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Neuroscience > Ch. 14: Cranial Nerves > Flashcards

Ch. 14: Cranial Nerves Flashcards

1
Q

How many pairs of cranial nerves are there?

A
  • 12 pairs
    • 11 exit anterior, 1 exits posterior…relative to brainstem
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2
Q

What do the cranial nerves innervate?

A

​Innervate head, neck, thorax, upper abdomen

(not lower abdomen)

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3
Q

What are the 4 basic functions of cranial nerves?

A
  1. Motor innervation.
  2. Somatosensory and special sensory innervation.
  3. Parasympathetic innervation
    • Head, neck, thorax, upper abdomen
  4. Corticobrainstem tracts: UMN’s of cranial nerve motor fxn
    • For those that innervate muscle - they are THEMSELVES the LMN’s
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4
Q

What is the name of Crainal Nerve I?

A

Olfactory

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5
Q

Is Cranial Nerve I sensory, motor or mixed?

A

Sensory

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6
Q

Where is the Olfactory NERVE itself contained?

A

Within the roof of the nasal sinus

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7
Q

Where is the Olfactory TRACT located?

A

Starts above the nasal sinus and travels back to the olfactory centers of the brain

(seen in gross disection)

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8
Q

What effect does traumatic brain injury of shaking have on Cranial Nerve I?

A
  • Can disconnect the nerve from the tract
    • Creates lack of smell
    • Can also lead to altered or lack of taste
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9
Q

What is the possible link between smell loss and Parkinson’s Alzheimer’s disease?

A

Could be an early sign of these diseases

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10
Q

What is the name of Cranial Nerve II?

A

Optic

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11
Q

Is Cranial Nerve II sensory, motor or mixed?

A

Sensory

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12
Q

What is the function of Cranial Nerve II?

A

Lets in light info from retina of eyeball

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13
Q

What is the path Cranial Nerve II (Optic) takes from the eye back to the brain?

A

Nerve → Chiasm → Tract

  • Nerve: Direct backward projection from the eye ball
  • Chiasm: Both cranial nerves come together at the mid line
  • Tract: Split apart again
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14
Q

In Cranial Nerve II (Optic), what information is sent from the optic tract to the occipital cortex?

A

Conscious vision

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15
Q

In Cranial Nerve II (Optic), what information is sent from the optic tract to the superior colliculus?

A

Uncoscious reflex responses

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16
Q

What dysfunctions are present with complete damage to Cranial Nerve II (Optic)?

A
  • Blindness
  • Disruption of pupillary light reflex
    • Shine light in eyes, no conscious or reflex function to constrict pupil
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17
Q

What are the names and numbers of the Cranial Nerves that are “Extraocular?”

A
  • Cranial Nerve III (Oculomotor)
  • Cranial Nerve IV (Trochlear)
  • Cranial Nerve VI (Abducens)
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18
Q

How many “extraocular” muscles are there?

A

6, three around each eye

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19
Q

What do the muscles innervated by CN III (Oculomotor) do?

A

Elevates, depresses and adducts eye

(everything the other two CN’s do not do)

[Dont need to know: Medial rectus, Superior rectus, Inferior rectus, Inferior oblique]

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20
Q

What do the muscles innervated by CN IV (Trochlear) do?

A

Move eye down toward tip of the nose

[Do not need to know: Superior Oblique]

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21
Q

What do the muscles innervated by CN VI (Abducens) do?

A

ABducts eye away from midline

[Do not need to know: Lateral Rectus]

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22
Q

What is the Medial Longitudinal Fasciculus?

A
  • Interconnects CN III, IV, & VI, vestibular nuclei, and spinal accessory nerve nuclei in brainstem
    • Connects all cranial nerve nuclei’s that move the eyes and connects all of those cranial nerves to vestibular nuclei or inner ear
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23
Q

What nucleus is responsible for Parasympathetic contribution to CN III?

A

Edinger-Westphal nucleus

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24
Q

What are the somatic actions of CN III?

A
  • adduct eyes
  • adjust pupil
25
Q

The parasympathetic innervation of the eye that travels with CN III innervates what two things to affect the eye?

A
  1. Pupillary Sphincter -> constricts pupil
  2. Ciliary Muscle -> Increase curvature of lens for near vision
26
Q

What is the Pupillary Light Reflex?

A
  • Constricts pupil to light
  • Relfex only
  • Optic (afferent) and occulomotor (efferent) nerves
    • Retina → brain stem (through midbrain) CN II → synapses w/ CN III → then goes right back to the eye
27
Q

What is the Consensual Light Reflex?

