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Neurology > CN V, VII, IX, X, XI, XII > Flashcards

CN V, VII, IX, X, XI, XII Flashcards

1
Q

Location of CN V nuclei?

A

-mid pons level

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2
Q

CN V

A

trigeminal nerve

-mixed motor & sensory

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3
Q

CN V Motor Fibers

A

-travel via its mandibular V3 branch to exit the calvarium via the foramen ovale

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4
Q

CN V (motor) innervates?

A
  • muscles of mastication (masseter & temporalis muscles)
  • tensor tympani (dampens sound)
  • tensor veli palatini (opens eustachian tube)
  • mylohyoid (elevates hyoid bone)
  • anterior belly of digastric (elevates hyoid)
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5
Q

What level does CN V exit the brainstem?

A

-mid pons level

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6
Q

Jaw Reflex

A

“jaw jerk”

  • tapping on lower jaw triggers muscle spindles in the masseter muscle to send an impulse through the sensory fibers of sensory cranial nerve V & synapsing in the mesencephalic nucleus of V
  • a short interneuron connects w/the motor nucleus of V to send an impulse to the masseter muscle to contract
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7
Q

How to test motor CN V?

A

-have patient bite down on a tongue depressor & test jaw strength; palpate the masseter & temporalis muscles (bilaterally)

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8
Q

Lesions of CN V or nuclei cause?

A
  • unilateral weakness of jaw closure, reduced jaw jerk, & atrophy of temporalis & masseter muscles
  • bilateral innervation (so unilateral lesion does not produce unilateral weakness, may inc. jaw jerk)
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9
Q

CN VII

A

Facial Nerve

-mixed motor, parasympathetic, sensory nerve

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10
Q

Location of CN VII motor nuclei?

A

-facial nucleus that lies at the mid pons level

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11
Q

CN VII innervates?

A

-muscles of facial expression & several smaller muscles (stapedius - dampens sound)

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12
Q

Superior Salivatory Nucleus

A

-lies near midline of rostral medulla & sends preganglioinic, parasympathetic fibers through to the nervus intermedius to join CN VII to synapse in various ganglia with secondary innervation of the lacrimal & salivary glands

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13
Q

How does CN VII exit the brainstem?

A

-at pontomedullary junction in a region called the cerebellopontine angle (initially pass dorsal medially & lop over the abducens nucleus)

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14
Q

Facial Colliculus

A

-the bulge on the floor of the 4th ventricle created from the facial nucleus axons

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15
Q

How does CN VII exit the calvarium?

A
  • via the auditory canal
  • opening is the internal auditory meatus
  • in auditory canal it bends ventrally to enter the facial canal & exits the skull via the stylomastoid foramen
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16
Q

How do you test CN VII?

A
  • ask patient to wrinkle their forehead, close their eyes tightly, and show their teeth
  • look for symmetric furrowing, close eyes, and retraction of mouth corners
  • note width of palpebral fissure b/c weakness of orbicularis oculi muscle will cause widening of eye opening at rest
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17
Q

CN VII Lesions?

A
  • bilateral for forehead, unilateral for lower face
  • unilateral lesions to motor cortex or corticobulbar fibers causes unilateral weakness of contralateral lower face muscles but spares the forehead
  • unilateral lower motor neuron: ipsilateral weakness of the lower face & forehead muscles, ipsilateral weakness & dry eye (Bell’s palsy - cause)
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18
Q

Corneal Reflex

A
  • motor VII controls efferent arm

- gently stroking cornea & observing eye closure

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19
Q

CN IX

A
  • glossopharyngeal nerve

- mixed motor, parasympathetic, sensory nerve

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20
Q

What serves the motor component of CN IX?

A

-nucleus ambiguus that lies near junction of pons & medulla

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21
Q

What does CN IX innervate?

