Chapter 11 Flashcards

accommodation
Dynamic changes in the lens of the eye that enable the viewer to focus. When viewing distant objects, the lens is made relatively thin and flat; for near vision, the lens becomes thicker and rounder and has more refractive power.
amacrine cells
Retinal neurons that mediate lateral interactions between bipolar cell terminals and the dendrites of ganglion cells.
bipolar cells
Retinal neurons that provide a direct link between photoreceptor terminals and ganglion cell dendrites.
ciliary body
Two-part ring of tissue encircling the lens of the eye. The muscular component is important for adjusting the refractive power of the lens. The vascular component produces the fluid that fills the front of the eye.
cones
Photoreceptor cells specialized for high visual acuity and the perception of color.
cornea
The transparent surface of the eyeball in front of the lens; the major refractive element in the optical pathway.
fovea
Area of the retina specialized for high acuity in the center of the macula; contains a high density of cones and few rods.
foveola
Capillary-free and rod-free zone in the center of the fovea.
glaucoma
Condition in which the eye's aqueous humor is not adequately drained, resulting in increased intraocular pressure, reduced blood supply to the eye, and eventual damage to the retina.
horizontal cells
Retinal neurons that mediate lateral interactions between photoreceptor terminals and the dendrites of bipolar cells.
macula lutea
The central region of the retina that contains the fovea (the term derives from the yellowish appearance of this region in ophthalmoscopic examination); also, the sensory epithelia of the otolith organs.
mesopic vision
Vision in light levels at which both the rods and cones are active.
opsins
Proteins in photoreceptors that absorb light (in humans, rhodopsin and the three specialized cone opsins).
optic disk
The region of the retina where the axons of retinal ganglion cells exit to form the optic nerve and where the ophthalmic artery and vein enter the eye. Also called the optic papilla.
optic nerve
The nerve (cranial nerve II) containing the axons of retinal ganglion cells; extends from the eye to the optic chiasm.
photopic vision
Vision at high light levels, which is mediated almost entirely by cone cells. Contrast with scotopic vision.
photoreceptors
The specialized neurons in the eye‚ rods and cones‚ that are sensitive to light.
phototransduction
The process by which light is converted in electrical signals in the retina.
pigment epithelium
Pigmented coat underlying the retina important in the normal turnover of photopigment in rods and cones.
pupil
The perforation in the center of the iris that allows light to enter the eye. The pupillary light reflex mediates pupillary constriction in full light and expansion (dilation) in dim light; these responses can also be induced by chemicals and by certain emotional states, and thus can be clinically important.
retina
Laminated neural component of the eye that contains the photoreceptors (rods and cones) and the initial processing machinery for the primary (and other) visual pathways.
rhodopsin
The photopigment found in rods.
rods
Photoreceptor cells specialized for operating at low light levels.
sclera
The external connective tissue coat of the eyeball.
scotoma
A small deficit in the visual field resulting from pathological changes in some component of the primary visual pathway.
scotopic vision
Vision in dim light, where the rods are the operative receptors.
transducin
G-protein involved in the phototransduction cascade.
trichromatic
Referring to the presence of three different cone types in the human retina, which generate the initial steps in color vision by differentially absorbing long, medium, and short wavelength light.
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