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PHTH 7303 Neuro > Exam 2 week 6 ppt 2 CN 3, 4, 6 > Flashcards

Exam 2 week 6 ppt 2 CN 3, 4, 6 Flashcards

1
Q

What cranial nerves innervate the extra-ocular muscles?

A

III (somatic motor component)

IV

VI

Oculomotor (III)

Trochlear (IV)

Abducens (VI)

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2
Q

How many extraocular muscles are there?

A

6

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3
Q

Name the 6 extraocular muscles:

and one related muscle

A
  1. Superior Rectus
  2. Inferior Rectus
  3. Medial Rectus
  4. Lateral Rectus
  5. Superior Oblique
  6. Inferior oblique
  7. Levator palpebrae superioris (eye lid)
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4
Q

What is conjugate movement?

A
  • Coordinated movment of the eyes to maintain normal vision
  • Requires cooperation of different CNs
  • Eyes move together with great precision
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5
Q

Where does the control of the conjugate eye movement arise from?

A

Brainstem gaze centers located in

  • Paramedian pontine reticular formation (PPRF) and the
  • Rostral interstitial nucleus (RIN) of the midbrain reticular formation
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6
Q

Brainstem gaze centers:

function (general)

location

A

Function

  • Coordination of conjugate eye movement

–Located in:

  • Paramedian pontine reticular formation (PPRF)
  • Rostral interstitial nucleus (RIN) of the midbrain reticular formation
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7
Q

PPRF

A

Paramedian Pontine Reticular Formation

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8
Q

RIN

A

Rostral Interstitial Nucleus

(of the midbrain reticular formation)

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9
Q

Brainstem gaze centers:

Details on function

A

•Brainstem gaze centers

  • –Regulate LMN activity in CN III, IV & VI nuclei
    • Hortizontal gaze coordination in PPRF
    • Vertical gaze in RIN
    • Via medial longitudinal fasciculus (MLF) (from the brainstem nuclei to these lower motor nuclei are via MLF)

–These centers are in turn controlled by frontal eye fields of cerebral cortex

These Brainstem gaze centers Regulate LMN activity in CN III, IV & VI nuclei. It appears that Hortizontal gaze coordination is in the Paramedian pontine reticular formation (PPRF) and Vertical gaze is controlled in the Rostral interstitial nucleus. Connections from these brainstem nuclei to the oculomotor lower motor nuclei are via the ascending medial longitudinal fasciculus (MLF). Activity in these brainstem centers are in turn controlled by frontal eye fields of cerebral cortex. The whole story is more complicated than that and involves several brain regions (as illustrated in the lower picture) but we will not go into this topic in that detail. Suffice it to say that loss of conjugate eye movement can result from damage to more than one brain region.

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10
Q

Where is horizontal gaze coordinated?

A

Paramedian pontine reticular formation

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11
Q

Where is vertical gaze controlled?

A

Rostral interstitial nucleus (RIN)

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12
Q

What Connects the PPRF and RIN to oculomotor lower motor nuclei?

A

Ascending medial longitudinal fasciculus (MLF)

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13
Q

MLF

A

Medial longitudinal fasciculus

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14
Q

What controlls the activity in the PPRF and RIN brainstem centers that control conjugate eye movements?

A

Frontal Eye fields of cerebral cortex

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15
Q

Where is the oculomotor nuclear complex?

A

Midbrain

Specifically the Dorsal Tegmentum just ventral to the periaqueductat gray.

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16
Q

What makes up the oculomotor nuclear complex? (2)

A
  1. Oculomotor nucleus (LMN with somatic motor function)
  2. Edinger-Westphal nucleus (parasympathetic prganglionic neurons with visceral motor function)
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17
Q

Oclulomotor nucleus:

UMN or LMN?

what type of function?

innervates what muscles? (5)

A

(Part of Oculomotor nuclear complex)

LMN with

somatic motor function

Innervates

  1. superior rectus
  2. medial rectus
  3. inferior rectus
  4. inferior oblique
  5. levator palpebrae muscle
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18
Q

action of superior rectus muscle:

A

elevation of eye

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19
Q

action of medial rectus muscle:

A

adduction of eye

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20
Q

action of inferior rectus muscle:

A

depression of the eye

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21
Q

action of inferior oblique muscle:

A

extorsion (lateral rotation)

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22
Q

what is extorsion?

A

lateral rotation

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23
Q

action of levator palpebrae superioris muscle:

A

raise eyelid

24
Q

Edinger-Westphal nulceus:

what type of function?

What does it do?

A

(Part of the Oculomotor Nuclear Complex)

Visceral Motor

pre-ganglionic neurons for Parasympathetic axons to pupillary sphincter and ciliary body

  • Puilary sphincter muscle produces pupillary constriction
  • Activiation of the ciliary body produces accommodation of the lens for near vision
25
Q

What nuclei and/or complexes serve the Oculomotor Nerve?

A

(CN III)

Oculomotor Nuclear Complex

  • Oculomotor Nucleus
  • Edinger-Westphal nucleus
26
Q

What does the Oculomotor nerve do?

