Cranial Nerves Flashcards
1
Q
Which cranial nerves are towards the midline?
A
CN III, IV, VI, XII
2
Q
Which cranial nerves are towards the lateral side?
A
CN V, VIII, VII, IX, X
3
Q
What is CN I?
A
Olfactory
4
Q
What is CN II?
A
Optic
5
Q
What is CN III?
A
Oculomotor
6
Q
What is CN IV?
A
Trochlear
7
Q
What is CN V?
A
Trigeminal
8
Q
What is CN VI?
A
Abducen
9
Q
What is CN VII?
A
Facial
10
Q
What is CN VIII?
A
Vestibulocochlear
11
Q
What is CN IX?
A
Glossopharyngeal
12
Q
What is CN X?
A
Vagus
13
Q
What is CN XI?
A
Accessory
14
Q
What is CN XII?
A
Hypoglossal
15
Q
What exits from the cribiform plate?
A
CN 1
16
Q
What allows for selectivity of light absorption amongst the four different types of photoreceptor?
A
Opsin
17
Q
Opsin is a peptide bound to what?
A
11-cis retinal
18
Q
___ is made up of 11-cis Retinal bound to Opsin
A
All photo pigment
19
Q
Phosphodiesterase is responsible for maintaining ___ levels in the blood
A
cGMP
20
Q
What is the order for the photoreceptors?
A
- Light strikes a photoreceptor (which has photo pigment)
- Opsin allows light absorption
- Light strikes the photopigment
- converts 11-cis retinal
21
Q
Decreased cGMP= ?
A
Hyperpolarization of that membrane
22
Q
What are the cells that process visual information and are between light entering and the photoreceptor
A
Retinal Cells
23
Q
The ___ has to convert light energy into energy of the nervous system. Light has to bounce through all the other layers of cells involved in processing before it reaches the photoreceptor
A
Photoreceptor
24
Q
What is the order of photoreception?
A
Photoreceptor > Bipolar Cell > Retinal Ganglion (axons of retinal ganglion become optic nerve)
25
Light comes in through the cornea and the lens and strikes the ___
Photoreception
26
* Most of the focusing of the light is done by the ___
* Fine tuning and focusing of light is done by the ___
* The most acute vision is in the ___
Cornea; lens; macula/fovea
27
The fovea only contains what?
Cones
28
Retinal ganglion cells converge from all over the retina to become the ___, which pierces the retina on its way out.
Optic nerve
29
There are no ___ in the optic nerve tract (causes a blind spot where it leaves)
Photoreceptors
30
Change in lens shape to focus light on the retina is called what?
Accommodation
31
Far Object to Near Object-the lens becomes more ___
Near Object to Far Object-the lens becomes more ___
Spherical-eyes adduct
Flat-eyes abduct
32
What regulates the amount of light that hits the photoreceptors?
Pupillary Light Reflex
33
Miosis is parasympathetic/sympathetic
Mydriasis is parasympathetic/sympathetic
Parasympathetic; sympathetic
34
If you shine a light in one eye both the eyes constrict, if in the left eye:
* ___ eye constriction – direct
* ___ eye constriction – consensual
Left; Right
35
Pupillary Light Reflex comes in through ___ and leaves through ___
Optic nerve; Oculomotor
36
What is it called when:
Left CN III is damaged
• Shine light on right eye > right eye constricts
• Shine light on left eye > right eye constricts
Pupillary Efferent Deficit (CN III)
37
What is it called when:
If left CN II is damaged
• Shine light on right eye > both eyes constrict
• Shine light on left eye > neither eye constricts
Pupillary Afferent Deficit (CN II)
38
Marcus Gunn Pupil is common in Multiple Sclerosis due to ___
Optic neuritis
39
What is it called when the pupil constricts as a result of accommodation reflex, not pupillary reflex
Argyll Robertson Pupil
40
Where is the lesion in an Argyll Robertson Pupil?
Lesion is in the Pretectum (needed for pupillary reflex, but not for accommodation reflex)
Seen in tertiary or neurosyphilis (was very common in prostitutes)
41
Temporal Retinal information stays ___
Nasal Retinal information is ___
Ipsilateral; Contralateral
42
The optic nerve projects to which structure? The ipsilateral fibers project to which nucleus? The contralateral fibers project to which nucleus?
Optic Nerve > Lateral Geniculate Nucleus (processes contralateral visual field)
Ipsilateral-2,3,5
Contralateral-1,4,6
43
What would it be called if you cut the right optic nerve? What would be the symptoms?
iIpsilateral Monocular Blindnesss
* Left eye normal
* Right will have no vision
44
What would it be called if cut the optic chiasm? What are the symptoms?
```
Bilateral Hemianopsia (half the visual
field is lost)
```
* Fibers from nasal retinas are affected
* No vision in either temporal field
45
What can a pituitary tumor cause?
Bitemporal Superior Quadrantanopia
| • Will affect inferior fibers in chiasm first
46
What will it be caused if you cut the right optic tract?
Contralateral Homonymous Hemianopia
• Right Optic Tract goes to right LGN
and process left visual field
47
What is the defect if LGN is damaged or if upper and lower optic radiation are damaged?
Contralateral Homonymous Hemianopia
48
What is it called when there is a Lesion of Upper Optic Radiation?
Contralateral Homonymous Inferior Quadrantinopia
49
What is it called when there is a Lesion of Lower Optic Radiation/ Meyer’s Loop lesion?
