Wolfe Chapter 2 Terms

cornea

transparent “window” to eyeball

aqueous humor

fluid that supplies O₂/nutrients and removes waste from crystalline lens and cornea

crystalline lens

lens inside eye that enables changing of focus

pupil

where light enters eye

iris

colored region of eye that controls dilation of pupil

vitreous humor

transparent fluid that fills vitreous chamber

vitreous chamber

largest cavity in eye, located between retina and lens

retina

light-sensitive membrane in back of eye that contains rods and cones, receives image from lens and sends to brain through optic nerve

accommodation

process where refractive power is altered by changing its shape, necessary for focusing on light rays

astigmatism

vertical/horizontal lines are focused slightly in front/behind retina, caused when cornea is not spherical

transduce

convert from one energy source to another

fundus

back surface of eye

photoreceptors

light-sensitive receptor in retina

rods

specialized light-sensitive photoreceptor cells in the retina of the eye that allow us to see in dim light and provide peripheral vision

cones

specialized light-sensing photoreceptor cells in the retina of the eye that enable color vision and sharp, detailed central vision in bright light

photoreceptor outer segment

part of a photoreceptor that contains photopigment molecules

photoreceptor inner segment

part of photoreceptor that lies between outer segment and cell nucleus

synaptic terminal

where axons terminate at synapse for transmission of information by releasing a chemical transmitter

chromophore

light-catching of visual pigment of retina

melanopsin

photopigment sensitive to ambient light

rhodopsin

visual pigment found in rods

photoativation

energy transfer activated by light from rhodopsin to chromophore

hyperpolarization

increases membrane potential such that inner membrane surface becomes more negative than outer membrane surface (closes Ca channels)

graded potentials

how photoreceptors pass information to bipolar cells (instead of action potential)

eccentricity

distance between retinal image and fovea

age-related macular degeneration (AMD)

disease associated with aging that affects macula

macula

central part of retina that has high concentration of cones

fovea

small pit in macula, has highest concentration of cones and no rods

scomata

blind spot in retinal field

horizontal cells

run perpendicular to photoreceptor, also contacts bipolar cells

lateral inhibition

enables signals that reach retinal ganglion cells to be based on differences with activation in nearby photoreceptors

amacrine cells

retinal cell found in the inner synaptic layer that makes synaptic connections with bipolar, ganglion, and other amacrine cells

bipolar cells

retinal cells that synapses with either rods or cones (not both) with horizontal cells, then passes signals on to ganglion cells

diffuse bipolar cell

bipolar retinal cell whose processes are spread out to receive input from multiple cones

midget bipolar cell

small bipolar cell in central retina that receives input from a single cone, sends signal to single ganglion cell

ON bipolar cell

responds to increases in light captured by cones

OFF bipolar cell

responds to decreases in light captured by cones

ganglion cells

receives visual information from photoreceptors via bipolar and amacrine cells, sends to brain and midbrain

P ganglion cell

small ganglion cell that gets information from single midget bipolar cells, sends to “small cell” layer (parvocellular) of lateral geniculate nucleus (LGN)

M ganglion cell

ganglion cell that gets excitatory information from diffuse bipolar cells, sends to “large cell” (magnocellular) layer of LGN

konicellular cells

neuron located between small and large layer of LGN

receptive field

region on retina in which visual stimuli influence a neurons firing rate (can be excitatory or inhibitory)

on-center cell

increased firing rate when light is turned on in center of receptive field

off-center cell

decreased firing rate when center light is turned on