involved in taste to the anterior 2/3 of the tongue and producing tears (lacrimal gland).

38
Q

The extracranial course of the facial course involves passing through the parotid gland (does not innervate this gland) - where it splits into 5 branches; what are they?

A 
Temporal branch
Zygomatic branch
Buccal branch
Marginal mandibular branch
Cervical branch

These branches are responsible for innervating the muscles of facial expression.

39
Q

Between the stylomastoid foramen (near the temporal bone), and the parotid gland, the facial nerve gives of three more motor branches; what are they?

A
  1. Posterior auricular nerve – innervates the intrinsic and extrinsic muscles of the outer ear.
  2. Nerve to the posterior belly of the digastric muscle – Innervates the posterior belly of the digastric muscle (a suprahyoid muscle of the neck). It is responsible for raising the hyoid bone.
  3. Nerve to the stylohyoid muscle – Innervates the stylohyoid muscle (a suprahyoid muscle of the neck). It is responsible for raising the hyoid bone.
40
Q

What is the 8th cranial nerve?

A

Vestibulocochlear nerve

41
Q

The Vestibulocochlear nerve has two main branches what are they?

A

Vestibular component

Cochlear component

42
Q

Where does the vestibulocochlear nerve arise and exit?

A

The cerebellopontine angle and exits the cranium via the internal acoustic meatus of the temporal bone

43
Q

What is the function of the 8th cranial nerve (vestibulocochlear)

A

Special Sensory Functions

It is responsible for the special senses of hearing (via the cochlear nerve), and balance (via the vestibular nerve).

44
Q

What is the 10th cranial nerve?

A

The vagus nerve is the 10th cranial nerve (CN X)

45
Q

What kind of nerve is the vagus nerve?

A

Both sensory and motor

46
Q

What are the sensory functions of the vagus nerve?

A

Innervates the skin of the external acoustic meatus and the internal surfaces of the laryngopharynx and larynx. Provides visceral sensation to the heart and abdominal viscera.

Special Sensory: Provides taste sensation to the epiglottis and root of the tongue.

47
Q

What are the motor and parasympathetic functions of the vagus nerve?

A

Motor: Provides motor innervation to the majority of the muscles of the pharynx, soft palate and larynx.

Parasympathetic: Innervates the smooth muscle of the trachea, bronchi and gastro-intestinal tract and regulates heart rhythm.

48
Q

What is the 11th cranial nerve?

A

The accessory nerve - It has a purely somatic motor function.

49
Q

What is the role of the accessory nerve?

A

Innervates the sternocleidomastoid and trapezius muscles.

50
Q

What is the 12th cranial nerve called?

A

The Hypoglossal nerve (XII)

51
Q

What is the role of the 12th cranial nerve?

A

A purely somatic motor function, innervating all the extrinsic and intrinsic muscles of the tongue (except the palatoglossus, innervated by vagus nerve).

52
Q

All the cranial nerves apart from two arise from the brainstem, what are these two and where do they arise?

A

The olfactory nerve (CN I) and optic nerve (CN II) originate from the cerebrum

53
Q

What cranial nerve arises from the midbrain?

A

Trochlear nerve (IV)

It has the longest intracranial length of all the cranial nerves.

54
Q

What cranial nerve arises from the midbrain-pontine junction

A

Facial

55
Q

What cranial nerve arises from the pons proper?

A

Trigeminal

56
Q

What cranial nerves arise from the medulla obloganta?

A

glossopharyngeal, vagus, accessory and hypoglossal

57
Q

What cranial nerve arises from the pontine-medulla junction

A

abducens, facial, vestibulocochlear

58
Q

What cranial nerve passes through the cribriform plate of the ethmoid?

A

Olfactory (CNI)

59
Q

What cranial nerve passes through the Optic canal?

A

Optic nerve (CNII)

60
Q

What cranial nerves passes through the Superior orbital fissure?

A

Occulomotor, ophthalmic (CNV1), trochlear, abducens

61
Q

What cranial nerve passes through the foramen rotundum?

