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Anatomy 6512 > CN V & VII > Flashcards

CN V & VII Flashcards

1
Q

Select the correct pair.
A) Trochlear nerve: Exits brainstem posteriorly
B) Oculomotor nerve: Superior oblique muscle
C) Abducens nerve: Inferior oblique
D) Lateral rectus: Eye adduction
E) Inferior rectus: Eye elevation

A

A) Trochlear nerve: Exits brainstem posteriorly

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2
Q

Select the correct statement.
A) Oculomotor nerve injury results in a mild deficit of eye movement
B) Trochlear nerve injury results in a large deficit of eye movement
C) Abducens injury results in medial strabismus
D) Oculomotor nerve injury results in a constricted pupil due to interruption of sympathetic fibers

A

C) Abducens injury results in medial strabismus

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3
Q

Select the correct statement about the pupillary reflex.
A) Efferent limb is the oculomotor nerve
B) Afferent limb is retina ganglion cell fibers in cranial nerve II
C) Input from cranial nerve II is sent to the Edinger Westphal nucleus bilaterally
D) Postganglionic fibers from the ciliary ganglion innervate the iris and supply the sphincter muscle of the pupil
E) All the above are true

A

E) All the above are true

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4
Q

Accommodation includes:
A) Contraction of the ciliary muscle to allow the lens to thicken centrally
B) Convergence of eyes by slight increase in medial rectus muscle tone bilaterally
C) Contraction of sphincter pupillae to constrict pupils
D) All the above are part of accommodation

A

D) All the above are part of accommodation

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5
Q

What is the main general sensory nerve for the head?

A

V

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6
Q

CN V transmits tactile, proprioceptive, pain and temperature from …

A

head to cortex, cerebellum, reticular formation

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7
Q

What are the 3 divisions of CN V?

A

1) Ophthalmic division (Vi), (V1)
- Upper face
- Sensory only
2) Maxillary division (Vii), (V2)
- Middle face
- Sensory only
3) Mandibular division (Viii), (V3)
- Lower face
- Sensory and Motor

*Sharp borders between divisions; varies among individuals

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8
Q

What are the trigeminal nuclei?

A

1) Midbrain - Trigeminal mesencephalic nucleus
2) Rostral Pons - Trigeminal principal
sensory nucleus, Trigeminal motor nucleus
3) Rostral Pons/Medulla - Trigeminal spinal
nucleus

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9
Q

What do Trigeminal Ascending Projections run from and to?

A

From: Trigeminal spinal nucleus
Contralateral projection to:
-Ventral posteromedial nucleus of thalamus (VPM)
-Internal capsule
-Postcentral gyrus parietal lobe (Brodmann’s Areas 3,1,2

From: Main trigeminal sensory nucleus
Bilateral projection to:
-Ventral posteromedial nucleus of thalamus (VPM)
-Internal capsule
- Postcentral gyrus parietal lobe (Brodmann’s Areas 3,1,2)

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10
Q

What are the Trigeminal Nerve Functional Components?

A
  • Sensory afferent - Region served:
    1) Face
    2) Oral cavity, teeth
    3) Meninges
  • Cell bodies: Trigeminal ganglion
    Terminates in: Main trigeminal sensory nucleus
    Senses: Discriminative touch and vibration
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11
Q

True or false: The sensory nuclei of CN V form a column of cells that is almost continuous through the brainstem.

A

True

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12
Q

True or false: The main sensory nucleus of CN V is at about mid-pons and is a bit lateral to the trigeminal motor nucleus

A

True

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13
Q

The spinal nucleus of CN V extends caudally into the ____

A

medulla

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14
Q

Mesencephalic nucleus extends into midbrain. It is rather thin and is accompanied by the mesencephalic trigeminal tract. The mesencephalic nucleus is odd in that is contains pseudounipolar neurons as seen in dorsal root ganglia of the cord, so it is as if a bit of a ganglion somehow got incorporated into the CNS. Myelinated processes from these pseudounipolar neurons form the mesencephalic tract. The peripheral processes go to …

A

spindles of muscles of mastication, mechanoreceptors of teeth, gums and hard palate.