A

Somatic Motor:

  • Contracts the following muscles:
    • Superior Rectus
    • Medial Rectus
    • Inferior Rectus
    • Inferior oblique
    • Levator palpebrae superioris
  • Parasympathetic activation
    • Pupillary constriction -pupillary sphincter
    • Accommodation of the lens for near vision - ciliary body
27
Q

what CN number is the trochlear nerve?

A

IV

28
Q

what kind of function does the trochlear nerve have?

A

Somatic Motor

29
Q

What is the complex and/or nuclei that serve the trochlear nerve?

A

Trochlear nucleus

in midbrain caudal to oculomotor complex

30
Q

Trochlear nucleus:

location

upper or lower motor nucleus?

What does fibers from it innervate?

A

in midbrain caudal to oculomotor complex

lower motor nucleus

innervates superior oblique

31
Q

What does the trochlear nerve innervate?

A

superior oblique muscle

32
Q

Function of superior oblque muscle:

A

intorsion (medial rotation)

33
Q

What gives the trochlear nerve its name?

A

The superior oblique muscle passes through a ligamentous ring called the trochlea

(the trochlear nerve innervates this muscle)

34
Q

How are the axons leaving the trochlear nucleaus unqiue? (2)

A
  1. they decussate and innervate the contralateral superior oblique muscle
  2. Trochlear nerve is the only cranial nerve to exit the dorsum of the brainstem
35
Q

CN number of Abducens Nerve

A

VI

36
Q

what type of function does the Abducens Nerve have?

A

Somatic Motor

37
Q

boxer puppy!

A

peek-a-boo!

38
Q

what is the nuclear complex or nucleus serving the abducens nerve?

A

Abducens nucleus

(located in caudal pons)

39
Q

where is the abducens nucleus located?

A

caudal pons

40
Q

what does the abducens nerve innervate?

A

lateral rectus muscle

41
Q

function of the lateral rectus muscle

A

ocular (eye) abduction

(hence name “abduc - ens”)

42
Q

Lateral rectus

Innervation

primary action

A

Innervation: Abducens (VI)

primary action: abduction

43
Q

medial rectus

Innervation:

primary action:

A

Innervation: Oculomotor (III)

primary action: adduction

44
Q

Superior rectus

Innervation:

primary action:

A

Innervation: Oculomotor (III)

primary action: elevation

45
Q

Inferior rectus

Innervation:

primary action:

A

Innervation: Oculomotor (III)

primary action: depression

46
Q

superior oblique

Innervation:

primary action:

A

Innervation: Trochlear (IV)

primary action: intorsion

47
Q

Inferior Oblique

Innervation:

primary action:

A

Innervation: Oculomotor (III)

primary action: Extorsion

48
Q

chart of all the extraocular muscles, innervations and primary & secondary actions

A

We DO NOT need to know the secondary actions.

(I asked Dr. Lake in an email)

49
Q

Movment of eyes to right requires the activation of which muscles?

A

left medial rectus (oculomotor nerve, III)
right lateral rectus (abducens nerve, VI)

50
Q

Movment of eyes to right requires the activation of which neurons?

A

Left oculomotor nucleus

right abducens nucleus

51
Q

Tilting the head to the right requires the activation of which extraocular muscles (and neurons) to compensate?

A

–Tilting head to the right, eyes compensate by torsion to maintain vertical alignment

  • §Left extorsion – inferior oblique & oculomotor nucleus (CN III)
  • §Right intorsion – superior oblique & trochlear nucleus (CN IV)
52
Q

Four Disosrders of Eye Movement

A
  1. Opthalmoplegia – paralysis of one or more of the extraocular muscles
  2. Strabismus – inability to direct both eyes to the same object
    • Lateral – due to paralysis of CN III
    • Medial-due to paralysis of CN VI
  3. Diplopia – double vision
  4. Ptosis – weakness of levator palpebrae superioris muscle
53
Q

what happens with Oculomotor (CN III) Opthalamoplegia? (3)

A
  1. –Lateral strabismus
    • Unopposed lateral rectus (CN VI)
  2. –Ptosis
    • Compensation with contract frontalis so raised eyebrow
  3. –Diplopia when looking downward
    • Reading & walking downstairs
    • Paresis or paralysis of inferior rectus on side of damage so only one eye will look down producing the double vision
54
Q

what happens with Trochlear (CN IV) Opthalamoplegia? (3)

A

–Paresis/paralysis of superior oblique

  1. Eye moves up & lateral
  2. Head tilt to unaffected side to reduce diplopia
  3. Diplopia again when looking downward as in reading & walking downstairs
55
Q

The three most common sources of injury to the Oculomotor nerve (CN III) or Trochlear nerve (CN IV)

A
  1. –Inflammation of meninges
  2. –Aneurysms of internal carotid artery or other circle of Willis arteries
  3. –Swelling in brain with increased venous pressure in cavernous sinus
56
Q

what happens with Abducens (CN VI) Opthalamoplegia? (2)

A

–Paresis/paralysis of lateral rectus

  1. –Eye moves medially due to unopposed action of the medial rectus
  2. –Head turned to affected side to reduce diplopia
57
Q

Is there just one spot in the brain that will affect conjugate eye movement if damaged?

A

No. loss of conjugate eye movement can result from damage to more than one brain region.

PHTH 7303 Neuro (89 decks)

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