A
  • Light in one eye will constrict both pupils
  • Reflex only
  • Optic (afferent) and occulomotor (efferent) nerves
    • Retina → brain stem (through midbrain) CN II → synapses (parasympathetic) w/ CN III → then goes right back to the eye
28
Q

What is the Accommodation Reflex?

A
  • Compensation to focus in near vision
    • Driven by consciousness vision (routes from occipital region)
    • Pupils constrict
    • Eye converge (adduct)
    • Lens becomes more convex
29
Q

What are the dysfunctions associated with damage to CN III?

What does it look like?

A
  1. Ptosis - Drooping of eyelid
  2. Affected eye looks down and out - When CN III not working, CN VI ABducts the eye out
  3. Diplopia - Double vision - 2 images superimposed on top of each other
  4. Difficulty moving eye medially, downward and upward.
  5. Dilation of pupil - CN III has parasympathetic - if it is gone, SNS wins and dilates pupil with out any
  6. Loss of pupillary light reflex and consensual light reflex - Loss of near vision
  7. Loss of constriction of pupil for focus on near object.
30
Q

What are the dysfunctions associated with damage to CN IV?

What does it look like?

A
  1. Cannot look down and in.
  2. Extorsion (“tilted head”) due to unopposed action of inferior oblique - Eye rolls lateral to left so patient tilts head to right
31
Q

What are the dysfunctions associated with damage to CN VI?

What does it look like?

A
  1. Inability to abduct eye - Cranial nerve II wins
  2. Resting position of the eye drifts medially.
32
Q

What is the name of CN V?

A

Trigeminal Nerve

33
Q

What does CN V (trigeminal) do?

A
  • SENSORY
    • for tongue but not taste on tongue
    • for face and jaw movement
34
Q

How many branches does the Trigeminal N (CN V) have?

A
  • 3 branches (like Kenny’s hood)
    • Opthalamic - above eye (forehead)
    • Maxillary - cheek bone
    • Mandibular
35
Q

What messages are sent through the Afferent pathways of the Trigeminal N (CN V)?

A
  • Discriminative touch: face, eye, tounge
  • Proprioception
  • Nociception: fast pain & slow pain

(bottom picture)

36
Q

What messages are sent through the Efferent pathways of the Trigeminal N (CN V)?

A

Muscles of mastication

(top picture)

37
Q

What are the reflexes for Trigeminal N (CN V)?

A
  • Blink reflex - touch eyeball
    • CN V sensory (in), CN VII motor (out) - better ways to test CN VII out
  • Jaw jerk reflex - finger on chin, hit metacarpal, quick stretch jaw and it closes fast
    • Tests CN V (in and out) on reflex level
38
Q

What signs and sx’s are present with CN V (Trigeminal) Dysfunction?

A
  • Loss of touch, pain, temperature on face
    • Wont be able to feel all or part of their face
  • Possible loss of blink reflex
    • ​Cant feel eye
  • Possible loss of jaw jerk reflex (with jaw deviation toward the involved side on active opening).
  • Trigeminal Neuralgia (neuropathic pain in trigeminal nerve).
    • Deep dull aching (its going to kill me pain)
    • Breeze hitting skin can cause pain
39
Q

What signs and sx’s are present with CN V II (Facial) Dysfunction?

A
  • Motor function: muscles of facial expression.
  • Parasympathetic function: Salivary, nasal and lacrimal glands.
    • Helps you cry, mouth water, nose run
  • Sensory function: Taste sensation from anterior 2/3 of tongue.
    • Sweet, salty and sour
40
Q

How do you test CN VII (Facial)?

A
  • Squeeze tightly closed
  • Open eyes wide
  • Smile real big and show all teeth
  • Lips together, puff out cheeks
41
Q

What signs and sx’s are present with CN V II (Facial) Dysfunction?

A
  • Paralysis or paresis of all ipsilateral muscles of facial expression (Bell’s Palsy).
    • Traumatic mylenopathy - Not working short term
    • Traumatic axonopathy - Not working long term (couple weeks to months)
  • Lack of closing eye lid, does not produce enough tears -> may have dry eye
42
Q

What are the functions of CN VIII?

A
  • Sensory
  • 2 divisions
    • ​Vestibular division (head movement and position)
    • Cochlear division (hearing)
  • Transduction of sound
    • Sound waves created by water waves
  • Frequency Coding
    • Wide at one end, narrow at other
  • Auditory fxn within CNS
43
Q

What three places does sound travel too?

A
  • Inferior Colliculus
    • ​Orientation of head and eyes toward sound
  • Reticular Formation
    • Sounds can inc or dec arousal (ex: tires screeching)
  • Conscious awareness and recognition of sounds​
    • Conscious identification & add meaning to sound
    • From ear to temporal lobe
44
Q

What are the dysfunctions of CN VIII?