A
  • stylopharyngeus muscle
  • parotid gland
  • elevate the pharynx during talking & swallowing
  • participates along with CN X in the motor (efferent) component of the gag reflex so testing the motor function of CN IX is difficult clinically
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22
Q

Inferior Salivatory Nucleus

A

CN IX
-lies near midline of medulla & sends preganglionic, parasympathetic fibers through CN IX to the lesser petrosal nerve to synapse in the otic ganglion with secondary innervation of the parotid gland

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23
Q

Where does CN IX exit the brainstem?

A

-at the junction between the pons & the medulla

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24
Q

Where does CN IX exit the calvarium?

A

-via the jugular foramen

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25
Q

CN IX lesions?

A

-upper & lower motor neuron lesions may produce dysphagia

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26
Q

CN X

A
  • vagus nerve

- mixed motor, parasympathetic, & sensory nerve

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27
Q

Motor Component of CN X

A
  • nucleus ambiguus that lies near the lateral medulla that innervates muscles of soft palate, pharynx, & larynx (elevate pharynx during talking)
  • dorsal motor nucleus lies near the midline of the medulla & sends preganglionic, parasympathetic fibers to the intramural ganglia associated with the heart, lung, & digestive tract
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28
Q

Where does CN X exit the brainstem?

A

-exits as a series of rootlets b/w the inferior olive & the inferior cerebellar peduncle

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29
Q

How does CN X exit the calvarium?

A

-via the jugular foramen

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30
Q

Lesions of CN X?

A
  1. Unilateral involving nucleus ambiguus or CN X will cause hoarseness, dysphagia, & inability to elevate the palate on the ipsilateral side
  2. Unilateral Upper Motor Neuron lesions cause less prominent symptoms b/c there is substantial bilateral upper motor neuron innervation of CN X nuclei
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31
Q

What does the dorsal motor nucleus of the vagus & its parasympathetic fibers influence?

A

-autonomic functions including HR, respiration, & digestion

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32
Q

CN XI

A
  • spinal accessory nerve

- pure motor nerve

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33
Q

CN XI controls?

A
  • head turning through innervation of the sternocleidomastoid muscles
  • shoulder elevation through trapezius muscels
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34
Q

CN XI receives motor axons from?

A
  • caudal portion of nucleus ambiguus and the spinal accessory nucleus
  • fibers traveling from ambiguus travel for only a short distance with CN XI before joining with CN X to innervate the pharynx & larynx
  • spinal accessory nucleus is comprised of neurons that lie in the intermediolateral gray area b/w the dorsal & ventral horns of the first 4-5 segments of teh cervical cord, fibers from accessory exit the cord b/w the dorsal & ventral roots & ascend alongside the spinal cord, enter the calvarium through the foramen magnum & exit through jugular foramen
35
Q

How does CN XI exit the brainstem?

A

-the lower medulla & upper spinal cord & joining together to form the spinal accessory nerve

36
Q

Entry & Exit of CN XI to calvarium?

A
  • entry via foramen magnum

- exit via the jugular foramen

37
Q

Lesions of CN XI?

A
  • unilateral lesions of CN XI or motor nuclei (lower) produce weakness & atrophy of both muscles ipsilateral to the lesion, thus there will be weakness of elevating the ipsilateral shoulder and ipsilateral SCM turning the head away from the lesion side
  • unilateral upper motor will cause weakness contralateral shoulder elevation & weakness of ipsilateral SCM muscles, weakness in elevating right shoulder and turning head right (left SCM)
38
Q

CN XII

A
  • hypoglossal nerve

- pure motor nerve

39
Q

CN XII controls?

A
  • tongue movement
  • served by hypoglossal nucleus that lies near the midline in the mid to posterior portion of the medulla
  • innervates all intrinsic & extrinsic tongue muscles
40
Q

How does CN XII exit the brainstem?

A

-ventrally b/w the inferior olives and the pyramids

41
Q

Where does CN XII exit the calvarium?

A

-hypoglossal foramen that lies along the posterior aspect of the petrous temporal bone

42
Q

Primary axons of CN XII?