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15
Q

What does main sensory nucleus of V sense?

A

Discriminative tactile (face and oral cavity) and some proprioception (jaw position)

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16
Q

What are the two ascending pathways of V main sensory nucleus?

A

Crossed pathway joins medial lemniscus on its way to VPL

Uncrossed, dorsal trigeminal tract, inside of mouth represented to VPM (ends near uncrossed taste pathway)

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17
Q

True or false: V main sensory nucleus is a homologue of posterior column nuclei

A

true

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18
Q

What are the functions of the Spinal trigeminal nucleus?

A

Nucleus blends with posterior horn of cord and divided into three segments based on histology

Functional differences between three parts is incompletely understood but still some functional correlations are possible

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19
Q

What are the three parts of the Spinal trigeminal nucleus?

A

1) Pars Oralis: Receives input from intraoral and perioral structures
2) Pars interpolaris proper
Activation of trigemino-autonomic reflexes
3) Caudalis-Interpolaris transition zone
Not somatotopically organized
Responds to pain stimuli from many areas served by V
May be involved in activation of pain suppression mechanisms

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20
Q

What fibers target Pars Caudalis?

A

fibers mediating:
Pain
Crude touch
Temperature sensation

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21
Q

What structures does Pars Caudalis supply?

A
  • Superficial structures including oral cavity and teeth
  • Deep structures including jaw muscles and TMJ
  • Convergence may be basis for referred pain
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22
Q

Select the correct pair.
A) Main trigeminal sensory nucleus: Posterior column- medial lemniscus system for head
B) Spinal trigeminal nucleus: Pain and temperature for head
C) Spinal trigeminal tract: Contains descending fibers from cell bodies in trigeminal ganglion
D) Spinal mesencephalic nucleus: Proprioception for jaw muscles
E) All of the pairs above are correct

A

E) All of the pairs above are correct

23
Q

Spinal trigeminal afferents descend thru ….

A

spinal trigeminal tract and synapse in caudal nucleus

24
Q

Spinal trigeminal second order neurons sends axons across …

A

midline, ascend and join spinothalamic tract, terminates in VPM

25
Q

Describe Pars Caudalis?

A
  • Laminar structure
  • Blends with posterior horn of cervical cord
  • Somatotopic organization
    1) Inverted representation of face
    2) ‘Onion Peel’ representation – rostral (oral) to caudal (peripheral face)
    3) Primarily pain fibers
  • Substantia gelatinosa (Lamina II)
    1) Contains excitatory and inhibitory interneurons
    2) Receives raphe spinal tract fibers (serotonin)
  • Receives afferents from cranial nerves
    1) VII, IX & X – all for area near ear
26
Q

What is the Somatotopic arrangement of pain-temperature afferents in Pars Caudalis?

A

1) Mandibular division: dorsal
2) Ophthalamic: ventral
3) Maxillary: in between
4) Fibers representing center of face end near obex
5) Fibers representing back of the face end in upper cervical cord

27
Q

What is the “Onion skin distribution of sensory loss”?

A

More caudal the spinal trigeminal tract injury the larger the area around the mouth that is spared of sensory loss

28
Q

Clinical correlation: Tooth pulp

A

1) 70 – 80% of fibers are A-delta (fast pain, thermal) and C (slow pain, itch, touch)
2) 20 – 30% of fibers are A-beta (spindle, touch & pressure)
From inferior alveolar nerves, enter root canals and form plexus in pulp, predentin and dental tubules
3) Fibers project to:
Trigeminal main sensory nucleus (heaviest projection - shared)
Trigeminal spinal nucleus
A) Pars oralis (heaviest projection – shared)
B) Pars interpolaris (modest projection)
C) Pars caudalis (light projection)
Upper cervical spinal cord

29
Q

Describe Trigeminal neuralgia?

A
  • Brief, episodes of excruciating pain in distribution of one (can be more) division of the trigeminal nerve
  • Mandibular division 70%
  • Ophthalmic division < 5%
  • No sensory trouble between attacks
  • Often a tactile stimulus triggers an attack
  • A number of cases due to trigeminal compression by a vessel, tumor etc.
  • Often responds to medications.
30
Q

What are the trigeminal neuralgia surgeries and results?