Contralateral Homonymous Superior Quadrantanopia
50
This is common in elderly because blood supply is very fragile and susceptible to CVA.
Contralateral Homonymous Superior Quadrantanopia
51
What is it called when there is a lesion to the occipital lobe?
Contralateral Homonymous Hemianopia with Macular Sparing
52
What is it called when there is a Lesion of Upper Calcarine Cortex?
Contralateral Homonymous Superior Quadrantanopia with Macular Sparing
53
What is it called when there is a Lesion of Lower Calcarine Cortex?
Contralateral Homonymous Inferior Quadrantanopia with Macular Sparing
54
If the muscle is superior then innervation is ___. All the rest are ___
Contralateral; ipsilateral
55
Adduction is controlled by ___ vs Abduction is controlled by ___
CN III; CN VI
56
If there is lateral Rectus muscle weakness in right eye, what are the symptoms?
```
• Can look up, down, or right
• Looking from left to right,
can’t abduct the right
• Left eye will adduct, right
eye will not abduct
• Diplopia (two images) and
the eye will suppress the
inappropriate image
• Strabismus (misalignment of one eye)
```
57
What is Strabismus?
```
• Leads to loss of visual
acuity (because brain begins
to ignore second image)
• CN VI palsy on the right
lateral rectus
• Children are often born with
conjugate weakness in one
eye muscle
• One leading cause of
strabismus in children is
Amblyopia (weakness in one of the eye muscles – usually
LR)
• Fixed by patching the good
eye to strengthen the weak
muscle in the affected eye
```
58
What is saccadic eye movement?
* Both eyes are moving rapidly together to find the target
* Controlled by Area 8 (frontal eye fields)
* If you stimulate area 8 on the left both eyes will conjugately deviate to the right
* Damage to area 8 on the left > both eyes deviate to the left
* Both eyes tonically deviated ipsilaterally
* If you ask patient to follow a target, both eyes will move right to primary gaze position and then deviate back to the left
59
What is smooth pursuit movement?
• Once you find a target both eyes conjugately move following the target
• Controlled by 17, 18, and 19
• If visual cortex is stimulated on the I left both eyes conjugately move to
the right
• If there is damage both eyes will be tonically deviated ipsilaterally
• A patient has both eyes tonically
deviated to the left, when you turn
the head to the right both eyes move
to the right and drift back to the left > CVA probably in area 8 on right
60
What is the Vestibular Oculomotor Reflex?
* If you spin someone to the left both eyes drift right and snap back to the left > Left Nystagmus
* Input comes from CN VIII, and Output is to CN III and VI, and goes through reticular formation
61
What is the Optokinetic Reflex?
* You sit inside an alternating black and white striped drum and spin the drum
* Eyes will drift in the direction of the spinning following a spinning stripe, then when it reaches its limit it snaps back to pick a new stripe > Nystagmus in opposite direction of spinning
* Input comes from CN II, and output is to CN III and VI
62
What is the difference between the two is the sensory input?
* Vestibular Oculomotor: Environment is Stationary, You are Moving
* Optokinetic: Environment is Moving, You are Sationary
63
Horizontal gaze is directed by what?
Horizontal gaze by PPRF
64
Downward gaze is directed by what?
Downward gaze regulated in the CN III nuclear complex in the Mesencephelon
65
Upward gaze is directed by what?
Upward gaze is regulated by superior colliculus, posterior commissure
66
What is Internuclear Opthalmoplegia?
* Loss of ipsilateral adduction to contralateral conjugate horizontal gaze
* If patient looks to the right, the left eye will not adduct
* Demyelination happens in the area of the lesion
* It is an early sign of MS
* Usually unilateral
* If there is a problem with the CN III on the left
* When patient looks to the right, the left eye will not adduct
67
How do you differentiate between Internuclear Ophthalmoplegia and CN III palsy?
* Tell patient to look ahead and bring in a target. If the left eye adducts to converge, CN III is intact
* If left eye adducts to converge but doesn’t when gazing (requires MLF) to the right, it’s Internuclear Ophtalmoplegia
68
What are the fibers projected to after the LGN to start the pupillary light reflex?
Superior Colliculus
Pretectal Area -> Edinger Westphal Nucleus -> Ciliary Ganglion -> Short Ciliary Nerves -> Ciliarus Muscle + Sphincter Pupillae
69
What occurs to help near vision?
- Ciliaris Contracts
- Zonules Relax
- Lens Buldges
- Pupil Constricts
70
What is the cascade for lacrimation?
1. Lacrima Fluid Produced
2. Moves lateral to medial
3. Lacrimal Puncta
4. Lacrimal Caniculi
5. Lacrimal Sac
6. Nasolacrimal Duct
7. Empties at lvl of Inferior Meatus of Nasal Cavity
71
What is myopia and hyperopia?
Myopia- Eyeball too long; image formed before retina, effects far vision (Nearsighted)
Hyperopia- Eyeball too short; image formed after retina, effects near vision (farsighted)
72
How do you fix myopia and hyperopia?
Myopia - Concave lens
| Hyperopia - Convex lens
73
Rods are important for what?
| Cones are important for what?
Rods-Retinal Sensitivity; scotopic vision
| Cones-Visual acuity and color vision; photopic vision
74
During dark to light adaptation, what occurs?
- Pupils constrict
- Increase bleaching of photopigments;
- Rhodopsin -> 11-trans retinal + opsin
- The rods turn off causing the retinal sensitivity to decrease
- Cones turn on causing increase of visual acuity