A

-come from hypoglossal nucleus & find their path to the tongue

43
Q

CN XII lesions

A
  • contraction of tongue muscles on the left pushes the tongue out the mouth toward the right
  • unilateral lesions will produce tongue protrusion towards the side of the lesion, unilateral atrophy & fasciculations
  • corticobulbar fibers from motor cortex cross over to control the contralateral CN XII motor nuclei, thus upper motor neuron lesions will cause the tongue to deviate away from the lesion
44
Q

Nuclei dorsal to the sulcus limitans are?

A

sensory (afferent), alar plate, more lateral

45
Q

Nuclei ventral to the sulcus limitans are?

A

motor (efferent), basal plate

46
Q

3 Sensory Nuclei for the Trigeminal

A
  • chief sensory
  • spinal
  • mesencephalic
47
Q

Chief Nuclei

A
  • discrete nuclei in the rostral pons, receives epicritic inputs from afferents for fine touch & vibration sense from the face (like posterior column nuclei)
  • epicritic afferents in the trigeminal nerve have their cell bodies in the trigeminal ganglion, its located outside of the brainstem & is analogous to the dorsal root ganglia associated with the spinal cord
  • the central process of these cells synapse in the chief sensory nucleus (fine touch afferents that run in other cranial nerves (VII, IX, X) have cell bodies in different peripheral ganglia but also synapse in the chief sensory nucleus of V
48
Q

Mesencephalic Nuclei

A
  • discrete nuclei in the mesencephalon
  • contains the cell bodies of proprioceptive afferents from the muscles of mastication
  • essentially a displaced peripheral ganglion in the tegmentum of the mesencephalon (peripheral processes of these cells forms the mesencephalic tract)
49
Q

Spinal Nuclei

A
  • extends as a column from the mesencephalon to the spinal cord where it is continuous with the substantia gelatinosa of the spinal cord (layers I & II of dorsal horn)
  • several cranial nerves (V, VII, IX, X) project into this nucleus
  • receives inputs from pain & temp afferents for the face that run in cranial nerve V as well as cranial nerves VII, IX, & X
  • pain & temp afferents in branches of V have their cell bodies in the trigeminal ganglion, the central processes of these cells project into & synapse in the spinal nucleus of V, these axons (& 2nd order axons from spinal nucleus of V) run in the associated spinal tract of V
50
Q

Vestibular Nuclei

A

body position

CN VIII

51
Q

Cochlear Nuclei

A

hearing

CN VIII

52
Q

Nucleus Solitarius

A
  • Rostral Part: concerned with taste (VII, IX, X)

- Caudal part: concerned with cardiorespiratory inputs

53
Q

CN I

A
  • Olfactory Nerve

- sensory (olfaction)

54
Q

Path of CN I

A
  • sensory receptors reside in the nasal epithelium
  • cells send very fine axons (olfactory nerves or filae) through the cribriform plate to synapse in the olactory bulb
  • axons of projection neurons in the bulb travel as the olfactory tract to synapse in olfactory cortex, amygdala, & related forebrain structures
55
Q

Anosmia

A

condition marked by loss of the sense of smell

56
Q

CN II

A
  • optic nerve
  • sensory: transmits visual input to the brain
  • receptors are located in the retina, at the rear of the eye
  • made up of axons of retinal ganglion cells
57
Q

Optic Nerve Path

A
  • nerves from each eye converge just outside the mesencephalon
  • 50% of fibers from each eye cross to the opposite side of the body at the optic chiasm “cross”
  • central to the chiasm, the fibers run as the optic tract
  • the optic tract runs along the outside of the mesencephalon to the lateral geniculate body (visual thalmus: LGN), which in turn projects to primary visual cortex (banks of calcarine fissure)
  • some optic nerve fibers bypass the LGN & instead travel in the brachium “arm” of the superior colliculus to synapse in the superior colliculus (tectum of mesencephalon)
  • input is important for visual “startle” reflexes
58
Q

3 Branches of CN V

A 
V1 = opthalmic
V2 = maxillary
V3 = mandibular
59
Q

CN V does what besides innervation of the muscles of mastication?

