NEUR 0010 - Chapter 9 Flashcards
What does the retina actually process, rather than a faithful representation of light intensity?
Differences in light intensity on different parts of it
What is the LGN?
First synaptic relay in the visual perception pathway; in thalamus; receives info from the optic nerves and sends it to the cerebral cortex
Why does the pupil appear dark?
Because of the light-absorbing retina that’s behind it
The cornea is continuous with what part of the eye?
The sclera
What are extraocular muscles?
Three pairs of muscles in the sclera
What is the sclera?
The white of the eye; tough outer wall of the eyeball
What is the conjunctiva?
The membrane that folds back from the eyelid inside and joins with the sclera
What is the macula?
The part of the retina used for central vision; distinguished by yellow color and lack of large blood vessels
What is the fovea?
A dark spot in the macula where the retina is thinner; marks the center of the retina, and so delineates nasal vs temporal retina
What are two specializations of the part of the retina dedicated to central vision?
Lack of large blood vessels, fovea is thinner
What is interesting about the nutrient system of the cornea?
Has no blood vessels, so receives nutrients from the aqueous humor behind it
What is the lens? How is its size controlled?
Behind the iris: suspended by zonule fibers that are attached to ciliary muscles
How is focal distance related to curvature of the lens?
The greater the curvature, the smaller the focal distance
What is the focal distance?
The distance from the refractive surface to the point at which refracted light rays converge
How does lens accommodation work?
The ciliary muscles contract and swell, loosening the zonule fibers and allowing the lens to thicken; or the ciliary muscles relax and the diminish, tightening the zonule fibers and forcing the lens to thin
What does it mean that the pupillary light reflex is consensual?
If you trigger a response in one eye, it happens in both eyes: one pupil won’t dilate without the other, etc.
Lack of consensual response for pupillary light reflex signifies a neurological disorder of what brain region?
Brainstem
What effect does pupil constriction have?
Increasing depth of focus (reduces blurriness of far objects)
What are two factors that affect visual acuity?
Spacing of photoreceptors in the retina; precision of the eye’s refraction
What is the most direct pathway for visual information to exit the eye?
From photoreceptors to bipolar cells to ganglion cells
Which retina cells fire action potentials?
Just the ganglion cells
What are horizontal cells?
Receive input from the photoreceptors, project neurites laterally to influence surrounding bipolar cells and photoreceptors
What are amacrine cells?
Receive input from bipolar cells, project neurites laterally to influence surrounding ganglion cells, bipolar cells, and other amacrine cells
What is the laminar organization of the retina from inner to outer?
Ganglion cell layer, inner plexiform layer (amacrine-ganglion/bipolar/amacrine synapses); inner nuclear layer (bipolar cells); outer plexiform layer (horizontal-bipolar/photoreceptor synapses); outer nuclear layer (photoreceptor cell bodies); layer of photoreceptor outer segments; pigmented epithelium
