Psychology Parts of the Eye

Pupil

the adjustable opening in the center of the eye; which controls the amount of light entering the eye (surrounded by the iris), in bright conditions the iris expands; making the pupil smaller, in dark conditions the iris contracts; making the pupil larger.

Cone

visual receptor cells located in the retina, can detect sharp details and color, need more light than rods, many cones are clustered in the fovea. (6 million cone cells)

Rod

visual receptor cells located in the retina, can only detect black, white, and gray, respond to less light than cones do. (120 million rod cells)

Iris

a ring of muscle tissue that forms the colored portion of the eye; creates a hole in the center of the iris (pupil), regulates the size of the pupil by changing its size- allowing more or less light to enter the eye.

Lens

a transparent structure behind the pupil in the eye that changes shape to focus images on the retina, muscles that change the thickness of the lends change how the light is bent thereby focusing the image, glasses or contacts correct problems in the lens' ability to focus.

Sclera

a white outer coating of the eye

Fovea

also known as macula; a small depression in the retina of the eye where visual acuity is highest. Many cones are clustered here.

3rd step in visual processing in the retina

bipolar cells then activate the ganglion cells, the axons of which converge to form the optic nerve. This nerve transmits information to the visual cortex in the brain's occipital lobe.

Choroid

blood vessels; the layer of blood vessels between the retina and the sclera; supplies nutrients to the back of the eye.

Bipolar cell

gather information from the rods and cones and pass it on to the ganglion cells; cells that form the middle layer in the retina.

1st step in visual processing in the retina

light entering eye triggers photochemical reaction and nerve impulses in rods and cones at back of retina.

Retina

light sensitive surface at the back of the eyeball, contains cells that convert light energy to nerve impulses, made up of three layers of cells: Receptor cells, Bipolar cells, Ganglion cells.

Ganglion cell

pass the information from the bipolar cells through their axons; together these cells form the optic nerve; the top layer of the cells in the retina.

Zonules

small fibers that connect the lens to the ciliary muscle.

2nd step in visual processing in the retina

stimulation from the rods and cones in turn activates bipolar cells.

Ciliary Muscle (body)

a muscle that connects or contracts/ relaxes the lens; it allows the lens to change its shape

Cornea

the clear, curved bulge on the front of the eyeball, begins to focus the light by bending it toward a central focal point; protects the eye.

Optic Nerve

the nerve that carries visual information from the eye to the occipital lobes of the brain.

Blind spot

the point at which the optic nerve travels through the retina to exit the eye, there are no rods and cones at this point, so there is a small blind spot in the vision.

Vitrous Humor

transparent liquid that fills the cavities of the eye; supplies with nutrients