A
  • fine touch
  • proprioception
  • pain & temperature afferents from the skin of the face region
60
Q

Back of the head is mostly innervated by?

A

-spinal nerves from C2

61
Q

Chief Sensory Nucleus

A

-the first integration center for all fine touch and vibration inputs for the face region

62
Q

Trigeminal Lemniscus

A
  • runs from the chief sensory nucleus of V to the ventroposteromedial nucleus (VPM) of thalamus
  • analogous to the medial lemniscus for spinal pathways
63
Q

Trigeminothalamic Tract

A
  • runs from the spinal nucleus of V to the VPM

- analogous to the spinothalamic tract for spinal pathways

64
Q

Somatotopy in Spinal Nucleus of V

A
  • afferents from the different cranial nerves & nerve branches remain segregated within the spinal tract & nucleus of V (somatotopic organization)
  • afferents from VII, IX, X are most dorsal
  • afferents from V3 are next (posterior)
  • afferents from V2
  • afferents from V1 are most ventral (anterior)
65
Q

Trigeminal: Cell bodies of Proprioceptive

A
  • afferents from muscles of mastication are located in the mesencephalic nucleus of V
  • these cells project bilaterally to the trigeminal motor nucleus to mediate monosynaptic stretch reflexes
66
Q

Trigeminal: Cell bodies of Fine touch & VIbration

A
  • afferents are located in ganglia outside of the brainstem (especially for trigeminal ganglion but also geniculate for VII, for inferior & superior glossopharyngeal for IX, inferior & superior vagal for X)
  • the central processes of these cells project to the chief sensory nucleus of V
  • second order projections from this nucleus cross the midline & travels in the trigeminal meniscus to the VPM (thalamus)
67
Q

Trigeminal: Cell bodies of Pain & Temperature

A
  • afferents are located in various ganglia
  • several cranial nerves contribute to this nucleus (V, VII, IX, X)
  • their central processes project into the spinal tract of V & synapse in the spinal nucleus of V
  • the second order projections cross the midline & travel in the trigeminothalamic tract
68
Q

Sensory Component of CN VII

A
  • taste sensation for the anterior 2/3 of the tongue
  • somesthetic afferents (fine touch, vibration, pain, & temperature) for a small area around the external auditory meatus
  • cell bodies for somesthetic afferents are located in the geniculate ganglion
  • central processes project to the chief sensory nucleus of V (epicritic) or spinal nucleus of V (pain & temp)
69
Q

Nucleus Solitarius

A
  • runs as a column through the pons & medulla
  • rostral portions of this nucleus are also called the gustatory nucleus and are concerned with taste sensation
  • gustatory nucleus receives inputs from CNs VII, IX & X
70
Q

Rostral Part of Nucleus Solitarius

A
  • is the gustatory nucleus
  • receives taste input from CNs VII (anterior 2/3 of tongue), IX (posterior 1/3 of tongue), and X (pharynx and epiglottis)
71
Q

Caudal part of the solitary nucleus

A
  • known as the cardiorespiratory nucleus

- receives visceral sensory input (glands, chemo/baroreceptors) carried by CNs VII, IX, and X

72
Q

CN VIII

A
  • vestibulocochlear
  • has one functional component (sensory) with 2 divisions:
    1. Vestibular (balance & acceleration)
    2. Auditory (hearing)
73
Q

CN VIII & Ear

A
  • sensory afferents for audition & vestibular sense are located in the inner ear
  • auditory receptors (hair cells) are located in the organ of Corti in the cochlea
  • these receptors are sensitive to airborne pressure waves, as transduced into fluid waves in the cochlea
  • depending on location in the cochlea, these receptors are tuned to different frequencies of sound (tonotopic organization)
  • auditory afferents travel in CN VIII
74
Q

