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Anatomy - Head and Neck > 3 - Cranial Nerves > Flashcards

3 - Cranial Nerves Flashcards

1
Q

What are the cranial nerves? How are they numbered?

A

Twelve pairs of nerves that emanate from the brainstem and pass through openings in the cranial cavity.

Numbered from rostral to caudal.

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2
Q

What are the functions of the cranial nerves?

A

Motor and sensory innervation of the head and neck

Innervation of special sense organs

Carry sympathetic and parasympathetic fibers of the ANS to structures in the head, neck, thorax, and abdomen.

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3
Q

Which cranial nerves are purely sensory?

A

I (olfactory tract), II (optic nerve), and VIII (vestibulocochlear)

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4
Q

Which cranial nerves are purely motor?

A

III (oculomotor), IV (trochlear), VI (abducent), XI (accessory), and XII (hypoglossal).

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5
Q

Which cranial nerves are mixed (sensory and motor)?

A

V (trigeminal), VII (facial), IX (glossopharyngeal), and X (vagus).

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6
Q

Which cranial nerves are general visceral efferent (autonomic function)?

A

III (oculomotor), V (trigeminal), VII (facial), and IX (glossopharyngeal).

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7
Q

What is cranial nerve I? What is it’s path?

A

The olfactory tract.

Located behind the bridge of the nose.

Cell bodies in olfactory epithelium project through olfactory foramina in the cribiform plate into the olfactory bulb.

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8
Q

What is the function of cranial nerve I (olfactory tract)?

A

Purely sensory and allows the special sense of smell.

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9
Q

What results from injury of the olfactory tract? Describe a scenario in which this could occur.

A

Injury to the cribiform plate could result in neurons being torn from the olfactory foramina.

Can result in anosmia (loss of smell).

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10
Q

What is cranial nerve II? What is its path?

A

The optic nerve.

Fibers from the retina come back along the optic nerve through the optic canal.

Medial fibers decussate at the optic chiasm while lateral ones go to the thalamus.

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11
Q

What is the function of the optic nerve (CN II)?

A

The special sense of vision. Purely sensory.

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12
Q

What can result from injury of the optic nerve? What can sometimes cause this?

A

Visual field defects.

Chiasm near pituitary, so pit tumors can results in visual field defects.

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13
Q

What is cranial nerve VIII? What is it’s path?

A

Vestibulocochlear nerve.

Cell bodies in the spiral ganglion (cochlea) and vestibular ganglion) pass through the internal auditory meatus and enter the brainstem at the pontomedullary junction.

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14
Q

What is the function of the vestibulocochlear nerve (CN VIII)?

A

Purely sensory - enable hearing and maintain balance.

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15
Q

What can result from injury to the vestibulocochlear nerve (CN VIII)?

A

Hearing impairment or loss.

Tinnitus (ringing in ears)

Balance issues/vertigo.

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16
Q

What is cranial nerve III? What is its path?

A

The oculomotor nerve.

Cell bodies in the oculomotor nucleus project through the superior orbital fissure of the sphenoid bone and cavernous sinus to enter the orbit.

Goes through common tendinous ring and branches to innervate most of the extraoccular muscles.

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17
Q

What cranial opening does the occulomotor nerve (CN III) pass through? What about the optic nerve (CN II)?

A

Oculomotor nerve (III): superior orbital fissure

Optic nerve(II): optic canal

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18
Q

What is the function of the oculomotor nerve (CN III)?

A

Purely motor - innervates most of the extra-occular muscles: Levator palpebrae superioris, inferior rectus muscle, medial rectus, and inferior oblique muscle.

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19
Q

What can injury to the occulomotor nerve (CN III) cause?

A

Oculomotor nerve palsy that causes drooping of the eyelid (can’t hold it open - called ptosis).

Most eye muscles wont work properly and those that are (superior oblique and lateral rectus muscle) will pull the eye laterally.

Fixed and dilated pupil.

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20
Q

What is cranial nerve IV? What is its path?

A

The trochlear nerve. (means pulley)

Originates from nucleus within the midbrain (only CN to emerge from dorsal surface of brainstem).

Passes through cavernous sinus and enters orbit through superior orbital fissure and goes to the superior oblique muscle.

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21
Q

What is the function of the trochlear nerve (CN IV)?

A

Purely motor - innervates the muscle going through the pulley: superior oblique muscle.

