Download 4 Vision The human eye

Vision
Although small in size, the eye is a very complex organ.
Basic Anatomy
Lets take a closer look at our eyes
Eyeball
Define Eyeball
Pupil: The opening in the eye that lets in light.
Iris: a band of muscle in the eye that controls the size of the pupil,
thereby controlling the amount of light entering the eye.
Sclera: The white part of your eyes
Eye Color
When people refer to a persons eye color, they are naming the
color of the iris muscle.
Retina: It is the inside surface at the back of the eye. This is
where the eye detects the presence of the light and turns it into a
message it can send to the brain.
Photoreceptors: they are special receptors that are sensitive
to light. There are two types of photoreceptors: Rods & cones
Rods: are highly sensitive to light. They give you black & white
vision. They allow you to see in very dim light.
Cones: detect color. They don’t function in low light.
Optic Nerve: The photoreceptors detect light and send this
message to the brain through a nerve called the Optic nerve.
Focusing the light.
Lens: Your eye has an adjustable double convex lens to focus the
light image on the retna.
There are muscles that pull on the edges of the flexible lens that
are able to change it’s shape and fine tune vision.
The image formed on the retina is upside down, but your brain
corrects for this and interprets the world right side up.
The image formed on the retina is upside down, but your brain
corrects for this and interprets the world right side up.
Questions. To be done by hand….
1. Name and define all the parts of an eye you have learned so far. (Note, do not just
‘cut & paste’ from these notes. Write them in your own words)
2. Explain why the image on the back of the eye is upside down.
3. Since the image on the retina is up side down, explain why the world we see
doesn’t look inverted.
4. When we say someone has blue eyes, what are we referring to the color of?
5. What structures allow you to see color?
6. What structures allow you to see black & white?
7. Which are more sensitive to light, rods or cones?
8. How does your eye change the shape of the lens?
9. How does your eye focus on an object?
10. Take out a blank piece of paper, and sketch an illustration of an eyeball. Be sure it
clearly shows all the parts we have learned and don’t forget to clearly label it.