Vestibular Receptors

A
  • Hair cells, located in the saccule, utricle, & three semicircular canals
  • vestibular afferents also travel in CN VIII
75
Q

Spiral Ganglion (hair cell tract)

A
  • contain cell bodies of auditory afferents
  • cells send axons in CN VIII to synapse in the dorsal & ventral cochlear nuclei (send axons in the cochlear division of the vestibulocochlear nerve)
  • hair cells synapse here
  • cochelar nerve fibers synapse in the ipsilateral dorsal & ventral cochlear nuclei (at pontomedullary junction)
  • from this point, auditory pathways ascend bilaterally to the inferior colliculus
  • neurons project in turn to the medial geniculate body (auditory thalamus)
  • the medial geniculate projects to auditory cortex (Heschel’s gyrus: transverse gyri in superior temporal lobe
76
Q

Organ of Corti

A

-comprised by hair cells & supporting cells

77
Q

CN VIII: Vestibular Division

A
  • the other division of CN VIII is vestibular
  • important for adjustment of posture, regulating muscle tone, and coordination of eye movements
  • hair cells are located in the semicircular canals, saculle & vestibule
  • hair cells synapse on cells in vestibular ganglion (Scarpa’s ganglion)
  • these cells send their axons in the vestibular division of the vestibulocochlear nerve
78
Q

Vestibular Pathways

A

-axons of cells from vestibular ganglion synapse in the vestibular nuclei (located in the pons & rostral medulla, near floor of 4th ventricle)

79
Q

4 Vestibular Nuclei

A

-superior, lateral, medial, inferior
Lateral: gives rise to the lateral vestibulospinal tract, a descending motor pathway (balance & extensor tone)
-Medial: arises from the medial & inferior vestibular nuclei (only extends to cervical levels of the cord & helps control neck & head position)
-Medial & Vestibular nuclei contribute to the medial longitudinal fasciculus (MLF) (important for eye movements)

80
Q

CN IX sensory function

A

-mediates taste from the posterior 1/3 of tongue, somatic sensation from the pharynx & posterior 1/3 of tongue, chemo/baroreception from the carotid sinus & carotid bodies, & fine touch & pain & temp. from the middle ear & a portion of the external ear

81
Q

CN IX

A
  • associated with several nuclei in the brainstem
  • nerve sub serves taste from posterior 1/3 of the tongue
  • these afferents terminate in the rostral solitary tract (gustatory nucleus)
  • afferents from baroreceptors (carotid sinus) & chemoreceptors (carotid body) are carried by IX and project to the caudal part of the solitary nucleus & tract
  • Nucleus Ambiguous is a motor nucleus containing neurons that project with CN IX & X
  • pain & temp afferents from post. 1/3 of tongue, pharynx, tonsils, tympanum, and a small area around the external ear travel in CN IX & project into the spinal tract & nucleus of V
  • afferent for epicritic touch for the post. 1/3 of the tongue, pharynx, tonsils, tympanum, and a small area around external ear travel in IX & project to the chief sensory nucleus of V
82
Q

Chemo & Baroreceptors

A

-afferents are carried by IX and project to the caudal part of the solitary nucleus & tract

83
Q

Sensory of CN X

A

-taste from pharynx & epiglottis (project to rostral solitary tract & nucleus) , visceral info from aortic arch baro and chemoreceptors (project to caudal solitary tract & nucleus) , somatic info from pharynx and larynx, post. meninges and touch & pain & temp from small portion of external ear (spinal tract & nucleus of V)

84
Q

Gag Reflex

A
  • to protect & clear airway in response to irritate to the palate, pharynx, & associated areas
  • afferent limb of this reflex is carried by afferents of CN IX projecting to the caudal solitary nucleus
  • an interneuron is interposed b/w the afferent & efferent in Nucleus Ambiguous
  • efferent response is mediated by mononeurons in N. Ambiguous whose axons travel with CN X

Neurology (18 decks)

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