PSYA01H3 Chapter Notes - Chapter 5.4: Vitamin A, Rhodopsin, Color Vision
The Eye and Its Functions
Cornea: transparent tissue covering front of eye – forms bulge at front of eye, lets light through
Sclera: tough outer layer of the eye (the white)
Iris: pigmented muscle of the eye that controls the size of the pupil
Space immediately behind Cornea is aqueous humour which nourishes cornea and other portions
of the front of the eye – fluid circulated and renewed
If produced too quickly or if passage that returns to blood blocked, damage vision (Glaucoma)
Lens: transparent organ behind the iris of the eye, focuses an image on the retina, curvature
causes images to be focused on inner surface of back of the eye
Cornea is fixed, Lens flexible and alters shape to obtain images of near or distant objects
Accommodation: changes in thickness of lens of the eye that focus images of near or distant
objects on retina
Length of eye matches bending of light rays produced by cornea and lens
If not matched retina is out of focus, (prescription glasses correct discrepancy)
Eye too long, nearsighted, concave|| Eye too short, farsighted, convex glasses
Retina: tissue at back inside surface of eye that contains photoreceptors and associated neurons
Performs sensory functions of the eye
Embedded are +130million photoreceptors: receptive cell for vision either rod or cone
Info from photoreceptors transmitted to neurons that send axons to the optic disc at the back of
the eye
Optic disc: circular structure located at the exit point from the retina of the axons and the
ganglion cells that form the optic nerve
There are no photoreceptors directly in front of the optic disc which is our blind spot
Johannes Kepler credited with suggestion retina not the lens that contains receptive tissue of eye
Christoph Scheiner demonstrated lens is simply focusing device(ox eye, peel sclera away and see
upside-down image of world)
Retina has three layers light passes through: Ganglion cell layer (front), bipolar cell layer
(middle), photoreceptor layer (back)
Bipolar cell: neuron in retina that receives info from photoreceptor and passes it on to ganglion
cells from which axons proceed through optic nerves to brain
Ganglion Cell: a neuron in the retina that receives info from photoreceptors by means of bipolar
cells and from which axons proceed through the optic nerves to the brain
Visual info passes through 3cell chain to brain: photoreceptor, bipolar, ganglion, brain
Single photoreceptor only responds to light in immediate vicinity; ganglion can receive info
from many different photoreceptors
Retina contains neurons that interconnects adjacent photoreceptors and adjacent ganglion cells
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Cornea: transparent tissue covering front of eye forms bulge at front of eye, lets light through. Sclera: tough outer layer of the eye (the white) Iris: pigmented muscle of the eye that controls the size of the pupil. Space immediately behind cornea is aqueous humour which nourishes cornea and other portions of the front of the eye fluid circulated and renewed. If produced too quickly or if passage that returns to blood blocked, damage vision (glaucoma) Lens: transparent organ behind the iris of the eye, focuses an image on the retina, curvature causes images to be focused on inner surface of back of the eye. Cornea is fixed, lens flexible and alters shape to obtain images of near or distant objects. Accommodation: changes in thickness of lens of the eye that focus images of near or distant objects on retina. Length of eye matches bending of light rays produced by cornea and lens.