A

Maxillary (CNV2)

62
Q

What cranial nerve passes through the foramen Ovale?

A

Mandibular (CNV3)

63
Q

What two cranial nerves pass through the internal acoustic meatus?

A

Facial & vestibulocochlear

64
Q

What cranial nerves pass through the jugular formanen?

A

Glossopharangeal, vagus and accessory

65
Q

What does the posterior auricular nerve do?

A

innervates the intrinsic and extrinsic muscles of the outer ear.

66
Q

What does the nerve to the posterior belly of the digastric muscle do?

A

Innervates the posterior belly of the digastric muscle (a suprahyoid muscle of the neck). It is responsible for raising the hyoid bone.

67
Q

What does the Nerve to the stylohyoid do?

A

Innervates the stylohyoid muscle (a suprahyoid muscle of the neck). It is responsible for raising the hyoid bone.

68
Q

Describe the extracranial course of the optic nerve?

A

The optic nerve is formed by the convergence of axons from the retinal ganglion cells. These cells in turn receive impulses from the photoreceptors of the eye (the rods and cones).

After its formation, the nerve leaves the bony orbit via the optic canal, a passageway through the sphenoid bone. It enters the cranial cavity, running along the surface of the middle cranial fossa (in close proximity to the pituitary gland).

69
Q

The optic nerve has a extracranial and intracranial course; where does it enter the brain to start the intracranial course?

A

It enters the cranial cavity, running along the surface of the middle cranial fossa (in close proximity to the pituitary gland).

70
Q

Within the middle cranial fossa, the optic chiasm is formed; what is this?

A

Within the middle cranial fossa, the optic nerves from each eye unite to form the optic chiasm. At the chiasm, fibres from the nasal (medial) half of each retina cross over to the contralateral optic tract, while fibres from the temporal (lateral) halves remain ipsilateral.

71
Q

After the formation of the optic chiasm; two optic tracts are formed; what are they?

A

Left optic tract – contains fibres from the left temporal (lateral) retina, and the right nasal (medial) retina.

Right optic tract – contains fibres from the right temporal retina, and the left nasal retina.

72
Q

The two optic tracts that converge from the optic chiasm, then travel to the Lateral Geniculate nucleus where they syanpse; where is this?

A

The thalamus

73
Q

After the two optic tracts synapse in the LGN of the thalamus; what happens now?

A

Axons from the LGN then carry visual information via a pathway known as the optic radiation - forms the upper and lower optic radiations

74
Q

What are the parasympathetic roles of the facial nerve?

A

Supplies many of the glands of the head and neck, including:
Submandibular and sublingual salivary glands.
Nasal, palatine and pharyngeal mucous glands.
Lacrimal glands.

75
Q

What is the sensory role of the facial nerve?

A

Provides special taste sensation to the anterior 2/3 of the tongue via the chorda tympani

76
Q

What is the motor role of the facial nerve?

A

Muscles of facial expression, posterior belly of the digastric, stylohyoid and stapedius muscles.

77
Q

What are the extracranial branches of the facial nerve?

A

Posterior auricular nerve. Nerve to the Posterior belly of the digastric muscle and to the Nerve to the stylohyoid muscle.

78
Q

Within the parotid gland; the facial nerve is described as extracranial and gives off 5 branches; what are they?

A 
Temporal branch
Zygomatic branch
Buccal branch
Marginal mandibular branch
Cervical branch
79
Q

What are the INTRAcranial branches of the facial nerve?

A

Greater petrosal nerve – parasympathetic fibres to mucous glands and lacrimal gland.

Nerve to stapedius – motor fibres to stapedius muscle of the middle ear.

Chorda tympani - 2/3rds of tongue

80
Q

The trigeminal nerve has three branches that all carry sensory information; however one also carries motor; which one is it?

A

The mandibular (V3)

  • Muscles of mastication
81
Q

What cranial nerve arises from the pontomedullary junction

A

Facial, abducens and trigeminal

Neurology Year 3 (22 decks)

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