A
  • Dizzines/Disequilibrium
  • Hearing loss
  • Difficulty locating sounds in space
45
Q

What are the types of hearing loss?

A
  • Conductive hearing loss (e.g., excessive wax or otitis media).
    • Air waves cant create water waves
  • Sensorineural hearing loss (e.g., damage to receptor cells or cochlear nerve).
    • Peripheral nerve (e.g., acoustic neuroma causing hearing loss and tinnitus) → Damage to cranial nerve itself
    • Cochlear nuclei/central pathways (e.g., brainstem stroke) → Hearing cells inside brain stem
46
Q

What are the functions of CN IX (Glosopharyngeal)?

A
  • Back of tounge and top of throat
  • Mixed sensory, motor and autonomic
  • Sensory component: Somatosensation from post tongue, soft palate and pharynx
    • Taste sensation from post 1/3 tongue → Bitter
    • Starts gag reflex (sensation)
47
Q

What are the dysfunctions of CN IX (Glosopharyngeal)?

A
  • Loss of afferent limb of gag reflex.
  • Loss of afferent limb of swallow reflex.
48
Q

What are the functions of CN X (Vagus)?

A
  • Mixed Sensory, Motor and Autonomic.
  • Sensory component: entire throat & upper abdominal viscera
  • Motor component: throat
    • Motor component of:
      • Gag reflex ->muscles to spit it out
      • Swallow reflex -> muscles to swallow
  • Autonomic component: head, throat, thorax & upper abdomen
    • Voluntary muscles of throat, wind pipe and voice box (pitch/tone/inflection of speech)
49
Q

What are the dysfunctions of CN X (Vagus)?

A
  • Difficulty speaking
  • Hoarse voice - cant get vocal cord to come together
  • Difficulty swallowing - motor component of swallow reflex - wind pipe doesn’t get closed - can lead to aspiration
    • Elect not to eat
    • Drool all the time
  • Asymmetric elevation of soft palate - when you go to dr and they have you say “ah”
    • If have sore throat and suspect nerve damage you can do the “ah” test to look for asymmetries
  • Loss of efferent limb of gag reflex.
  • Loss of efferent limb of swallow reflex.
  • Poor digestion & may get constipated
50
Q

What are the functions of CN XI (Accessory)?

A
  • Motor: Traps & SCM
    • ​Turn head and elevate soulders
51
Q

What are the functions of CN XII (Hypoglossal)?

A
  • Motor: Intrinsic & extrinsic muscle of the tounge
    • Chew: moves food around in mouth
    • Swallow: “scoop” loader dumps food in back of throat
    • Speak: constant sounds
52
Q

What are the dysfunctions of CN XII (Hypoglossal)?

A
  • Atrophy of ipsilateral tongue
    • Atrophy of denervation
  • Tongue drifts toward side of lesion when “stuck out” asymmetrically (ipsilateral)
  • Difficulty speaking and swallowing
    • Softening of hard constants
53
Q

What are the CN’s involved in the Oral Stage of swallowing?

A
  • CN V, VII, XII [5,7,12]
    • V: Moves jaw
    • VII: Closes lips
    • XII: Stirs around so you can chew
54
Q

What are the CN’s involved in the Laryngeal/Pharyngeal Stage of swallowing?

A
  • CN IX, X [9,10]
    • IX: Sense food at back of throat
    • IX: yummy = swallow OR yucky = spit out
    • X: food down throat into stomach
55
Q

What are the CN’s involved in the Esophageal Stage of swallowing?

A
  • CN X
    • If not working = aspiration is a potentail problem
56
Q

What cranial nerves are involved in speaking?

A
  • CN X (Vagus)
    • Larynx - Control throat and vocal cords
    • Soft palate - Raise/lower for resonance of speech
  • CN VII (Facial)
    • Lips - Especially the lips to produce “B,” “P,” “M”
  • CN V (Trigeminal)
    • Jaw - Moves jaw to put teeth in right place OR open jaw to allow sound to come out
  • CN XII
    • Tongue - Moves tongue - where tongue presses against hard palate or the teeth
      • Dysfunction: dysarthria - mechanical aspects of speech not good
57
Q

What is the Corticobrainstem Tract?

A

Upper motor neurons that control motor function of all cranial nerves

58
Q

What nerves are affected with a swallowing dysfunction?

A

May indicate problems with UMN or LMN of CN V, VII, IX, X and/or XII

59
Q

What nerves are affected with dysarthria?

A

May indicate problems with UMN or LMN of CN V, VII, X, and/or XII.

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