Vision 1 & 2 Flashcards
(50 cards)
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