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22
Q

What can result from an injury to the trochlear nerve (CN IV)?

A

Inability to look down when the eye is adducted (diplopia)

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23
Q

What is cranial nerve VI? What is its path?

A

The abducent nerves.

From abducent nucleus in the pons, it passes through the cavernous sinus and superior orbital fissure, common tendinous ring, and innervates the lateral rectus muscle.

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24
Q

What is the function of the abducent nerve (CN VI)?

A

Purely motor: innervates the lateral rectus muscle to abduct the eye (pull pupils laterally).

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25
Q

What can result from an injured abducent nerve (CN VI)? What can sometimes cause this in adults?

A

Inability to abduct the eye. The eye would be turned inward (esotropia), resulting in double vision.

An aneurysm of the internal carotid artery could harm the abducent nerves and cause esotropia.

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26
Q

What is cranial nerve XI? What is its path?

A

The accessory nerve.

Cell bodies in anterior horn of cervical region, rootlets enter the skull through the foramen magnum and leave through the jugular foramen.

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27
Q

What is the function of the accessory nerve (CN XI)?

A

Purely motor - innervate the sternocleidomastoid muscle and the trapezius.

Branchial motor function for head and neck movement.

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28
Q

What can result from injury to the accessory nerve (CN XI)? ?

A

Weakness in turning head to opposite side.

Weakness in shrugging shoulders.

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29
Q

What is cranial nerve XII? What is its path?

A

The hypoglossal nerve.

Cell bodies in the hypoglossal nucleus of the medulla pass through the hypoglossal canal of the occipital bone and curve forward superior to the ansa cervicalis.

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30
Q

What is the function of the hypoglossal nerve (CN XII)?

A

Purely motor - swallowing, sucking, chewing, tongue protrusion.

Innervates all intrinsic tongue muscles and extrinsic muscles except platoglossus.

31
Q

What can result from injury of the hypoglossal nerve (CN XII)?

A

Protruded tongue deviates toward the side of injury (think broken wheel barrow). due to paralysis of muscles on that side.

32
Q

What is cranial nerve V? What are its parts? What is each made of?

A

The trigeminal nerve - mixed motor and sensory.

Opthalmic (VI) - purely sensory
Maxillary (V2) - purely sensory
Mandibular (V3) - sensory and motor

33
Q

What is the path of the opthalmic portion of the trigeminal nerve (CN V)?

A

Cell bodies in the trigeminal ganglion, passes through the superior orbital fissure.

34
Q

What can injury to the opthalmic division of the trigeminal nerve (CN V) cause?

A

Anesthesia (loss of pain and touch sensation) on the skin of the forehead, scalp, and nasal mucous membranes.

35
Q

What is the path of the maxillay portion of the trigeminal nerve (CN V)?

A

Cell bodies in the trigeminal ganglion pass through the foramen rotundum.

36
Q

What can injury to the maxillary portion of the trigeminal nerve cause?

A

Anesthesia of the skin of the upper lip, prominence of cheeck, palate, and maxillary sinus.

Tic douloureux.

37
Q

What is the path of the mandibular SENSORY portion of the trigeminal nerve (CN V)? What is its function?

A

Cell bodies in the trigeminal ganglion and pass through the foramen ovale.

Sensory from skin of lower jaw and mucosa on anterior 2/3 of the tongue.

38
Q

What is the path of the mandibular MOTOR portion of the trigeminal nerve (CN V)? What is its function?

A

Cell bodies from motor nucleus of V in the pons through the foramen ovale.

Branchial motor functions in chewing and swallowing.

39
Q

What muscles are innervated by the mandibular MOTOR portion of the trigeminal nerve (CN V)?

A

Muscles of mastication, tensor veli palatini, tensor tympani, myolohyoid, and anterior belly of the digastric muscle.

40
Q

Damage to the motor portion of the mandibular part of the trigeminal nerve will result in what?

A

Difficulty chewing due to paralysis of the muscles of mastication.

41
Q

What is cranial nerve VII? What are its three functions?

A

The facial nerve.

Somatic sensory, special sensory, and motor.

42
Q

What is the somatic sensory function of the facial nerve (CN VII)? What is its path?

A

Sensory from skin behind eat, external acoustic meatus, and tympanic membrane.

Cell bodies in geniculate ganglion enters temporal bone through internal acoustic meatus and exits through the stylomastoid foramen.