A

Surgical procedures include cutting nerve root, introducing a lesion in trigeminal ganglion

Result: loss of all tactile sensation not just pain to the area

Also
- Section spinal trigeminal tract slightly caudal to obex
- Remove afferents to caudal nucleus
A) Tactile sensation is intact (main sensory nucleus)
B) Abolishes pain sensation over half of the face
- High mortality rate: Compromise medullary cardiovascular & respiratory centers

31
Q

What is microvascular decompression?

A

Branches of the superior cerebellar artery are most frequently involved in cases of trigeminal neuralgia that due to vascular cause

32
Q

Select the true statement.
A) Trigeminal neuralgia cases due to vascular causes are often attributed to branches of the posterior cerebellar artery
B) Trigeminal neuralgia attacks are often precipitated by a tactile stimulus
C) Trigeminal neuralgia patients experience severe pain between attacks
D) The somatotopic arrangement of fibers entering the main trigeminal sensory nucleus lead to the onion-skin pattern of sensory loss
E) None of the above are true

A

B) Trigeminal neuralgia attacks are often precipitated by a tactile stimulus

33
Q

What are sensory afferent functional components of trigeminal nerve?

A
  • Cell bodies: Trigeminal mesencephalic nucleus
  • Centrally directed process terminates in:
    a) Trigeminal motor nucleus - jaw jerk reflex
    b) Supratrigeminal nucleus - chewing movements
  • Senses: proprioception; spindles in muscles of mastication, mechanoreceptors in gums, teeth and hard palate
34
Q

What is the function of the Mesencephalic nucleus?

A

Proprioception

35
Q

Describe the mesencephalic nucleus.

A
  • Receptors:
    Neuromuscular spindles of mastication muscles
    Pressure/tension receptors in periodontal ligaments
  • Cell body of origin:
    Unipolar cell bodies
    Trigeminal mesencephalic nucleus
  • Projects to:
    Trigeminal motor nucleus
    Supratrigeminal nucleus (masticatory generator)
  • Controls distance between mandible and maxilla
    Occlusal vertical dimension (vertical dimension of occlusion)
36
Q

What is the trigeminal branchial motor?

A 
- Cell bodies: Trigeminal motor nucleus
Terminates in: Muscles of mastication
Function: Jaw closure
Lesion:
Jaw closure is weakened
a) Opened jaw will deviate 
b) toward side of lesion
37
Q

Where/what is the Supratrigeminal nucleus?

A
  • Near V motor nucleus
  • Actually part of reticular formation
  • Pattern generator for masticatory rhythm
38
Q

What does Trigeminal motor nucleus innervate?

A

Innervates muscles of mastication, tensor tympani and tensor palati (“MOM & the tensor twins”)

39
Q

What does Branchial motor nucleus innervate?

A

1st arch muscles

40
Q

Jaw-jerk reflex

A
  • Monosynaptic reflex
  • Downward tap on chin, stretches masseter
  • Afferent limb: mesencephalic V neuron innervating masseter spindle
  • Efferent limb: V motor nucleus
  • Like other reflexes it is enhanced with UMN damage, used to determine level of injury
41
Q

Select the true response.
A) Cell bodies sending fibers to masseter muscle spindles are located in the mesencephalic nucleus
B) Fibers from the trigeminal ganglion synapse in the main sensory nuclei
C) Fibers from the trigeminal ganglion synapse in the spinal trigeminal nucleus
D) Fibers from the trigeminal motor nucleus innervate muscles of mastication
E) All the above are true

A

E) All the above are true

42
Q

What are major connections of CN V?

A

1) Peripheral branches of mesencephalic neurons innervate masseter muscle spindles and other mechanoreceptors
2) Tactile afferents
3) Motor neuron fibers: muscles of mastication
4) Pain-temperature afferents

43
Q

What are the actions of CN VII?

