Vision 1 & 2 Flashcards
Visual System 1
Which cranial nerves are responsible for eye movements?
III, IV, and VI
Innervates almost all of the muscles of the eye (except lateral rectus and superior oblique). Is responsible for eye movements, constricting the pupil, and lens shape. The cell bodies are in the midbrain. They are very medial in the Edinger-Westphal nucleus. The fibers exit at the level of the superior colliculus (green) and on the anterior (front) side.
Oculomotor (III) Nerve
It is the only cranial nerve to exit the brain dorsally. It also is the only cranial nerve to cross over to the other (contralateral) side. Fibers emerge at the level of the PAG (Periacqueductal Gray). This nerve innervates just one muscle, the superior oblique. This moves the eye downward.
Trochlear (IV) nerve
This nerve innervates the lateral rectus muscle on the same (ipsilateral) side. The Abducts of the eye (i.e. moves it away from the midline). It is important for moving both eyes together. Damage to the abducens nucleus in the lower pons (at the level of the 4th ventricle) results in double-vision or an inability to focus both eyes on the same object.
Abducens (VI)
Outermost covering of the eye, tough
Sclera
Clear, mucous membrane that covers sclera, lubricates the eye.
Conjunctiva
Transparent anterior portion that covers iris, pupil, lens, sensitive to pain (CN V)
Cornea
Middle layer of the eye, vascularized
choroid
Innermost layer of the eye
retina
Nearsightedness: anterior-posterior diameter of eyeball is too LARGE
Myopia
Farsightedness: anterior-posterior of eyeball is too SMALL
Hyperopia
Opaque, colored portion of eye. Pupil: opening
Iris
Space between cornea & lens
Contains aqueous humor- watery fluid
Anterior chamber
Space between iris & lens
contains aqueous humor- watery fluid
Posterior chamber
Space between lens & retina
contains vitreous humor- thick, gelatinous material, removes cellular debris
Vitreous chamber
Increased buildup of aqueous humor increases total intraocula pressure, reduces blood supply and damages retina
Glaucoma
Forms blood-ocular barrier to regulate influx of nutrition and drugs
Pigment Epithelium
Cones (day) Rods (night)
Photoreceptors
Photoreceptors pass through this; contains muller cells: glia cells, regulate neurotransmitters
External limiting membrane
- bipolar: relay signal from photoreceptors to ganglion, glutamate
- horizontal: integrate signals from multiple photoreceptors, GABA
- amacrine: integrate signals from multiple bipolar cells, connect multiple ganglion cells
Intermediate layer
Axons on ganglion cells form CN II
Ganglion layer
What photoreceptor matches the following description?
- Most prevalent in the CENTRAL RETINA, found in the fovea
- Sensitive to moderate to high levels of LIGHT
- Provide information about hue
- provide excellent acuity
- 4 million/eye
Cones
What photoreceptor matches the following description?
- Most prevalent in the PERIPHERAL RETINA, not found in fovea
- sensitive to low levels of light
- provide only monochromatic information
- provide poor acuity
- 100 million/ eye
Rods
T/F
Photoreceptors do not have action potential but do release neurotransmitters GABA & glutamate.
TRUE (has phototrasnduction and involves membrane potential)
T/F
Rhosopsin is found in rods and contains opsin and retinal (Vitamin A)
TRUE
Deficiency of what vitamin during development causes night blindness (nyctalopia: rods) which may progress to dry eye (xerophthalmia) & photoreceptor destruction, impacts children in developing countries
Prolonged Vitamin A deficiency
T/F
Color blindness is more prevalent in males and is caused by Genetic X linked and lesions of V8
TRUE
Which of the following is normal and which is atypical?
a. Trichromats: 3 cones, ____
b. Dichromats: 2 cones, ____
Trichromats are normal
Dichromats are atypical
How is color blindness identified?
Ishihara charts
Yellow pigmented area with the highest visual acuity
Macula
What is the following ocular disorder?
1. Cause unknown, retinal pigmental epithelium detaches from photoreceptors
2. Risk factors: smoking, hypertension, age
3. Most common form of vision loss, effects center
4. May involve cellular debris (dry-90%) or increased vascularization (wet-10%)
Macular degeneration
Contrast is mediated by what?
Ganglion cells
T/F
Temporal retina is rightmost and Nasal retina is left most
TRUE
Organized from ventral (1) to dorsal (6)
Magnocellular: large, movement, layers 1 & 2
Parvocellular: small, acuity & color, layers 3, 4, 5, & 6
Retina to LGN pathway (odd?)
L temporal: L 2, 3, 5
L nasal: R 1, 4, 6
R nasal: L 1, 4, 6
R temporal: R 2, 3, 5
Lateral Geniculate Nucleus
What tract projects visual radiation to the occipital cortex?
The Genicolocalcarine Tract
What divides the occipital cortex horizontally?
The calcarine sulcus
- Upper peripheral quadrant of retina
- Upper quadrant of macula
- Lower quadrant of macula
- Lower peripheral quadrant of retina
What does this describe?
Retinotopic organization of primary visual cortex (V1)
T/F
Suprachiasmatic Nucleus of hypothalamus: 24 hour rhythms
T/F
Superior Colliculus: controls pupil diameter & eye movements
TRUE
TRUE
Begins processing (edges, orientation), smaller visual fields
V1
Continued processing, larger visual fields
V2, V3, Ventral Parietal (VP)
Motion
V3A
T/F
V4v and V7 region function is hard to determine
TRUE
Motion & control of movement
Middle temporal, V5
color vision
V8
- Deficit in awareness and attention to one side
- Vision is normal
- Usually contralateral (Right parietal damage -> Left neglect)
Vision Neglect (Hemispatial neglect)
Photoreceptors functional but damage to extra-striate visual cortex (V8), visual world is described as gray shades
Cerebral Achromatopsia
Motion blindness (Middle Temporal)
Cerebral akinetopsia
An inability to recognize faces (Facial Fusiform Area)
Prosopagnosia
Stimulation of one sensory modality causes unusual experiences in a different, unstimulated modality (grapheme-color)
Synesthesia