43
Q

What can result from injury to the somatic sensory portion of the facial nerve (CN VII)?

A

Anesthesia to the skin behind the ear, external acoustic meatus, and the tympanic membrane.

44
Q

What is the special sensory function of the facial nerve (CN VII)? What is its path?

A

Taste from the anterior 2/3 of the tongue and from the palate.

Cell bodies in the geniculate ganglion enter the temp bone through the int acoustic meatus and exit through the petrotympanic fissure.

45
Q

What is the motor function of the facial nerve (CN VII)? What is its path?

A

Branchial motor function for facial expression.

Cell bodies in the motor nucleus VII of the pons. Enters through the internal acoustic meatus and exits through the stylomastoid foramen.

46
Q

What muscles do the motor parts of the facial nerve innervate?

A

Muscles of facial expression: platysma, buccinator, frontalis, occipitalis, orbicularis oculi, orbicularis oris.

Stapedius, styolohyoid, and posterior belly of the digastric muscle.

47
Q

What are the branches of the facial nerve?

A

Tell Ziggy Bob Marley Called

Temporal, Zygomatic, Buccal, Mandibular, and Cervical

48
Q

What does injury to the motor parts of the facial nerve result in?

A

Bells palsy

  • inability to close eyelids due to paralysis of orbicularis oculi
  • angle of mouth droops
  • forehead doesn’t wrinkle due to paralysis of frontalis
49
Q

What is cranial nerve IX? What are it’s four functions?

A

The glossopharyngeal nerve.

  1. somatic sensory
  2. visceral sensory
  3. special sensory
  4. branchial motor
50
Q

Describe the somatic sensory function of the glossopharyngeal nerve (CN IX)?

A

Sensory from mucosa of posterior 1/3 of the tongue, tonsils, soft palate, pharynx, middle ear, auditory tube, and mastoid air cells.

51
Q

Describe the visceral sensory function of the glossopharyngeal nerve (CN IX)?

A

Chemoreceptors in the carotid body monitor O2 and baroreceptors in the carotid sinus monitor BP.

52
Q

Describe the function of the special sensory portion of the glossopharyngeal nerve (CN IX)?

A

Taste from the posterior 1/3 of the tongue.

53
Q

What is the path of the somatic sensory, visceral sensory, and special sensory neurons of the glossopharyngeal nerve (CN IX)?

A

Cell bodies located in the inferior ganglion of IX and pass through the jugular foramen.

54
Q

What is the function of the motor portion of the glossopharyngeal nerve (CN IX)? What is its path?

A

Branchial motor - elevates pharynx in speech and swallowing. Innervates the stylopharyngeus.

Cell bodies in the nucleus ambiguus of the medulla pass through the jugular foramen.

55
Q

Injury to the motor portion of the glossopharyngeal nerve (CN IX) can result in what?

A

Dysphagia (difficulty swallowing) and/or dysarthria (speech difficulty).

56
Q

What is cranial nerve X? What are it’s four functions?

A

The vagus nerve.

  1. Somatic sensory
  2. Visceral sensory
  3. Special sensory
  4. Branchial Motor
57
Q

Describe the somatic sensory of the vagus nerve (CN X)? What is its path?

A

somatic sensory from pharynx, larynx, external ear, external auditory canal, tympanic membrane, meninges in posterior cranial fossa.

Cell bodies in superior ganglion of X, passes through jugular foramen.

58
Q

Describe the visceral sensory of the vagus nerve (CN X)? What is its path?

A

Sensory from muscles and mucous membranes in the pharynx, larynx, thoracic and abdominal viscera, chemoreceptors in aortic body and stretch receptors in the wall of aortic arch.

Cell bodies in the inferior ganglion of X, passes through jugular foramen.

59
Q

Describe the special sensory of the vagus nerve (CN X)? What is its path?

A

Taste from epiglottis.

Cell bodies in the inferior ganglion of X, passes through the jugular foramen.

60
Q

Describe the motor portion of the vagus nerve (CN X)? What is its path?

A

Branchial motor for speech.

Cell bodies in the nucleus ambiguus (some are cranial roots) and passes through the jugular foramen.

61
Q

What structures are innervated by the motor portion of the vagus nerve (CN X)?

A

Skeletal muscles of the soft palate (except stylopharyngeus and tensor veli palatini)

Pharyngeal constrictor muscles 
Levator veli calatini 
Salpingopharyngeus
Palatoglossus
Cricothyroid
Muscles of the larynx
62
Q

What can result from injury to the motor portion of the vagus nerve?