A

1) Muscles of facial expression
- Closes eye
- Closes lips
2) Stapedius muscle
- Modulates sound volume
3) Taste: Anterior 2/3 of tongue
4) Sensory: Palatine tonsil & posterior nasal cavity
- Geniculate ganglion
- Solitary nucleus
5) Salivation
6) Lacrimation
- Lubricates cornea

44
Q

What are the somatic sensory functions of CN VII?

A
  • Skin of outer ear
  • Fibers enter spinal trigeminal tract, dorsomedially situated
  • Act exactly as trigeminal afferents
45
Q

Facial nerve functions include.
A) Innervation of Orbicularis oculi and Orbicularis oris muscles
B) Lubrication of the cornea
C) Produce saliva from submandibular gland
D) Sensory information from skin of outer ear
E) All the above

A

E) All the above

46
Q

Corticobulbar pathway lesions

A

Selective weakness of lower facial muscles

47
Q

Bell’s palsy

A

1) Type of unilateral (80%)
-Some denture wearers experience discomfort
2) Cause unknown, by definition
3) Believed to be an inflammatory condition resulting in facial nerve swelling in facial canal
4) Commonly shows rapid onset with partial or complete paralysis; can occur overnight
5) Usually improves over time and function restored, normal or near-normal function restored most of the time, steroids improve outcome
6) Paresis of facial muscles above & below the eye
7) Irritation of the cornea
Often eye on affected side cannot be closed, must be protected from drying, permanent corneal damage may result
8) Hyperacusis (stapedius)
9) Reduced lacrimation & salivation

48
Q

Corneal blink reflex

A

1) Touch cornea and both eyes blink
2) Afferent limb: Vi to SpV tract
3) Efferent limb: VII elicited by bilateral projection from SpV nucleus/ reticular formation
4) Clinical test of V, VII & central connections

49
Q

Jaw opening & closing reflexes

A

1) Jaw closing reflex
Food in contact with oral membranes
2) Jaw opening reflex
Periodontal afferents activated by dental occlusion
Pain afferents from mucosal membranes
3) Input (VII) from:
Jaw muscles (proprioception – trigeminal mesencephalic nucleus)
Tactile information (food in mouth – trigeminal main nucleus)
Pain information (trigeminal spinal nucleus)
4) Output (VII) to:
Muscles of mastication

50
Q

Select the correct pair.
A) The afferent limb of the jaw-jerk reflex is mesencephalic fibers; the efferent limb is motor of VII
B) The afferent limb of the blink to light reflex is cranial nerve II; the efferent limb is oculomotor nerve
C) The afferent limb of the sound attenuation reflex is the cochlear nucleus; the efferent limb is motor VII
D) The afferent limb of the jaw closing reflex is V; the efferent limb is VII
E) All of the above are correct pairs

A

C) The afferent limb of the sound attenuation reflex is the cochlear nucleus; the efferent limb is motor VII

51
Q

Taste

A

1) Complex sensation; not just taste bud information
2) Flavor is due to:
-Direct chemical stimulation of taste buds
-Olfactory receptors respond to food vapors
-Chemosensitive and somatosensory free nerve endings of V (IX & X) in mucus membranes of oral cavity
Respond to temperature, spiciness, texture of food

52
Q

Taste buds: distribution and innervation

A
  • Average tongue has about 5000 taste buds, but number of papillae and taste buds is highly variable
  • Some have 100x more taste buds in fungiform papillae than others do
  • Likely accounts for 100-fold variation in threshold concentration of various substances among people
53
Q

Where is Nervus Intermedius?

A

Aligns with VII nerve distal to genu

54
Q

Taste pathways in the CNS

A
  • Gustatory afferents reach nucleus of the solitary tract via the solitary tract
  • Second order fibers do 2 things:
    1) Reflex activities: swallowing, salivation
    2) Project uncrossed to thalamus (VPM), then to gustatory cortex (insula, medial surface of frontal operculum)
  • Gustatory cortex projects to orbitofrontal cortex, integrated there with olfactory info, reaches amygdala, from there to limbic system & hypothalamus

Anatomy 6512 (26 decks)

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