PSYCH 3220 Exam 2 Unit 1: Eye and Retina

what are the two types of photoreceptors, and what are they especially useful for

rods (vision in dim light) cones (color vision)

what does “P = Pretty” mean

P cells are associated with cone information and color

what are M cells also called

magnocellular cells

what are p cells also called

parvocellular cells

what path does light take through the eye before reaching the retina

it passes through the cornea and lens

what does the cornea do, and can it adjust its shape

it provides about 80% if the eye’s focusing power, it’s shape is fixed

what does the lens do, and how much of the focusing power does it provide

20% of focusing power, and changes shape to help focus on objects at different distances

which muscles change the lens’s shape

the ciliary muscles

what is accommodation

changing the lens’s shape to bring objects at different distances into focus

what is the fovea

a small retinal area corresponding to the point of fixation and central vision

what is the peripheral retina

the much larger area of the retina outside the fovea, associated with the rest of what we see

how is the image on the retina oriented

it is flipped: objects in the right visual field appear on the left side of the retina

what are the main retinal cell types listed in the notes

photoreceptors (rods and cones), bipolar cells, ganglion cells, horizontal cells, and amacrine cells

what is transduction in the photoreceptors

the process by which light-sensitive visual pigments respond to light

what are visual pigments made of

opsin and retinal

what happens when light hits a visual pigment

it causes isomerization, a change in the pigment’s shape

what is visual pigment regeneration

the visual pigment changing back into a shape that allows it to be activated again

what is dark adaptation

increased sensitivity to dim light

what is spectral sensitivity

how sensitive visual receptors are to different parts of the visible spectrum

what does an absorption spectrum show

the amount of light a visual pigment absorption peaks at different wavelengths

how many absorption peaks do rods and cones have

rods have one peak; cones have three

which cone pigment wavelength are associated with which colors

short wavelengths: blue; medium: green; long: red

what is convergence

when many cells synapse onto one cell

how do rods and cones differ in convergence

more rods that cones feed into a single ganglion cell

where is there less convergence in the retina

in the fovea; there is more convergence in the peripheral retina

how does convergence affect rods’ and cones’ abilities

rods have better sensitivity; cones provide better detail vision

what is a receptive field

the area oon a receptor surface where stimulation affects a neuron’s firing

how are ganglion cell receptive fields described

large and overlapping

what is center-surround antagonism associated with

how ganglion cells code information

what is lateral inhibition

inhibition that is transmitted sideways across a nerve circuit

which retinal cells are associated with lateral inhibition

horizontal cells and amacrine cells

what does lateral inhibition help us perceive

enhances edges and contrast, which help us detect edges

what is the preferential looking (PL) technique used for

measuring perception in infants by observing how they look at two stimuli

what behavior is measured in the PL technique

how long an infant looks at each stimulus

what do infants spontaneously prefer to look at

objects with contours, such as edges and lines, rather than homogenous areas that all look the same

how does visual acuity develop in early life

it is poor at one month, increases rapidly from six to nine months, and reaches full acuity after one year

what is visual pigment bleaching

when light changes retinal pigment from its bent 11-cis form to its straight all-trans form. the pigment is then regenerated so it can respond to light

what is macular degeneration

Damage to the macula, the retinal area responsible for sharp central vision. Age-related macular degeneration can make central vision blurry or wavy

what is retinitis pigmentosa

a group of usually inherited eye diseases that gradually damage retinal cells, often causing difficulty seeing in dim light and loss of peripheral vision

what is a detached retina

When the retina pulls away from its normal position at the back of the eye. A sudden increase in floaters, flashes, or a curtain-like shadow can be warning signs that need urgent eye care