A

Sagging soft palate, difficulty swallowing, coughing, and clearing throat.

Dysphagia (due to paralysis of muscles of the soft palate)

63
Q

Describe the “relay race” of autonomic nervous system neurons?

A

Cell bodies of the preganglionic neurons in the brain nucleus or sp. cd. gray matter are the starting line.

Preganglionic fibers travel with the cranial nerves (runners).

Pregang synapse onto postganglionic neurons whose cell bodies are i na peripheral nucleus (baton exchange).

Postgang fibers travel with CNs (second runner).

Postgang fibers innervate target organs which respond (celebrate).

64
Q

Describe the relay race of cranial nerve III (oculomotor)?

A

Cell bodies in the upper midbrain (edinger-westphal nucleus)

Pregang travel with CN III and synapse with postgang cell bodies in ciliary ganglion attached to V1.

Postgang fibers travel with short ciliary nerves to the sphincter pupillae to cause pupil contriction and the ciliary muscle for lens accomodation.

65
Q

What can result from injury to the oculomotor nerve (CN III)?

A

Mydriasis (pupil dilation) due to paralysis of sphincter pupillae muscle.

Loss of accommodation.

66
Q

What results from injury to CN VII (facial nerve) distal to the stylomastoid foramen?

A

Facial muscle paralysis

67
Q

What results from injury to CN VII (facial nerve) proximal to the branching off of chorda tympani?

A
  1. Facial muscle paralysis
  2. Loss of taste in anterior 2/3 of tongue
  3. Loss of salivation from sublingual and submandibular glands
68
Q

What results from injury to CN VII (facial nerve) distal to the geniculate ganglion?

A
  1. Facial muscle paralysis
  2. Loss of taste in anterior 2/3 of tongue
  3. Loss of salivation from sublingual and submandibular glands
  4. Hyperacusis (sensitivity to loud sounds) due to paralysis of stapedius
69
Q

What results from injury to CN VII (facial nerve) with involvement of the greater petrosal nerve?

A
  1. Facial muscle paralysis
  2. Loss of taste in anterior 2/3 of tongue
  3. Loss of salivation from sublingual and submandibular glands
  4. Hyperacusis (sensitivity to loud sounds) due to paralysis of stapedius
  5. Loss of taste
  6. Loss of lacrimation
70
Q

Describe the location of cell bodies, route of pregang, postgang, and target organ response of the facial nerve to the lacrimal gland.

A

Cell bodies in the superior salivatory nuleus.

Preganglionic fibers through nervous intermedius and geniculate ganglion via the greater pretrosal nerve to the nerve of pterygoid canal.

Postgang cell bodies at the Pterygopalatine ganglion (attached to V2) and
Postgoing fibers via zygomaticotemporal (V2) and lacrimal n (V1)

Target organ: lacrimal gland and mucosa of nasal cavity. Results in lacrimation.

71
Q

What can result from injury of the facial nerve (CN VII) that goes to the lacrimal gland?

A

Loss of lacrimation leading to cry cornea.

72
Q

Describe the location of cell bodies, route of pregang, postgang, and target organ response of the facial nerve to the salivary gland (except parotid)?

A

Cell bodies in the superior salivatory nucleus.

Pregang fibers through nervous intermedius and geniculate ganglion via the chorda tympani (VII) and joins the lingual n. (V3)

Postgang cell bodies in the submandibular ganglion attached to V3).

Travel to submandibular and sublingual salivary glands to cause salivation.

73
Q

Describe the location of cell bodies, route of pregang, postgang, and target organ response of the glossopharyngeal nerve (CN IX)?

A

Cell bodies in the inferior salivatory nucleus. Preganglionic fibers exit the brain with CN IX fibers and pass through the tympanic n. and lesser petrosal n.

Postgang cell bodies travel via the auriculotemporal n. and go to the parotid gland to cause salivation.

74
Q

Describe the location of cell bodies, route of pregang, postgang, and target organ response of the vagus nerve?

A

Cell bodies in the dorsal motor nucleus of X in the medulla.

Pregang fibers travel with CN X.

Postgang cell bodies are located in autonomic ganglia near or within the walls of the target organ.

Target is smooth muscle and glands of the GI tract, pulm, and CV systems.

Anatomy - Head and Neck (13 decks)

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